Adaptive sliding-mode control for two-wheeled inverted pendulum vehicle based on zero-dynamics theory

The two-wheeled inverted pendulum vehicle yields wide application prospects due to its compact construction, convenient operation, high maneuverability, and low fuel consumption. However, influenced by the underactuated characteristic, it is very difficult to achieve satisfactory control performances besides holding the vehicle body to be stable. In this study, based on the nonlinear dynamic model, the overall system is considered as three subsystems: rotational motion, longitudinal motion, and zero dynamics. Particularly, the tilt angle of the vehicle is treated as zero dynamics where the longitudinal acceleration is taken as the control input. With the control effects, the zero-dynamics subsystem could come up to be stable. Based upon the zero dynamics, the controllers for rotational and longitudinal subsystems are constructed in the following. In addition, the sliding-mode control techniques are used to derive the controllers since their insensitive characteristic to parameter variation and disturbance rejection.