Characterizing what types of exoskeleton gaits are comfortable for users, and understanding the science of walking more generally, require recovering a user's utility landscape. Learning these landscapes is challenging, as walking trajectories are defined by numerous gait parameters, data collection from human trials is expensive, and user safety and comfort must be ensured. This work proposes the Region of Interest Active Learning (ROIAL) framework, which actively learns each user's underlying utility function over a region of interest that ensures safety and comfort. ROIAL learns from ordinal and preference feedback, which are more reliable feedback mechanisms than absolute numerical scores. The algorithm's performance is evaluated both in simulation and experimentally for three non-disabled subjects walking inside of a lower-body exoskeleton. ROIAL learns Bayesian posteriors that predict each exoskeleton user's utility landscape across four exoskeleton gait parameters. The algorithm discovers both commonalities and discrepancies across users' gait preferences and identifies the gait parameters that most influenced user feedback. These results demonstrate the feasibility of recovering gait utility landscapes from limited human trials.
Optimizing lower-body exoskeleton walking gaits for user comfort requires understanding users' preferences over a high-dimensional gait parameter space. However, existing preference-based learning methods have only explored low-dimensional domains due to computational limitations. To learn user preferences in high dimensions, this work presents LineCoSpar, a human-in-the-loop preference-based framework that enables optimization over many parameters by iteratively exploring one-dimensional subspaces. Additionally, this work identifies gait attributes that characterize broader preferences across…
The most concentrated application of lower-limb rehabilitation exoskeleton (LLE) robot is that it can help paraplegics "re-walk". However, "walking" in daily life is more than just walking on flat ground with fixed gait. This paper focuses on variable gaits generation for LLE robot to adapt complex walking environment. Different from traditional gaits generator for biped robot, the generated gaits for LLEs should be comfortable to patients. Inspired by the pose graph optimization algorithm in SLAM, we propose a graph-based gait generation algorithm called gait graph optimization (GGO) to gener…
California Institute of Technology（加州理工学院）；Tsinghua University（清华大学）
This paper presents a personalized gait optimization framework for lower-body exoskeletons. Rather than optimizing numerical objectives such as the mechanical cost of transport, our approach directly learns from user preferences, e.g., for comfort. Building upon work in preference-based interactive learning, we present the CoSpar algorithm. CoSpar prompts the user to give pairwise preferences between trials and suggest improvements; as exoskeleton walking is a non-intuitive behavior, users can provide preferences more easily and reliably than numerical feedback. We show that CoSpar performs co…
ETH Zurich（苏黎世联邦理工学院）；Balgrist University Hospital（巴尔格里斯特大学医院）；University of Zurich（苏黎世大学）
Spinal cord injuries frequently impair the ability to walk. Powered lower limb exoskeletons offer a promising solution to restore walking ability. However, they are currently restricted to even ground. We hypothesized that compliant exoskeleton knees could decrease required effort to maneuver on uneven terrain, and increase gait velocity and stability. We describe a case study of a motor-complete spinal cord injury user (AIS A, Th12) walking with a powered exoskeleton on even and uneven ground over multiple sessions after extensive training. Measurements with compliant or rigid exoskeleton kne…
University Hospital of Freiburg（弗莱堡大学医院）；Scuola Superiore Sant’Anna（圣安娜高等研究院）
Lower limbs exoskeletons provide assistance during standing, squatting, and walking. Gait dynamics, in particular, implies a change in the configuration of the device in terms of contact points, actuation, and system dynamics in general. In order to provide a comfortable experience and maximize performance, the exoskeleton should be controlled smoothly and in a transparent way, which means respectively, minimizing the interaction forces with the user and jerky behavior due to transitions between different configurations. A previous study showed that a smooth control of the exoskeleton can be a…
The City University of New York, City College（纽约市立大学城市学院）
Pediatric exoskeletons offer great promise to increase mobility for children with crouch gait caused by cerebral palsy. A lightweight, compliant and user-specific actuator is critical for maximizing the benefits of an exoskeleton to users. To date, pediatric exoskeletons generally use the same actuators as adult exoskeletons, which are heavy and resistive to natural movement. There is yet no easy way for robotic exoskeletons to accommodate the changes in design requirements that occur as a child ages. We developed a lightweight (1.65 kg unilateral mass) and compliant pediatric knee exoskeleton…
Positive biomechanical outcomes have been reported with lower-limb exoskeletons in laboratory settings, but these devices have difficulty delivering appropriate assistance in synchrony with human gait as the task or rate of phase progression change in real-world environments. This paper presents a controller for an ankle exoskeleton that uses a data-driven kinematic model to continuously estimate the phase, phase rate, stride length, and ground incline states during locomotion, which enables the real-time adaptation of torque assistance to match human torques observed in a multi-activity datab…
Therapist-Exoskeleton-Patient Interaction for Gait Therapy
Shirley Ryan AbilityLab；Center for Robotics and Biosystems（机器人与生物系统中心）；Department of Biomedical Engineering（生物医学工程系）；Department of Mechanical Engineering（机械工程系）；Department of Physical Medicine and Rehabilitation（康复医学系）
Synthesizing Robust Walking Gaits via Discrete-Time Barrier Functions with Application to Multi-Contact Exoskeleton Locomotion
Georgia Institute of Technology（佐治亚理工学院）；School of Electrical and Computer Engineering（电气与计算机工程学院）；Woodruff School of Mechanical Engineering（伍德拉夫机械工程学院）；California Institute of Technology（加州理工学院）；Department of Computation and Neural Systems（计算与神经系统系）；Department of Mechanical and Civil Engineering（机械与土木工程系）；Department of Control and Dynamical Systems（控制与动力学系）
Lower extremity exoskeleton has been developed as a motion assistive technology in recent years. Walking pattern generation is a fundamental topic in the design of these robots. The usual approach with most exoskeletons is to use a pre-recorded pattern as a look-up table. There are some deficiencies with this method, including data storage limitation and poor regulation relating to the walking parameters. Therefore modeling human walking patterns to use in exoskeletons is required. The few existing models provide piece by piece walking patterns, only generating at the beginning of each stride …
California Institute of Technology（加州理工学院）；Wandercraft（Wandercraft公司）
This paper presents and experimentally demonstrates a novel framework for variable assistance on lower body exoskeletons, based upon safety-critical control methods. Existing work has shown that providing some freedom of movement around a nominal gait, instead of rigidly following it, accelerates the spinal learning process of people with a walking impediment when using a lower body exoskeleton. With this as motivation, we present a method to accurately control how much a subject is allowed to deviate from a given gait while ensuring robustness to patient perturbation. This method leverages co…
California Institute of Technology（加州理工学院）；Wandercraft SAS（旺德工艺有限公司）
This paper presents an active stabilization method for a fully actuated lower-limb exoskeleton. The method was tested on the exoskeleton ATALANTE, which was designed and built by the French start-up company Wandercraft. The main objective of this paper is to present a practical method of realizing more robust walking on hardware through active ankle compensation. The nominal gait was generated through the hybrid zero dynamic framework. The ankles are individually controlled to establish three main directives; (1) keeping the non-stance foot parallel to the ground, (2) maintaining rigid contact…
Unidirectional Human-Robot-Human Physical Interaction for Gait Training
The Biorobotics Institute, Scuola Superiore Sant’Anna（圣安娜高等学校生物机器人研究所）；Department of Excellence in Robotics & AI, Scuola Superiore Sant’Anna（圣安娜高等学校机器人与人工智能卓越系）；Shirley Ryan AbilityLab（雪莉·瑞安能力实验室）；Center for Robotics and Biosystems of Northwestern University（西北大学机器人与生物系统中心）；Department of Biomedical Engineering, Northwestern University（西北大学生物医学工程系）；Department of Physical Medicine and Rehabilitation, Northwestern University（西北大学物理医学与康复系）
Human Locomotion Implicit Modeling Based Real-Time Gait Phase Estimation
Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education（生物力学与机械生物学重点实验室（北京航空航天大学）教育部）；Key Laboratory of Innovation and Transformation of Advanced Medical Devices, Ministry of Industry and Information Technology（先进医疗设备创新与转化重点实验室（工业和信息化部））；National Medical Innovation Platform for Industry-Education Integration in Advanced Medical Devices (Interdiscipline of Medicine and Engineering)（先进医疗设备产业教育融合国家级创新平台（医学与工程交叉学科））；School of Biological Science and Medical Engineering, Beihang University（生物科学与医学工程学院（北京航空航天大学））
The Impact of Gait Pattern Personalization on the Perception of Rigid Robotic Guidance: A Pilot User Experience Evaluation
Cognitive Robotics Department, Delft University of Technology（代尔夫特理工大学认知机器人学系）；Department of Rehabilitation Medicine, Erasmus Medical Centre（伊拉斯姆斯医学中心康复医学系）；Department of Biomechanical Engineering, Delft University of Technology（代尔夫特理工大学生物力学工程系）；Institute of Automatic Control, RWTH Aachen University（亚琛工业大学自动控制研究所）；Department of Mechanical Engineering, FUM Center of Advanced Rehabilitation and Robotics Research (FUM CARE), Ferdowsi University of Mashhad（菲尔多西大学机械工程系先进康复与机器人研究中心）；Walker Department of Mechanical Engineering, University of Texas at Austin（德克萨斯大学奥斯汀分校沃克机械工程系）
The ability to generate robust walking gaits on bipedal robots is key to their successful realization on hardware. To this end, this work extends the method of Hybrid Zero Dynamics (HZD) -- which traditionally only accounts for locomotive stability via periodicity constraints under perfect impact events -- through the inclusion of the saltation matrix with a view toward synthesizing robust walking gaits. By jointly minimizing the norm of the extended saltation matrix and the torque of the robot directly in the gait generation process, we demonstrate that the synthesized gaits are more robust t…
Hong Kong University of Science and Technology（香港科技大学）
Recently, the lower limb exoskeletons which providemobility for paraplegic patients to support their daily life havedrawn much attention. However, the pilots are required to applyexcessive force through a pair of crutches to maintain balanceduring walking. This paper proposes a novel gait trajectorygeneration algorithm for exoskeleton locomotion on flat groundand stair which aims to minimize the force applied by the pilotwithout increasing the degree of freedom (DoF) of the system.First, the system is modelled as a five-link mechanism dynam-ically for torque computing. Then, an optimization ap…
Detecting Heel Strike and toe off Events Using Kinematic Methods and LSTM Models
School of Artificial Intelligence and Robotics, Hunan University（湖南大学人工智能与机器人学院）；School of Mechanical and Aerospace Engineering, Nanyang Technological University（南洋理工大学机械与航空航天工程学院）；Fourth Hospital of Changsha, Hunan Normal University（长沙第四医院，湖南师范大学）；Department of Stomatology, Hunan Provincial People’s Hospital, Hunan Normal University（湖南省级人民医院口腔科，湖南师范大学）；Rehabilitation Research Institute of Singapore, Lee Kong Chian School of Medicine, Nanyang Technological University（新加坡康复研究中心，李光前医学院，南洋理工大学）
This work presents a description of the EXOSMOOTH project, oriented to the benchmarking of lower limb exoskeletons performance. In the field of assisted walking by powered lower limb exoskeletons, the EXOSMOOTH project proposes an experiment that targets two scientific questions. The first question is related to the effectiveness of a novel control strategy for smooth assistance. Current assist strategies are based on controllers that switch the assistance level based on the gait segmentation provided by a finite state machine. The proposed strategy aims at managing phase transitions to provid…
