Simultaneous balancing and trajectory tracking control for two-wheeled inverted pendulum vehicles: A composite control approach

This paper is concerned with a novel composite controller for an underactuated two-wheeled inverted pendulum vehicle with an unstable suspension subject to nonholonomic constraint. The presented composite controller is consisted with an adaptive sliding mode technique to construct an additional disturbance-like signal, and particularly a direct fuzzy controller to approximate the optimal velocity tracking control effort by the adaptive mechanism. Unlike the traditional control strategies, this composite control approach offers a coordinate control objective for the vehicle with an unstable equilibrium and second-order nonholonomic constraints. In addition, with the aid of a posture controller aiming to the tracking error dynamics, the nonholonomic vehicle can track an arbitrary trajectory given by the earth-fixed frame. Numerical simulation results confirm that the proposed controllers can maintain the balance of the unstable suspension, drive the vehicle globally to track any reference trajectory, and guarantee all the signals of the closed-loop system convergent within a compact set.