Dynamical Output Feedback Variable Structure Control

Chapter 4 considers dynamical output feedback control design for systems with mismatched uncertainties/disturbances. Compared with Chapter 3, all the uncertainties involved in this chapter are bounded by nonlinear functions of the system state variables instead of the output variables. The bounding functions are assumed to be known and thus it is possible to use them for system analysis and control design to reduce the effects of uncertainties on the systems. A sliding surface is designed which is independent of the designed observer, and then a sliding mode control is synthesised based on the designed observer and system outputs. The controller design and the observer design are separated which means that the designed controller can be used with any observer but the developed approach requires that the considered system is minimum phase. In a second approach, a dynamical compensator is designed first. A sliding surface is then designed for the augmented system formed by the considered system and the error dynamics. It is not required that the nominal system is minimum phase. Applications to control of the High Incidence Research Model (HIRM) aircraft are given. Both longitudinal and lateral aircraft dynamics based on different trim values of Mach number and height are employed in the simulation study.