Stand Loading Symmetry and Timing Through Unified Variable Impedance Control of a Powered Knee-Ankle Prosthesis Journal Article uri icon

Overview

abstract

  • Individuals using passive prostheses typically rely heavily on their; biological limb to complete sitting and standing tasks, leading to; slower completion times and increased rates of osteoarthritis and lower; back pain. Powered prostheses can address these challenges, but have; control methods that divide sit-stand transitions into discrete phases,; limiting user synchronization across the motion and requiring long; manual tuning times. This paper extends our preliminary work using a; thigh-based phase variable to parameterize optimized data-driven; impedance parameter trajectories for sitting, standing, and walking,; with only two classification modes. We decouple the stand-to-sit and; sit-to-stand equilibrium angles through a knee velocity-dependent; scaling term, reducing the model fitting error by approximately half; compared to our previous results. We then experimentally validate the; controller with three individuals with above-knee amputation performing; sitting and standing transitions to/from three different chair heights.; We show that our controller implemented on a powered knee-ankle; prosthesis produced biomimetic joint mechanics, resulting in; significantly reduced sit/stand loading symmetry and time to complete a; 5x sit-to-stand task compared to participants’ passive prostheses.; Integration with a previously developed walking controller also allowed; sit/walk transitions between different chair heights. The controller’s; biomimetic assistance may reduce the overreliance on the biological limb; caused by inadequate passive prostheses, helping improve mobility for; people with above-knee amputations.

publication date

  • May 31, 2023

has restriction

  • hybrid

Date in CU Experts

  • June 13, 2023 7:15 AM

Full Author List

  • Welker C; Best T; Gregg R

author count

  • 3

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