One of the main criteria for the establishment of the performance of a forming process by material removal is based on cutting tool wear. Wear is usually caused by different mechanisms, however, only one is usually considered as predominant or the controller of the process. This experimental research is focused on the application of Pin-on-Disc wear tests, in which the tribological interference between UNS A92024-T3 Aluminum–Copper alloy and tungsten carbide (WC–Co) has been studied. The main objective of this study is focused on the determination of the predominant wear mechanisms involved in the process, as well as the characterization of the sliding and friction effects by using SEM and Energy Dispersion Spectroscopy (EDS) techniques, as applied to WC–Co /Al  which are widely used in the aerospace industry. Performed analysis prove the appearance of abrasive wear mechanisms prior to adhesion. This fact promotes adhesion mechanisms in several stages because of the surface quality deterioration, presenting different alloy composition in the form of a Built-Up Layer (BUL)/Built-Up Edge (BUE). Light alloys, mainly aluminum and titanium, are commonly used in different manufacturing fields especially because of their high performance—weight rate, their excellent physical-chemical properties and their advantageous economic cost. In this context, the aluminum market has greatly benefited thanks to its wide application in the aerospace industry, among others.Continuous growth in the use of these alloys, and constant requirements to improve the performance of their manufacturing processes follow an important tendency to gradually increase the development of different research lines. The aim of these is to find the optimum conditions for the forming procedures of aluminum alloys.Material removal, or machining, is among the main applications of aluminum alloy forming processes for aerospace applications. However, in the last decades machining processes have been characterized by a reorientation towards less aggressive environmental processes by means of the minimization or elimination of the use of cutting fluids in the cutting process. Under these conditions, cutting tools show an intensification of their wear mechanisms, causing deviations on the initial design specifications in the machined part ,2. For tIn general terms, when aluminum alloys are machined by chip removal processes, the tool wear process is mainly characterized by the appearance of secondary or indirect adhesion mechanisms . This weTool wear mechanisms can be studied under lab conditions using Pin-on-Disk or Pin-on-Flat tests ,8,9,10 rPin-on-Disc tribological tests (PoD) were carried out under dry conditions, using a MT/60/NI Microtest Tribometer   samples of 90 × 90 mmThen, (WC-6%Co) carbide metal bars with 30 mm length (l) and 4 mm diameter (d) hemispherical ends were used to simulate tool displacement (pins). The average and maximum Hertz contact pressure for the tribological pair were calculated as 0.91 and 1.37 GPa, respectively.3) as a function of the sliding length. All samples were carefully cleaned using petroleum ether and alcohol (50%). The weight of the aluminum probes were evaluated by a precision scale  before (P0) and after (PF) the development of the tribotests. The precision scale used in the weight evaluation of the samples have a 0.0001 g resolution. This scale resolution is the recommended by the ASTM G99 for the evaluation of results in Pin-on-Disc tribological tests.Wear evaluation was carried out following the guidelines of the ASTM G99-04 standard, expressing the friction effects in terms of material volume loss  with the aim of analyzing the effects and consequences of the wear mechanisms involved in the process. The wear track was also measured by a profilometer Taylor Hobson Form Talysurf Series 2 .Specific areas of the carbide pins and aluminum discs were established to perform deeper evaluation with a Scanning Electron Microscopy (SEM) and Energy Dispersion Spectroscopy (EDS) microcompositional characterization, by using a FEI Quanta 200  with EDAX Phoenix.The friction coefficient behavior and wear mechanisms involved in the process were studied on the contact surface of the carbide pins. The tribological wear effects were evaluated through volume loss of aluminum discs as a function of sliding length. Additionally, a study on the tribological wear behavior between empirical and theoretical models was carried out taking the Archard coefficient as control parameter.The friction coefficient (μ) of the specimens shows specific behavior for different sliding lengths. These phenomena may be mainly caused by the wear mechanisms involved in each stage of the friction process. In this way, through analyzing the obtained values for the friction coefficient, three stages were detected, with different behavior during the sliding course, The first stage is observed up to 200 m of sliding length, where the “stick-slip” phenomena takes place. This effect is developed in the dynamic contact between both surfaces, resulting in unstable movements along the sliding track. In the first friction instant, a significant increase in the contact force and μ were caused by the detachment of initial asperities which come from the surface material of the tribological pair. These asperities may cause specific roughness values, leading to a smaller contact surface between the pin and the disc, resulting in higher contact pressures. The action of high contact pressures on rough surfaces tend to remove soft asperities, favoring the detachment of wear debris on the sliding track, and giving place to high amplitude in the friction coefficient values and the appearance of the effects of abrasive wear mechanisms. In this aspect, an important increase of amplitude values implies a growth in the instability during the initial length of the process, especially because of the lack of uniformity of the circular trace, The increase in μ values is mainly caused by the movement of the pin over wear debris from initial aluminum asperities, involving a quick growth of the temperature in the contact area. A combination of friction and temperature conditions also favor adhesive phenomena from the aluminum particles to carbide surface.The next stage starts with a decrease in μ values and a stabilization of the pin temperature. An important reduction in the oscillations amplitude of μ was also detected. This behavior is mainly due to a growth of the adhesion layer of aluminum alloy formed from the slip track over the pin in stratified sections. Under these conditions, adhesion of wear debris over the slip track and pin surface induces the modification towards softer topographies between contact elements, resulting in a sliding process where surfaces of the same material contact each other, In the last stage, the detachment is produced by aluminum adhered debris from the pin surface, as a result of reaching an excessive critical volume. Under these conditions, the adhered layer becomes unstable and may be removed as a consequence of the friction forces on the contact area. In this way, the carbide surface is subjected to wear from the adhered aluminum layer, promoting the lost of particles from the hemispheric surface. Because of this effect, wear debris of aluminum and carbide (harder than the disc) are deposited again over the sliding track. The material debris on the wear trace results in an increase of the μ values and the temperature of the pin, When the carbide pin’s surface is analyzed, the existence of three different sections subjected to specific wear mechanisms are observed, The material volume loss was selected as the control parameter in order to study the sliding wear effects on the aluminum specimens. In this way, weight variations caused by the Pin-on-Disc test were measured on test probes with different sliding length configurations. The material volume loss was obtained by using the aluminum alloy density:In order to simplify analysis considerations and following the indications of the ASTM G99 Standard , the weaAs was expected, a relevant increase in the values of volume lost for the aluminum discs was detected as a function of sliding length, fitting to a linear behavior and confirming previous research findings . RegardiThe appearance in the first instants of several negative values in the variation of volume of the pins should be noticed; this indicates the existence of a slight abrasive wear process prior to the adhesive phenomena. In this respect, SEM confirmed this behavior .This wear effect was observed in the first instant of sliding tests, as has been commented previously, in which the stick-slip phenomena takes place. The abrasive wear effect finishes when the surface tension of the material breaks, stabilizing the forces involved in the process and allowing the appearance of the first stage of adhesive mechanisms . Furtherhardness .The coefficient exposed in Equation (2) allowed us to carry out the marginal analysis of Archard ratio as a function of the sliding length, taking special care of the fact that the proportionality coefficient is not a constant value, where direct [These considerations can differentiate the theoretical model from the real conditions. For this reason, marginal studies can be carried out by the approximation of the experimental results to an empirical model. In this way, a potential model has been selected, following the research lines with a specific interest in material removal ,18,19,20This equation can be linearity expressed by logarithmic expression:sK coefficients obtained from empirical and theoretical models.The potential model is shown in Ks) and empirical model (Ks’), a relevant difference can be observed in the exponent which govern the sliding length. This disparity may be justified by the existence of specific wear mechanisms that are not taken into account in the theoretical model.Comparing the Archard theoretical model (H), normal load (N), and wear volume (ΔV) are considered constant in this model. However, these components are direct or indirect variables of the process, making Material hardness  of a machining process. This allowed us to isolate the wear due to continuous friction between the contact pair, making it easy to characterize and to verify wear behavior.The obtained results show an initial abrasion mechanism in the WC/Co pin, which is followed by the secondary adhesion of the aluminum alloy.This adhesion takes place in two different stages. Firstly, thermomechanical effects (pre-fusion/adhesion) lead to the generation of a thin layer of pure aluminum, which comes from the aluminum matrix. After that, other layers with a similar composition to the Al–Cu alloy are adhered in a stratified way over the first one. This adhesion is due to mechanical effects. With the PoD tests it has been verified that, for pressures close to the ones achieved in finishing machining, the Built-Up Edge and Built-Up Layer effect can be studied for UNS A92024 alloy and WC–Co tribology pair. They are the main wear mechanisms for this pair against abrasion or erosion.Furthermore, the classical model for the evaluation of Archard wear coefficient do not provide solid results, not taking into account variation of the process as it happens with the superficial hardness of the disc or the orientation of the pin.


In the last decades, the increasing use of laminate materials, such as carbon fibre reinforced plastics, in several engineering applications has pushed researchers to deeply investigate their mechanical behavior, especially in consideration of the delamination process, which could affect their performance. The need for improving the capability of the current instruments in predicting some collapse or strength reduction due to hidden damages leads to the necessity to combine numerical models with experimental campaigns. The validation of the numerical models could give useful information about the mechanical response of the materials, providing predictive data about their lifetime. The purpose of the delamination tests is to collect reliable results by monitoring the delamination growth of the simulated in situ cracking and use them to validate the numerical models. In this work, an experimental campaign was carried out on high performance composite laminates with respect to the delamination mode I; subsequently, a numerical model representative of the experimental setup was built. The ANSYS Workbench Suite was used to simulate the delamination phenomena and modeFRONTIER was applied for the numerical/experimental calibration of the constitutive relationship on the basis of the delamination process, whose mechanism was implemented by means of the cohesive zone material (CZM) model. The use of composite materials has been steadily increasing worldwide in the last decades because of the development of tailoring facilities, allowing for the manufacturing of high performance structures for specific purposes. This characteristic makes such materials highly attractive for applications in different engineering fields in replacement of traditional structural materials such as metals or concrete. It is not unusual to use composite materials for structural applications in aerospace, automotive, and maritime fields, as well as in civil engineering and for sport equipment. Nevertheless, this type of materials is exposed to numerous damage mechanisms that can strictly affect their performance, even in the absence of externally visible damages. This drawback is connected to the presence of technologically different constituent materials, more sensitive to damages with respect to the conventional ones. Interface cracking, that is to say, the loss of cohesion between layers, even known as delamination, is one of the most dangerous and common problems in composite layered materials. The interlaminar deterioration may occur as a result of several reasons, such as low energy impact; high in-service loading; and aggressive conditions, manufacturing defects, or high stress concentration in correspondence with geometrical and/or material discontinuities. This damage mode is particularly critical for structural integrity, because it introduces splitting of the piece into two or more parts, reducing bending stiffness and inducing both local reduction of the strength and the buckling phenomenon, leading to compromised functionality of the parts until they become impracticable in service. Therefore, the quality of the layers’ adhesion strongly influences the safety of a structural layered composite material. The feasibility of fully exploiting the advantages of composite materials requires careful analysis of this critical damage mechanism, as well as a study of the material characteristics corresponding to fracture toughness ,2. The iThe proposed study is related to a research project that involves the development of a structural analysis platform with the aim to perform diagnosis and prognosis in the presence of damaged and/or defected composite material structures. The focus of the research project was the identification, discrimination, classification, and analysis of the most typical composite materials damages/defects experienced in recent years, distinguishing between those that involve materials and those that involve structure components ,8.I fracture toughness of composite material, by following the indication of the ASTM D5528-01 [I available energy release rate matches or overcomes the critical value, GIC. Precise evaluation of GIC is a crucial phase for better identifying the damage tolerances and the durability of the composites. In this paper, a specific class of composite materials is analyzed; it is the well-known class of carbon fiber reinforced plastics (CFRP). CFRPs hold many benefits, such as high value of strength and stiffness. Designing a specific composite material, considering delamination and other forms of internal damages, means to define its damage resistance. This last part represents the aptitude of the material to not collapse at the starting point of damage. The material selection and product development need to be seriously supported by a deep knowledge of the interlaminar resistance of composite laminates . Indeed,D5528-01 . The calIn this work, a numerical model was carried out in addition to the experimental tests performed in accordance with the ASTM D5528-01 procedure ,20,21. T3. Laminates were made by applying a co-bonding process in autoclave curing phase (at 180 °C and at 6 bar of pressure). The half of the plate was firstly cured, then a non-adhesive insert and the not-cured half of the plate were placed on the first part, after which a final curing phase was applied. An even number of unidirectional layers composed the laminates and the delamination growth stirring along the fibers’ direction. A non-adhesive insert was introduced at the midplane of the laminates for inducing the delamination onset [Instron 1342, at constant displacement rate (1 mm/min) and at environmental controlled conditions, with T = 23 °C. In The experimental campaign includes nine CFRP DCB specimens. They were realized by combining carbon fibers and CYCOM® 977-2 resin. The fibers were high performance fibers having both intermediate modulus of elasticity (265-320 GPa) and strength (IMS), the filament diameter was about 5–7 µm, and the resin was a thermosetting one with a density of 1.31 g/cmBefore each test, a digital grid was realized and calibrated on the specimen. It substituted the manual reference, suggested by the standard, for live monitoring the crack growth. It was superimposed on live recorded images acquired by Charge-Coupled Device camera Marlin AVT. This is a black and white fire-wire camera, having a 1636 × 1252 pixel matrix, running at 12.75 frames per second in this experiment. The entire tests were recorded by placing the optical system in front of each sample; the images were acquired in continuous mode. 0 in the standard calculation, represents the preliminary delamination length included between the pin of the hinge and the end of the non-adhesive insert. The red grid was used for estimating the real crack opening during the test. The total length obtained by combining a0 and the real crack opening is defined as a in all the calculation methods.The blue grid reported in Tsai-Wu, Tsai-Hill, Hashin-Rotem, Chang-Chang, etc.) were proposed [Different fracture criterions exist for identifying the damage in the materials, and each of them is based on some specific hypothesis. A failure index is evaluated by the stress-based criterions; its critical value is the same as that of the energy-based criterions. Several stress-based criterions  as the modification of the potential energy U referring to the crack length a [B to the specimen width, and U represents the total potential deformation energy of the sample. Crack initiation or propagation may occur if the energy release rate matches the critical value, G = GC.The Griffith–Irwin approach is based on linear elastic fracture mechanics. The stress intensity factor or the critical strain energy release rate ruled both the crack initiation and propagation. A remarkable feature is that Griffith’s principle is appropriate to handle the singularity nature of the problem. Griffith’s criterion defines the energy release rate length a : (1)G=−dIc values. They consisted of a beam theory method (BT), a modified beam theory (MBT), a compliance calibration method (CC), and a modified compliance calibration method (MCC). However, the MBT method yielded the most conservative values of GIc. Four types of data reduction methods were calculated in all the tests for estimating GThe BT expression for the strain energy release rate of a perfectly built-in double cantilever beam is as follows: 1/3), with respect to the delamination length.Equation (2) considers a built-in condition in correspondence with the double cantilever beam clamping to the delamination front. The possibility of rotation at the end of the beam, owing to the real clamping conditions, leads to a correction of the previous formulation in favor of the MBT, which provides a new calculation of the strain energy release rate, as follows:i/Pi) as opposed to log (ai), by considering the onset values and the propagation values visually accounted along the delamination. Then, the best least-squares fit was drawn through the data. Finally, the exponent n representing the slope of this line was used to calculate the mode I interlaminar fracture toughness as follows:The CC method is based on the generation of a least squares plot of log  model. In detail, the modeling of the composite parts was done by means of ANSYS Composite PrepPost tool. The CZM approach consisted of introducing fracture mechanisms by adopting softening relationships between tractions and separations, which in turn introduced a critical fracture energy that was also the energy required to break apart the interface surfaces . The intIn particular, the CZM model was based on contact elements, which means that the interfacial separation was defined in terms of contact gap or penetration and tangential slip distance. In particular, cohesive zone modeling with contact elements included two different traction separation laws; namely a bilinear traction separation law and an exponential traction separation law. For this study, the bilinear behaviour with linear softening characterized by maximum traction and critical energy release rate was chosen. According to this behaviour, as described by Alfano , mode I P is the normal contact stress (tension), nK is the normal contact stiffness, nu is the contact gap, and nd is the debonding parameter.nd = 0 for Δn ≤ 1, and 0 < nd ≤ 1 for Δn > 1 withThe debonding parameter for mode I debonding is defined as follows:maxσ is the maximum normal contact stress.The normal critical fracture energy is computed as follows:As far the actual tests are concerned, the numerical model see  was reprThe numerical model was built by means of solid elements , one laThe mesh sensitivity analysis was carried out by considering four kinds of mesh sizes, named “double-fine”, “fine”, “coarse”, and “double-coarse” . The perIn I) reaches the critical value (GIC) so that the delamination starts. After that point, the material response becomes non-linear. The curves related to the samples 3 and 5 are quite overlapped and the related GI energy values are close as well, a bit higher than the average value (about 11%). In I energy values is reported for the different computation approaches [In order to carry out the experimental/numerical calibration of the CZM model, it was necessary to identify idoneous comparison curves (load versus time) among the experimental ones; all the experimental curves were examined, but the tests in which a detachment of the hinges occured were disregarded. In such a way, the number of useful curves was reduced to five , and they are plotted in proaches .The curve related to specimen number 3 was chosen as a target. To take into account the possible influence of the adhesion force of the teflon insert , the FEM model was made parametric. The workflow of modeFRONTIER is reported in Two different types of DoEs (designs of experiment) and one optimization algorithm were used during the numerical experimental calibration with modeFRONTIER, in order to target the calibration in a fast and efficient way.In particular, in different steps, the utilized DoEs are as follows : n intervals with the same probability and a random value is selected in each interval. ULH also tries to minimize correlations between input variables and to maximize the distance between the generated designs. In this way, the points are relatively uniformly distributed over the variable range. This algorithm is particularly suitable for generating the initial dataset for the optimization with a genetic algorithm and RSM training. Uniform Latin hypercube (ULH): this is a stochastic DoE algorithm that generates random numbers conforming to a uniform distribution. It is particularly suited for optimization with genetic algorithms and Response Surface Methodology training. ULH is an advanced form of Monte Carlo sampling; more precisely, it is constrained Monte Carlo sampling in which the constraint refer to the way each variable is sampled. The uniform statistical distribution is split in Incremental space filler (ISF): this is an augmenting algorithm thta sequentially adds new design configurations to a database by maximizing the minimum distance from the existing points (optimization of the maximin criterion). This algorithm is particularly suited for generating a dataset for response surface training as it improves both the RSM approximation quality and reliability, as well as the numerical stability of the training. In general, new points are added in such way to uniformly fill the input space. However, if the zone filling option is enabled, the new points will be added in hyperspheres centered around the marked designs from the existing database and with a defined radius, expressed as a percentage of the variable ranges.On the other hand, the optimization algorithm was MOGA-II (Multi-Objective Genetic Algorithm II) . It is tThe algorithm starts from an initial population, with an empty elite set, and uses the MOGA operators to generate offspring (next generation). Each new design is generated with one of the available operators.The fitness of all individuals in the generation is computed to determine which are the best designs.All non-dominated designs are copied and stored as the elite set. Each time this operation is performed and new designs are added to the elite set, duplicated and dominated designs are removed and the elite set is reduced to the population size by randomly removing designs in excess.The next generation is computed by applying the MOGA operators and using the designs from the parent population (selected from the previous generation based on their fitness) and the elite set.Steps 2–4 are iterated until the maximum number of generations is reached.If elitism is not used, each next generation is computed only using the designs from the parent generation. MOGA-II handles constraints by applying the penalty policy. Error designs are always dominated by valid designs, whether feasible or unfeasible. Unfeasible designs can lie on the Pareto front only if there are no feasible designs. When a generation is complete, all its designs are taken into account, even error designs, for the computation of the new generation, ensuring the continuation of the optimization.In this work, the DCB samples were loaded by following the suggested requirements of ASTM D5528 , with thI with respect to the correct one (MBT), and both CC and MCC. This confirms that the BT hypothesis of ideal perfect constraint at the crack tip does not correspond to the real conditions of the specimens.In 2. The obtained result is depicted in 2) of the GI energy delamination. The numerical/experimental calibration showed that the adhesion force of the Teflon does not affect the first part of the delamination curve, which is always characterized by a gap between the numerical data and the experimental data. The delamination was caught by the numerical model with a good approximation . The comparison of the experimental delamination energies  suggesteIn this paper, mode I delamination tests were carried out. The experimental tests were compared with the numerical model in order to validate the numerical results. The overlapping of the delamination curves was kept in good approximation by the numerical model. One specimen value for fracture toughness was taken into account for running the selected design. The value corresponds to the MBT and confirmed the robustness of the numerical calibration in modeling the real mechanical response of CFRP specimens.


Place cells and grid cells in the hippocampal formation are thought to integrate sensory and self-motion information into a representation of estimated spatial location, but the precise mechanism is unknown. We simulated a parallel attractor system in which place cells form an attractor network driven by environmental inputs and grid cells form an attractor network performing path integration driven by self-motion, with inter-connections between them allowing both types of input to influence firing in both ensembles. We show that such a system is needed to explain the spatial patterns and temporal dynamics of place cell firing when rats run on a linear track in which the familiar correspondence between environmental and self-motion inputs is changed. In contrast, the alternative architecture of a single recurrent network of place cells  cannot reproduce the place cell firing dynamics. These results support the hypothesis that grid and place cells provide two different but complementary attractor representations . Our results also indicate the specific neural mechanism and main predictors of hippocampal map realignment and make predictions for future studies. The place cells in the rat hippocampus show strong behavioral correlates by firing only when the animal visits a particular localised region of the surrounding environment  and grid cells (implementing path integration)  corresponds to its preferred firing location in the environment, so that the firing pattern over the neural ensemble forms an “activity bump.” The connection strength between any two neurons is inversely related to the distance between their locations, which, together with a global feedback inhibition, produces a plane attractor . These pathways need to transmit activity determined by the agent's movement direction and speed, as suggested for place cells  that inputs to the layer of place cells are provided by three modules of grid and grid by head-direction cells, each with different grid scaling. Each module includes 441 grid cells which grid-like firing patterns have the same spatial scale but an offset phase relative to each other, in accordance with experimental findings. All grid cells within a module are recurrently connected in a manner that could result via Hebbian learning from the hexagonal topology of multiple firing fields of individual cells. The grid scale of each successive module is a factor 0.72 smaller (or 1.39 larger) than the next, which is similar to the ratio found by Stensola et al. . The staGothard et al.  recordedThe rat's internal spatial representation, defined by place cell population activity, was quantified in terms of population vectors. Then the similarity of the population activity on the full-length journey to the population activity on each of the four types of shortened journeys was tested by correlating point by point the population vectors computed for each spatial location. The results of these correlation procedures for a single rat are represented graphically in The principal finding was that when a mismatch existed between the rat's internal spatial representation and the rat's coordinates in the external reference frame centered on the reward site the rat was running to, a dynamic correction process took place. The correction always took place after some initial delay, which was longer for the longer outbound journeys and shorter for the shorter ones. On longer tracks with moderate mismatches the activity realignment usually occurred already past the midpoint, in the second half of the journey. On some outbound journeys the internal representation remained more aligned with the distance from the box for about 1 meter, even though the start box was right behind the rat, outside its field of view. For moderate mismatches, the internal representation, after some initial delay, was shifted continuously through intervening states, faster than the actual speed of rat, until it was closely aligned with the landmarks corresponding to the end of the track the rat was approaching. The shorter the track, the more rapid the correcting shifting of the activity. In case of large mismatches, however, the internal representation jumped abruptly to the new position, skipping the intervening states, which occurred in the first half of journey, before the midpoint between the front of the start box and the end boundary.Based on the results of this work and also of their earlier study  the sensory inputs from ahead of the rat may be coming predominantly from the room wall, rather than the mismatched box that is much smaller, which may explain the observed dynamics . Because of this ambiguity, we focus on the outbound journeys, in which path integration from the start box mis-matches with constant environmental sensory inputs from all around the rat, excepting only the small start box directly behind it. Any sensory input from the box is likely cancelled out by the conflicting sensory input from the wall behind the rat in the overall sensory input from behind the rat. Therefore, in our outbound runs simulations we assume that there is no sensory influence on the rat from the movable box.In a subsequent study, Redish et al.  randomlyDetailed analysis of Redish et al.'s  data” part of “Results,” where we analyse Redish et al.'s data using our simulation results.The study replicated and extended that of Gothard et al.  through G in the model, in the range between 1 and 3, in order to investigate its influence on the model. The strength of synaptic connections from place cells to grid cells (P) we keep constant and equal to 10, to make the place cell input strength comparable to the strength of the combined input of the three grid cell modules, since the synaptic transmission threshold is higher for place cells  in our model (A.11), is comprised of an input from the BVC tuned to the boundaries ahead of the rat and inputs from two BVCs tuned to the boundaries in the lateral directions. The sum of the three BVC inputs is thresholded using a fixed threshold T that we set equal to the sum of the two laterally tuned BVCs inputs, which remain constant along the track since the rat runs parallel to the track side borders. Each individual BVC i input bi is given by (A.7), with the following parameters: A0 = 4.5, σ0 = 21.5, α = 0.109, β = 0.016, γ = 0.101.As explained in the “V = 15 cm/s across all trials.During simulations the starting position of the rat was changed in such a way as to represent the ranges of track lengths in both Gothard et al.'s  and RediFor comparison, using the same settings, we also simulate a “place cell only” model in which there are no grid cells and only a single continuous attractor network. As for the place cell–grid cell model simulation, we use a similar 2-D sheet of recurrently connected place cells (a plane attractor) that covers the full length of the familiar 160 cm track. Path integration is performed via asymmetric connections between the place cells, which strength is modulated by the rat's direction and velocity signals. At the same time sensory inputs to the place cells are provided by BVCs, in the same way as in the main model (A.11). Further details of the place cell only model (A.12) implementation are given in the G = 2.1 , provides a good qualitative fit to the behaviour of place cells on outbound journeys in Gothard et al.'s (The behaviour of the place cell–grid cell model (A.11), with et al.'s  study, aDuring moderate self-motion and sensory information mismatches (as on the longer two of the shortened tracks), after a pronounced initial delay, the place cell activity bump was continuously shifted through intervening positions until its location was in agreement with the sensory inputs provided by the BVCs tuned to the approaching end of the track. The speed of transition depended on the mismatch size, with a larger mismatch resulting in a more rapid transition, following an initial delay , top. WhIn the place cell only model (A.12), in contrast, on the two longest of the shortened tracks the shift realignment begins practically straight from the start, even though BVC inputs there are quite weak, and completes in the first half of the journey , top. ThWe first consider the mechanism behind the dynamics of the place cell only model, and then how the dynamics of the place cell–grid cell model differ from this simpler model. In the place cell only model, the symmetrical connections between place cells (PCs) act to maintain a single activity bump on the PC sheet, whereas asymmetric connectivity, mediated by place by direction cells (Equation A.12), acts to shift the bump, performing path integration Zhang, .For moderate mismatches  the BVC input to the PC sheet overlaps the activity bump sufficiently to make it shift , and there are no grid cell projections to stop the bump shifting to align with the BVC input immediately , top. InFor the place cell–grid cell model, the PC activity bump is supported by symmetrical recurrent connections, and receives inputs from BVCs, but, unlike the place cell only model, the path integrative input to place cells comes from the grid cell (GC) layers, rather than asymmetric connectivity between PCs. In this case, mismatches between BVC inputs and the PC bump have to affect place cell firing before this change can spread to the GC sheets and change their firing before finally affecting the path integrative input to the PC sheet.For moderate mismatches  when the BVC input overlaps the PC bump sufficiently to make it shift, the PC bump is still receiving a location-specific PI input from the GC layers, preventing any shift faster than that indicated by the rat's speed. It takes some time for the BVC input to push some of the receiving place cells firing rates above the threshold necessary for synaptic transmission to the GC layers, which initially produces elongation of the PC bump. When the place cells exceed the firing threshold, they start providing inputs to the GC layers, producing shifting of the GC bumps. Feedback from the additionally shifting GC bumps finally allows the PC bump to start to shift faster than the rat's speed to eventually realign with the frame of reference of the approaching end of the track.The larger the mismatch between the path integration and BVC inputs , the more elongated between the two misaligned inputs the PC activity bump initially becomes, before inducing the realignment of GC bumps by which it is being held back. Therefore, the larger the mismatch, the larger the shifting input to grid cells from place cells, the faster the subsequent activity transition , top. DuG , the bump jumps sooner on the 80 cm track than on the 100 cm track (G = 2.1) is much longer than in the place cell only model  the BVC input does not overlap the PC bump and can cause it to jump from its original location to the new one, if the BVC input is sufficiently strong to overcome the self-support of the initial bump and the input from the grid cell modules that holds it in its original location. The BVC input strength, in addition to determining the possibility of realignment, also determines its rapidity, with stronger inputs producing faster place cell activity buildup. Thus, with all values of cm track , bottom,G). Larger values of G increase the influence of grid cell activity on the PC bump, therefore requiring greater BVC input buildup to start the place cell activity transition, leading to a longer initial delay (see P) also affects the dynamics of the PC and GC bumps. The value of P was set sufficiently high so that changes to the place cell activity affect the GC bumps without significant delay. In shift realignments, this avoids slowing of the rate of shifting of the GC and PC bumps which occurs for low values of P. In jump realignments, reducing P increases the delay required for the GC bumps to jump, but this delay is relatively short, since, in contrast to the PC bump, only the self-support of the original GC bumps resists their realignment .In both shift and jump realignments, the dynamics are influenced by the strength of grid cell–place cell connections , as seen in the data  Rats rely on path integration for a certain distance from their starting location, predicting that realignment locations should be distributed as a Gaussian in the box-aligned coordinate frame; (2) Rats use path integration until the room-cues, like the barrier at the end of the track, are perceived, predicting that realignment locations should be distributed as a Gaussian in the room-aligned coordinate frame; (3) Specific landmarks have influence over their own local space, predicting that realignments should occur around the halfway point of the journey. (4) Place cells are part of a dynamic system in a semi-stable state that needs to overcome an energy barrier in order to transit into another semi-stable state, predicting that realignment should at least partially depend on the time passed since the mismatch between the sensory and self-motion information occurred.For 20 time windows throughout the journey, the first window where place cell activity became more coherent with the room-aligned than box-aligned coordinate frame was determined. This was considered to be the transition point at which the realignment occurred. The consistency of the distribution of the transitions was measured with respect to: (1) the box-aligned coordinate frame; (2) the room-aligned coordinate frame; (3) the midpoint between the box and the end barrier; (4) the time since the rat started the journey. The mutual information between each of the four domains and the transition occurrence was measured, to see which of the four would be a more consistent predictor of the realignment occurrence.The time passed since leaving the box was found to be a more consistent predictor than any of the three spatial parameters examined, indicating that the shift between coordinate frames is at least partially controlled by a time-dependent process. Redish et al. explained the temporal delay before realignment as a stochastic switch happening somewhere in the system, the stochasticity reflecting noise in the neural network. They concluded that the time preceding the transition reflected the accumulation of sufficient energy for the switch to occur, i.e., for an energy barrier to be surpassed. It was noted that some combination of the four hypotheses could possibly predict the data more completely. The nature of the switch and the specific mechanism and time course of the activity transition itself were left for future research. Below, we address these questions by interpreting the Redish et al. data in terms of the jump and shift mechanisms in our simulations.G = 2.1) are also shown for comparison in all four different coordinate frames.G = 2.1, blue and green dots in Histogram In the time histogram Histogram Consistently with histograms Thus the delay in place cell activity realignment, attributed to a stochastic switch by Redish et al. , may resRedish et al.  suggesteThe place cell–grid cell model (A.11) can also account for the changes in firing fields of individual place cells on different outbound journeys, as seen in Gothard et al.'s  study. IThe firing field centred at ~1/3 of the full length track , cell 2 The field centred at ~2/3 of the full length track , cell 3 What happens to grid cells during the place cell realignment? This experiment . The model reproduces well the place cell firing rate data from the experiments with conflicting sensory and self-motion inputs, which supports the plausibility of the hypothesised architecture.Our simulations of the place cell–grid cell model provide explanations for the experimental results of Gothard et al.  and RediThe hypothesised model architecture is supported by comparison to the simulations of our place cell only model, which is unable to reproduce Gothard et al.  and RediSheynikhovich et al.  also simByrne et al.  also simIn contrast to the single-attractor models, the coupled place cell–grid cell system captures the dynamics caused by mis-matching path integration and sensory inputs due to a competitive interaction between two subsystems with semi-independent dynamics. Recent findings suggest that path integration and sensory information influence the behaviour of CA3 place cells with comparable strengths , either via grid cell activity packets shifting (concurrently with place cell activity shifting), or via grid cell activity jumping (following place cell activity jumping).The realignment dynamics are determined by the length of the shortened track on a particular journey. The shortened track length defines the rat's starting distance to the boundaries ahead (and thus forward-tuned BVC inputs' strength) and the mismatch magnitude , which determine the initial delay (increasing with the track length) and the time-course of the population activity transition. The larger the mismatch magnitude, as the track length is progressively shortened, the more rapid the continuous activity shifts, which turn into jump transitions when the mismatch magnitude increases above a certain value. Jumps typically occur much earlier on the track than shift realignments, because, according to our model, in jump realignments place cells initially realign alone, with grid cell activities following slightly later. In shift realignments, on the contrary, place cell activity continuously pulls along grid cell activity, which slows the realignment.The results of our simulations show that an architecture of interconnected recurrent networks of place cells  and grid cells (implementing path integration) can explain the spatial firing patterns and temporal dynamics seen in place cell firing rate data from experiments where the familiar correspondence between environmental and self-motion inputs is manipulated . And the grid cell activity should either realign concurrently with the place cell activity shifting or soon after the abrupt place cell activity jump, depending on the amount of track shortening. The realignment should occur simultaneously across all the grid cell modules with different spatial scales (due to the inputs from the same group of place cells), as well as coherently among the grid cells within each module (due to their recurrent connectivity).All datasets generated for this study are included in the manuscript/supplementary files.DL and NB conceptualised the model and the study. DL designed and implemented the computational model, performed the simulations, and data analysis. DL and NB wrote the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Background. This study assessed the effect of cooling the soft tissue site on the perception of pain in children undergoing local anesthesia for routine dental procedures. Methods. One hundred children, 6‒14 years of age, were assigned to either of the two study groups, i.e., group 1 (infiltration) and group 2 (block anesthesia). One side of the arch served as the test side, where an ice pretreatment (IP) of the soft tissue of the injection site was carried out using a tube of ice for one minute, whereas the opposite side served as the control, where no ice pretreatment (WIP) was carried out. This was followed by the gradual injection of local anesthetic solution. The children’s pain perception was assessed by VAS, WB-FPRS and SEM scales. The data were analyzed statistically.Results. WBS, VAS and SEM scores were significantly different between the WIP and IP in both groups, indicating that ice was effective in reducing the pain perception in children. Intergroup comparison revealed no significant differences (P>0.05), indicating that cooling was equally effective in infiltration and block anesthesia.Conclusion. Cooling the soft tissue site helped decrease pain perception during injection in children. Other techniques that were in use include mechanical devices such as Computer Controlled Local Anesthesia Delivery System (CCLAD), Wand5 and Comfort Control Syringe (CCS)6 that regulate the flow rate and accelerate the speed of injection to minimize pain. Vibrotactile devices like Vibraject7 and Dental Vibe8 provide mechanical vibrations to the surrounding tissues and act as a counter stimulation. Needleless injector9 is a jet injection-based technology which creates a high-pressure blast of local anesthetic solution sprayed against the soft tissue, leading to penetration with minimal discomfort. However, these advanced techniques involve high cost, and the complex appearance of the equipment might further aggravate the child’s behavior. Despite the advancements in dentistry, to date, pain and anxiety continue to be a problem with injections.The traditional syringe still is the primary means of injecting local anesthesia; therefore, it is the focus of attention. Pediatric dentistry is all about managing pain effectively. There exists an ongoing search for ways by which the pain perceived during an injection can be minimized by producing a comfortable environment for children undergoing dental procedures. Although complete pain-free injection is almost impossible to achieve, various methods have been advocated to decrease the discomfort associated with intraoral injections.Some of these methods are the application of topical anesthetics,12 Limited studies are available on the role of topical cooling in dentistry. In 1989, Harbert13 observed decreased pain perception by the patients who underwent cooling in the palatal region before injection. Although the concept of cooling the soft tissue prior to injection procedures is established, the literature lacks such kind of application in orodental procedures, especially in children, with a few exceptions.17 Hence, this study was undertaken to assess whether the application of ice on the soft tissue site has any effect on the pain perceived by children undergoing injections. The objective was to introduce a cost-effective method which is less technique-sensitive but clinically very effective and can replace the traditional methods of inducing local anesthesia.Cooling the injured tissues has a long-standing history in medicine. The technique of local external cooling is being used for treating musculoskeletal pain, fractures, sports injuries, sprains, etc. Various studies have shown the benefits of postoperative and preoperative cooling therapy to decrease wound pain and edema.The study protocol was approved by the ethics committee of Teerthanker Mahaveer Dental College and Research Centre, Moradabad, India. The parents or guardians of the selected subjects were provided with complete details of the study, who willingly allowed their children to participate in the study after signing the consent form. The sample size was calculated after power analysis which was 85% for this study. One hundred children aged six 6‒14, who met the inclusion criteria from 328 patients reporting to the Department of Pedodontics, were assigned to either group 1 or group 2.Patients requiring local anesthesia (infiltration/block) bilaterally on either the maxilla or mandible for various dental proceduresCooperative patients (Frankel’s Class III or IV)Healthy patients meeting the criteria of ASA physical status ‘I’Patients having significant behavioral problemsPatients with underlying systemic conditionsChildren who were physically or mentally subnormalHistory of a specific phobia or unpleasant experiences related to dental or medical settingsPatients allergic to anesthetic agentsGroup 1: Fifty children requiring local infiltration anesthesiaGroup 2: Fifty children requiring block anesthesiaSince each patient in both groups required local anesthesia administration bilaterally on either the maxilla or mandible, one side of the arch served as the test side , whereas the opposite side served as the control . The injection procedure was carried out on both sides on two different occasions. To determine whether the child would be treated for the test side or the control side on the first visit, randomization was carried out using the chit system.Each child was asked to pick a folded chit containing the term IP/WIP before the start of the procedure. The ice tubes were prepared by filling water in tube-shaped plastic containers . A woode18 and Wong Baker-Faces Pain Rating Scale (WB-FPRS)19 that were used in the assessment of pain. Behavior modification of the children was carried out using the tell-show-do method. A piece of sterile gauze was used to dry the soft tissue site prior to the intervention. For the test side, an ice pretreatmentof the soft tissue of the injection site was carried out using a tube of ice for one minute in the first visit. On the other hand, no ice pretreatment was carried out for the control side in the subsequent visit and vice-versa, based on the randomization protocol.The needle was then positioned on the appropriate site and slowly inserted. After successful negative aspiration, local anesthesia was administered gradually in 20‒30 seconds for infiltration and one minute in the case of the nerve block. The needle was withdrawn slowly after deposition of the solution.All the participating children were provided the necessary information regarding the injection procedure, familiarized with visual analog scale (VAS)20  scale during injections, which indicated the condition of each child ranging from ‘comfort’ to ‘severe discomfort’ on the basis of three variables, i.e., the child’s sounds , eye signs and body movements . Significantly higher scores of VAS, WBS and SEM were obtained in WIP than IP, indicating the positive effect of ice on the pain perception in children. Pre-cooling was effective in reducing pain, irrespective of the kind of the local anesthesia administered due to the absence of differences between the groups. The results are also consistent with Aminabadi et al26 surveyed the pain response to three different site preparations  prior to the greater palatine nerve block. They reported no significant VAS differences between the test groups and concluded that all of them were almost equally effective. The course of action of cooling in the reduction of pain can be explained by numerous theories. Cold stimulates myelinated ‘A’ fibers and activates pain pathways of inhibition, and thus the pain threshold is raised.27 In the present study, cylindrical tubes of ice were prepared and used for the technique of pre-cooling. The advantages of this technique are that it is comfortable, safe and physiologically effective. Also, ice is inexpensive and readily available everywhere. It is a material which is familiar to the patients; therefore, it is less likely to induce anxiety and subjective fear, especially in children.Wiswall et alBlinding the subjects and the evaluator was not possible due to the sensation of cold upon pre-cooling, and we consider it as a limitation. The temporary anesthesia produced by ice is of very short duration; therefore, the injection procedure had to be carried out very rapidly. Also, as pain is affected by a wide variety of contextual variables, the perception of pain varied from child to child, and the anticipated discomfort could be a critical factor in obtaining the results. The rate at which the anesthetic solution is deposited and the location of the injection site are other factors that could vary with each appointment. Prior experience of children with injections also plays a critical role in reaction to pain stimulus. Those subjects who were calm and readily accepted their first injection also reacted positively to the local anesthesia during the second visit, and vice versa. The reliability of the results could have been further improved by videotaping the injection procedure and allowing a third investigator to evaluate it. Keeping various advantages of local anesthesia in mind, this study was an effort towards delivering painless injections to reduce pain, increase patient compliance and improve the quality of care, and all the clinicians should be made familiar with this strategy.Cooling the soft tissue site significantly decreased the perception of pain (both infiltration and block anesthesia) in children during routine dental procedures. It proved to be an easy, reliable and cost-effective method of local anesthetic administration.The authors declare no conflict(s) of interest related to the publication of this work.SB: Contributed to the design, implementation of research, analysis of the results and writing of the manuscript. NG: Contributed to the design of the research, analysis and interpretation of the results and critical evaluation and editing of the manuscript. LP: Contributed to analysis and interpretation of the results and critical evaluation of the manuscript. RY Contributed to the design of the research, analysis and interpretation of the results and critical evaluation and editing of the manuscript.None.Self-funded.The authors state that the Institutional Ethics Committee of Teerthanker Mahaveer Dental College & Research Centre affiliated to Teerthanker Mahaveer University, Moradabad, India has approved the design of the research and informed written consent was obtained from patient’s parent/guardian before the beginning of this study.


A cable-driven parallel robot has benefits of wide workspace, high payload, and high dynamic response owing to its light cable actuator utilization. For wide workspace applications, in particular, the body frame becomes large to cover the wide workspace that causes robot kinematic errors resulting from geometric uncertainty. However, appropriate sensors as well as inexpensive and easy calibration methods to measure the actual robot kinematic parameters are not currently available. Hence, we present a calibration sensor device and an auto-calibration methodology for the over-constrained cable-driven parallel robots using one-dimension laser distance sensors attached to the robot end-effector, to overcome the robot geometric uncertainty and to implement precise robot control. A novel calibration workflow with five phases—preparation, modeling, measuring, identification, and adjustment—is proposed. The proposed calibration algorithms cover the cable-driven parallel robot kinematics, as well as uncertainty modeling such as cable elongation and pulley kinematics. We performed extensive simulations and experiments to verify the performance of the suggested method using the MINI cable robot. The experimental results show that the kinematic parameters can be identified correctly with 0.92 mm accuracy, and the robot position control accuracy is increased by 58%. Finally, we verified that the developed calibration sensor devices and the calibration methodology are applicable to the massive-size cable-driven parallel robot system. A cable-driven parallel robot  is a special type of parallel robot system that is actuated by multiple cables instead of rigid links to control the robot end-effector (EE)’s six degree-of-freedom (DOF) postures. The cable-driven parallel robot is composed of four basic components: a robot EE, cables, pulleys, motor-winches, and a robot frame. The robot EE is designed with respect to the required robot task and positioned within a workspace to fulfill a specific work. The cables are connected to the EE and generate six DOF spatial motions of the EE. The motor winches control the respective cable’s length and tension for a specific task, and a rigid frame composed of steel frames and walls constitutes the robot’s workspace and maintains all the cable and EE parts inside its configuration. The cable robot has advantages of large workspace and heavy payload ability in comparison with conventional parallel robots in industrial applications owing to its easy remounting, convenient transportation, and the low-inertia benefits of the actuator and EE ,2,3. Heni denotes the cable number, and m is the absolute number of cables. Further, Despite those advantages, problems still remain in cable robots. First, more actuators than the necessary DOF movements are required to implement free spatial motions owing to the unidirectional actuation (pulling) nature of the cables. Next, a large frame is required to secure the workspace of the cable robot. The first problem causes the over-constrained robot kinematics issues discussed in , and theai−x−Rbi . The geoGenerally, to calibrate the kinematic model, the model must include the most significant geometric and nongeometric parameters that influence the control accuracy. For the cable robot, three types of geometric errors exist. The first type is a machining error of winches such as the drum diameter or the pitch length. The second is EE’s geometric parameters. The third is the position errors of the EE’s cable connection points and the pulley where the cable comes out . NongeomParallel robotic calibration methods ,12 have n-DOFs robot contains m > n internal sensors. However, no specified sensors are available hitherto for the convenient and inexpensive calibration that can be performed in a short time. Further, most of the previous studies focused on the EE posture calibration based on the lumped uncertain kinematic parameters that may cause different kinematic calibration parameters for the different postures or motions of the robot. Further, the cables provide only unidirectional actuation as they can only transmit tension force, not compression force; thus, the cable elongation must be considered for the robot calibration. Among some kinematic uncertainties contained in the cable robot, the position error of the EE’s cable connection points can be minimized by machining the EE with a three-dimensional (3D) printer  in the flowchart of The parameter identification procedure using optimization with the iterative searching method is summarized in To obtain the calibrated robot kinematics under the assumption above, we define the geometric parameter vector, As we know the measured cable length, nematics  using thTo solve the forward kinematics in the given equation, a general Newton–Raphson iterative method is used. However, when a numerical method is applied when an error exists in the frame shape, the solution does not converge and leaves a certain amount of error. The proposed calibration algorithm optimizes the geometric parameters to reduce these error values. The predicted cable length The estimated distance from the laser distance sensor is obtained by the predicted position As we know the actual distance from the laser distance sensor measurement, , which are independent variables to be calibrated. In the error function, Error is a nonlinear function involving the numerical iteration for forward kinematics, and the best-case result is Error = 0. In other words, Error function’s solution. Hence, we calculate the discrete Jacobian matrix J as the following Equation (11), and the (J as shown in Equation (12):λ (0 < λ < 1) represents the under-relaxation parameter for convergence safety. The iteration computation is continued until the absolute value of Error becomes less than the preset Estop  of the controller to implement the online calibration procedures. The ADS is the communication protocol of TwinCAT. It enables the data exchange between two different devices. The ADS is media-independent and can communicate via serial or network connections, and the necessary hardware interfaces are provided for communication with third-party software such as MATLAB. We programmed the identification algorithm in MATLAB and implemented the online auto-calibration method using ADS in real-time communication with a PLC controller for the robot motion control. Finally, we can obtain the real-time geometry parameter through MATLAB and adjust the calibrated pulley geometric parameters to the actual on-site controller.We conducted the cable robot EE control experiments for different pulley position information by referencing ISO9283 standards that describe robot accuracy measurements. The performance of the suggested method can be verified by comparing the actual EE’s position and the posture accuracy comparison for the different values of Although significant efforts are undertaken in the design, manufacturing, and assembly of the robots to build the robot accurately according to the design specifications, errors and uncertainties in the geometry of the robot are inevitable. Using costly procedures, the errors can be reduced but not eliminated. While machine parts such as drums, pulleys, and guidance systems can be manufactured with narrow tolerances by virtue of manufacturing technology advances, the setup of large machine frames still suffers from assembling errors. Thus, the improvement in the accuracy by calibration during the initial operation of the robot must be addressed. A detailed technical definition of the robot accuracy and measuring process are subject to ISO 9283, where a calibration is defined as the procedure to estimate the actual numerical values of the geometrical design parameters of the robot; the accuracy is shown as a key performance indicator for all kinds of robotic devices, and the position accuracy of a robot describes its ability to move its reference points to the desired absolute position in space. Regarding this, the experimental results show that the proposed calibration method could be a novel online geometry error compensation method to satisfy the industrial cable robot’s requirements and to improve the accuracy of the cable robot system.We present herein a geometry calibration methodology for a cable-driven parallel robot system utilizing a single commercially available laser distance sensor. To improve the accuracy of the calibration against structured and unstructured kinematic uncertainty, a polynomial polymer cable model, an extended pulley kinematics, and a cable robot kinematics were incorporated. Further, we suggested step-by-step procedures of the cable robot calibrations comprising five stages from the pre-calibration of the structured component in the cable robot system to the auto-calibration method for practical implementation in the real world.The suggested methodology could overcome the uncertain kinematic parameters of the cable robot such as cable elongation and pulley inclusion error, and estimate the cable robot configuration by identifying the pulley position on the cable robot frame. The simulation and experimental results conducted on the MINI cable robot system could verify the performance of the proposed calibration methods. Considering the cable robot application with a large workspace and a frame size, the suggested method has the potential to overcome the unstructured and structured uncertainties in the cable robot kinematics, especially for spatial pulley position estimation that is essential for computing the forward and inverse kinematics of the cable robot.Compared to the previous cable robot calibration method that incorporates multimodal measurements from expensive sensors, we could achieve inexpensive and convenient but accurate methods to calibrate the cable robot by a model-based approach composed of kinematic parameters and experimental-data-driven mathematical models. In this study, we proved that even with insufficient sensor measurements for the cable robot calibration, the mathematical modeling of the unknown parts and the experimental data could overcome the insufficient sensor measurements. Moreover, the error modeling of the sensors will improve the accuracy of the cable robot calibration . In compIn our future works, more sophisticated modeling of the uncertain components of the cable robot system, such as the strict cable deformation and elongation modeling and the pulley friction and dynamic effects on the cable, will be studied to improve the robot EE position and posture control performance as well as long-term calibration free operating. Also, the quantification analysis and sensitivity analysis between the laser distance sensor accuracy and the cable robot calibration performance will be accomplished to provide a sensor selection guideline for the real-world application of the proposed methods.


Multi-sensor fusion system has many advantages, such as reduce error and improve filtering accuracy. The observability of the system state is an important index to test the convergence accuracy and speed of the designed Kalman filter. In this paper, we evaluate different multi-sensor fusion systems from the perspective of observability. To adjust and optimize the filter performance before filtering, in this paper, we derive the expression form of estimation error covariance of three different fusion methods and discussed both observable degree of fusion center and local filter of fusion step. Based on the ODAEPM, we obtained their discriminant matrix of observable degree and the relationship among different fusion methods is given by mathematical proof. To confirm mathematical conclusion, the simulation analysis is done for multi-sensor CV model. The result demonstrates our theory and verifies the advantage of information fusion system. Multi-sensor network technology is extensively used in modern life. It has many advantages over single sensor network. However, it faces some new challenges, such as low observability and large data delay ,2,3. To For the modern control theory, the observability, which is a qualitative index, can generally be expressed by a variable with two values “0” and “1”. Namely, the result is Boolean value. For zero value, it means that the system is unobservable, which means that the system state is not fully recovered by the measurement. As the quantitative variable, the observable degree is used to measure the observability ability . In 10]10], an aThe observable degree analysis with estimation performance measure (ODAEPM) proposed by Ma et al.,  is a greHowever, the ODAEPM in  only disThe rest of the paper is organized as follows. First, we review the ODAEPM in n is the state dimension. m is the observation dimension. n-dimensional Gaussian process noise and m-dimensional Gaussian observation noise.The associate models of linear time-varying discrete estimation system is considered as ,18:(1)xkODAEPM  is a metIn We define the optimal observability discriminant matrix as:Because the non-recursive information form Normally, if the system is stable, the system filtering accuracy is independent of the initial value. It may be assumed that Equation  can be wTherefore,The main contributions of ODAEPM towards observable degree analysis are as follows. First, by constructing observability discriminant matrix by jointly using WLS and Cauchy Schwartz inequality, the uncertainty from the observability effects of observation noise are taken into account. Second, by substituting observability discriminant matrix into the estimation error covariance matrix of KF under the assumption that the initial value of the estimation error covariance matrix tends to be infinite, the relationship between filter estimation performance and observability analysis is clearly established. Finally, by defining the local observable degree (LOD) and global observation degree (GOD), the estimation abilities can be expressed from different scale levels.Multi-sensor fusion system integrating signals from different sensors has the great advantage of overcoming the uncertainty and limitation under single sensor measurement condition ,19. To oL local sensors. The target moving model isDistributed multi-sensor track fusion system contains ith local sensor observation model is shown asi of matrix H and v is the sensor index. n is the state dimension. ith local sensor observation vector, where m is the observation dimension. ith local sensor linear observation matrix. n-dimensional Gaussian process noise and m-dimensional Gaussian observation noise. The covariances of process noise The There are many forms for multi-sensor fusion system; in this paper, we expound three present major fusion technologies in detail: the distributed multi-sensor fusion without feedback, the distributed multi-sensor fusion with feedback and the centralized multi-sensor sequential fusion.The structure of distributed multi-sensor fusion without feedback is shown in The distributed multi-sensor fusion system without feedback contains several local sensors. Each sensor performs Kalman filtering on its own observation data, transmitting the state estimation value The structure of distributed multi-sensor fusion with feedback is shown in The form of distributed multi-sensor fusion with feedback is similar to the former fusion technology. The most important difference between these two methods is that the fusion with feedback needs to return the fusion result The structure of centralized multi-sensor sequential fusion is shown in i reaches the sensor number L, the sequential fusion is finished, and the results The centralized multi-sensor sequential fusion is different from the other two fusion methods shown in this paper. This fusion technology only contains one sequential fusion filter at fusion center ,22. Not Although the ODAEPM proposed by Ma et al.,  providesAccording to Ma et al., , the obsk is the same as the ODAEPM performed on single sensor observation system, shown asa and time b.In distributed multi-sensor fusion system without feedback , the locIts estimation error covariance matrix of fusion center is:Discarding the process noise, Equation  can be rk, thus changing Equation ith locale matrix , Following the rule of ODAEPM, the GOD of local sensor and fusion center are defined as:From Equation  and propThus, it is obvious thatjth state component of local sensor and fusion center is defined asj of observable degree discriminant matrix means the jth diagonal element of the observable degree discriminant matrix.The LOD of To discuss the LOD, we need to extract the diagonal elements by the following equationThen,Thus, we can get the same result of LOD between local sensor and fusion center as the GOD:Furthermore, if the local sensor in the fusion system has the same observation matrix Equation  is rewriNext, we discuss the the relationship of observation degree between local filter and fusion center in distributed multi-sensor fusion system with feedback. According to Equations  and 21)21), we tEquation , makingFollowing the same operation as Equations –(43), weFrom the above proof, we come to the conclusion that, in distributed multi-sensor fusion system, whether there is feedback or non-feedback in the fusion method, both LOD and GOD of fusion center are greater than them getting the local filter. That means both in state components and system level, the fusion center obtains better filter performance than local sensor. In addition, it proves that the multi-sensor information fusion can improve the observation performance of the system from the aspect of observable degree.After we get the relationship between fusion center and local filter of distributed multi-sensor fusion system, we discuss the observable degree among different fusion methods.According to Equations , 20) an an20) anFirst, we compare the observable degree of local filter in distributed multi-sensor fusion system with or without feedback. Doing the same as Equation , Following the same operation as Equations –(43), thSecondly, compare the observable degree between local filter in distributed multi-sensor fusion system with feedback and different steps during sequential fusion. Consider that the ranking of sequential input of sequential fusion system is in ascending sort order of index of the sensor number. Following the same operation as above,Thus, the result isThe relationship of observable degree among the local filter in distributed multi-sensor fusion system with or without feedback and different step during sequential fusion is concluded as followsAccording to , the obsIn two different distributed multi-sensor fusion systems, both GOD and LOD of the fusion center are better than the local filters.That means both in state components and system level the fusion center obtains better filter performance than local sensor. In addition, it proves that the multi-sensor information fusion can improve the observation performance of the system from the aspect of observable degree.In two different distributed multi-sensor fusion systems, the feedback information from the fusion center can improve the filtering performance of the local filter, but with or without feedback information, the fusion solution at the fusion center is equivalent. That means both in state components and system level the local filter of distributed multi-sensor fusion systems with feedback obtains better filter performance than the local filter of distributed multi-sensor fusion systems without feedback.ith step during time k.This improvement is superior to the distributed multi-sensor with feedback system for the improvement of local filter filtering performance.From the perspective of observability, in centralized multi-sensor fusion systems, the fusion solution at the fusion center is equivalent to the others. The filtering performance of the fusion center is also improved at To validate the effectiveness of the mathematical proof of relationship of observable degree among information fusion system, computer simulation was performed to demonstrate the target tracking with three different observation sensors. The sensors used in this paper are only used to obtain the speed and displacement of CV models, so we only use the velocity sensor and the displacement sensor. The target motion is the typical two-dimensional linear discrete motion models as constant velocity (CV) model.The state transition matrix is given as:The observation matrix of three different sensors are:The observation covariance matrix of them are:H and R correspond to same index sensor.The subscripts of The simulation results are shown in Furthermore, to make the relationship clearer, the observable degree analysis in the normalized form, asThen, to prove the result shown in Equation , if the In Based on the simulation results presented in In this paper, observable degree analysis for multi sensor fusion system is addressed. Three different multi-sensor fusion system methods were studied, and the observability of three different fusion methods was calculated according to the definition of ODAEPM. It is also proved mathematically that, in two different distributed multi-sensor fusion systems, both GOD and LOD of their respective fusion centers are higher than their local filter, that is, the filtering performance is also better, which also illustrates the advantages of multi-sensor fusion system. The local filter performance of the distributed multi-sensor fusion system with feedback is better than without feedback. This shows that the feedback information from the fusion center can effectively improve the performance of the local filter. To confirm the mathematical proof, we simulated three different kinds of fusion methods operating on two-dimensional linear discrete motion constant velocity models and established three different observation sensors. We can verify our mathematical conclusions based on the simulation. It is clear from simulation that the feedback mechanism for distributed multi-sensor systems can significantly improve the performance of local filter. Therefore, in a multi-sensor system, the feedback mechanism should be introduced to the local nodes as much as possible, which can improve the filtering performance of the local filter.


Healthcare delivery is a highly complex, deeply personal and costly endeavour that involves multiple specialties and services. There is an imbalance in knowledge between the healthcare provider and consumer that may contribute to doubts and uncertainty over treatment and outcomes. It is unsurprising that conflict and dispute can develop between healthcare providers and patients and their next-of-kin. The use of mediation in the healthcare setting has recently been promoted in many developed countries, including Singapore. We administered a detailed 32-item survey in a large tertiary-care teaching hospital to improve our understanding of the knowledge, attitude and practice of dispute resolution among clinicians to pave the way for better strategies to improve the adoption of mediation in healthcare setting. Ninety-seven respondents had an average of 62% (SD: 12%) knowledge score. The most common misconceptions held by the respondents about mediation were: (1) mediation was about fact-finding, (2) mediation is limited to only certain types of dispute, (3) mediation proceeds by both parties giving their account of the dispute, then a third party decides a settlement, (4) the average time it takes to resolve a dispute through mediation, (5) the cost of mediation, (5) the venue of mediation, (6) the person determining the outcome of mediation, (7) confidentiality of mediation. In general, the respondents were positive about the use of mediation as a dispute resolution tool. When asked to indicate the relative importance of different outcomes of dispute resolution, financial compensation and waiver of hospital bill attracted mixed responses while understanding facts of dispute, assurance that the same error would not recur, and offering corrective treatment were rated as being important. By contrast, seeking an apology from the complainant was considered neutral to somewhat important and the respondents were least concerned with the publicity of the dispute. Direct negotiation with the complainant was considered the most time- and cost-efficient means of resolving a dispute while the opposite was true for litigation. Mediation was considered the approach where the clinicians are most likely to achieve their desired outcome while litigation was considered least likely to produce a favourable outcome. Approximately half of the respondents reported having personal experience or known of a colleague who had been involved in a medico-legal dispute. A quarter of these cases were resolved by direct negotiations with the complainant while lawyers, the judge and mediation, resolved approximately 15% each, respectively. The knowledge base of the clinicians in this study about mediation was moderate and probably reflected the general lack of direct experience in the resolution of a dispute or training in mediation. This further corroborated with the general response that the uptake of mediation in the healthcare setting is currently poor in Singapore due to the lack of awareness and perceived lack of avenue among the surveyed clinicians. Any further work to be done with clinicians may be in the direction of (1) increasing general understanding of mediation, (2) increasing awareness of avenues for mediation, and (3) becoming better aware of when to propose mediation. Healthcare delivery is a highly complex and costly endeavour that involves multiple specialties and services. It is also deeply personal and often evokes strong emotions not only in the patient, but also the caregivers. Moreover, there is an imbalance in knowledge between the healthcare provider and consumer that may contribute to doubts and uncertainty over treatment and outcomes ,2. It isThere is an increasing number of disputes in the healthcare setting being sent for litigation ,4. More The use of mediation in the healthcare setting has recently been promoted in many developed countries, including Singapore. We undertook a detailed survey in a large tertiary-care teaching hospital to improve our understanding of the knowledge, attitude and practice of dispute resolution among clinicians to pave the way for better strategies to improve the adoption of mediation in healthcare setting.The National University Hospital, Singapore is a 1100-bed tertiary-care teaching public hospital serving the Western half of Singapore. It is affiliated to the National University of Singapore and provides a complete suite of medical and surgical services that encompasses obstetrics and gynaecology, paediatrics surgery and medicine, adult surgery and medicine, and orthopaedics. We received ethics approval for this study .We developed a 32-item questionnaire that probed the knowledge, attitude and practice  of mediation and dispute resolution of the clinicians through a mix of open- and close-ended questions . The resThe respondents voluntarily participated in the survey and provided implied consent to have their data analysed in an anonymised, aggregated manner. The survey did not collect personal or identifiable data.The survey responses for each question were summarised using simple descriptive statistics. The percentage of the response was calculated with the total number of participants (i.e. n = 97) as the denominator. Subsequently, the participants were then divided into those who had prior experience in managing conflict and those who had not. The responses to the knowledge and attitude questions (i.e. Questions 1 to 17) between the two groups of participants were compared using Fisher's exact test (two-tailed).The knowledge of the participants was also scored against idealised/preferred answers for Questions 1 to 13, which were determined by the investigators. For questions with only one 'model' answer, a matched response was given a score of 1 while any other response was scored 0. For questions with multiple preferred answers, the respondents were scored 1 if they have fully matched responses, 0.5 if they had partially matched responses and 0 if they have fewer than half matched responses. The scores were then expressed as a percentage of the maximum of 13. The knowledge scores were correlated with the preferences of the clinicians for Questions 14, 15 and 20 in the Attitude section. A p-value of <0.05 was considered significant in this study.In total, we received 97 responses from the clinicians, representing a response rate of 8.7% from 1121 eligible clinicians in our hospital. Nearly two-thirds of the respondents were senior staff who had more than 6 years of working experience , followed by junior staff who had 0–3 years of working experience  and those with 4–6 years of experience . Correspondingly, 62 (64%) clinicians had postgraduate qualifications. Just less than half  of the clinicians were female.italic.The responses to the individual questions are summarised in The respondents had an average of 62% (SD: 12%) knowledge score. The most common misconceptions held by the respondents about mediation were (see Questions 1 to 13): (1) mediation was about fact-finding, (2) mediation is limited to only certain types of dispute, (3) mediation proceeds by both parties giving their account of the dispute, then a third party decides a settlement, (4) the average time it takes to resolve a dispute through mediation, (5) the cost of mediation, (5) the venue of mediation, (6) the person determining the outcome of mediation, (7) confidentiality of mediation.In general, the respondents were positive about the use of mediation as a dispute resolution tool (Questions 14 and 15). The knowledge scores did not correlate with the inclination of the clinicians to learn or use mediation as a dispute resolution tool (correlation coefficient <0.3). An overwhelming majority (94%) of respondents felt that maintaining a good relationship with the complainant was important (Question 16a). When asked to indicate the relative importance of different outcomes of dispute resolution (Question 16b), financial compensation and waiver of hospital bill attracted mixed responses while understanding facts of dispute, assurance that the same error would not recur, and offering corrective treatment were rated as being important. By contrast, seeking an apology from the complainant was considered neutral to somewhat important and the respondents were least concerned with the publicity of the dispute.Direct negotiation with the complainant was considered the most time- and cost-efficient means of resolving a dispute while the opposite was true for litigation (Questions 17–19). Mediation was considered the approach where the clinicians are most likely to achieve their desired outcome of dispute resolution (Question 17) while litigation was considered least likely to produce a favourable outcome.Just over half of the respondents (54%) had experience managing a dispute with patients (Question 22). Of these, half had managed five or more disputes in the past. Interestingly, prior experience in managing dispute did not produce statistically different responses to the knowledge- and attitude-related questions (Questions 1 to 17). Nevertheless, the overall knowledge score was higher in respondents with experience managing a dispute with patients compared to those without such experience . Approximately half of the respondents reported having personal experience or known of a colleague who had been involved in medico-legal dispute (Question 25). A quarter of these cases were resolved by direct negotiations with the complainant while lawyers, the judge and mediation, resolved approximately 15% each, respectively.When the clinicians were asked to put themselves in the shoes of the patients (or their next of kin), they mostly preferred to raise concerns about their care with a fellow clinician (Question 27). The clinicians would choose not to raise a negative experience with a hospital when they consider it as a minor issue (61%) or because they wish to maintain a good relationship with the colleague/ hospital (36%)(Question 28). They were somewhat likely to resolve the matter through a neutral third party or raising it to the hospital authority than considering legal advice (Question 29).Traditionally, public healthcare institutes have in-build mechanisms to manage disputes. The majority of cases are handled by such quality service management mechanism, the “direct negotiation” route, where a hospital representative will investigate the complaints and respond to the patient or next-of-kin appropriately. Direct negotiation is generally the preferred tool that a healthcare institution uses to resolve dispute since it is important for the parties to establish direct communication to ascertain the details of the dispute. This tool is particularly useful if the communication/ content is straightforward, and there is no ill will between the parties and parties are clear about their positions. However, in the event of escalation, the dispute will proceed in the direction of litigation, where the insurers and lawyers of both the hospital and the clinician, will be activated to defend against the claims.Mediation is a voluntary and confidential conflict resolution process where a neutral third party, the mediator, works alongside the parties to find mutually agreeable solutions to the dispute at hand. It is useful when the relationship between the parties is strained and direct communication has reached an impasse. It is also useful if one party is seeking non-monetary resolution , which the litigation process cannot provide for. The mediation process caters a confidential platform for parties to explain, exchange and clarify information, restore relationship/ trust. These are elements to an amicable settlement, or sets parties on the path to reach a sustainable and enforceable settlement. There are various accreditation schemes in Singapore to train and accredit mediators. Such training equips mediators with a framework and skillsets to facilitate discussion between disputing parties to achieve better communication, appreciate different perceptions, manage emotions, and overcome impasses. The mediators do not make any orders or decisions on the outcome.The mediation movement in Singapore became relatively more active in the 1990s and since then the courts actively promote and encourage the use of mediation for suitable disputes [The Honourable the Chief Justice, Sundaresh Menon, highlighted in his speech of 28 October 2014 to the Obstetrical & Gynaecological Society of Singapore that (1) the tort of negligence and the adversarial nature of the litigation system do not provide a holistic solution for disputes relating to bad medical outcome; (2) an increase in medical malpractice law suits will lead to more clinicians practising defensive medicine and result in a lose-lose situation for both individuals and clinicians.Identifying the main issues of disputes in healthcare industry as “dashed expectations and miscommunications”, mediation, which is a process that focuses on improving communication, active listening and extra-judicial resolutions, was proposed to be the first port of call for potential medical negligence disputes .Some pertinent observations from this survey:There is an expectation of mediation to go beyond 7 days (Question 5) and yet a large group shows willingness to use mediation to resolve dispute (Question 15).Despite not having training in mediation, the majority of the surveyed participants showed above average knowledge of mediation.Mediation may be a suitable platform for clinicians to explain the circumstances and treatment to the patients or their next-of-kind, as compared to litigation. This is because the clinicians surveyed had indicated that “understanding the facts of the dispute” as an important outcome of mediation. Aside from mediation, direct negotiation could also be explored as achieving this outcome, albeit without the presence of a moderating third party (mediator).Most clinicians find that the litigious route is the least likely to obtain desired outcome and will be most time consuming and resource intensive. While the majority perceived direct negotiation to be the least time consuming and least expensive.The study shows that the majority of respondents are keen to use mediation in the event of a conflict and are sufficiently interested to learn about mediation, even though mediation may not be the most resource efficient option to them.The majority has no training in relation to management of conflict/dispute in the hospital setting (Question 23a) and are keen to learn more about it.Based on the above observations, clinicians do see the advantages of mediation and that their desired outcome cannot be achieved by litigation if there is a material dispute with patients or their next-of-kin. Any further work to be done with clinicians may be in the direction of (1) increasing general understanding of mediation, (2) increasing awareness of avenues for mediation, and (3) become better aware of when to propose mediation. It is hoped that an increase in educational effort in these areas will improve the uptake of this dispute resolution tool. Nevertheless, the need for continued professional training in clinical care may reduce the priority in the learning of a non-medical related topic. The challenge therefore is how to build the mindset that learning to prevent or resolve disagreement is a key component of holistic patient care, as important as learning about the effects of the latest drug.This study provided helpful insights into the knowledge, attitude and practice of mediation and dispute resolution in a public healthcare institution in Singapore. The knowledge base of the clinicians in this study about mediation was moderate and probably reflected the general lack of direct experience in the resolution of a dispute or training in mediation. This further corroborated with the general response that the uptake of mediation in the healthcare setting is currently poor in Singapore due to the lack of awareness and perceived lack of avenue among the surveyed clinicians. To help equip future generation of doctors with the necessary skills to navigate an increasingly litigious healthcare environment, medical students should be introduced to mediation and negotiation skills that have been tailored to the healthcare setting and introduced through existing modules relating to patient communication.There are several limitations to this study. Firstly, this study was conducted in only one tertiary-care teaching hospital and the findings may not be easily generalisable to other clinical settings (e.g. primary-care). Secondly, the response rate from the clinicians is low, which may increase the risk of non-response bias. This may skew the overall responses towards respondents who already have an interest in mediation and have better knowledge about it. Consequently, the results obtained from this survey should be interpreted with care and should be seen as a 'best case' scenario. Nevertheless, the spread of the experience respondents is representative of the overall clinician population in our hospital and should provide a reasonably representative view of the clinicians in our institution.