Design and evaluation of bio-inspired control strategies for transfemoral prosthesis

Despite recent developments in solutions to replace the missing limb of transfemoral amputees and restore natural locomotion, the use of these solutions remains limited. To date, the potential benefit of using powered prostheses is strongly impacted by the challenges that are yet to be addressed regarding their development, both on their design and control methods. An emerging trend for building the control strategies for the prostheses actuators takes advantage of bio-inspiration, i.e. the control laws rely on biological principles that have been highlighted in healthy locomotion. In this dissertation, bio-inspired control strategies for a powered transfemoral prosthesis are presented. The following biological concepts are explored throughout this work: (i) Central Pattern Generators (CPGs), which can be seen as a set of coupled oscillators responsible for providing the rhythmic characteristics of locomotion; (ii) motor primitives, which are considered to be the principal components of muscles stimulations; and (iii) the inverse internal models of the cerebellum, which plays an essential role in motor learning and adaptation. This dissertation presents three bio-inspired controllers for a representative compliant prosthesis equipped with series-elastic knee and ankle joints. The three control architectures rely on compliant position tracking by combining a feed-forward torque component with an impedance-based torque component for both joints of the prosthesis. The first controller simply incorporates reference torque and angle profiles associated to healthy walking that were taken from the literature, and it is mainly used to validate the feasibility of torque-based control strategies for the prosthesis without the need for torque sensing. The second version of the controller includes artificial, Gaussian-like torque and angular primitives which, through proper recombination, generate the reference torque and angle patterns for both joints. It also integrates an artificial CPG implemented by an adaptive oscillator which continuously detects the global locomotion parameters. The last version of the controller incorporates an iterative learning mechanism to compute a feed-forward prediction torque component for both joints. This adaptive process uses the Locally Weighted Projection Regression (LWPR) algorithm to continuously learn the inverse internal model of the prosthesis joints. The dissertation reports three sets of experiments performed to validate the developed controllers. The first experiment involved a transfemoral amputee walking on a treadmill. It aimed at validating the feasibility of implementing torque control strategies on the actuated elastic transfemoral prosthesis and used the first controller. It showed that static modelling of the prosthesis geometrical and elastic relationships is appropriate for converting desired torques for the prosthesis joints into positions for its actuators. The next set of experiments investigated the use of artificial primitives in the second controller and the role of the feed-forward torque component for the knee and ankle joints. Two experiments were conducted with a transfemoral amputee walking on a treadmill, first at self-selected speed and then at different speeds. They emphasized the relevance of the primitives-based, feed-forward torque component for both joints and its capacity to increase the controller's compliance. They also revealed that combining artificial primitives with an adaptive oscillator is appropriate for the control of transfemoral prostheses, although the capacity of the controller to adapt the delivered torque patterns to the walking speed could not be demonstrated. The third set of experiments assessed the performance of the iterative learning mechanism included in the third controller. It was performed on a simulated biped walker with a transfemoral amputation as a first validation of the controller before its implementation on a real prosthesis. The simulations highlighted the capacity of LWPR to act as the inverse internal model of the prosthesis joints and to provide accurate feed-forward torque commands to achieve a desired state, while being robust to speed changes. The contribution of the feed-forward component allowed to significantly decrease the gains of the feedback torque component, increasing the controller's compliance.(FSA - Sciences de l'ingénieur) -- UCL, 202

Glaubwürdigkeit oder Greenwashing? Welches Ziel verfolgt das Design von Nachhaltigkeitsberichten

Nachhaltigkeit als Leitidee bedingt einen Diskurs, mit dem Ziel eine Balance zwischen den Dimensionen Ökologie, Ökonomie, Soziales und Kultur (je nach herangezogenem Modell) herzustellen. Um die dazu not-wendigen nachhaltigen Aktivitäten, Ziele, Werte usw. umsetzen zu können ist ein fortlaufender Kommunikationsprozess erforderlich. Im Rahmen dieses Diskurses spielt Design eine bedeutende Rolle vor allem in Bezug auf das kommunikative Wirkziel: Glaubwürdigkeit schaffen. Ins-besondere in Systemen wie Unternehmen und Organisationen, denen eine Mitschuld an den Problemen der Erde und der Menschheit gegeben wird, ist die Kommunikation ihrer Verantwortung und damit verbundenen Aktivitäten für eine nachhaltige Entwicklung unerlässlich, um ihre Legitimität zu sichern. Die Corporate Social Responsibility (CSR) Kommunikation von Unternehmen und Organisationen manifestiert sich hauptsächlich in Form eines Rechenschaftsberichts (Nachhaltigkeitsbericht, CSR-Report) wobei dieser als gestaltetes Medium sowohl auf der textlichen als auch auf der visuellen Ebene argumentiert und mittels Glaubwürdigkeit das Vertrauen der Stakeholder und Leser gewinnen soll. Glaubwürdigkeit ist in Zeiten von Greenwashing und ‚Fake News‘ das wichtigste Qualitätskriterium auch für die visuelle Kommunikation

Online Learning of the Dynamical Internal Model of Transfemoral Prosthesis for Enhancing Compliance

Powered prostheses hold promises to restore adaptive and robust locomotor functions to lower-limb amputees. However, their daily use is still challenged by several shortcomings, on top of which those related to their control methods. This paper reports the development of a compliant controller for a transfemoral prosthesis that combines an online predictive torque component with a feedback error correction mechanism. The controller architecture relies on joint position tracking. The predictive module is based on the Locally Weighted Projection Regression (LWPR) algorithm that achieves nonlinear function approximation of a dynamic model of the prosthesis joints. The performance of the proposed control strategy are assessed with a simulated biped walker with a unilateral transfemoral amputation. Results show that the LWPR-based module provides accurate predictions of the ankle and knee torques, resulting in a precise position tracking. This allows reducing the gains of the feedback error correction mechanism by one order of magnitude, leading to a feedback contribution to the total joint torque lower than 3\% and 8\% for the ankle and the knee joints respectively. The prosthesis compliance for both joints is enhanced accordingly. In addition, the control architecture is robust to speed changes while the joint dynamic internal model is continuously learned. This approach is thus promising for the development of adaptive controllers for lower-limb prostheses

Torque control of an active elastic transfemoral prosthesis via quasi-static modelling

Developing mechanical devices to restore natural locomotion for transfemoral amputees still raises many challenges. One of them is the development of an efficient control strategy for the prosthesis active joints, with the objective of making it flexible and intuitive to use. This paper focuses on the transfemoral CYBERLEGs Beta-Prosthesis, an actuated elastic ankle–knee prosthesis embedding bio-inspired mechanisms targeting the minimization of its total power consumption. We provide the development of a bio-inspired, torque-based, controller for this device, requiring no torque sensing. Torque control is achieved by means of static modelling of the prosthesis geometrical and elastic relationships. Bench testing of the prosthesis was performed to show that this static model is able to accurately predict the actual behaviour of the device. The model was then used to build the low-level controller of the prosthesis, converting desired torques into reference positions for the joint actuators. Next, a walking experiment with a transfemoral amputee was conducted to assess the feasibility of a torque-based control approach for the prosthesis, with a simple high-level controller combining reference torque trajectories and bio-inspired joint impedances. Results validated the use of our static model for implementing the low-level controller of such an elastic and redundant prosthesis

Policy fellowship schemes as a vehicle for co-production - insights from Welsh Government fellowships

Executive Summary Objectives: Engagement between academic researchers and policymakers is becoming increasingly common. Although approaches to the so-called Science-Policy Interface (SPI) can vary substantially based on disciplines, different degrees of engagement and focus on research co-production, there are some common challenges and opportunities which this paper discusses. Analytic/Methodological Approach: We draw on the experience of four academic policy fellowships with the Welsh Government (WG) running in 2021-2023; we explore the different roles social sciences researchers can play working with governments, and how these map onto different research phases and user needs. Our discussion builds on established SPI literature to reflect on how policy fellowships can offer a platform for deeper and fully-fledged SPI focused on co-production. Key Findings: We find that policy fellowships can be effective mechanisms to embed research and research co-production in policymaking. These schemes are highly variable but present some common challenges and opportunities. In particular, while they enable researchers to have deeper insights into government working, it is important to have a clear communication about reciprocal expectations and need when defining the focus and scope of the research. Furthermore, policy fellows can be exposed to organisational challenges, such as high job turnover. Clearly aligning research projects conducted by fellows to overarching organisational priorities can help overcoming some of these challenges. Conclusions: As policy fellowships can vary substantially even within the same scheme, the fellowship holder has the opportunity to negotiate and define their roles within the host organisations to match the research needs and maximise research impact. We also identify new challenges that policy fellowships can bring about for academic researchers engaging in extensive SPI projects and call for the SPI community (funders, research institutions and host organisations) to openly discuss how to best support researchers pursuing a SPI-focussed career. Recommendations: Governments and public policy organisations should consider policy fellowships as effective mechanisms to embed research and research coproduction practice in policymaking. When hosting a policy fellow, they should allow time and space to develop reciprocal knowledge of needs and expectations. The research community and host organisations need to clearly articulate the added value and the tangible and intangible benefits of policy fellowships beyond traditional academic metrics

Compliant Control of a Transfemoral Prosthesis Combining Predictive Learning and Primitive-Based Reference Trajectories

This paper reports the development of a novel compliant controller for a transfemoral prosthesis that combines a feed-forward prediction torque component with a feedback error correction. The controller architecture aims to track primitive-based reference trajectories by the prosthetic joints. It relies on Locally Weighted Projection Regression, a function approximator that acts as an inverse internal model of the prosthesis. The proposed strategy is validated in a simulation environment

Policy fellowship schemes as a vehicle for co-production – insights from Welsh Government Fellowships

Engagement between academic researchers and policy makers is becoming increasingly common. Although approaches to the so-called Science-Policy Interface (SPI) can vary substantially – based on disciplines, different degrees of engagement and focus on research co-production – there are some common challenges and opportunities, which this paper discusses

Motor and cognitive combined control system for upper limb robot assisted rehabilitation after stroke

Question: Despite intensive rehabilitation, stroke patients keep neurological impairments limiting their activities of daily living. To improve upper limb (UL) rehabilitation, current guidelines recommend robotic assisted therapy (RAT). To date, RAT relies on assisted-as-needed (AAN) principles. New treatment modalities, combining simultaneous motor and cognitive rehabilitation, aim for better recovery outcomes. Our team developed ROBiGAME, a serious game that simultaneously rehabilitates motor and cognitive functions and continuously regulates game difficulty. Exercise characteristics are continuously adapted according to the patients’ performances during the game. This study investigated whether this dynamic difficulty adjustment is optimal according to neurorehabilitation principles of variable practice and increasing difficulty (using as optimal success rate of 75%). Method: 9 stroke patients were enrolled in a 5-day protocol. Clinical and robot-based assessment (including Fugl-Meyer Assessment (FMA) and Action Research Arm Test (ARAT)) was done during the first two sessions. Then, every participant completed three 30 minutes sessions of RAT playing with ROBiGAME. Initial low level of game difficulty was set to be the same for every participant at the beginning of the first session. Patients’ performance and the serious game’s exercise characteristics were recorded throughout the sessions. Results: Motor difficulty parameters oscillate towards a steady state half-way through the first session (after 10 to 15 exercises) underlying a rapid adaptation of the system to every individual. In addition, mean success rates average 74,55% ±3% indicating an optimal success rate to maintain patients’ motivation. Finally, FMA and ARAT scores strongly correlated to haptic assistance indices (FMA:r=0,95 p<0,001; ARAT: r=0,87 p=0,005) showing that motor difficulty adapts well to the severity of patients’ motor impairment. Conclusions: This study demonstrates that continuous motor difficulty adjustment when using ROBiGAME is adapted to the patients’ degree of impairment and remains optimal throughout treatment. Further investigations on how cognitive parameters influence game difficulty adjustment and arm kinematics indices should be done

INNOVATIONS EN MÉDECINE PHYSIQUE ET RÉADAPTATION QUE RETENIR DE 2016 ?

Suite à une lésion cérébrale, les troubles moteurs et cognitifs sont fréquents et leur rééducation constitue un défi de longue haleine pour les patients et les thérapeutes. Ces dernières années, la robotique et les jeux sérieux se sont fortement développés dans ce domaine afin d’augmenter la récupération fonctionnelle des patients. La robotique permet d’intensifier la thérapie, d’assister le mouvement du patient et de lui fournir un feedback. Quant aux jeux sérieux, ils rendent la rééducation ludique et motivante et le niveau de difficulté du jeu s’adapte continuellement aux performances du patient. Ces deux technologies complémentaires sont donc prometteuses dans la rééducation des patients cérébro-lésés

L’apport de nouvelles technologies dans la rééducation motrice et cognitive des patients cérébro-lésés

Suite à une lésion cérébrale, les troubles moteurs et cognitifs sont fréquents et leur rééducation constitue un réel défi pour les patients et les thérapeutes. Ces dernières années, la robotique et les jeux sérieux se sont fortement développés dans ce domaine afin d’augmenter la récupération fonctionnelle des patients. La robotique permet d’intensifier la thérapie, d’assister le mouvement du patient et de lui fournir un feedback. Quant aux jeux sérieux, ils rendent la rééducation ludique et motivante et le niveau de difficulté du jeu s’adapte continuellement aux performances du patient. Ces deux technologies complémentaires sont donc prometteuses dans la rééducation de patients cérébro-lésés