Super-twisting control using higher order disturbance observer for control of SISO and MIMO coupled systems

In this paper, accuracy of the existing disturbance observer (DO) for disturbance estimation is increased by increasing its order. Stability of the proposed higher order disturbance observer (HODO) is analysed. Furthermore, a new HODO based super-twisting control (STW) algorithm is presented for the system with the bounded matched disturbances. A HODO based sliding mode control (SMC) algorithm with the integral sliding surface is proposed where the controller gains depend on the disturbance estimation error bound instead of the disturbance magnitude. Therefore, controller gains required in the proposed approach for the disturbance rejection are lesser as compared to the STW. As a result of which, with the proposed control, substantial chattering attenuation better than the STW is achieved. The proposed control technique is successfully applied to the single-input single-output (SISO) Industrial Emulator system with matched disturbance and the multi-input multi-output (MIMO) coupled 2-DOF Helicopter system with complex disturbances. The simulation and experimental outcomes illustrate the effective implementation of the proposed control strategy for tracking desired input, achieving stabilization and robustness of the system in the existence of bounded complex matched disturbances.