Frequency shaping and other dynamic compensation methods for sliding mode control

In this dissertation, we are mainly interested in designing sliding mode controllers for systems with modelling and parametric uncertainties considering unmodelled actuator and sensor dynamics. Furthermore, the drawbacks of sliding mode control such as high gain, high frequency control inputs are attenuated by extending the controlled system through adding compensator dynamics. This design approach is quite reasonable since most of the analytical models of the plants to be controlled have uncertainties, unmodelled dynamics and limited control capacity. Our approach to designing a sliding mode controller is to filter the discontinuous control inputs using frequency-shaping and dynamic compensation methodologies while satisfying robustness against both matched and unmatched bounded disturbances based on Lyapunov stability. Transient performance improvement and finite time convergence to the switching surface have been assured by this methodology. Dynamic compensator schemes offer more degrees of freedom for controller design and they also improve the transient performance of the closed loop system that may be degraded by the high feedback gains due to conservative choice of the disturbance's upperbounds.