This paper proposes a trajectory control scheme for a car-like four-wheeled mobile robot. The proposed control scheme consists of a trajectory generator, a motion control law, and a steering control law. First, a real-time trajectory generator is designed based on the nonholonomic kinematic constraints of the robot, in which the reference driving speed and time rate of heading angle are computed in real time for a given desired trajectory of the robot. Next, motion and steering control laws are designed based on the dynamic model of the robot. The motion and steering control laws are used to control the robot speed and steering angle. Finally, the validity of the proposed control scheme is shown by realistic computer simulations with one sampling time delay in the control loop. In this study, the Lyapunov stability theorem and the loop shaping method are used as mathematical design tools. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. The proposed method of control design is much simpler than the back-stepping method.

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