Design of a Position Controller for a Mechanical System Using a Sliding Mode Disturbance Observer-based Controller

In most electro-mechanical systems, robust controller design is an important issue to deal with various uncertainties including external disturbances. The sliding mode control is widely known as a robust control technique for many practical control applications. In applying classical sliding mode techniques, however, the chattering phenomenon caused by switching operation is a main factor that deteriorates the control performance. To achieve the desired control performance with a relatively low switching function gain, this paper presents a robust position controller for a class of mechanical systems under parameter uncertainties and an external disturbance by using an integral sliding mode controller combined with a sliding mode disturbance observer. The sliding mode controller is adopted to reduce the steady state error. The sliding mode disturbance observer is designed to estimate the relatively slowly varying part in an equivalent disturbance. The control objective can be achieved with a relatively low switching function gain by compensating the disturbance through the proposed sliding mode disturbance observer that constructed without using the switching control input. To verify the performance of the proposed controller, comparative computer simulations are carried out with classical sliding mode controllers for a position control system. The control performance of the proposed controller is confirmed through analysis of the simulation results. Copyright © The Korean Institute of Electrical Engineers