The discrete-time controller design based on sliding mode for manipulators

Deals with the sliding mode tracking control problems for the computer control of a continuous plant with bounded parameter variations and external disturbances. The variable structure control approach with boundary layer is developed in discrete-time systems, where the concept of `boundary layer´ is extended which is not only used to eliminate chattering, but also used as a more strong sufficient and necessary condition for a fast reaching to the switching surface, a relationship among boundary layer, vibration coefficient and system parameter uncertainty (including sampling interval) is given, and a new balance condition from the careful consideration on bandwidth of plant dynamics and the features of VSS controller is established. The effect of sampling interval on system dynamic tracking precision is analyzed, and the method of disturbance compensation for further improving tracking precision is also proposed. A practical design of the sliding mode controller with this approach for a six degree of Freedom Arm PuMA560 is given