A gain scheduled sliding mode control scheme using filtering techniques with applications to multilink robotic manipulators

Abstract

In this paper, a gain scheduled sliding mode control (SMC) scheme is proposed for tracking control tasks of multilink robotic manipulators. In the new scheme, filtering techniques play the key role in acquiring equivalent control signals and scheduling the switching control gain automatically. Once the system enters the sliding motion, two classes of low-pass filters are introduced to work concurrently for the purpose of acquiring equivalent control, reducing the switching gain effectively, and as a result eliminating chattering. By virtue of equivalent control theory, one class of filters is designed to capture the "average" profile of the switching quantity, which is in proportion to the desired control input. Meanwhile, another class of low-pass filters is added to scale down the gain of the switching control. The convergence property of the proposed control scheme is rigorously analyzed in time domain and the frequency domain knowledge can be easily incorporated into the construction of the two classes of filters. Excellent tracking performance is achieved with the direct manipulation of switching control input using filtering technology and with the integration of both time domain and frequency domain system knowledge in controller design.