Cascaded adaptive integral backstepping sliding mode and super-twisting controller for twin rotor system using bond graph model

Abstract

This work presents a bond graph (BG) model and a robust cascaded controller for a twin-rotor system (TRS). The BG model accounts for all the energetic and dynamical couplings. An adaptive integral backstepping sliding mode (AIBSM) controller is used in the outer loop to control the slow yaw and pitch dynamics of the mechanical sub-system whereas a higher-order sliding mode (HOSM) observer-based super-twisting algorithm (STA) controller is used in the inner loop to control the fast electromechanical actuator dynamics. The gain of the discontinuous control term of the integral backstepping sliding mode (IBSM) controller is adjusted by using an adaptive switching gain law, where the adaptive gain decreases or increases as the system state variables move closer to or away from a sliding surface; thereby reducing chatter and discontinuities near the sliding manifold, and ensuring a nearly smooth reference signal to the inner-loop controller. The unavailable states are estimated by using an unscented Kalman filter. All the used controllers are shown to be Lyapunov stable. The performance of the developed controller is validated through simulation and experiment, and it is further compared with other existing robust controllers. The proposed controller is robust against un-modeled dynamics and external disturbances, and it performs better, in terms of trajectory tracking error and disturbance rejection, than presently existing controllers for the TRS.