Toward Phase-Variable Control of Sit-to-Stand Motion with a Powered Knee-Ankle Prosthesis

• Main Authors: Raz, Daphna, Bolivar-Nieto, Edgar, Ozay, Necmiye, Gregg, Robert D.
• Format: Conference Proceeding
• Language: English
• Subjects: Analytical models; Biological system modeling; Mathematical models; Thigh; Torque; Torso; Trajectory
• ISSN: 2768-0762; 2768-0770
• DOI: 10.1109/CCTA48906.2021.9658844

This paper presents a new model and phase variable controller for sit-to-stand motion in above-knee amputees. The model captures the effect of work done by the sound side and residual limb on the prosthesis, while modeling only the prosthetic knee and ankle with a healthy hip joint that connects the thigh to the torso. The controller is parametrized by a biomechanical phase variable rather than time and is analyzed in simulation using the model. We show that this controller performs well with minimal tuning, under a range of realistic initial conditions and biological parameters such as height and body mass. The controller generates kinematic trajectories that are comparable to experimentally observed trajectories in non-amputees. Furthermore, the torques commanded by the controller are consistent with torque profiles and peak values of normative human sit-to-stand motion. Rise times measured in simulation and in non-amputee experiments are also similar. Finally, we compare the presented controller with a baseline proportional-derivative controller demonstrating the advantages of the phase-based design over a set-point based design.