Design of an Online Nonlinear Optimal Tracking Control Method for Unmanned Ground Systems

A nonlinear tracking error model for unmanned ground systems (UGS) was developed, and the constraints and objective function were established; the tracking control problem for UGS was converted to a continuous nonlinear optimal control problem. In order to solve the complex problem, a symplectic pseudospectral method based on the third kind of generation function is proposed. This approach largely reduces the sensitivity of the initial guess for costate variables, and the characteristics of the original system are not lost after discretization, which is not the case for other methods. Subsequently, by considering the influences of random disturbances in the environment, the symplectic pseudospectral method and the receding horizon control principle are combined to solve the nonlinear tracking problem; this method overcomes the problem that a nonlinear optimal control method is difficult to apply for online tracking. Finally, the proposed method is verified using simulation experiments, and it is demonstrated that the proposed method achieves online and real-time tracking control of a standard trajectory in the presence of random disturbances and it provides great maneuverability and feasibility for practical applications.