Bounded-velocity motion control of four wheel steered mobile robots

In this paper, we address the problem of motion control for a mobile robot with four independently steer and drive wheels. Our solution fully takes advantage of steerability of all wheels and provide capability of independent control of translation and rotation of the robot. Using non-linear control techniques, we provide a motion control law that makes the base follow a given desired smooth path and heading profile. Derivation of motion control is three folded. Assuming velocity vector orientation and angular velocity of the base as control signals, control laws are derived to solve the path and heading profile following problem. Then these control signals are mapped to eight actuator signals (driving and steering). In a later stage, robot base speed magnitude is controlled in such a way to keep the control signals under predefined limits. Simulations as well as experiment on a real robot show the efficacy of the proposed method.