Composite active disturbance rejection robust control for a prototype of an active damping artificial ankle prosthesis

Abstract

The problem of robust control applied to adjust the configuration of an ankle prosthesis based on disturbance estimation has been addressed in this study. Active disturbance rejection control was the paradigm used for controlling the robotic prosthesis by means of a direct active estimation. Based on this active estimation, the robust controller implemented the disturbance cancellation providing a fast converge to the origin of the tracking error. The uncertainties affecting the prosthesis dynamics were identified by a high‐order extended state high gain observer. This identification was used to force the tracking between the actual position and force needed in the ankle prosthesis and some reference values obtained by a biomechanical gait cycle analysis. Therefore, the estimated states were used to implement a robust output feedback controller that was effective to reject actively the perturbations. This rejection implemented within the controller forced the trajectory tracking to a small vicinity of the origin. A strategy based on composite Lyapunov function served to prove that tracking problem for the prosthesis was successfully solved despite the switching nature of the gait cycle. The controller was implemented in numerical simulations for showing the convergence of the tracking error. The convergence of this tracking error to the region around the origin was obtained within the first second of simulation.

An Improved Active Disturbance Rejection Control for Bode's Ideal Transfer Function

“…Then, Theorem 3.1 will present the bounded-input boundedoutput (BIBO) stability of the error system (19), when h if o is bounded. Theorem 3.2 gives the BIBO condition for the closed-loop system using characteristic equation method.…”

“…The integer-order active disturbance rejection control (IO-ADRC) proposed by Gao [16] provides a strategy for control system design with uncertainties. The core idea of IO-ADRC is to improve the robustness of the system using extended state observer (IO-ESO, or extended high-gain observer) [17], [18] to estimate the total disturbances, including internal disturbance caused by system uncertainties and external disturbance [19], [20]. Inspired by the ADRC structure, a fractional-order ADRC (FO-ADRC) was proposed in [15], and approximately converted a class of integer-order systems into a weighted Bode's ideal transfer function (WBITF).…”

The control methods of Knee‐Ankle‐Toe Active Transfemoral Prosthesis in stance phase

“…Compared with powered transfemoral prostheses, passive prostheses can provide some support assistance for amputees, but they cannot provide energy for amputees, which limit amputees' outdoor activities [1]. Wearing powered prosthesis can provide energy and prevent them from falling [2,3]. The active prosthesis not only meet the normal living needs but also enhance their ability to walk stably on various outdoor terrains [4][5][6].…”