A coordinated control algorithm based on the caster-like motion for a car transportation system -iCART-

The car transportation system, which termed as iCART (intelligent Cooperative Autonomous Robot Transporters), is developed for handling the car in the narrow space, substituting the parking and unmanning the transportation of cars. iCART is composed of two robots and these robots transport the car in coordination based on a leader-follower type distributed motion control algorithm. To avoid damaging the surface of the car, tires of the car are putted on, not grasped by, the end-effecter of robots. Thus, when force/moment applied to the car by robots becomes large, the slip at the contact of the robot with the car occurs. Due to the slip, the relative position between robots is changed. In a conventional algorithm, the relative position is used for the control. Thus, after the contact of the robot with the car slips, occasionally, robots could not coordinate. For overcoming this problem, the motion control algorithm based on the caster-like motion is applied to the car transportation system iCART in this paper. Since this algorithm does not use the relative position information, the system becomes robust against the slip at the contact of the robot with the car. The proposed motion control algorithm is applied to iCART and experimental result illustrates the validity of the proposed algorithm.