Double Closed-loop Integral Terminal Sliding Mode for a Class of Underactuated Systems Based on Sliding Mode Observer

Abstract

Aiming to solve the tracking control problem of a class of second-order underactuated mechanical systems with unknown model parts, external disturbances and noise disturbances, a double closed-loop layered integral terminal sliding mode control method based on sliding mode observer is proposed. At the outset, the Lagrange model of the system is transformed into an affine model, and a sliding mode observer is designed according to the system structure. Neatly, the outer loop controller is designed using the observer’s estimated state, and the output value of the outer loop controller is filtered with a low pass filter. Then the inner loop controller is designed by using hierarchical sliding mode control method. On a premise of ensuring tracking performance, the control method can maximally improve convergence speed and reduce chattering even if there are unknown model parts, external interference and noise interference phenomena in the system. This simulation results distinctly display the effectiveness of the control tactics.