The side effects of chemotherapy, specifically chemotherapy-induced nausea and vomiting, are a concern for patients. To relieve these side effects, antiemetic drugs are recommended. However, some patients report that these drugs are not sufficiently effective. Moreover, patients with chronic disease, including cancer, are increasingly interested in complementary and alternative medicines, and express the desire for nonpharmacological treatments to be used in hospitals. Foot reflexology is a holistic approach that is reported to significantly reduce the severity of chemotherapy-induced nausea and vomiting in patients with breast cancer. Some of the chemotherapy treatments for patients with lung and digestive system cancer are moderately or highly emetic.The primary objective of this study is to assess the benefits of foot reflexology, together with conventional treatments, on the severity and frequency of chemotherapy-induced nausea and vomiting in patients with lung or digestive system cancer. The secondary objectives to be assessed are quality of life, anxiety, and self-esteem.This study is an open-label randomized controlled trial conducted over 22 months (18 months intervention and 4 months follow-up). Eligible participants are patients with a lung or digestive system cancer with an indication for platinum-based chemotherapy. Participants are randomized into two groups: conventional care with foot reflexology and conventional care without foot reflexology. Foot reflexology sessions (30 minutes) are performed on an outpatient or inpatient basis. It was estimated that 40 participants per group will be required. The benefits of foot reflexology will be assessed by comparing the relative change in the severity of nausea and vomiting, as assessed by a visual analogue scale, and the frequency of these side effects between the two groups. The secondary objectives will be assessed with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire; Hospital and Anxiety Depression Scale; and Body Image Questionnaire.This study was approved by the regional ethics committee (Île de France X CPP) on April 3, 2018 (No. ID RCB 2018-A00571-54). Enrollment started in June 2018. Data analysis will be performed during the second quarter of 2020 and results will be published in the last quarter of 2020.The lack of knowledge regarding the efficacy and safety of foot reflexology limits oncologists to recommend it for this use. This study will provide evidence of the benefits of foot reflexology. If efficacy is confirmed, foot reflexology may be a promising complement to conventional antiemetic drugs.Clinicaltrials.gov NCT03508180; https://www.clinicaltrials.gov/ct2/show/NCT03508180.DERR1-10.2196/17232 Patients with cancer are increasingly interested in complementary and alternative medicines (CAMs) . AccordiAt the time of writing, the most frequently provided CAMs in private and public oncology centers in European countries are mind-body techniques, acupuncture, homeopathy, energy therapies, health promotion, traditional herbal medicine, as well as manipulation and body-based practices  . Foot reIn 2018, in both sexes combined, lung cancer was the leading global cause of cancer death (18.4%), followed by digestive system cancer including colorectal (9.2%), stomach (8.2%), and liver (8.2%) . AccordiThe aim of this study is to determine whether foot reflexology decreases the side effects induced by chemotherapy  in patients with lung or digestive system cancer.An open-label randomized controlled trial (RCT) will be carried out, in which patients are randomized to one of two groups at a 1:1 ratio: (1) conventional care with foot reflexology (40 patients) and (2) conventional care without foot reflexology (40 patients). Randomization is stratified on the type of cancer (digestive system or lung) and the presence or absence of metastases. The sponsor is the Hospices Civils de Lyon. The principal investigator is PJS. To design this trial, we used the CONSORT Statement for Randomized Trials of Nonpharmacologic Treatments .Eligibility requirements for this study are the following: patients aged ≥18 years; patients with lung cancer  or digestive system cancer ; patients on platinum-based chemotherapy with or without radiation therapy concomitant ; World Health Organization performance status ≤2; patients affiliated to the national social security system or equivalent; patients able to complete the questionnaires ; and patients who provide written informed consent. The exclusion criteria are phlebitis; vena cava syndrome; weight loss >5% in the 3 months before inclusion date; uncontrolled pain; patients receiving morphine or morphine derivatives; brain metastases; patients receiving foot reflexology outside the study; patients under guardianship or curatorship or who have been deprived of their rights. All data will be collected from outpatients and inpatients.The patients randomized to the intervention group will benefit from a foot reflexology session (30 minutes) at each chemotherapy session for four cycles. The reflexology sessions will be given during chemotherapy infusion every 2 or 3 weeks, depending on the chemotherapy protocol. The sessions will be administered by two qualified reflexologists (they were trained at the French school École des Techniques en Réflexologie).In a meta-analysis study, Lee et al  determinFoot reflexology is CAM, based on the principle of acupressure, that helps the body restore homeostasis. It is a holistic approach that allows one to understand the body as a whole. Each part of the body is represented by a zone or reflex point on the foot. The reflexologist stimulates each reflex zone using specific thumb and finger techniques on the patient’s feet. Depending on the objective, the zones on the feet are stimulated using different types of pressure. During a session focused on the treatment of CINV, the reflexologist mainly stimulates the reflex points related to the digestive system, the lymphatic system, and kidneys to help the body eliminate toxins. The reflexology chart used in this clinical study is based on the one proposed by Eunice Ingham .The reflex zones of the whole body are also found on the hands. During the first reflexology session, the reflexologist shows the patient the appropriate zones on the hands to relieve nausea. The patient will be able to stimulate these reflex points between each cycle if necessary (self-practice at home). Adherence of participants to reflexology is assessed with a diary. They have been instructed to use a diary every day between each cycle of chemotherapy to note episodes of nausea and vomiting. They also note if they took at least one antiemetic drug (on-demand treatment). If the patient uses self-massage, they note whether it has been effective.The protocol of intervention was standardized by the reflexologists involved in this study. Over the course of the session, relaxation movements were incorporated after each stimulated reflex point. To calm nausea and vomiting, the reflexologist stimulated the upper and lower digestive reflex points, as well as smooth muscle reflex points . Encouraging deep relaxation to target anxiety involved the stimulation of the diencephalon reflex points, scapular belt reflex points, reflex points of the diaphragm, and reflex points of the spine.Participants will be enrolled by physicians at the Lyon Sud Hospital Centre thoracic and hepatogastroenterology departments. Eligible participants who wish to participate in the study are asked to sign a written informed consent form. The randomization procedure is performed by the Interactive Web Response System (IWRS) via ClinSight software . Participants are allocated to the intervention group (with foot reflexology) or to the control group (without foot reflexology) before starting their treatment. Clinical research assistants generate the random allocation sequence and assign participants to the intervention.The primary objective is to assess the benefits of foot reflexology on CINV (from platinum-based chemotherapy) in patients with lung or digestive system cancer.The secondary objectives are to assess the benefits of foot reflexology in terms of overall quality of life, anxiety, and self-esteem.The primary outcome is the relative change in the severity of nausea and vomiting, as assessed with a visual analogue scale (VAS). The patient is asked to mark their current nausea level on the horizontal line with anchor statements on the left  and on the right . Unlike vomiting, which is measurable by the number of episodes per day, nausea is a subjective experience. For that reason, we will use a VAS to evaluate the severity of nausea in patients . For patAll patients will continue to receive standard antiemetic drugs . According to chemotherapy protocols, oral antiemetic agents are included, and patients are instructed to complete the course.The benefits of foot reflexology on CINV will also be assessed with the diary completed every day by patients between the first and fourth cycle of chemotherapy. Every day, the patient assesses the frequency of nausea and vomiting, recording each episode of nausea and emesis, and assessing the intensity of nausea and vomiting when it is at its highest with a Likert scale .The benefits of foot reflexology on quality of life will be assessed by the relative change in the overall European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) score . The patThe benefits of foot reflexology on anxiety will be assessed by the relative change in the overall Hospital and Anxiety Depression Scale (HADS) score . The patThe benefits of foot reflexology on the level of self-esteem will be assessed at the end-of-study visit using the Body Image Questionnaire (BIQ) , which mAll adverse events are collected during this study and the assessment of causality with foot reflexology is at the physician's discretion.In a study reported by Billhult et al , the meaStudy data are entered into a password-protected Excel spreadsheet  accessible only to the project manager. Quantitative data will be described for the entire population, using the following descriptive statistics: the number, the number of missing values, the mean, the standard deviation, the median, the interquartile range, and the range. Qualitative variables will be summarized for the entire population using the following descriptive statistics: the frequency and percentage for each category of the variable and the missing values .For the primary endpoint, comparison of the relative change in the VAS between the two groups will be performed using a linear model adjusted on the type of cancer (digestive system or lung) and the presence of metastases (randomization stratification factors). This model allows the estimation of the difference in mean relative variation of VAS between the two groups, adjusted on potential confounding factors, with a 95% confidence interval. The VAS score may be transformed satisfy the assumptions of the linear model. If the assumptions of the model cannot be verified, the comparison between the two groups will be done using the van Elteren test. Specific estimates of the difference in relative VAS variation between the groups will be provided for both types of cancer, and by metastatic status.The comparison of the frequency of episodes of CINV between chemotherapy cycles between the two groups will be performed using a mixed effects Poisson model, integrating the number of intercycle days as offset. The model will consider the intervention group and stratification criteria as fixed effects, and will incorporate one random intercept per patient.The proportion of chemotherapy cycles in which the patient took at least one antiemetic drug will be compared between the two groups using a mixed effect logistic regression model. The model will consider the intervention arm and stratification criteria as fixed effects, and will incorporate one random intercept per patient.The comparison of quality of life and anxiety between the two groups will be done using a Wilcoxon test.The comparison of self-image between the two groups will be done using a linear model adjusted on the baseline self-esteem evaluated with the Rosenberg scale. A possible transformation of the BIQ score will performed to satisfy the assumptions of the linear model.The analysis will be performed according to the intention-to-treat principle, considering all patients that completed the endpoint evaluation in the group that was allocated to them by the randomization. The time point for the primary endpoint has been defined to minimize the risk of missing data.For the primary endpoint, a secondary analysis will be performed per protocol, including patients with the endpoint assessment, and for whom the strategy allocated during randomization was fully implemented .This study was approved by the regional ethics committee (Île de France X CPP) on April 3, 2018 (No. ID RCB 2018-A00571-54). This study complies with the Reference Methodology (MR-001) developed by the French Data Protection Commission , amended in October 2010, relating to the processing of personal data in clinical trials. This study follows the SPIRIT  guidelines .Patients provide written informed consent that is dated and signed by the patient and the investigating physician. Patients in the control group will receive foot reflexology sessions at the end of their participation (two 30-minute sessions).This study takes place in a university hospital. Each caregiver and investigator involved ensures optimal patient management. The project manager ensures communication and a close link between the caregivers, investigators, reflexologist, sponsor, and patients.This study was approved by the regional ethics committee (Île de France X CPP) on April 3, 2018 (No. ID RCB 2018-A00571-54). Enrollment started in June 2018. Data analysis will be performed during the second quarter of 2020 and results will be published in the last quarter of 2020.According to a European survey reported by Molassiotis et al , 35.9% oThis RCT , which began in June 2018, assesses the benefits of foot reflexology. The expected results are a decrease in CINV and anxiety, as well as an improvement in quality of life and self-esteem. This will also allow the investigation of any potential difference in benefit between patients with lung cancer and patients with digestive system cancer, and patients with different stages of cancer (metastatic and nonmetastatic). The results will be available in the last quarter of 2020.This study does have limitations. First, the results may not be representative of all cancers; patient recruitment was only done at one cancer center. Even if conventional treatments are similar within the various private and public health care centers in France, a larger multicenter study would ensure that the results are generalizable.In conclusion, the current management of patients with cancer involves treatment with conventional medicine while offering supportive oncological care. If the results of this study are significant, foot reflexology may be a promising complement to conventional antiemetic drugs.


Recently, there has been a strong interest in the climate emergency and the human health impacts of climate change. Although estimates have been quoted, the modeling methods used have either been simplistic or opaque, making it difficult for policy makers to have confidence in these estimates. Providing central estimates of health impacts, without any quantification of their uncertainty, is deficient because such an approach does not acknowledge the inherent uncertainty in extreme environmental exposures associated with spiraling climate change and related health impacts. Furthermore, presenting only the uncertainty bounds around central estimates, without information on how the uncertainty in each of the model parameters and assumptions contribute to the total uncertainty, is insufficient because this approach hides those parameters and assumptions which contribute most to the total uncertainty. We propose a framework for calculating the catastrophic human health impacts of spiraling climate change and the associated uncertainties. Our framework comprises three building blocks: (A) a climate model to simulate the environmental exposure extremes of spiraling climate change; (B) a health impact model which estimates the health burdens of the extremes of environmental exposures; and (C) an analytical mathematical method which characterizes the uncertainty in (A) and (B), propagates the uncertainty in-between and through these models, and attributes the proportion of uncertainty in the health outcomes to model assumptions and parameter values. Once applied, our framework can be of significant value to policy makers because it handles uncertainty transparently while taking into account the complex interactions between climate and human health. In May 2019, the UK Parliament declared a climate change emergency  with a suitable level of complexity , should be the basis of any model used to calculate catastrophic human health impacts due to spiraling climate change. For this purpose, we advocate the use of standalone state-of-the art climate and human health impact models, used in conjunction with analytical mathematical approaches which link these two sets of models. We assert that only an analytical mathematical approach is able forensically to thread the connections between the various models and which has, at its base, a method for uncertainty quantification, propagation and attribution, through the models. We outline one such potential framework below.per se but to promote the use of mathematical methods to deal with the uncertainty in a series of linked models. Current approaches for handling uncertainty treat the uncertainty in each model separately without linking the uncertainties in the series of models from the climate model to the health model via environmental exposures. This is a weakness of many environmental health models because, ideally, the uncertainty should be propagated coherently throughout the series of models  and (B), propagates the uncertainty in-between and through these models, and attributes the proportion of uncertainty in the health outcomes to model assumptions and parameter values.Before describing these building blocks in more detail, we must first consider our desired final outcome, namely the catastrophic human health burden of spiraling climate change (and the associated uncertainty in this estimate). Calculating such burdens requires knowledge of the likelihood of the events causing them and the extent of the damage that they could cause. Historically, there has always been an interest in calculating the likelihood and impacts of all types of catastrophic events ranging from physical, astronomical and biological events , to social and political events  . The impIn the illustrative schematic given in Since we are interested in the extremes of environmental exposures, such as extreme temperatures, these are best represented by time-varying (non-stationary) Generalized Extreme Value (GEV) distributions. A GEV describes the probability distribution of an extreme variable . Moving onto building block (B), the change in the distribution of an environmental exposure impacts human health, which can be calculated via an exposure-response relationship. E1 to En) such as extreme temperatures, pollution and rainfall. The figure shows mortality and morbidity impacts. If these impacts are expressed by a common health metric such as Quality Adjusted Life Years (QALYs) or Disability adjusted Life Years (DALYs), the total health impact is given by the sum of the mortality and morbidity impacts. For example, there is ample epidemiological evidence on the health effects of extreme hot temperatures on mortality and morbidity including cardiovascular, respiratory and renal diseases , the curvature could be less steep.H) are additive. However, the human health impacts can also be sub-additive or supra-additive. Sub-additivity means that, if changes in two environmental exposures  occur simultaneously, then their combined health impact is less than or equal to the sum of the impacts of the two exposures if they had instead occurred far apart in time . Conversely, supra-additivity means that, if changes in the two exposures occur simultaneously their impact is greater than or equal to the sum of their health impacts if the exposures had instead occurred far apart in time . To illustrate these hypothetical concepts, consider first a heatwave and an extreme episode of air pollution. If these events occur far apart in time, the total health impact is expected to be additive because there is no interaction between the two impacts. On the other hand, if the two events occur simultaneously, then the total health impact is likely to be supra-additive because health is already compromised by one of the extreme events. Finally, sub-additivity is likely to occur if, for example, there is physiological adaptation to a repeated exposure over a prolonged period, e.g., if the human body copes better over time with repeated exposure to extreme heat. Most health impact frameworks, such as Comparative Risk Assessment (CRA) in the global burden of disease calculations, assume that the health impacts of different environmental exposures are additive , heatwave duration (P2) and heatwave intensity (P3). As shown in P, two-way interactions between parameters P and the three-way interaction between parameters P(1P2P3). It is just as important to quantify this decomposition of total uncertainty across parameters as it is to estimate the total uncertainty itself.As It is imperative that the potential catastrophic impacts of an inadequate response to climate change are determined with confidence. Our framework above provides a systematic approach for calculating the catastrophic human health impacts of spiraling climate change which we believe is sufficiently transparent to allow for open scrutiny. Each of its components, the climate model, the human health impact model and the analytical mathematical approach for quantifying the uncertainty, stand on their own merits and can be updated or replaced as and when necessary.We have proposed a framework to provide estimates of the catastrophic human health impacts and the associated uncertainties which, once applied, can be of great value to policy makers. We believe our framework combines three main tenants of importance to policy makers: transparency, acknowledging the complexity of interactions between the environment and human health, and handling uncertainty.Policy makers are often presented with uncertainty estimates without recourse on how to use them to support decision-making. Because of its forensic approach to dealing with uncertainty, our framework can be linked in a straight-forward manner to a decision analytical framework for handling extreme and catastrophic risks, for example, the Partitioned Multiobjective Risk Method  which haWhen operationalised, the usefulness of our framework can be demonstrated against deterministic frameworks by showing the added value of appropriately handling uncertainty in model predictions of the health impacts of spiraling climate change. We argue that ignoring or inadequately handling uncertainty gives a false sense of the accuracy from model predictions and weakens confidence in them.The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.ZC led on the intellectual ideas within the piece while AF helped develop these further, especially in terms of the visual conceptualization of the framework and the overall communication of ZC's ideas. ZC wrote the initial draft of the perspective and then both authors jointly revised this iteratively. Both authors contributed to the article and approved the submitted version.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.


Realizing autonomous inspection, such as that of power distribution lines, through unmanned aerial vehicle (UAV) systems is a key research domain in robotics. In particular, the use of autonomous and semi-autonomous vehicles to execute the tasks of an inspection process can enhance the efficacy and safety of the operation; however, many technical problems, such as those pertaining to the precise positioning and path following of the vehicles, robust obstacle detection, and intelligent control, must be addressed. In this study, an innovative architecture involving an unmanned aircraft vehicle (UAV) and an unmanned ground vehicle (UGV) was examined for detailed inspections of power lines. In the proposed strategy, each vehicle provides its position information to the other, which ensures a safe inspection process. The results of real-world experiments indicate a satisfactory performance, thereby demonstrating the feasibility of the proposed approach. Power line inspection is an important task performed by energy distribution companies. This inspection is essential to ensure steady energy delivery and avoid service interruptions. The inspection process involves different tasks, depending on the objective of the operation. The Brazilian National Electrical Energy Agency broadly classifies the activities of transmission line inspection as corresponding to terrestrial, aerial, or detailed inspection . TerrestOwing to the extensive range of inspection segments, a long-duration energy supply must be provided to the small aircraft.Owing to the high complexity of the pylon metallic structures and energy cables, conventional sensors may find it challenging to detect obstacles.The electrical and magnetic fields present around the structure owing to the high voltage energy transmitted can likely interfere with the UAV’s navigation hardware and sensors .Foreign elements may be present in the vicinity of the distribution line, such as trees and buildings, which may lead to accidents.Obtaining physical access to the pylon area may be difficult owing to restricted areas or dangerous terrain; thus, the aircraft must take-off from a safe distance.It is challenging to fly near the pylon (2–5 m) to obtain images and data for analysis.Maintaining the position and orientation of the aircraft during the image acquisition process may be challenging owing to the presence of gusts and uncertainty in the standard positioning sensor data.In recent decades, detailed inspection has been increasingly performed using small aircraft, specifically, unmanned aerial vehicles (UAVs), instead of by humans. UAVs can carry an extensive range of small sensors, such as regular, thermal, and multi-spectral cameras, 3D light detection and ranging (LIDAR) equipment, and radio frequency (RF) discharge detectors, which can enhance the data quality and process efficacy . In suchTo alleviate the risks in such operations, a promising approach is to use an autonomous UAV flight system. Nevertheless, precise positioning must be realized to implement autonomous operation. A typical approach to provide accurate positioning data to a UAV is through the Differential Global Navigation Satellite System (DGNSS). In this approach, a static GNSS base reference (base station) sends the position data to the mobile module (rover) and calculates the position with an accuracy down to the centimeter level. This technique is a highly effective solution for providing precise horizontal positioning for small aircraft; however, it is effective only under specific operational conditions. The presence of obstacles, base antenna shadowing by constructions or trees, interference communication links among the modules , and cloIn this regard, in this work a cooperative UAV–unmanned ground vehicle (UGV) positioning architecture was investigated, especially for carrying out detailed inspections of power distribution infrastructure. An augmented reality tag (AR-Tag) was used to create a relative positioning reference, allowing the exchange of position data between the vehicles. Real-world experiments were performed to evaluate the feasibility of the proposal by determining the accuracy of the acquired position data during the flight and the influences of the environmental conditions, camera performance, and AR-Tag operation conditions on the accuracy.Autonomous UAV-based inspection has gained considerable attention in the last decade due to the developments in platforms, process and control hardware, and sensor technology for small aircraft. The literature presents an extensive number of works in this specific area. In the paper , the autUse of cooperative UAV–UGV autonomous systems is a powerful approach for several applications, including inspection tasks. The specific characteristics of each vehicle provide a complementary gain in capability and enhance data collection, payload capability, and the maneuverability and range of operation of the vehicles. Many review studies on cooperative UAV–UGV applications have been presented so far, which describe the main application domains of such cooperative systems, such as SLAM, positioning, inspection, transportation, formation control, and swarming ,18,19,20Some researchers proposed a visual feedback cooperative system between an AR-Drone quadcopter and a Pioneer UGV . The sysA cooperative UAV–UGV inspection architecture is presented in this study. Based on the above literature review, it can be concluded that there are gaps in the state-of-art with regard to UAV-based detailed inspection problems of power pylons. To the best of our knowledge, none of the studies that used a cooperative UAV–UGV architecture have applied it to power pylon or power line inspection. Moreover, the cooperative positioning method can also be considered to be novel. To present a comparative review, Simple application, based on low-cost commonly available sensors resources .Compared with IMU and RTK-GPS sensors, the position sensing method is robust against electric and magnetic field disturbances in the inspection area ,30.The cooperative inspection platform can enhance the capability of inspection data acquisition, allowing the use of multiple sensors embedded in each vehicle in a cooperative arrangement, such as optical zoom sensors, thermal and multi-spectral image sensors, high range LIDAR, and RF spark detectors, thereby generating a collaborative sensing inspection data set.This work’s key contribution is the investigation of a new collaborative positioning system architecture to realize power line pylon inspection by providing redundant data to increase the safety of the autonomous displacements of the UAV and UGV during the inspection process. We also investigated a complementary positioning method for power line inspection applications to be used when the DGNSS method fails. Visual positioning methods are susceptible to visual obstacles in every situation. Besides, the RTK-GPS is the primary positioning system used by the UAV in the proposal. In this study, the UGV uses RTK-GPS data when the UAV is carried by it to the nearby pylon. UGV visibility presents some limitations because of obstacles in the field. Thus, the method proposes that the UGV seeks the UAV so that it is always visible to the aircraft, thereby preventing the aforementioned problems. The advantages of the proposed method are as follows:A viable terrain to realize the UGV path following may not be available in all energy power sites.Due to the low accuracy of AR-Tag position readings at long distances, a large tag must be used to provide accurate data.The limitations and assumptions of the method are as follows:It is important to reinforce that this paper presents the first part of an extensive research project, including power line following and multiple pylon inspection processes. This long-range collaborative inspection demands additional intelligent algorithms to face the common problems encountered in practice, including collision avoidance and path planning. The development of these solutions is a work-in-progress for our research group. In this paper, the group chose to work in a particular set of controlled conditions as a preliminary approach to evaluate the main proposal of the collaborative positioning system.As the energy power inspection process is similar to that of other structures, the proposed architecture can be extended to similar applications, such as the inspections of buildings, bridges, silos, cell towers, and dams. To the best of our knowledge, the proposed approach is the first of its kind among the available cooperative inspection systems.The system architecture is composed of a small quadrotor aircraft, a small UGV, a base station computer, and a RTK-GPS system. The agents collect data and send them to the base station, where the necessary calculations are performed. The base station defines the behavior of each vehicle and sends the position control data to the vehicles. All the architecture components use the Robot Operating System (ROS) to exchange information. ROS is an open-source, flexible, robust set of tools that provides information exchange standard messages between robots, sensors, processing hardware, software, and other robot tools .The validation experiments were implemented using a Parrot Bebop drone with an embedded Emild Reach RTK-GPS module. The Bebop drone is suitable for autonomous algorithm development because it offers a stabilized flight performance and an embedded Full-HD resolution camera. The camera gimbal stabilization minimizes the image shifts during the data acquisition. The Emild Reach RTK modules  represenThe UGV is a Pioneer P3 four-wheel vehicle, controlled by an Intel Core i5 processor, with an 8 GB RAM running Ubuntu 16.4 LTS and ROS Kinect, developed by Generation Robots . The veh®  HD Graphics 520 (Skylake GT2) board. The base station runs the ROS Bebop Autonomy package [A computer running Ubuntu 16.4 LTS and ROS Kinect was used as the base station. The computer system includes an Intel Core i7 processor with 16 GB RAM and an Intel package  to realiThe communication between the agents and base station was implemented through three Wi-Fi network links, at frequencies of 5.8, 2.4, and 2.4 GHz from Bebop, RTK-GPS module, and Pioneer P3, respectively. The base station concentrates all the ROS messages and sends commands to the agents to execute their activities.ar_pose_marker ROS Node. The Ar-Track Alvar Augmented Reality solution  was usedThe inspection procedure that serves as a reference for this research is based on technical information exchange with the local energy distribution company. Using this framework, the operational parameters of the UAV inspection system can be clearly defined, namely, the safe distance between the tower and UAV, average flight height, and navigation velocity during the inspection. These parameters were defined based on the practical experience of engineers involved in UAV energy power inspection. In general, the inspection process consists of capturing the images of the structure and components in various sites and line segments using commercial UAVs. To a significant extent, the pilot’s expertise determines the level of safety of the inspection tasks; however, in some scenarios, the environmental conditions may pose a significant safety threat. It is a common perception among professionals that an autonomous flight solution could notably enhance the process safety. The autonomous flight limits for safe operation are specified in It must be noted that these limits take into account the expertise of the operation engineer to recreate the same conditions for the autonomous flight as those present in a human-controlled flight in such inspection processes.This subsection describes the inspection process used in this study. Although the focus of this work is the evaluation of the positioning system, the description of the complete inspection process is important to understand the overall functioning of the system. To execute an inspection procedure, the UAV and UGV start at the base station position. The base station is where the supervising equipment, RTK-GPS base antenna, and central control of the system are located. For the first displacement from the base station to the nearby pylon, the UAV is carried by the UGV to save battery. To execute this displacement, the UGV uses the RTK-GPS data received by the UAV to feed the path following control algorithm, enhancing the vehicle position information’s accuracy.When the UGV reaches the first inspection point around the pylon, the UAV takes off and performs an inspection path in the face of the pylon. This path is programmed carefully to ensure that the down-pointing camera of the UAV maintains a visual link with the AR-Tag placed at the top of the UGV. If the RTK-GPS module exhibits a loss of accuracy for any reason, the AR-Tag offers a redundant position reference to the UAV displacements, thereby enhancing the safety of the inspection process. The UAV captures the pylon images from the top, and the UGV simultaneously captures the image and data information from the base of the pylon. After the UAV finishes the inspection of a pylon segment, re-positioning of the UGV begins. At this time, positioning data are provided to the UGV by the AR-Tag reference system. The UAV remains in static flight above the desired end-point and sends a message to the ground vehicle to initiate its movement. The UGV receives the relative position data obtained from the AR-Tag tool and follows the UAV to immediately reach the point below it. If the vehicle encounters an obstacle, it performs a detour process based on readings from its frontal LIDAR. After reaching the final position with a preset position tolerance, the UGV stops moving, and the UAV begins a new pylon segment inspection. This process repeats until the UAV and UGV cover all the inspection points programmed in the path. After the last inspection point, the UAV reaches the UGV position and lands on its roof. The UGV returns to the base station carrying the UAV.RTK-GPS provides the primary position reference of the UAV during the pylon inspection process. In this case, the AR-Tag is a redundant position system for the UAV displacements. Otherwise, the UGV position system considers the UAV/AR-Tag position information for all the pylon inspection displacements, and this framework represents the primary positioning system for the ground vehicle. The architecture generates a swinging positioning reference, enabling cooperative position data acquisition from each vehicle and the constant exchange of this information among them. Sharing the RTK-GPS sensor when the vehicles are coupled is key to decreasing the hardware necessary to implement the solution.As different referential systems work to control each vehicle, it is necessary to set the origin point to execute the reference transformations. The RTK base antenna is set as the origin  of the system, and the UAV position is calculated based on this point. It is vital to precisely set the antenna’s position relative to the power pylon before commencing the inspection process. This setup is performed using the geo-referenced positions of the pylons present on the energy company’s database.The UGV referential system is set in accordance with the UAV position during the inspection process, and therefore, it represents a moving referential system. In each displacement, the UGV searches the position directly below the UAV, considering it as the  point. The UGV path is always set by the position of the UAV, in a "following the lead" process. This framework ensures that the ground vehicle remains below the UAV during the entire inspection process, maintaining tag visibility to serve as an optional reference point to the aircraft when a new inspection stage begins.Considering that the AR-Tag reference system is associated with the UAV camera axis, the relative orientation between the UAV camera and AR-Tag placed on top of the UGV when the vehicles are not aligned with one another creates an error in the tag position reading related to the world coordinate axis. θ to match the camera axis with the world axis. The camera angle correction is calculated with a 2D standard rotation matrix algorithm using the AR-Tag horizontal orientation information. Equation  and the camera rotation Equation  presentsA set of real-world experiments was conducted to investigate the accuracy of the AR-Tag position and orientation readings in the proposed scheme. The objective was to estimate the error of the AR-Tag position and orientation readings in an outdoor environment under flight conditions and to evaluate the UGV control algorithm under the actual application conditions. A link for a Youtube video presenting the experiments is available in the TM RTK-GPS worked as a ground truth positioning system for the outdoor measurements. A LIDAR Lite sensor pointed to the ground provided the ground truth to the height measurements. The measurement site was an open field with no natural and artificial obstacles to the satellite visibility, which facilitated the realization of a proper reception signal to the base station and rover receiver installed in the UAV.The Emlid ReachThe data exchange between the RTK modules and base station computer was realized using the Reach RTK ROS Node Package . The Bebgeometry_msgs:Twist ROS message sent by the base station provided the position and orientation data for the UGV guidance. This data were extracted from the AR-Tag position readings.The Pioneer P3 vehicle involved an embedded PC that executed a regular PID position control algorithm. A p’—read value, p—real value, and n—number of samples.A base PC worked as the ROS master, receiving the node data from all the agents and running the control and calculation codes. All the ROS nodes were captured simultaneously to synchronize the data collected and recorded in the ROS bag files. Equations  and 3)  3) were The AR-Tag Alvar tool is primarily applied in augmented reality systems; however, its flexibility makes it suitable for use in robot position applications. Nevertheless, the use of these tags in real-world outdoor environments presents certain challenges in the form of long-distance readings, lighting conditions, and shadowing of the tag.An experiment was performed to evaluate the use of the tag in outdoor long-distance conditions. The Bebop drone was placed in a fixed position over a table, and the tag was fixed on a tripod. A 30.0-m-long measurement tape with an accuracy of 0.5 cm was fixed on the ground to serve as a distance reference. The error position and orientation were measured three times for each meter. The process was repeated using tags of two different sizes (50.0 and 90.0 cm). Camera resolutions of Four hundred samples were captured for each measurement. Equations  and 3)  3) were As shown in In addition, sunlight influenced the data position and orientation error as well. Direct and indirect sunny conditions did not significantly affect the measurements. However, cloudy conditions increased the positioning error by approximately 10%. A unique situation occurred in the presence of partial tag shadowing. Specifically, the detection of the tag was compromised because the algorithm could not effectively detect the border of the white and black external square of the tag. This situation must be avoided during an inspection operation.This subsection presents the results of the outdoor flight tests performed using the Bebop drone with the embedded RTK module and a fixed tag placed in the ground. The objective was to evaluate the tag position readings under the flight conditions and investigate the influences of the UAV displacement, camera vibration, and twist and detection distance limits on the readings.The experiments were conducted in 10 flights performed at various heights. Post-processing calculations were performed to determine the accuracy of the collected information. The experiments were conducted on sunny days, with direct sunlight incident on the tag, between 10:00 and 17:00, at a maximum observed wind velocity of 10.0 km/h. The flight velocity was limited to 0.5 m/s. Tag size was 0.5 × 0.5 m. The images of the flight were collected at 640 × 368 pixels from the Bebop autonomy video transmission and at 1280 × 720 pixels from the Bebop drone on-board recording.FIX mode, which presents a position accuracy of at least 1.0 cm, provided the ground truth for the position readings from Bebop odometry and AR-Tag. Emild RTK-GPS data running in The blue, red, and yellow lines represent the ground truth, AR-Tag position, and Bebop drone odometry data, respectively. Compared with the odometry data, the AR-Tag presents significantly smaller error, thereby demonstrating the potential of this tool in providing proper position data for the UAV flight. The position error increases with the absolute distance from the tag, which is a vulnerability of the method. To ensure suitable implementation of the position control algorithms, the maximum distances between the UAV and tag must be maintained within a certain limit in addition to the safe levels. Compared with that of the regular GPS, the accuracy of the proposed method is significantly higher, demonstrating its promising potential for use in practical application UAV positioning systems. The results indicate that under normal conditions, the AR-Tag position’s accuracy corresponds to the inspection flight parameters defined for the project.The flight direction change and stop points must be focused on because of the camera twist movement, as shown in the highlighted region a–c in Another critical point to be considered is the image degradation and loss of image frames because of the transmission to the base station, considering that this computer executes all the processing. A regular Wi-Fi connection produces this kind of loss, and the AR-Tag algorithm does not process the position in this situation correctly. Embedded processing in the UAV is recommended, leaving the base station only for the operational control. The Bebop drone does not present powerful embedded hardware and does not allow one to embed an external processing platform such as Raspberry-Pi because of payload limitations. A new UAV with a higher payload is being built to enable these experiments.The position data must have higher accuracy than the limits of operation for the autonomous flight defined for the project, as described in The horizontal orientation is a key parameter to maintain the correct heading of the UAV during flight. Navigation hardware commonly includes a compass sensor with a standard accuracy of An experiment was performed to evaluate the influences of the dynamic flight conditions on the horizontal orientation readings. The Bebop drone odometry orientation data provided the ground truth for the measurements. The tag size used in the experiment was 0.5 × 0.5 m. Ten flight tests were conducted at different heights, in a straight line above the tag. Images were collected in two different resolutions, The graphs indicate that the AR-Tag orientation measurement readings were similar to those of the Bebop odometry. These results demonstrate the feasibility of using the tag to provide orientation data for the drone flight.The accuracy of the UAV height must be ensured to realize autonomous flight near the pylon while preventing collision with cables and structural parts. The Bebop drone uses an ultra-sound sensor with a range of 8.0 m for the height readings, along with an IMU barometer sensor.To provide a high-accuracy ground truth for the height experiments, a LIDAR-Lite  sensor wThis subsection describes the UGV displacement control experiment performed using the AR-Tag position reference provided by the UAV camera. The objective was to investigate the capability of the ground vehicle in precisely reaching a position setpoint, given the data provided by the UAV/AR-Tag schema.The first experiment evaluated the control of the UGV using only the AR-Tag position information in a controlled condition. The execution was done in an indoor site, with the Bebop drone fixed in support at The next experiment investigated the influences of outdoor flight conditions on the autonomous control of the UGV. Some factors such as camera vibration, drone twists, missing of image frames, and variation of light can affect the control algorithm. Ten experiment rounds were performed with different start points. The UAV was commanded to take-off and stay in a static position above the UGV displacement area. In each round, the UGV reached the setpoint and stopped at the tolerance distance. At the end of each displacement, the total position error was measured to examine the accuracy using an image of the final point reached by the robot. This paper reports on the general concept of a cooperative inspection architecture with a UGV and a UAV to create a positioning system for power pylon inspection applications. In this work, the objective was to evaluate a redundant positioning proposal based on the cooperative position reference data obtained using AR-Tags. Real-world experiments were conducted to confirm the feasibility of the arrangement.UAV flight position experiments showed adequate results in horizontal position data readings for regular flight operation, with respect to the distance limits. The orientation data confirmed proper performance for the required application. While the height error was inadequate because of the inaccuracy in the The UGV positioning experiments were successful, both in controlled and in outdoor environments, indicating that the AR-Tag solution is viable for providing a simple and effective solution for such applications. The positioning error generated by the algorithm is small, and the robustness of the control using the AR-Tag data is adequate.A limitation of this approach corresponds to the large tag required to inspect energy pylons at a large height; for instance, the tag size must be larger than This paper presents the first part of a more extensive power distribution inspection system. In general, the inspection process of power pylons is challenging owing to the highly accurate position control required to ensure safe operation. In addition, certain other aspects must be investigated to practically implement the collaborative inspection system in future works, such as the autonomous landing of the UAV at the UGV base, power line segment following, ground path following, UAV and UGV intelligent obstacle avoidance, long-range communication among the agents, inspection data treatment, and data fusion. Our group is actively working to develop solutions for these aspects and other technical challenges.


Crack localization in running rotors is very important and full of challenges for machinery operation and maintenance. Characteristic deflection shapes or their derivatives based methods seem to be promising for crack localization in rotors. Despite the substantial advantages, several critical issues still need to be addressed to enhance the efficiency of this kind of method for practical applications. Two problems are considered in this work: 1. How to localize single or multiple cracks accurately avoiding the interference of commonly existing steps without baseline information on pristine rotors; 2. How to improve the crack localization performance under a noisy environment. To circumvent the issues, a novel baseline-free adaptive crack localization method is proposed based on data fusion of multiscale super-harmonic characteristic deflection shapes (SCDSs). In this method, crack induced asymmetry and nonlinearity of crack breathing are utilized to simultaneously eliminate the interference from the steps without a reference model. To enhance the noise robustness, the multiscale representations of SCDSs are made in Gaussian multiscale space, and Teager energy operator is applied to the multiscale SCDSs to amplify the crack induced singularities and construct the multiscale Teager super-harmonic characteristic deflection shapes (TSCDSs). Moreover, fractal dimension is designed as an evaluator to select the proper multiscale TSCDSs for data fusion adaptively. Then, a new damage index is derived for crack localization by Dempster-Shafer’s (D-S) evidence fusion of the adaptively selected multiscale TSCDSs. Finally, the feasibility and the effectiveness are verified by both numerical and experimental investigations. Crack monitoring and diagnosis in rotors based on vibration signals has been widely investigated and is an important field in the structural health monitoring (SHM) of rotating machines. According to the level of identification attempted, the relevant studies could be classified into four levels , which aFor crack localization, it is necessary to have enough spatial information. Crack localization by modal parameters, such as natural frequencies and mode shapes or their derivatives, has been widely investigated in structures ,26,27,28Similar with the mode shape, a more general concept called the characteristic deflection shape (CDS) was proposed by Cao and Ouyang  to localFrom this aspect, Prawin et al.  developeCracks in rotors of critical machines are the most dangerous faults. The occurrence of cracks will lead to local stiffness reduction of the rotor which will generate discontinuities or distortions at crack locations. The commonly existing steps in shafts will also cause discontinuities or distortions, which will affect the crack localization. The localization results could be misguided, if there is no baseline model of the rotor or prior location information of the steps. However, one key point we should note is that the cracks in rotors are usually fatigue cracks, which cyclically open and close  with the rotation of rotors, which make the system nonlinear. Therefore, the crack breathing phenomenon is a unique feature of fatigue cracks. If crack induced nonlinearity and stiffness reduction could be explored simultaneously, cracks in stepped rotors could be localized exclusively.Utilizing the distinct feature between nonlinear cracks and linear steps, a crack localization method based on super-harmonic characteristic deflection shapes (SCDSs) was proposed by the authors . In thatTo circumvent the noise-robustness issue, a Bayesian fusion method was proposed for crack localization using the SCDSs in multiscale space by the authors . HoweverIn view of the aforementioned issues, a novel baseline-free adaptive crack localization method for operating stepped rotors based on D-S evidence fusion of multiscale SCDSs is developed. To address the robustness issue, Gaussian multiscale analysis is adopted to transform the SCDSs into multiscale SCDSs, and Teager energy operator is applied to the multiscale SCDSs to obtain the multiscale Teager super-harmonic characteristic deflection shapes (TSCDSs), which enhances the weak singularities that are induced by cracks. Furthermore, a fractal dimension is proposed and designed as an evaluator to adaptively select the proper multiscale TSCDSs. After this, the selected proper multiscale TSCDSs are utilized to construct a damage index by D-S evidence fusion. Finally, numerical simulations and rig experiments are performed to show the performance of the proposed method.A novel baseline-free adaptive crack localization method for rotating stepped rotors with single or multiple cracks is developed and validated numerically and experimentally.A novel damage index based on data fusion of multiscale TSCDSs with D-S evidence theory is derived to overcome the interference of steps and improve the robustness of the crack location method.The fractal dimension is designed as an evaluator to adaptively select the optimal multiscale TSCDSs for data fusion.The main contributions of the work are in the following:The remainder of the paper is arranged as follows. Detail presentation of the proposed method is introduced in The proposed SCDS is a spatial shape of multi-sensor signals at a super-harmonic frequency which can be extracted by using frequency domain decomposition (FDD) ,41. The i, l is the length of each response, and n is the number of sensors.First, the system response matrix After obtaining the response matrix, its corresponding correlation matrix Then the power spectral density matrix From the expression of uency ωi . Thus, uS (SCDS) .For cracked rotors, nonlinear super-harmonic components induced by the breathing and asymmetry of cracks are recognized as common practice. Hence, the extracted SCDSs contain both the crack induced nonlinearity and stiffness reduction, which could be useful to eliminate the interference from steps, as the steps are linear and there is no nonlinear super-harmonics generated by them.Heavy noise contamination is the common case in rotating machines. To make the SCDS-based crack localization method more robust to noise, the multiscale representations of SCDSs are made by Gaussian multiscale analysis (GMA). According to GMA, the multiscale SCDS can be expressed as the convolution between Gaussian kernel As the crack induces weak singularities in the SCDSs, the Teager energy operator (TEO) is applied to the obtained multiscale SCDS to generate the multiscale TSCDS, which is defined as :(8)T to evaluate the selected multiscale TSCDS automatically. Here a fractal dimension (FD)  scale sen points The FD of a curve with fined by :(9)FD=lgW is applied to truncate the curve, and with a sliding step of one point. Then the FD in the jth window of a multiscale TSCDS with a scale of j is the midpoint position in the window.In order to show the local complexity of a multiscale TSCDS, a sliding window with width of In order to realize scale selection adaptively, an evaluation index (EI) must be defined to judge if the current scale is satisfied. The EI of the multiscale TSCDS with scale From the expression of EI, one can see that when the local complexity of the multiscale TSCDS is higher and the mean complexity of the rest curve is lower, then the EI will be larger and the corresponding scale is more possible to be selected, which satisfies the scale selection requirement. After obtaining the EIs of all scales, by sorting them from large to small, then, the multiscale TSCDSs with larger evaluation index values are selected automatically for data fusion.In the following, a novel baseline-free and robust damage index is derived by fusing the multiscale TSCDS based on D-S evidence theory .Let a finite set Then the basic probability assignment (BPA) is defined by a function i = 1, 2…, n) in the kth scale is expressed as Equation (20):In this work, the probability of a crack which occurs at location kth scale.From the equation, one can see that the value of S1 to SM, where, M is the number of information sources used for fusion corresponding to the scale numbers, and M sources.Then, the BPAs can be fused by the D-S evidence combination rule. In this work, information sources are defined as the multiscale TSCDS with any scale parameter from S1 and S2 can be expressed as follows:S1 and S2, are in full contradiction.Here, the combination rule of the first two data sources Then, fuse the remaining sources in the same way, which can be summarized as:According to the above descriptions, the general procedure of the proposed baseline-free adaptive crack localization method is summarized in Step1:Obtain the vertical responses of the investigated rotors via distributed measurement using multiple sensors, and assemble the response matrix;Step2:Extract the SCDSs by frequency domain decomposition, and select the sensitive SCDS to avoid the interference of the steps in shafts;Step3:Obtain the multiscale TSCDSs Step4:Adaptively select the optimal multiscale TSCDSs  is time-varying and state-dependent because of crack breathing. In order to solve this nonlinear equation and obtain the responses, the Newmark method  is adoptTo study the performance of the crack localization method, the proposed method is applied to the simulation cases in From N is the length of the SCDS. To evaluate the robustness of the proposed method, rotors in simulations 1–3 under different noise levels are investigated for crack localization by using 2× SCDSs. As is known, the SCDSs extraction by FDD are able to reduce noise to some degree. Therefore, to emphasize the contribution of multiscale data fusion in improving the robustness of the proposed method, white noise is directly added to the extracted unpolluted SCDS The noise-polluted 2× SCDSs of the three simulations are shown in Based on the noise-polluted 2× SCDSs, the proposed crack localization method is applied to these, and It can be seen from It should be mentioned that no intact rotor simulation is considered, and the reasons are as follows. For an intact rotor, if there are no other obvious factors generating higher order frequency components, no higher order SCDSs could be extracted. Therefore, there will be no crack and no need to perform crack localization. Moreover, if there are some nonlinear factors which will generate higher order frequency components, such as nonlinear bearings or misalignment in the coupling, the 2× or higher order SCDSs can be obtained. But the effects of these nonlinearities on the SCDSs will be global, and the continuity of the SCDSs in the range of measurement points will not be affected. Therefore, the proposed method will still be effective. To sum up, by considering the properties such as linearity of an intact rotor and its smoothness of the SCDSs, the proposed method can realize crack localization without the baseline date on pristine rotors.D), 1.54mm (0.154D) and 3.29 mm (0.329D), respectively. The step shaft is simulated by a ring slot. Detail parameters of the cracks and steps in the experimental rotors are tabulated in In this section, experiments will be carried out to verify the proposed crack localization method. The test rig is shown in For the rotor without steps in case 1, the localization results can be seen in From the experimental results above, the conclusion can be drawn that the proposed method is effective and robust against noise for crack localization in stepped rotors based on D-S evidence fusion of multiscale 2 × TSCDSs, and shows promise in real applications.To show the necessity and superiority of the method by adaptively selecting scales for crack localization, three different scale parameter intervals are manually selected for crack localization. The three scale intervals are ,  and  with a step size of 0.1, named scale cases 1 to 3, where scale case 1 is the whole scale interval after ignoring the boundary of the first five and last five scales. The above three scale intervals corresponding multiscale TSCDSs are fused to localize the cracks in simulation 3 under different noise levels, and their localization results are demonstrated in From In order to demonstrate the advantages of the proposed method, a single-scale crack localization method by gapped smoothing method (GSM)  with 2 ×To perform the comparison, the GSM method is applied to the same rotors in the three simulations in From A novel baseline-free adaptive crack localization method for operating stepped rotors based on D-S evidence fusion of multiscale super-harmonic characteristic deflection shapes (SCDSs) was proposed. In the proposed method, the cracks were localized exclusively under the commonly existing interference of steps in the shaft, by extracting the singularities on the SCDSs induced by cracks only. The robustness of the method was improved by transforming the SCDSs into multiscale TSCDSs with Gaussian multiscale analysis and a Teager energy operator. Then, an adaptive scale selection method with fractal dimension was developed to select the proper multiscale TSCDSs. After that, the selected proper multiscale TSCDSs were used to construct a new damage index by D-S evidence fusion theory for crack localization. Both numerical and experimental investigations validated the effectiveness, accuracy and robustness of the proposed method. The comparison with a single-scale-based gapped smoothing method indicated the superiority of the proposed method in heavy noise condition.The proposed method is baseline-free, output-only and scale selection adaptive, and the interference from the commonly existing steps can be eliminated, which would be helpful for real applications. The resolution of localization results depends on measurement points, and so the higher the resolution demanded, the more measurement points are required, which should be balanced when the proposed method is applied in practice.


We propose an objective measure capable of capturing tension profile according to different tonal music parameters, namely, tonal distance, dissonance, voice leading, and hierarchical tension. We performed two experiments to validate the proposed model of tonal tension profile and compared against Lerdahl’s model and MorpheuS across 12 chord progressions. Our results show that the considered four tonal parameters contribute differently to the perception of tonal tension. In our model, their relative importance adopts the following weights, summing to unity: dissonance (0.402), hierarchical tension (0.246), tonal distance (0.202), and voice leading (0.193). The assumption that listeners perceive global changes in tonal tension as prototypical profiles is strongly suggested in our results, which outperform the state-of-the-art models.In tonal music, musical tension is strongly associated with musical expression, particularly with expectations and emotions. Most listeners are able to perceive musical tension subjectively, yet musical tension is difficult to be measured objectively, as it is connected with musical parameters such as rhythm, dynamics, melody, harmony, and timbre. Musical tension specifically associated with melodic and harmonic motion is called tonal tension. In this article, we are interested in perceived changes of tonal tension over time for chord progressions, dubbed  Musical tension is widely associated with musical expression, particularly with expectations and musical emotions ,2. Most tonal tension as a specific aspect of musical tension created by melodic and harmonic motion. For example, in the tonal context, it is widely agreed [tonal tension of chord progressions, whose fundamental role within Western tonal music has been historically acknowledged [chord designates a set of three or more musical notes played simultaneously, and chord progression designates temporal sequences of chords [The role of harmony in musical tension has long been investigated ,10,12,13y agreed ,8,10 thaowledged ,19,20. Itonal function a chord plays within a particular key, their sensory dissonance, and the horizontal motion between the voices in the chord sequence [roughness has long been used to explain tonal dissonance [Tonal tension can be explained from the perspective of music theory ,20 or musequence ,26,27. Tsequence ,4,21,22.sequence . Finallysequence . For exassonance ,23,24. Sssonance ,29,30. Fssonance .Tonal tension can be associated with specific musical events , short-term contexts  or long-term contexts . Bigand et al.  investigsurface tension parameter assigns integers between 0 and 4 to musical properties of the chords  and estimates the final value as the sum of the individual scores. Consequently, the surface tension scale of the model is not constructed to be linear. Ideally, if chord To date, Lerdahl’s model of tonal tension is one of the most influential and validated theories of tonal tension ,5,10,33,spiral array [Recently, Herremans and Chew  presenteal array , incorpoal array  presenteal array  into a fal array , a tonalal array ,40,41,42al array ,39.tonal tension profile of a chord progression that extends the previous work by Navarro-Cáceres et al. [This article proposes a computational model of s et al. . This tes et al. . The oris et al. ,29,30. Fs et al.  in betteinstantaneous tonal tension. We asked expert musicians to move the slider upwards or downwards as they listened to the chord progressions to reflect increasing or decreasing tonal tension, respectively. The second experiment (Experiment 2) is an online listening test that aims to assess the global perception of changes in tonal tension associated with chord progressions. We proposed five prototypical curves that represent global tonal tension profiles and then we asked the listeners to select the curve that best represents the overall perceived changes in tonal tension of twelve chord progressions. Finally, we compare the results of the proposed model with two representative state-of-the-art models of tonal tension, namely Lerdahl’s [tonal tension, whereas the comparison with MorpheuS [To evaluate our tonal tension profile model, we conducted two new experiments with contrasting approaches, whose designs were inspired by Farbood . Both exerdahl’s  and Morperdahl’s . The comerdahl’s  model aiMorpheuS  highlighinstantaneous tonal tension in the TIS [The remainder of this paper is structured as follows.  the TIS , with a global tension profile, the hierarchical structure, the chord progression, the model of tonal tension profile, and the instantaneous tonal tension profile. The entry point is the chord progression because the other levels depend on it. The global tension profile is represented by a prototypical curve that represents the changes in tonal tension over time experienced by the listener after the chord progression is played. In the case of analytical rules to construct a tree from the chord progression based on the generative procedure proposed by Rohrmeier [tonal distances divided into tonal distance between chords, tonal distance from the key and the tonal distance from the tonal function; dissonance, voice leading and hierarchical tension. The final tonal tension associated with each chord in the progression is obtained as a linear combination of the model components. Finally, our proposed model fits a curve to the time-series of instantaneous tonal tension values to estimate the instantaneous tonal tension profile associated with the chord progression.In this section, we present an overview of the approach we propose to model the tonal tension profile of chord progressions. ohrmeier . Betweeninstantaneous tonal tension of the second chord (F Major). The measure of consonance only depends on the chord itself (highlighted with an ellipse in green), whereas the calculation of both tonal distance between two chords (red rectangle) and voice leading (orange rectangle) use a sliding window spanning two chords, the current (F Major), and the previous one. The measure of tonal distances from the key and from the tonal function uses the tonal context and hierarchical tension uses the tree that represents the hierarchical structure of the entire chord progression to compare the current chord with all its parents nodes. Finally, these six tonal indicators are linearly combined into the final instantaneous tonal tension. Then, the sliding window shifts forward by one chord and the instantaneous tonal tension value is estimated for the next chord. This process is repeated until the end of the chord progression is reached, resulting in a set of discrete instantaneous tonal tension estimations that comprise the instantaneous tonal tension profile. The aim of this work is to evaluate how well the instantaneous tension profile resulting from the model captures both the instantaneous tonal tension profile and the global tonal tension profile experienced by the listener. For such, we need to evaluate four components of the model, namely, the instantaneous tonal tension profile experienced by the listener, how it is associated with the instantaneous tonal tension profile predicted by the model, and the global tonal tension profile perceived by the listener and its association with the instantaneous tonal tension profile predicted by the model.instantaneous tonal tensionM of a chord P as a combination of the following four components:Tonal Distances   perceptual similarity between two consecutive chords, (ii) perceptual similarity between the chord and the key of the chord progression, and (iii) perceptual similarity between the chord and the tonal function. This last property measures how the chord is related to the most important chords in the tonal music: the Tonic, Subdominant, and Dominant.Our proposal incorporates all four components into a fully automated computational model that does not require manual calculations due to the representation in the TIS see . The tondissonance measures the psychoacoustic dissonance of chords in a progression from the interaction among the vertical component notes of each chord (closely related to the psychoacoustic concept of roughness). In our work, surface dissonance results from measuring the Euclidean distance between the chord encoded in the TIS and the center of the space.The Voice leading captures the melodic attraction between consecutive chords per voice. Voice leading is a horizontal measure that estimates the tension of each note in a voice according to the previous note. In our work, the number of semitones and the relationship between the notes can affect the evaluation of the voices. Therefore, we measure the voice leading in the TIS as the distance of both notes in semitones and the perceptual similarity between the notes of the two consecutive chords.hierarchical tension captures the tension of the multiple levels of the musical structure by adopting tree-based structures driven from functional harmonic categories  in a similar fashion to the syntactic trees from early generative linguistics [Finally, guistics . We analM in detail. An important contribution of our work that is also explained in detail in analytical rules to automatically extract a tree to represent the hierarchical structure of chord progressions based on Rorhrmeier’s generative rules.M of a chord P asi-th-chord of the progression P, and M is expressed as the linear combination of the tonal indicators detailed in tonal distance (between chords)  that represents the key  (dissonance (c), voice leading (m), and hierarchical tension (h). As illustrated in M estimates the instantaneous tonal tension of each chord P, resulting in a time series m is the last chord in the progression P. M results from an adaptation of Lerdahl’s tonal indicators [https://github.com/merismeris/tonal-tension-TIS.Equation  computesion P asMTi,P=ω1ddicators . The nexdicators  for furtC is an alternative representation with twelve binary positions corresponding to the pitches comprising the chromatic scale arranged in ascending frequency. The value 1 in a specific position indicates the presence of that pitch, and 0 indicates absence. For example, the chroma vector representation of the C major chord is The twelve pitches commonly used in Western tonal music can be represented by whole numbers from 0 to 11. Thus, the C major chord can be written as the row vector T with the DFT. The six dimensions are weighted by empirical ratings of dyads’ consonance to enhance the perceptual basis of the space. TIVs [T, which is the distance of each TIV from the origin, can be used as a measure of dissonance [An advantage of the chroma vector representation is that all vectors have twelve dimensions independently of the number of pitches present. However, distance measures commonly used in vector spaces such as the Euclidean distance do not capture musical properties of the pitches encoded as chroma vectors. Instead, Fourier analysis can be used to explore the harmonic relations between pitch classes represented as binary chroma vectors ,44,45,46ce. TIVs  are usefssonance . Note thssonance  or Chew’ssonance .k is each component of the vectors T. The dot product between In the TIS, two fundamental measures are used to compare two tonal interval vectors lated asT1·T2=∥T1Bernardes et al.  showed ts et al. , Bernards et al. , and Navs et al. .M in Next, The tonal distances of chord Equation , so θ have smaller distances from the key . Tkey isEquation  from thec of the chord c results in small values of c value corresponds to a single pitch class and the maximum to a pitch configuration with all classes . Within this range, the dissonance c of chords results from the contribution of all intervallic dimensions of the space. Refer to Bernardes et al. [In the TIS, the magnitude s et al.  for a com of chord m is calculated asV is the number of voices, s is the number of semitones between the l-note of the inspected chord l-note in the previous chord Equation  computesh following the conceptual basis of Lerdahl [P asN is the length of the path between the chord node and the root, P, and Equation  computes Lerdahl . It accoEquation . The comchord progression from a starting node. In this work, we adopt Rohrmeier’s grammatical rules to invert the process and generate a hierarchical tree structure given a chord progression P. Rohrmeier’s rules can be automated and the resulting tree can be used to compute neighboring hierarchical relations in Equation , each parent node is replaced and we move up to the the next level until the top level is reached . The parent nodes with only one child are automatically replaced by the leaf chord. The parents whose children represent different tonal regions are automatically replaced by the child with the same tonal function or region as the parent to maintain the same tonal region. Finally, the node with children of the same tonal regions is replaced by the chord that gets a lower value according to its tonal distance.A simple example considering the tree of instantaneous tonal tension, whereas Experiment 2 focuses on global tonal tension. In Experiment 1, we asked the participants to move a slider up or down while listening to the chord progressions to reflect increasing or decreasing perception of tonal tension as the progression unfolds. In Experiment 2, we conducted an online listening test that asks the participants to listen to the same chord progressions from Experiment 1 and choose a curve that best represents conceptually the global tonal tension profile associated with it.This section details two experiments designed to assess how well the proposed computational model of tonal tension captures the tonal tension profiles experienced by listeners exposed to Western tonal music. Experiment 1 focuses on We validate the proposed model of instantaneous tonal tension in Equation  using thEquation  in explaEquation . SectionPrevious empirical studies ,26 have Rhythm: All chord progressions were regularly played one chord every two seconds to avoid the influence of rhythmic patterns on the perception of tonal tension.Timbre: All chord progressions were synthesized using Finale’s default piano synthesizer to avoid the influence of timbral changes on the perception of tonal tension.Length: We aim to minimize the influence of the number of chords in the perception of tonal tension, so we use chord progressions with varying numbers of chords. All chord progressions used in the evaluation have between 5 and 10 chords because the number of chords in the progression affects the perception of global tonal tension. In general, short progressions prevent the perception of the overall structure, whereas long progressions can affect the perception of hierarchical tonal structures [ructures .Number of notes: The chords used in these experiments are constructed with four notes as is usual in Western tonal music.Tree structures: The chord progressions selected correspond to different tree structures to enable the investigation of the effect of the tree structures in the ability of the model to capture tonal tension profiles. All the selected chord progressions are different from one another, containing either different chords or the same chords in a different order. Consequently, the hierarchical structure associated with the chord progressions will be different and so will the tree structures. The tree structures are automatically created by applying the algorithm described in Keys: In this work, we have designed progressions in different keys. However, according to Farbood [ Farbood , pitch hglobal tonal tension profile associated with the selected chord progressions. The curves can be explained as follows:(a): The perceived tension increases globally.(b): The perceived tension decreases globally.(c): The perceived tension increases at first but, at some point, starts decreasing.(d): The perceived tension decreases at first but, at some point, starts increasing.(e): The perceived tension fluctuates without a noticeable trend.(f): None of the curves capture the perceived tonal tension profile.globaltonal tension profiles meant to be interpreted conceptually. For example, (a) represents a global trend to increase. However, the perception of tonal tension might not increase linearly  and there may be perceived fluctuations in increasing tonal tension. Overall, option (a) represents increasing tension without resolution and (b) represents decreasing tension towards relaxation. Similarly, for (c) and (d), the point where the slope changes might not be exactly in the middle. Options (c) and (d) represent respectively increasing tension followed by resolution and decreasing tension followed by a buildup. Option (e) represents the case where there is no perceived global trend in tonal tension and option (f) was included to account for cases where the listener perceives a more intricate pattern of tonal tension not captured by the previous options.The curves shown in Progression 1: “Ach wie Fluchtig, ach wie nichtig” BWV 26, by J. S. Bach.Progression 2: “Piano sonata n. 9 in D major” K. 311 by W. A. Mozart.Progression 3: “Prelude” op. 28 n. 4 by F. Chopin.Progression 4: “Warum” op. 12 n. 3 by R. Schumann.Progression 5: “Drei Intermezzi” op. 117 by J. Brahms.Progression 6: “Claire de lune” by C. Debussy.The selected chord progressions should fit one of the options in https://github.com/merismeris/tonal-tension-TIS). Our hypothesis is that these five global tonal tension profiles are able to represent the prototypical curves categories associated with the selected chord progressions. Option (f) None was included among the options in Experiment 1 to test this hypothesis. We further hypothesize that longer musical passages may have more intricate associated tonal tension profiles that may be expressed as combinations of these basic categories. For example, (a) followed by (b) followed by (a), as in the work of Farbood [Additionally, we used the theoretical rules of tonal music to construct six chord progressions (Progressions 7–12) whose tension profiles correspond to one of the curves shown in  Farbood . It is oinstantaneous tonal tension defined in Equation . On the one hand, as the chord progressions are totally different, we can state that the samples are independent, therefore we comply with the first condition. On the other hand, to test for homoscedasticity, we applied Levene’s test, which verifies that the samples are homogeneous, and that we have concordance in the inter-subject variance. The null hypothesis for this test is that there exists equality of variances. The p-value resulting from ANOVA was Since the two conditions are accomplished, we applied ANOVA analysis to compare the mean of the 15 curves drawn by the users. The null hypothesis of the ANOVA test is that there is no significant difference in means. The …, I15 corresponds to what participants drew with the slider. The resampled curves are the result of merging the points of the raw curves to get a curve with one point per chord. Finally, the mean curve is obtained when we calculated the mean of the values that are located in the same ith position.The instantaneous tonal tension profile that our model proposes gives one single value per chord, whereas the raw curves that the participants drew  and a stable region (during which the slider remains relatively stable). We are interested in samples in the stable region to represent the instantaneous tonal tension associated with each chord. Therefore, the resampling operation ignores the samples in the delay region and takes the mean of the samples in the stable region. The segmentation procedure uses the difference between adjacent samples to approximate the time derivative of the samples of the slider position. The stable region is defined to be the contiguous region where the derivative is in the interval ith point of the mean curve is the result of calculating the mean of the points that are located in the ith position of the resampled curves.M, which measures the tonal distance to the previous chord, the tonal distance to the key, the tonal distance to the function, the dissonance, the voice leading, and the hierarchical distance. First, we aim to analyze which features influence the perception of the tonal tension. For this purpose, we calculated the Pearson correlation to know if all the musical features are related to the tonal tension perceived.In this section, we compare the mean curves of each chord progression with the instantaneous tonal tension profiles proposed by our model We calculated the correlation with all the musical properties, by combining them in any possible way to know which combination of features can capture the instantaneous tonal tension profile of the chord progressions best. Finally, the model with the best adjustment included four properties, namely, the tonal distance to the key, the dissonance, the voice leading, and the hierarchical tension. The Pearson correlation M computes the tonal distance of a given chord i from the previous chord The statistical results discarded the tonal distance between consecutive chords and the distance between the chord and its tonal function. In Equation , M compuThe tonal distance between a chord from its tonal function captures the stability of chord within the tonic, subdominant and dominant functions. We expected the metric to contribute to disambiguate subtle differences across multiple chords which share the same function . However, this relationship might be misleading in capturing tonal tension, as the finer degrees of functional stability must be observed under a larger context. For example, the distance between a stable and unstable tonic can be relatively similar to the distance between a stable and unstable dominant. While resulting in similar values, the difference between the two tonic and dominant functions is expected to be different in terms of tension.M can capture 56.3% of the curves depicted by the participants.We calculated the weights M from Equation . The rounded blue markers connected linearly with a blue semi-dotted line shows the curve that our measure M obtained. The instantaneous tonal tension values of Lerdahl’s proposal are represented with rounded markers and connected with an orange line-dot-dot line, whereas a dotted yellow line with rhomboid markers is the curve depicted by MorpheuS. Finally, the mean curve representing the perception of the participants is represented with a green continuous line and square markers. Visual comparison of the curves of the models against the mean curves of the participants reveal that the instantaneous tonal tension profiles that the participants perceive match the instantaneous tonal tension profile that our model M predicts for several cases. Therefore, to statistically validate the visual results shown in M (presented in the column 2), Lerdahl’s (column 3) and MorpheuS (column 4). The highest M captures the instantaneous tonal tension profile of the chord progression quite well, as we obtained high Pearson Correlation In this work, we also compare and analyze the results for each chord progression individually. Interestingly, the tonal tension profile of P12 is poorly captured by all models under consideration as it shows the lowest results for adjustment. However, careful consideration of the curves resulting from the participants and the models in global perception of tonal tension associated with the chord progressions selected in global variation of tonal tension over time. The goal of Experiment 2 is to investigate the Both Experiment 1 and Experiment 2 are measuring tonal tension from a different point of view. https://usalinvestigacion.eu.qualtrics.com/jfe/form/SV_cSChvf8II2LwlD. In Experiment 2, the participants are asked to listen to all twelve chord progressions one by one and choose one curve among those shown in global tonal tension profile. The order of presentation of the chord progressions was randomized for each participant. Participants were free to listen to each chord progression as many times as they wished before selecting one of the options and they had to make a selection to proceed to the next chord progression. In total, 73 people completed the experiment. The profile of the participants was varied, we have 51 people with musical training, and 22 without any musical training. The results of the selection and the significance of the subjective ratings will be explained in Experiment 2 aimed to associate a prototypical curve to the perceived global tonal tension profile of chord progressions with an online listening test, which can be found at In line with the results of Progression 12 in Experiment 1, the participants of the listening test have shown a smaller degree of agreement for this progression, with 19.178% of the participants unable to fit the perceived global tonal tension to any prototypical curve. The participants selection for Progression 3 equally raises the interesting question of the subjectivity and difficulty of the task at hand. Progression 3 has a surprisingly number of participants selecting contrasting ascending (46.575%) and descending (32.877%) curves. Considering the broad scope of diversity in the musical expertise of the participants in the listening test (from no training to advanced training), we believe that, in this progression, pitch height may have played an unintended impact. Despite our attempts to minimize differences in pitch height, the progression along with its highest voice unfold across two octaves. The interval of a tenth in the highest voice may have imposed a tendency for participants to select a descending curve. However, our expectation was the selection of the ascending prototypical tonal tension curve due to the tree structure that supports the chord progression. Our expectation is nonetheless verified in Experiment 1, where all the participants declared the advanced musical expertise from at least six years of musical training. Participant selection for Progression 5 also has conflicting views. The participants selected three prominent curves: descending (33.333%), convex (29.167%) curves and fluctuating (26.389%). We believe that the conflicting views across the descending and convex curves may be due to the early tension peak in the second chord of the progression. Participants may have neglected the first chord and considered that the descending line better captures the overall tension profile. However, as shown in In this section, we validate the participants’ selection in the listening test by presenting their agreement in selecting a prototypical curve. If the results are positive, we will process the responses of the listening test and compare them with our model. With categorical data, we cannot apply ANOVA as in Experiment 1. In this case, we used the kappa test  in the chords. There are many different styles in classical music, like Baroque, Classical, or Romantic compositions, in which the number of voices are stable in whole compositions. We were based in these styles to create our excerpts and, therefore, did not consider a variable number of voices. Future work will study how to overcome this limitation computationally in our model and how the lack of voice leading in some voices can influence the perception of tonal tension.tonal tension profile of a chord progression by encoding the chords in the Tonal Interval Space (TIS) [instantaneous tonal tension of each chord considering factors such as dissonance, the tonal distances to measure the similarity with the previous chord, with the tonal function and with the key, voice leading, and the hierarchical tension of the chord with respect to the rest of the progression. To create the tonal tension profile, we connect the values associated with each individual chord and create a curve that represents the tonal tension profile of the chord progression. We considered the TIS as an appropriate representation for multiple reasons. Firstly, multi-level pitch configurations can be represented, such as chord with different number of notes, or keys. Therefore, we can handle chord progressions written in different keys or different modes. Additionally, topological properties of the space reflect musical properties of the tonal system. Consequently, we have constructed a flexible computational analysis framework which allows for excluding annotations on the analyzed musical data by encoding pitch configurations and capturing their musical properties systematically.In this work, we proposed a model that captures the ce (TIS) . We measThe evaluation of a chord progression depends on the musical context. This is influenced by both linear properties, related to how the progression is changing along the time and hierarchical properties, related to the structure of the whole progression. Our measure is appropriate, as it captures linear properties of the chord progressions, namely, dissonance, the tonal distances and the voice leading; and the hierarchical properties, such as the hierarchical tension of the chord with respect to the rest of the progression.instantaneous and global tonal tension profile of the chord progressions proposed in the experiments. In both experiments, we also compared the results obtained with present model and with Lerdahl’s [M proposed was a better indicator of tonal tension profiles.In order to evaluate how our measure predicts the tonal tension profile of a chord progression, we performed two experiments. For both, we used 12 chord progressions in different keys, with different trees , and different tonal tension profiles. Experiment 1 aimed to evaluate if our model captures the instantaneous tonal tension profile while the participants are listening to a chord progression, and which musical properties are essential to predict the tension of a progression. Experiment 2 was intended to evaluate if our measure captures the general perception of the tonal tension profile after the participants listened to a chord progression. In both cases, statistical analysis showed that the subjective ratings correlate with the objective values, validating the objective model as a proxy for the subjective measure of erdahl’s  and HerrFinally, it is important to highlight that both global and instantaneous tonal tension are high-level properties of music, so tonal tension can be musically perceived and subjectively rated differently. Despite the limitations, one of the contributions of this model is the beginning of a generalization function that can study a long-term chord progression based on both hierarchical and linear structures in different tonalities. The adaptation of Lerdahl’s space to the TIS to explain the tonal properties of a chord besides tonal tension and voice leading can also be considered a contribution for the community. The positive results are encouraging to apply this measure to real analysis problems and computational generative systems.Future work will study how to extend this analysis and extrapolate the model to any chord progression that has been composed following the tonal music standards. We will also analyze properties like pitch height and rhythm, which also influences the tension perception. Additionally, we will also investigate how to improve a system to generate chord progressions using an artificial immune system described in a previous work  with thi