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Active Loading Control Design for a Wearable Exoskeleton with a Bowden Cable for Transmission

Authors :
Zhipeng Wang
Seungmin Rho
Chifu Yang
Feng Jiang
Zhen Ding
Chunzhi Yi
Baichun Wei
Source :
Actuators, Vol 10, Iss 6, p 108 (2021)
Publication Year :
2021
Publisher :
MDPI AG, 2021.

Abstract

Exoskeletons with a Bowden cable for power transmission have the advantages of a concentrated mass and flexible movement. However, their integrated motor is disturbed by the Bowden cable’s friction, which limits the performance of the force loading response. In this paper, we solve this problem by designing an outer-loop feedforward-feedback proportion-differentiation controller based on an inner loop disturbance observer. Firstly, the inner loop’s dynamic performance is equivalent to the designed nominal model using the proposed disturbance observer, which effectively compensates for the parameter perturbation and friction disturbance. Secondly, based on an analysis of the stability of the inner loop controller, we obtain the stability condition and discuss the influence of modeling errors on the inner loop’s dynamic performance. Thirdly, to avoid excessive noise from the force sensors being introduced into the designed disturbance observer, we propose the feedforward-feedback proportion-differentiation controller based on the nominal model and pole configuration, which improves the outer loop’s force loading performance. Experiments are conducted, which verify the effectiveness of the proposed methods.

Details

Language :
English
ISSN :
20760825
Volume :
10
Issue :
6
Database :
Directory of Open Access Journals
Journal :
Actuators
Publication Type :
Academic Journal
Accession number :
edsdoj.877e74aeb05b4dc78e9968c80f5d0908
Document Type :
article
Full Text :
https://doi.org/10.3390/act10060108