Design and Evaluation of Robust Control Methods for Robotic Transfemoral Prostheses

Nitish Thatte
2019
Amputees face a number of gait deficits due to a lack of control and power from their mechanically-passive prostheses. Of crucial importance among these deficits are those related to balance, as falls and a fear of falling can cause an avoidance of activity that leads to further debilitation. In this thesis, we investigate the role that prosthesis control strategies play in maintaining balance with a powered robotic transfemoral prosthesis. Our approach involves comparing state-of-the-art
more » ... esis controllers on a common platform and learning from this experiment to propose two new prosthesis controlstrategies that directly address observed causes of falls in both the swing and stance phases. We begin by designing and manufacturing our own powered transfemoral prosthesis capable of large torques for stumble recovery and accurate reproduction of desired torques from different controlstrategies. We also propose a pair of optimization methods that allow us to select prosthesis control parameters using qualitative preference feedback from the user. Next, we test a hypothesis that a stance control approach based ona model of the human neuromuscular system may help improve gait robustness and user satisfaction over the commonly used impedance control method. This hypothesis stems from previous research applying neuromuscular control to simulated biped models and to poweredankle prostheses that suggests that this approach can adapt to changes in speed, incline, and rough ground. While our experiment did not find a significant reduction in falls using neuromuscular control, it did reveal that a lack of robust gait phase estimation caused a large number of falls for the impedance control strategy and that both controllers suffered from trips during swing. Therefore, we next proposed and tested two new control strategiesthat directly address these causes of falls. In the first, we use information from an inertial measurement unit and a LIDAR distance sensor to estimate the position, orientation and fu [...]
doi:10.1184/r1/8397551 fatcat:ouzitvlnqfa2zgudsuwjpz26ha