Sensorless control system for assistive robotic ankle-foot

Mouaz Al Kouzbary,Ahmad Khairi Abdul Wahab,Noor Azuan Abu Osman

doi:10.1177/1729881418775854

Mouaz Al Kouzbary, Ahmad Khairi Abdul Wahab + Show 1 more

Open Access

https://doi.org/10.1177/1729881418775854

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Abstract

This article presents a novel sensorless control system of assistive robotic ankle-foot prosthesis, two estimation algorithms were developed and an analogy between them has been made. The system actuator’s motor is a permanent magnet synchronous motor, unlike other powered ankle-foot, where the brushless DC motor and DC motor were used. Utilizing the permanent magnet synchronous motor will reduce the torque ripples and increase system ability to be overloaded compared to systems which utilize the brushless DC motor. Moreover, the ability of the machine to operate in all speed range makes this machine more suitable for the application. Both estimation algorithms are built using C-code and assessed in MATLAB Simulink. The estimation algorithms are used to provide motor and powered ankle-foot’s angular speed and position. Two-level control system is used to evaluate the estimation algorithms; the control system role is to mimic biological ankle-foot performance during normal ground level walking speed. Based on the result of this article the unscented Kalman filter (UKF) is applicable for the application, as a result of the observer ability to estimate the motor load and angular position. On the other hand, extended Kalman filter (EKF) accuracy is affected by the load applied to the motor. Furthermore, the angular position is evaluated by integration of the angular speed which means integration of angular speed estimation error.

Highlights

It is believed that ankle plantar flexion (PF) has an important role during the gait cycle.[1]
Ankle PF muscles are responsible for generating approximately 80% of the torque required by the gait cycle, which has an important distribution to regulate the whole-body angular momentum (H).[2]
A light weight robotic ankle-foot with a novel damping controller developed by Wang et al.,[12] the design and control system were amended to reach the final prototype in 2015.13 the damping controller has a slow response, so the problem of asymmetric gait cycle was not solved

Summary

Introduction

It is believed that ankle plantar flexion (PF) has an important role during the gait cycle.[1]. A light weight robotic ankle-foot with a novel damping controller developed by Wang et al.,[12] the design and control system were amended to reach the final prototype in 2015.13 the damping controller has a slow response, so the problem of asymmetric gait cycle was not solved Another prototype was developed by Shultz et al.,[14] researchers introduced a mechanical system prototype with ground level walking control algorithm, design was enhanced by replacing the 4-pole brushless DC (BLDC) motor with 14-pole one to reduce motor torque ripples and introducing a fifth-order impedance controller.[15] The new controller used with new high level controller to master walking in different speed and standing adaptively according to ground slopes, walking on uneven terrain as shown by Shultz et al.[16,17] A more descriptive reviews on robotic prostheses’ control algorithms and mechanical prototypes given in the literatures.[18,19,20]. Rs, Ls, P, and f, are motors parameters

À RsTs Ls

À TsB J

Findings

Conclusion