An experimental robotic testbed for accelerated development of ankle prostheses

Caputo, Joshua M.; Collins, Susan M.

doi:10.1109/icra.2013.6630940

Cited by 34 publications

(31 citation statements)

References 29 publications

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“…5), we measured net ankle joint work values of À4.8 6 0.7, 2.2 6 0.8, 7.9 6 1.3, 14.4 6 1.9, and 20.9 6 2.6 J, again including variability due to natural variations in human stride kinematics. Average stance duration was 0.58 6 0.02 s and average stride period was 1.15 6 0.05 s. These results demonstrate incremental improvements on results from earlier walking trials with an able-bodied subject wearing a simulator boot [49].…”

Section: Resultssupporting

confidence: 61%

A Universal Ankle–Foot Prosthesis Emulator for Human Locomotion Experiments

Caputo

Collins

2014

Journal of Biomechanical Engineering

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139

107

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Robotic prostheses have the potential to significantly improve mobility for people with lower-limb amputation. Humans exhibit complex responses to mechanical interactions with these devices, however, and computational models are not yet able to predict such responses meaningfully. Experiments therefore play a critical role in development, but have been limited by the use of productlike prototypes, each requiring years of development and specialized for a narrow range of functions. Here we describe a robotic ankle-foot prosthesis system that enables rapid exploration of a wide range of dynamical behaviors in experiments with human subjects. This emulator comprises powerful off-board motor and control hardware, a flexible Bowden cable tether, and a lightweight instrumented prosthesis, resulting in a combination of low mass worn by the human (0.96 kg) and high mechatronic performance compared to prior platforms. Benchtop tests demonstrated closedloop torque bandwidth of 17 Hz, peak torque of 175 Nm, and peak power of 1.0 kW. Tests with an anthropomorphic pendulum "leg" demonstrated low interference from the tether, less than 1 Nm about the hip. This combination of low worn mass, high bandwidth, high torque, and unrestricted movement makes the platform exceptionally versatile. To demonstrate suitability for human experiments, we performed preliminary tests in which a subject with unilateral transtibial amputation walked on a treadmill at 1.25 ms À1 while the prosthesis behaved in various ways. These tests revealed low torque tracking error (RMS error of 2.8 Nm) and the capacity to systematically vary work production or absorption across a broad range (from À5 to 21 J per step). These results support the use of robotic emulators during early stage assessment of proposed device functionalities and for scientific study of fundamental aspects of human-robot interaction. The design of simple, alternate end-effectors would enable studies at other joints or with additional degrees of freedom.

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Section: Resultssupporting

confidence: 61%

A Universal Ankle–Foot Prosthesis Emulator for Human Locomotion Experiments

Caputo

Collins

2014

Journal of Biomechanical Engineering

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139

107

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“…In pilot tests with the Beta device, we found that very stiff or very compliant elastic elements worsened torque tracking errors. This was not the case for a prosthetic device we recently developed [22], in which the Bowden cable itself seemed to provide sufficient series compliance. This may be because the prosthesis is in series with the limb, and therefore receives more predictable loading from the user.…”

Section: Discussionmentioning

confidence: 98%

Design of two lightweight, high-bandwidth torque-controlled ankle exoskeletons

Witte

Zhang

Jackson

et al. 2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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103

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Abstract-Lower-limb exoskeletons that can comfortably apply high torques at high bandwidth can be used to probe the human neuromuscular system and assist gait. We designed and built two tethered ankle-foot exoskeletons with strong lightweight frames, comfortable three-point contact with the leg, and series elastic elements for improved torque control. Both devices have low mass (< 0.87 kg), are modular and structurally compliant in selected directions, and are instrumented to measure joint angle and torque. The exoskeletons are actuated by an offboard motor, and torque is controlled using a combination of proportional feedback, damping injection and iterative learning. We tested closed-loop torque control by commanding 50 N·m and 20 N·m linear chirps in desired torque while the exoskeletons were worn by human users, and measured bandwidths greater than 16 Hz and 21 Hz, respectively. During walking trials, we demonstrated 120 N·m peak torque and 2.0 N·m RMS torque tracking error. These performance measures compare favorably with previous devices and with human ankle musculature, and show that these exoskeletons can be used to rapidly explore a wide range of control techniques and robotic assistance paradigms as elements of versatile, high-performance testbeds. Our results also provide insights into desirable properties of lower-limb exoskeleton hardware, which we expect to inform future designs.

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“…This large dynamic range is attributed to the tethered system that enabled large power capability without the commensurate cost of added actuator mass. Others have made use of this type of platform for this reason [30,31]. Unlike other researchers, however, our use of a cable linkage mitigates transmission losses in the cable drive compared to a pure Bowden cable transmission, since only part of the cable is in contact with the conduit surfaces.…”

Section: Discussionmentioning

confidence: 95%

Development and Evaluation of a Powered Artificial Gastrocnemius for Transtibial Amputee Gait

Eilenberg

Kuan

Herr

2018

Journal of Robotics

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Existing robotic transtibial prostheses provide only ankle joint actuation and do not restore biarticular function of the gastrocnemius muscle. This paper presents the first powered biarticular transtibial prosthesis, which is a combination of a commercial powered ankle-foot prosthesis and a motorized robotic knee orthosis. The orthosis is controlled to emulate the human gastrocnemius based on neuromuscular models of matched nonamputees. Together with the ankle-foot prosthesis, the devices provide biarticular actuation. We evaluate differences between this biarticular condition and a monoarticular condition with the orthosis behaving as a free-joint. Six participants with transtibial amputation walk with the prosthesis on a treadmill while motion, force, and metabolic data are collected and analyzed for differences between conditions. The biarticular prosthesis reduces affectedside biological knee flexion moment impulse and hip positive work during late-stance knee flexion, compared to the monoarticular condition. The data do not support our hypothesis that metabolism decreases for all participants, but some participants demonstrate large metabolic reductions with the biarticular condition. These preliminary results suggest that a powered artificial gastrocnemius may be capable of providing large metabolic reductions compared to a monoarticular prosthesis, but further study is warranted to determine an appropriate controller for achieving more consistent metabolic benefits.

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An experimental robotic testbed for accelerated development of ankle prostheses

Cited by 34 publications

References 29 publications

A Universal Ankle–Foot Prosthesis Emulator for Human Locomotion Experiments

A Universal Ankle–Foot Prosthesis Emulator for Human Locomotion Experiments

Design of two lightweight, high-bandwidth torque-controlled ankle exoskeletons

Development and Evaluation of a Powered Artificial Gastrocnemius for Transtibial Amputee Gait

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