Active control of flexible one-link manipulators using wavelet networks

Abstract

The design of control laws for flexible manipulators is known to be a challenging problem, when using a conventional actuator, i.e., a motor with gear. This is due to the friction of the nonlinear actuator, which causes torque dead zone and stick-slip behavior, thereby hampering the good performance of the control system. The torque needed to attenuate the vibrations, although calculated by the control law, is consumed by the friction inside the actuator, rendering it ineffective to the flexible structure control. Nonlinear friction varies with different operational conditions of the actuator and a friction compensation mechanism based on these models cannot always keep a good performance. This study proposes a new control strategy using wavelet network to friction compensation. Experimental results obtained with a flexible manipulator attest to the good performance of the proposed control law.

Modelling the temperature in joint friction of industrial manipulators

“…In fact, in this case the use of interpolation method might fail because of the temperature variation. Note that, although static friction is also a significant element that is detrimental for performance when the robot moves at very low velocities [14], in this paper we focus on dynamic friction and therefore on relatively high speed tasks, as the polynomial model is very effective in this case.…”