Decoupled backstepping sliding mode control of underactuated systems with uncertainty

The purpose of this thesis is to design a decoupled backstepping sliding mode control method for underactuated systems under uncertainties and disturbances. The sliding mode control technique is an effective robust control approach to overcome model uncertainties and external disturbances. However, the sliding mode control method can manage parametric uncertainties only in combination with other methods such as backstepping control. The backstepping control design is mainly used to deal with the control of the nonlinear systems with parametric uncertainties. In the present thesis, the sliding mode control technique and the backstepping control technique are combined owing to their merits using a decoupling algorithm to control underactuated systems. Since the design methodology is based on the Lyapunov theorem, the stability of the system is guaranteed. The effectiveness of the proposed method is verified by the experimental results of the controller which is applied to an inverted pendulum on a cart system as an example of underactuated systems. The simulations and the experimental results show that the decoupled backstepping sliding mode control achieves a satisfactory control performance and the proposed method provides a robust performance to overcome parametric uncertainties where the decoupled sliding mode control fails.