A Semi-Powered Ankle Prosthesis and Unified Controller for Level and Sloped Walking

Bartlett, H.; King, Serina; Goldfarb, Michael; Lawson, Brian E.

doi:10.1109/tnsre.2021.3049194

Cited by 29 publications

(31 citation statements)

References 51 publications

(78 reference statements)

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“…While [33], [37], [38], [42] enabled variable-speed walking and [38] enabled obstacle crossing, these approaches were limited to level ground and relied on an FSM to switch between regions of the nonlinear quasi-stiffness curve during stance. Similarly, a quasi-passive ankle prosthesis presented in [43] enabled variable-incline walking with limited tuning by implementing a constant external quasi-stiffness relationship between the global shank angle and ankle torque. This external quasi-stiffness relationship was shown to be invariant across inclines during midstance, obviating the need for real-time incline estimation.…”

Section: Related Workmentioning

confidence: 99%

Data-Driven Variable Impedance Control of a Powered Knee–Ankle Prosthesis for Adaptive Speed and Incline Walking

et al. 2023

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Most impedance-based walking controllers for powered knee-ankle prostheses use a finite state machine with dozens of user-specific parameters that require manual tuning by technical experts. These parameters are only appropriate near the task (e.g., walking speed and incline) at which they were tuned, necessitating many different parameter sets for variable-task walking. In contrast, this paper presents a datadriven, phase-based controller for variable-task walking that uses continuously-variable impedance control during stance and kinematic control during swing to enable biomimetic locomotion. After generating a data-driven model of variable joint impedance with convex optimization, we implement a novel task-invariant phase variable and real-time estimates of speed and incline to enable autonomous task adaptation. Experiments with aboveknee amputee participants (N=2) show that our data-driven controller 1) features highly-linear phase estimates and accurate task estimates, 2) produces biomimetic kinematic and kinetic trends as task varies, leading to low errors relative to able-bodied references, and 3) produces biomimetic joint work and cadence trends as task varies. We show that the presented controller meets and often exceeds the performance of a benchmark finite state machine controller for our two participants, without requiring manual impedance tuning.

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Section: Related Workmentioning

confidence: 99%

Data-Driven Variable Impedance Control of a Powered Knee–Ankle Prosthesis for Adaptive Speed and Incline Walking

et al. 2023

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“…By relaxing the actuation speed and torque requirements, these semi-active and quasi-passive prostheses can be made lighter and smaller and still achieve longer battery life than fully powered prostheses. For example, designing the knee actuator to power only stair ambulation (33,34) or only the swing phase of gait (32,40) leads to a lighter and smaller prosthesis. Similarly, lighter and smaller ankle/foot prostheses can be developed by avoiding net-positive energy injection (41), limiting the active control of movements to non-weight-bearing activities (38,42), or adjusting the mechanical stiffness of the prosthetic joint (37).…”

Section: Introductionmentioning

confidence: 99%

A lightweight robotic leg prosthesis replicating the biomechanics of the knee, ankle, and toe joint

et al. 2022

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Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.

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“…Joint quasi-stiffness during human walking has been useful in control systems of robotic exoskeletons, prostheses, and bipedal robots which mimic the normal biomechanical behaviour of the human lower limb [10][11][12]. A common control method for wearable robotics is to set the relative impedances (e.g.…”

Section: Introductionmentioning

confidence: 99%

Effects of simulated reduced gravity and walking speed on ankle, knee, and hip quasi-stiffness in overground walking

MacLean

Ferris

2022

PLoS ONE

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Quasi-stiffness characterizes the dynamics of a joint in specific sections of stance-phase and is used in the design of wearable devices to assist walking. We sought to investigate the effect of simulated reduced gravity and walking speed on quasi-stiffness of the hip, knee, and ankle in overground walking. 12 participants walked at 0.4, 0.8, 1.2, and 1.6 m/s in 1, 0.76, 0.54, and 0.31 gravity. We defined 11 delimiting points in stance phase (4 each for the ankle and hip, 3 for the knee) and calculated the quasi-stiffness for 4 phases for both the hip and ankle, and 2 phases for the knee. The R2 value quantified the suitability of the quasi-stiffness models. We found gravity level had a significant effect on 6 phases of quasi-stiffness, while speed significantly affected the quasi-stiffness in 5 phases. We concluded that the intrinsic muscle-tendon unit stiffness was the biggest determinant of quasi-stiffness. Speed had a significant effect on the R2 of all phases of quasi-stiffness. Slow walking (0.4 m/s) was the least accurately modelled walking speed. Our findings showed adaptions in gait strategy when relative power and strength of the joints were increased in low gravity, which has implications for prosthesis and exoskeleton design.

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A Semi-Powered Ankle Prosthesis and Unified Controller for Level and Sloped Walking

Cited by 29 publications

References 51 publications

Data-Driven Variable Impedance Control of a Powered Knee–Ankle Prosthesis for Adaptive Speed and Incline Walking

Data-Driven Variable Impedance Control of a Powered Knee–Ankle Prosthesis for Adaptive Speed and Incline Walking

A lightweight robotic leg prosthesis replicating the biomechanics of the knee, ankle, and toe joint

Effects of simulated reduced gravity and walking speed on ankle, knee, and hip quasi-stiffness in overground walking

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