Disturbance Observer-Based Trajectory Tracking Control for Nonholonomic Wheeled Mobile Robot Subject to Saturated Velocity Constraint

The problem of trajectory tracking control for a nonholonomic mobile robot is discussed in this study, in which both the dynamic behaviors of disturbance adaptability and the velocity saturation constraint are considered simultaneously. To realize this objective, a double closed-loop control structure is presented. On the outer loop, an improved velocity saturated controller based on hyperbolic tangent function is established; on the inner loop, an integral sliding mode controller, which possesses a fast transient response property with less steady-state error, is developed. In addition, to alleviate the inherent chattering behavior of sliding mode technology and enhance the external disturbance adaptability, an adaptive scheme as a disturbance observer is adopted by which one could estimate the uncertain disturbance acting on the mobile wheels rapidly. Simulation results verify the effectiveness of the proposed control theories.