Imperial College London

ProfessorEtienneBurdet

Faculty of EngineeringDepartment of Bioengineering

Professor of Human Robotics
 
 
 
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e.burdet CV

 
 
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4.05Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

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284 results found

Li Y, Eden J, Carboni G, Burdet Eet al., 2020, Improving Tracking through Human-Robot Sensory Augmentation, IEEE ROBOTICS AND AUTOMATION LETTERS, Vol: 5, Pages: 4399-4406, ISSN: 2377-3766

Journal article

Phan G-H, Hansen C, Tommasino P, Budhota A, Mohan DM, Hussain A, Burdet E, Campolo Det al., 2020, Estimating Human Wrist Stiffness during a Tooling Task., Sensors (Basel), Vol: 20

In this work, we propose a practical approach to estimate human joint stiffness during tooling tasks for the purpose of programming a robot by demonstration. More specifically, we estimate the stiffness along the wrist radial-ulnar deviation while a human operator performs flexion-extension movements during a polishing task. The joint stiffness information allows to transfer skills from expert human operators to industrial robots. A typical hand-held, abrasive tool used by humans during finishing tasks was instrumented at the handle (through which both robots and humans are attached to the tool) to assess the 3D force/torque interactions between operator and tool during finishing task, as well as the 3D kinematics of the tool itself. Building upon stochastic methods for human arm impedance estimation, the novelty of our approach is that we rely on the natural variability taking place during the multi-passes task itself to estimate (neuro-)mechanical impedance during motion. Our apparatus (hand-held, finishing tool instrumented with motion capture and multi-axis force/torque sensors) and algorithms (for filtering and impedance estimation) were first tested on an impedance-controlled industrial robot carrying out the finishing task of interest, where the impedance could be pre-programmed. We were able to accurately estimate impedance in this case. The same apparatus and algorithms were then applied to the same task performed by a human operators. The stiffness values of the human operator, at different force level, correlated positively with the muscular activity, measured during the same task.

Journal article

Takagi A, Maxwell S, Melendez-Calderon A, Burdet Eet al., 2020, The dominant limb preferentially stabilizes posture in a bimanual task with physical coupling, Journal of Neurophysiology, Vol: 123, Pages: 2154-2160, ISSN: 0022-3077

Humans are endowed with an ability to skillfully handle objects, like when holding a jar with the non-dominant hand whilst opening the lid with the dominant hand. Dynamic-dominance, a prevailing theory in handedness research, proposed that the non-dominant hand is specialized for postural stability, which would explain why right-handers hold the jar steady using the left hand. However, the underlying specialization of the non-dominant hand has only been tested unimanually, or in a bimanual task where the two hands had different functions. Using a dedicated dual robotic wrist interface, we could test the dynamic-dominance hypothesis in a bimanual task where both hands carry out the same function. We examined how left- and right-handed subjects held onto a vibrating virtual object using their wrists, which were physically coupled through the object. Muscular activity of the wrist flexors and extensors revealed a preference for cocontracting the dominant hand. Such stabilization action contradicts the dynamic-dominance hypothesis. While the reliance on the dominant hand was partially explained by its greater strength, the Edinburgh inventory was a better predictor of the difference in the cocontraction between the dominant and non-dominant hands. When provided with redundancy to stabilize the task, the dominant hand preferentially cocontracts to absorb perturbing forces.

Journal article

Huang HY, Arami A, Farkhatdinov I, Formica D, Burdet Eet al., 2020, The Influence of Posture, Applied Force and Perturbation Direction on Hip Joint Viscoelasticity, IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING, Vol: 28, Pages: 1138-1145, ISSN: 1534-4320

Journal article

Huang Y, Burdet E, Cao L, Phan PT, Tiong AMH, Phee SJet al., 2020, A Subject-Specific Four-Degree-of-Freedom Foot Interface to Control a Surgical Robot, IEEE-ASME TRANSACTIONS ON MECHATRONICS, Vol: 25, Pages: 951-963, ISSN: 1083-4435

Journal article

Borzelli D, Burdet E, Pastorelli S, d'Avella A, Gastaldi Let al., 2020, Identification of the best strategy to command variable stiffness using electromyographic signals, JOURNAL OF NEURAL ENGINEERING, Vol: 17, ISSN: 1741-2560

Journal article

Ivanova E, Carboni G, Eden J, Kruger J, Burdet Eet al., 2020, For Motion Assistance Humans Prefer to Rely on a Robot Rather Than on an Unpredictable Human, IEEE Open Journal of Engineering in Medicine and Biology, Vol: 1, Pages: 133-139

Journal article

Dahiya R, Yogeswaran N, Liu F, Manjakkal L, Burdet E, Hayward V, Jorntell Het al., 2019, Large-Area Soft e-Skin: The Challenges Beyond Sensor Designs, PROCEEDINGS OF THE IEEE, Vol: 107, Pages: 2016-2033, ISSN: 0018-9219

Journal article

Huang Y, Burdet E, Cao L, Phuoc TP, Tiong AMH, Zheng P, Phee SJet al., 2019, Performance evaluation of a foot interface to operate a robot arm, IEEE Robotics and Automation Letters, Vol: 4, Pages: 3302-3309, ISSN: 2377-3766

We developed a foot interface enabling an operator to control a robotic arm with four degrees of freedom in continuous direction and speed, for operating one of the multiple tools required during robot-aided surgery. In this letter, we first test whether this pedal interface can be used to carry out complex manipulation as is required in surgery. Second, we compare the performance of ten naive operators using this new interface and a traditional button interface providing axis-by-axis constant-speed control. Testing is carried out on geometrically complex path-following tasks similar to laparoscopic training. Movement precision, time and smoothness are analyzed. The results demonstrate that the continuous pedal interface can be used to control a robot in complex motion tasks. The subjects kept the average error rate at a low level of around 2.6% with both interfaces, but the pedal interface resulted in about 30% faster operation and 60% smoother movement, which indicates improved efficiency and user experience as compared with the button interface. A questionnaire shows that controlling the robot with the pedal interface was more intuitive, comfortable, and less tiring than with the button interface.

Journal article

Arami A, Poulakakis-Daktylidis A, Tai YF, Burdet Eet al., 2019, Prediction of gait freezing in Parkinsonian patients: a binary classification augmented with time series prediction, IEEE Transactions on Neural Systems and Rehabilitation Engineering, Vol: 27, Pages: 1909-1919, ISSN: 1534-4320

This paper presents a novel technique to predict freezing of gait in advance-stage Parkinsonian patients using movement data from wearable sensors. A two-class approach is presented which consists of autoregressive predictive models to project the feature time series, followed by machine learning based classifiers to discriminate freezing from nonfreezing based on the predicted features. To implement and validate our technique a set of time domain and frequency domain features were extracted from the 3D acceleration data, which was then analyzed using information theoretic and feature selection approaches to determine the most discriminative features. Predictive models were trained to predict the features from their past values, then fed into binary classifiers based on support vector machines and probabilistic neural networks which were rigorously cross validated. We compared the results of this approach with a three-class classification approach proposed in previous literature, in which a pre-freezing class was introduced and the problem of prediction of the gait freezing incident was reduced to solving a three-class classification problem. The twoclass approach resulted in a sensitivity of 93±4%, specificity of 91±6%, with an expected prediction horizon of 1.72 seconds. Our subject-specific gait freezing prediction algorithm outperformed existing algorithms, yields consistent results across different subjects and is robust against the choice of classifier, with slight variations in the selected features. In addition, we analyzed the merits and limitations of different families of features to predict gait freezing.

Journal article

Perez NP, Tokarchuk L, Burdet E, Farkhatdinov Iet al., 2019, Exploring user motor behaviour in bimanual interactive video games, ISSN: 2325-4270

© 2019 IEEE. Video games have proved very valuable in rehabilitation technologies. They guide therapy and keep patients engaged and motivated. However, in order to realize their full potential, a good understanding is required of the players' motor control. In particular, little is known regarding player behaviour in tasks demanding bimanual interaction. In this work, an experiment was designed to improve the understanding of such tasks. A driving game was developed in which players were asked to guide a differential wheeled robot (depicted as a rocket) along a trajectory. The rocket could be manipulated by using an Xbox controller's triggers, each supplying torque to the corresponding side of the robot. Such a task is redundant, i.e. there exists an infinite number of input combinations to yield a given outcome. This allows the player to strategize according to their own preference. 10 participants were recruited to play this game and their input data was logged for subsequent analysis. Two different motor strategies were identified: an "intermittent" input pattern versus a "continuous" one. It is hypothesized that the choice of behaviour depends on motor skill and minimization of effort and error. Further testing is necessary to determine the exact relationship between these aspects.

Conference paper

Lotay R, Mace M, Rinne P, Burdet E, Bentley Pet al., 2019, optimizing self-exercise scheduling in motor stroke using Challenge Point Framework theory, 2019 IEEE 16th International Conference on Rehabilitation Robotics (ICORR), Publisher: IEEE, Pages: 435-440

An important challenge for technology-assisted self-led rehabilitation is how to automate appropriate schedules of exercise that are responsive to patients’ needs, and optimal for learning. While random scheduling has been found to be superior for long-term learning relative to fixed scheduling (Contextual Interference), this method is limited by not adequately accounting for task difficulty, or skill acquisition during training. One method that combines contextual interference with adaptation of the challenge to the skill-level of the player is Challenge Point Framework (CPF) theory. In this pilot study we test whether self-led motor training based upon CPF scheduling achieves faster learning than deterministic, fixed scheduling. Training was implemented in a mobile gaming device adapted for arm disability, allowing for grip and wrist exercises. We tested 11 healthy volunteers and 12 hemiplegic stroke patients in a single-blinded no crossover controlled randomized trial. Results suggest that patients training with CPF-based adaption performed better than those training with fixed conditions. This was not seen for healthy volunteers whose performance was close to ceiling. Further data collection is required to determine the significance of the results.

Conference paper

Mehring C, Akselrod M, Bashford L, Mace M, Choi H, Bl├╝her M, Buschhoff A-S, Pistohl T, Salomon R, Cheah A, Blanke O, Serino A, Burdet Eet al., 2019, Augmented manipulation ability in humans with six-fingered hands, Nature Communications, Vol: 10, Pages: 2401-2401, ISSN: 2041-1723

Neurotechnology attempts to develop supernumerary limbs, but can the human brain deal with the complexity to control an extra limb and yield advantages from it? Here, we analyzed the neuromechanics and manipulation abilities of two polydactyly subjects who each possess six fingers on their hands. Anatomical MRI of the supernumerary finger (SF) revealed that it is actuated by extra muscles and nerves, and fMRI identified a distinct cortical representation of the SF. In both subjects, the SF was able to move independently from the other fingers. Polydactyly subjects were able to coordinate the SF with their other fingers for more complex movements than five fingered subjects, and so carry out with only one hand tasks normally requiring two hands. These results demonstrate that a body with significantly more degrees-of-freedom can be controlled by the human nervous system without causing motor deficits or impairments and can instead provide superior manipulation abilities.

Journal article

Mutalib SA, Mace M, Ong HT, Burdet Eet al., 2019, Influence of visual-coupling on bimanual coordination in unilateral spastic cerebral palsy., IEEE Int Conf Rehabil Robot, Vol: 2019, Pages: 1013-1018

Controlling two objects simultaneously during a bimanual task is a cognitively demanding process; both hands need to be temporally and spatially coordinated to achieve the shared task goal. Children with unilateral spastic cerebral palsy (USCP) exhibit severe sensory and motor impairments to one side of their body that make the process of coordinating bimanual movements particularly exhausting. Prior studies have shown that performing visually-coupled task could reduce cognitive interference associated with performing 'two tasks at once' in an uncoupled bimanual task. For children with USCP, who also present with cognitive delay, performing this type of task may allow them to process and plan their movement faster. We tested this hypothesis by examining the grip force control of 7 children with USCP during unimanual and visually-coupled bimanual tasks. Results demonstrated that despite the visual coupling, the bimanual coordination of these children remained impaired. However, there may be a potential benefit of visually-coupled task in encouraging both hands to initiate in concert. The implication of the study for children with USCP is discussed.

Journal article

Kager S, Hussain A, Cherpin A, Melendez-Calderon A, Takagi A, Endo S, Burdet E, Hirche S, Ang MH, Campolo Det al., 2019, The effect of skill level matching in dyadic interaction on learning of a tracing task., IEEE Int Conf Rehabil Robot, Vol: 2019, Pages: 824-829

Dyadic interaction between humans has gained great research interest in the last years. The effects of factors that influence the interaction, as e.g. roles or skill level matching, are still not well understood. In this paper, we further investigated the effect of skill level matching between partners on learning of a visuo-motor task. Understanding the effect of skill level matching is crucial for applications in collaborative rehabilitation. Fifteen healthy participants were asked to trace a path while being subjected to a visuo-motor rotation (Novice). The Novices were paired with a partner, forming one of the three Dyad Types: a) haptic connection to another Novice, b) haptic connection to an Expert (no visuo-motor rotation), or c) no haptic. The intervention consisted of a Familiarization phase, followed by a Training phase, in which the Novices were learning the task in the respective Dyad Type, and a Test phase in which the learning was assessed (haptic connection removed, if any). Results suggest that learning of the task with a haptic connection to an Expert was least beneficial. However, during the Training phase the dyads comprising an Expert clearly outperformed the dyads with matched skill levels. The results point towards the same direction as previous findings in literature and can be explained by current motor-learning theories. Future work needs to corroborate these preliminary results.

Journal article

Farkhatdinov I, Ebert J, van Oort G, Vlutters M, van Asseldonk E, Burdet Eet al., 2019, Assisting human balance in standing with a robotic exoskeleton, IEEE Robotics and Automation Letters, Vol: 4, Pages: 414-421, ISSN: 2377-3766

This letter presents an experimental study on balance recovery control with a lower limb exoskeleton robot. Four participants were subjected to a perturbation during standing, a forward force impulse applied to their pelvis that forced them to step forward with the right leg for balance recovery. Trials with and without exoskeleton assistance to move the stepping legs thigh were conducted to investigate the influence of the exoskeletons control assistance on balancing performance and a potential adaptation. Analysis of the body kinematics and muscle activation demonstrates that robotic assistance: first, was easy to use and did not require learning, nor inhibited the healthy stepping behavior; second, it modified the stepping leg trajectories by increasing hip and knee movement; third, increased reaction speed and decreased the step duration; and finally, generally increased biceps femoris and rectus femoris muscle activity.

Journal article

Farkhatdinov I, Ebert J, Van Oort G, Vlutters M, Van Asseldonk E, Burdet Eet al., 2019, Assisting Human Balance in Standing With a Robotic Exoskeleton, IEEE Robotics and Automation Letters, Vol: 4, Pages: 414-421

© 2016 IEEE. This letter presents an experimental study on balance recovery control with a lower limb exoskeleton robot. Four participants were subjected to a perturbation during standing, a forward force impulse applied to their pelvis that forced them to step forward with the right leg for balance recovery. Trials with and without exoskeleton assistance to move the stepping legs thigh were conducted to investigate the influence of the exoskeletons control assistance on balancing performance and a potential adaptation. Analysis of the body kinematics and muscle activation demonstrates that robotic assistance: first, was easy to use and did not require learning, nor inhibited the healthy stepping behavior; second, it modified the stepping leg trajectories by increasing hip and knee movement; third, increased reaction speed and decreased the step duration; and finally, generally increased biceps femoris and rectus femoris muscle activity.

Journal article

Takagi A, Hiroshima M, Nozaki D, Burdet Eet al., 2019, Individuals physically interacting in a group rapidly coordinate their movement by estimating the collective goal, eLife, Vol: 8, ISSN: 2050-084X

How can a human collective coordinate, for example to move a banquet table, wheneach person is influenced by the inertia of others who may be inferior at the task? We hypothesizedthat large groups cannot coordinate through touch alone, accruing to a zero-sum scenario whereindividuals inferior at the task hinder superior ones. We tested this hypothesis by examining howdyads, triads and tetrads, whose right hands were physically coupled together, followed a commonmoving target. Surprisingly, superior individuals followed the target accurately even when coupledto an inferior group, and the interaction benefits increased with the group size. A computationalmodel shows that these benefits arose as each individual uses their respective interaction force toinfer the collective’s target and enhance their movement planning, which permitted coordination inseconds independent of the collective’s size. By estimating the collective’s movement goal, itsindividuals make physical interaction beneficial, swift and scalable.

Journal article

Li Y, Carboni G, Gonzalez F, Campolo D, Burdet Eet al., 2019, Differential game theory for versatile physical human–robot interaction, Nature Machine Intelligence, Vol: 1, Pages: 36-43, ISSN: 2522-5839

The last decades have seen a surge of robots working in contact with humans. However, until now these contact robots have made little use of the opportunities offered by physical interaction and lack a systematic methodology to produce versatile behaviours. Here, we develop an interactive robot controller able to understand the control strategy of the human user and react optimally to their movements. We demonstrate that combining an observer with a differential game theory controller can induce a stable interaction between the two partners, precisely identify each other’s control law, and allow them to successfully perform the task with minimum effort. Simulations and experiments with human subjects demonstrate these properties and illustrate how this controller can induce different representative interaction strategies.

Journal article

Mutalib SA, Mace M, Burdet E, 2019, Bimanual coordination during a physically coupled task in unilateral spastic cerebral palsy children, Journal of NeuroEngineering and Rehabilitation, Vol: 16, ISSN: 1743-0003

BackgroundSingle object bimanual manipulation, or physically-coupled bimanual tasks, are ubiquitous in daily lives. However, the predominant focus of previous studies has been on uncoupled bimanual actions, where the two hands act independently to manipulate two disconnected objects. In this paper, we explore interlimb coordination among children with unilateral spastic cerebral palsy (USCP), by investigating upper limb motor control during a single object bimanual lifting task.Methods15 children with USCP and 17 typically developing (TD) children performed a simple single-object bimanual lifting task. The object was an instrumented cube that can record the contact force on each of its faces alongside estimating its trajectory during a prescribed two-handed lifting motion. The subject’s performance was measured in terms of the duration of individual phases, linearity and monotonicity of the grasp-to-load force synergy, interlimb force asymmetry, and movement smoothness.ResultsSimilar to their TD counterparts, USCP subjects were able to produce a linear grasp-to-load force synergy. However, they demonstrated difficulties in producing monotonic forces and generating smooth movements. No impairment of anticipatory control was observed within the USCP subjects. However, our analysis showed that the USCP subjects shifted the weight of the cube onto their more-abled side, potentially to minimise the load on the impaired side, which suggests a developed strategy of compensating for inter-limb asymmetries, such as muscle strength.ConclusionBimanual interaction with a single mutual object has the potential to facilitate anticipation and sequencing of force control in USCP children unlike previous studies which showed deficits during uncoupled bimanual actions. We suggest that this difference could be partly due to the provision of adequate cutaneous and kinaesthetic information gathered from the dynamic exchange of forces between the two hands, mediated through the phy

Journal article

van der Kooij H, van Asseldonk E, van Oort G, Sluiter V, Emmens A, Witteveen H, Tagliamonte NL, Tamburella F, Pisotta I, Masciullo M, Arquilla M, Molinari M, Wu A, Ijspeert A, Dzeladini FF, Thorsteinsson F, Arami A, Burdet E, Huang HY, Gregoor W, Meijneke Cet al., 2019, Symbitron: Symbiotic man-machine interactions in wearable exoskeletons to enhance mobility for paraplegics, Biosystems and Biorobotics, Pages: 361-364

© Springer Nature Switzerland AG 2019. The main goal of the Symbitron project was to develop a safe, bio-inspired, personalized wearable exoskeleton that enables SCI patients to walk without additional assistance, by complementing their remaining motor function. Here we give an overview of major achievements of the projects.

Book chapter

Abdi E, Bouri M, Burdet E, Bleuler Het al., 2018, Development and Comparison of Foot Interfaces for Controlling a Robotic Arm in Surgery, IEEE International Conference on Robotics and Biomimetics (ROBIO), Publisher: IEEE, Pages: 414-420

Conference paper

Balasubramanian S, Garcia-Cossio E, Birbaumer N, Burdet E, Ramos-Murguialday Aet al., 2018, Is EMG a viable alternative to BCI for detecting movement intention in severe stroke?, IEEE Transactions on Biomedical Engineering, Vol: 65, Pages: 2790-2797, ISSN: 0018-9294

Objective: In light of the shortcomings of current restorative brain-computer interfaces (BCI), this study investigated the possibility of using EMG to detect hand/wrist extension movement intention to trigger robot-assisted training in individuals without residual movements. Methods: We compared movement intention detection using an EMG detector with a sensorimotor rhythm based EEG-BCI using only ipsilesional activity. This was carried out on data of 30 severely affected chronic stroke patients from a randomized control trial using an EEG-BCI for robot-assisted training. Results: The results indicate the feasibility of using EMG to detect movement intention in this severely handicapped population; probability of detecting EMG when patients attempted to move was higher (p <; 0.001) than at rest. Interestingly, 22 out of 30 (or 73%) patients had sufficiently strong EMG in their finger/wrist extensors. Furthermore, in patients with detectable EMG, there was poor agreement between the EEG and EMG intent detectors, which indicates that these modalities may detect different processes. Conclusion : A substantial segment of severely affected stroke patients may benefit from EMG-based assisted therapy. When compared to EEG, a surface EMG interface requires less preparation time, which is easier to don/doff, and is more compact in size. Significance: This study shows that a large proportion of severely affected stroke patients have residual EMG, which yields a direct and practical way to trigger robot-assisted training.

Journal article

Donadio A, Whitehead K, Gonzalez F, Wilhelm E, Formica D, Meek J, Fabrizi L, Burdet Eet al., 2018, A novel sensor design for accurate measurement of facial somatosensation in pre-term infants, PLoS ONE, Vol: 13, ISSN: 1932-6203

Facial somatosensory feedback is critical for breastfeeding in the first days of life. However, its development has never been investigated in humans. Here we develop a new interface to measure facial somatosensation in newborn infants. The novel system allows to measure neuronal responses to touching the face of the subject by synchronously recording scalp electroencephalography (EEG) and the force applied by the experimenter. This is based on a dedicated force transducer that can be worn on the finger underneath a clinical nitrile glove and linked to a commercial EEG acquisition system. The calibrated device measures the pressure applied by the investigator when tapping the skin concurrently with the resulting brain response. With this system, we were able to demonstrate that taps of 192 mN (mean) reliably elicited facial somatosensory responses in 7 pre-term infants. These responses had a time course similar to those following limbs stimulation, but more lateral topographical distribution consistent with body representations in primary somatosensory areas. The method introduced can therefore be used to reliably measure facial somatosensory responses in vulnerable infants.

Journal article

Borzelli D, Cesqui B, Berger DJ, Burdet E, d'Avella Aet al., 2018, Muscle patterns underlying voluntary modulation of co-contraction, PLoS ONE, Vol: 13, ISSN: 1932-6203

Manipulative actions involving unstable interactions with the environment require controlling mechanical impedance through muscle co-contraction. While much research has focused on how the central nervous system (CNS) selects the muscle patterns underlying a desired movement or end-point force, the coordination strategies used to achieve a desired end-point impedance have received considerably less attention. We recorded isometric forces at the hand and electromyographic (EMG) signals in subjects performing a reaching task with an external disturbance. In a virtual environment, subjects displaced a cursor by applying isometric forces and were instructed to reach targets in 20 spatial locations. The motion of the cursor was then perturbed by disturbances whose effects could be attenuated by increasing co-contraction. All subjects could voluntarily modulate co-contraction when disturbances of different magnitudes were applied. For most muscles, activation was modulated by target direction according to a cosine tuning function with an offset and an amplitude increasing with disturbance magnitude. Co-contraction was characterized by projecting the muscle activation vector onto the null space of the EMG-to-force mapping. Even in the baseline the magnitude of the null space projection was larger than the minimum magnitude required for non-negative muscle activations. Moreover, the increase in co-contraction was not obtained by scaling the baseline null space projection, scaling the difference between the null space projections in any block and the projection of the non-negative minimum-norm muscle vector, or scaling the difference between the null space projections in the perturbed blocks and the baseline null space projection. However, the null space projections in the perturbed blocks were obtained by linear combination of the baseline null space projection and the muscle activation used to increase co-contraction without generating any force. The failure of scaling rul

Journal article

Li Y, Ganesh G, Jarrasse N, Haddadin S, Albu-Schaeffer A, Burdet Eet al., 2018, Force, impedance, and trajectory learning for contact tooling and haptic identification, IEEE Transactions on Robotics, Vol: 34, Pages: 1170-1182, ISSN: 1552-3098

Humans can skilfully use tools and interact with the environment by adapting their movement trajectory, contact force, and impedance. Motivated by the human versatility, we develop here a robot controller that concurrently adapts feedforward force, impedance, and reference trajectory when interacting with an unknown environment. In particular, the robot's reference trajectory is adapted to limit the interaction force and maintain it at a desired level, while feedforward force and impedance adaptation compensates for the interaction with the environment. An analysis of the interaction dynamics using Lyapunov theory yields the conditions for convergence of the closed-loop interaction mediated by this controller. Simulations exhibit adaptive properties similar to human motor adaptation. The implementation of this controller for typical interaction tasks including drilling, cutting, and haptic exploration shows that this controller can outperform conventional controllers in contact tooling.

Journal article

ogrinc M, Farkhatdinov I, Walker R, Burdet Eet al., 2018, Sensory integration of apparent motion speed and vibration magnitude, IEEE Transactions on Haptics, Vol: 11, Pages: 455-463, ISSN: 1939-1412

Tactile apparent motion can display directional information in an intuitive way. It can for example be used to give directions to visually impaired individuals, or for waypoint navigation while cycling on busy streets, when vision or audition should not be loaded further. However, although humans can detect very short tactile patterns, discriminating between similar motion speeds has been shown to be difficult. Here we develop and investigate a method where the speed of tactile apparent motion around the user & #x0027;s wrist is coupled with vibration magnitude. This redundant coupling is used to produce tactile patterns from slow & amp;weak to fast & amp;strong. We compared the just noticeable difference (JND) of the coupled and the individual variables. The results show that the perception of the coupled variable can be characterised by JND smaller than JNDs of the individual variables. This allowed us to create short tactile pattens (tactons) for display of direction and speed, which can be distinguished significantly better than tactons based on motion alone. Additionally, most subjects were also able to identify the coupled-variable tactons better than the magnitude-based tactons.

Journal article

Dall'Orso S, Steinweg J, Allievi AG, Edwards AD, Burdet E, Arichi Tet al., 2018, Somatotopic mapping of the developing sensorimotor cortex in the preterm human brain, Cerebral Cortex, Vol: 28, Pages: 2507-2515, ISSN: 1047-3211

In the mature mammalian brain, the primary somatosensory and motor cortices are known to be spatially organized such that neural activity relating to specific body parts can be somatopically mapped onto an anatomical "homunculus". This organization creates an internal body representation which is fundamental for precise motor control, spatial awareness and social interaction. Although it is unknown when this organization develops in humans, animal studies suggest that it may emerge even before the time of normal birth. We therefore characterized the somatotopic organization of the primary sensorimotor cortices using functional MRI and a set of custom-made robotic tools in 35 healthy preterm infants aged from 31 + 6 to 36 + 3 weeks postmenstrual age. Functional responses induced by somatosensory stimulation of the wrists, ankles, and mouth had a distinct spatial organization as seen in the characteristic mature homunculus map. In comparison to the ankle, activation related to wrist stimulation was significantly larger and more commonly involved additional areas including the supplementary motor area and ipsilateral sensorimotor cortex. These results are in keeping with early intrinsic determination of a somatotopic map within the primary sensorimotor cortices. This may explain why acquired brain injury in this region during the preterm period cannot be compensated for by cortical reorganization and therefore can lead to long-lasting motor and sensory impairment.

Journal article

Ogrinc Ms M, Farkhatdinov PhD I, Walker Ms R, Burdet Eet al., 2018, Horseback riding therapy for a deafblind individual enabled by a haptic interface, Assistive Technology: The Offical Journal of RESNA, Vol: 30, Pages: 143-150, ISSN: 1949-3614

We present a haptic interface to help deafblind people to practice horseback riding as a recreational and therapeutic activity. Horseback riding is a form of therapy which can improve self-esteem and sensation of independence. It has been shown to benefit people with various medical conditions-including autism. However, in the case of deafblind riders, an interpreter must stand by at all times to communicate with the rider by touch. We developed a simple interface that enables deafblind people to enjoy horseback riding while the instructor is remotely providing cues, which improves their independence. Experiments demonstrated that an autistic deafblind individual exhibits similar responses to navigational cues as an unimpaired rider. Motivation is an important factor in therapy, and is frequently determinant of its outcome; therefore, the user attitude toward the therapy methods is key. The answers to questionnaires filled by the rider, family, and the instructor show that our technique gives the rider a greater sense of independence and more joy compared to standard riding where the instructor is walking along with the horse.

Journal article

Takagi A, Usai F, Ganesh G, Sanguineti V, Burdet Eet al., 2018, Haptic communication between humans is tuned by the hard or soft mechanics of interaction, PLoS Computational Biology, Vol: 14, ISSN: 1553-734X

To move a hard table together, humans may coordinate by following the dominant partner's motion [1-4], but this strategy is unsuitable for a soft mattress where the perceived forces are small. How do partners readily coordinate in such differing interaction dynamics? To address this, we investigated how pairs tracked a target using flexion-extension of their wrists, which were coupled by a hard, medium or soft virtual elastic band. Tracking performance monotonically increased with a stiffer band for the worse partner, who had higher tracking error, at the cost of the skilled partner's muscular effort. This suggests that the worse partner followed the skilled one's lead, but simulations show that the results are better explained by a model where partners share movement goals through the forces, whilst the coupling dynamics determine the capacity of communicable information. This model elucidates the versatile mechanism by which humans can coordinate during both hard and soft physical interactions to ensure maximum performance with minimal effort.

Journal article

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