An Adaptive Hybrid Control Architecture for an Active Transfemoral Prosthesis

Abstract

The daily usage of a prosthesis for people with an amputation consists of phases of intermittent and continuous walking patterns. Based on this observation, this paper introduces a novel hybrid architecture to control a transfemoral prosthesis, where separate algorithms are used depending on these two different types of movement. For intermittent walking, an interpolation-based algorithm generates control signals for the ankle and knee joints, whereas, for continuous walking, the control signals are generated utilizing an adaptive frequency oscillator. A switching strategy that allows for smooth transitioning from one controller to another is also presented in the design of the architecture. The individual algorithms for the generation of the joints angles' references, along with the switching strategy were experimentally validated on a pilot test with a healthy subject wearing an able-bodied adapter and a designed transfemoral prosthesis. The results demonstrate the capability of the individual algorithms to generate the required control signals while undergoing smooth transitions when required. Through the use of a combination of interpolation and adaptive frequency oscillator-based methods, the controller also demonstrates its response adaptation capability to various walking speeds.INDEX TERMS Prosthetics, rehabilitation robotics, control design.

Toward Controlling Transtibial Prostheses Using a Single Degree of Freedom Inertial Sensor System

“…process by which the required motor speed during a gait segment was calculated by dividing the standard gait-segment speed by the ratio of standard gait cycle time [36] to the time taken by the subject during the previous gait cycle, ensured the possibility of an infinitely varying gait speed. In the current implementation, the determination of whether the subject is at rest or walking is achieved by counting the number of steps taken with the prosthesis [37]. As long as the step count remains 0, the prosthesis is considered to be at rest, and the controller maintains a neutral angle.…”

“…However, due to the nature of the data in the Y axis throughout the gait cycle, it is difficult to directly utilize the Y accelerometer data alone to uniquely identify the stance and swing phases of the gait. To use the Y accelerometer data for this characterization, it is possible to couple it with an oscillator of variable phase and frequency, as shown in our previous work [37]. However, since changes to the oscillator parameters require at least a couple of gait cycles, an alternative control method is investigated in this study.…”

Design, Kinematics and Gait Analysis, of Prosthetic Knee Joints: A Systematic Review

“…Investigation of kinematic and kinetic parameters showed that weight-activated braking knee had prolonged swing-phase duration, a higher range of motion, earlier ankle push-off, and greater anterior pelvic tilt. Moreover, two distinct algorithms for intermittent and continuous walking created command signals for the knee and ankle joints, as well as a transition strategy from one method to the other [50]. They followed knee accelerations, number of steps taken, knee and ankle joint references, gait phase, and detected mode of the prosthesis to produce requisite command signals for smooth switching as per requirement.…”