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Active vibration control of flexible-joint manipulators using accelerometers

Pu Zhao (Huazhong University of Science and Technology, Wuhan, China)
Yunfei Zhou (Huazhong University of Science and Technology, Wuhan, China)

Industrial Robot

ISSN: 0143-991x

Article publication date: 26 November 2019

Issue publication date: 16 January 2020

271

Abstract

Purpose

Manipulators are often subjected to joint flexibility caused by various causes in industrial applications, such as shaft windup, harmonic drives and bearing deformation. However, many industrial robots are only equipped with motor-side encoders because link-side encoders and torque transducers are expensive. Because of joint flexibility and resulted slow response rate, control performance of these manipulators is very limited. Based on this, the purpose of this paper is to use easy-to-install and cheap accelerometers to improve control performance of such manipulators.

Design/methodology/approach

First, a novel tip-acceleration feedback method is proposed to avoid amplifications of approximation errors caused by inversion of the Jacobian matrix. Then, a new control scheme, consisting an artificial neural network, a proportional-derivative (PD) controller and a reference model, is proposed to track motor-side position and suppress link-side vibration.

Findings

By using the proposed tip-acceleration feedback method, each link’s vibration can be suppressed correlatively. Through the networks, smaller motor-side tracking errors can be obtained and unknown dynamics can be compensated. Tracking and convergence performance of the network-based system can be improved by using the additional PD controller.

Originality/value

The originality is based on using accelerometers to improve link-side vibration suppression and control performance of flexible-joint manipulators. The previously used methods need expensive link-side sensors or accurate robot model, which is unavailable for many industrial robots only equipped with motor-side encoders. The report proposed a novel acceleration feedback method and used networks to solve such problems.

Keywords

Acknowledgements

Disclosure statement: No conflict of interest exists in the submission of this manuscript, and manuscript is approved by all authors for publication.

Citation

Zhao, P. and Zhou, Y. (2020), "Active vibration control of flexible-joint manipulators using accelerometers", Industrial Robot, Vol. 47 No. 1, pp. 33-44. https://doi.org/10.1108/IR-07-2019-0144

Publisher

:

Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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