Tracking control of an electrohydraulic manipulator in the presence of friction

TitleTracking control of an electrohydraulic manipulator in the presence of friction
Publication TypeJournal Article
Year of Publication1998
AuthorsTafazoli, S., C. W. De Silva, and P. D. Lawrence
JournalControl Systems Technology, IEEE Transactions on
Pagination401 -411
Date Publishedmay.
Keywordsacceleration control, automated fish processing, compensation, electrohydraulic manipulator, error analysis, feedback, food processing industry, friction, industrial manipulators, manipulator dynamics, nonlinear observer, observers, parameter estimation, servosystems, tracking, tracking control

Analysis and estimation of friction and compensation for its effects in the control of an electrohydraulic manipulator is addressed. The specific hydraulic manipulator is an integral part of an automated fish processing machine which has been developed in our laboratory. The analysis reveals that considerable static and dynamic friction exists in the system. An available nonlinear observer for Coulomb friction, is modified to simultaneously estimate friction, velocity, and acceleration. A novel observer-based friction compensating control strategy is developed for improved tracking performance of the manipulator. The approach is based on acceleration feedback control. Experimental investigations show that this controller significantly outperforms the conventional PD controller. The general approach presented in this paper, may be applied to compensate for friction in any servomechanism, particularly when the actuator dynamics is not negligible


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