A sensor guided parallel parking system for nonholonomic vehicles

A parallel parking system for nonholonomic vehicles with embedded microprocessor and ultrasonic sensors is described. A general four-wheel vehicle is modelled as a nonholonomic system to reflect the motion constraints applied to the vehicle. Then automated environment detection is discussed. Using the ultrasonic scanning data acquired, a collision-free path is generated. The path may require a few backward and forward manoeuvres if the parking space is tight or the range of steering angle is narrow. Speed control during the manoeuvre is discussed and a scheme of speed variation is presented. The parking system has been installed on a mobile robot, and experiments have been carried out, which proves that parking spaces are detected correctly, and the path thus produced are feasible. The robot followed these paths into parking spaces safely. The system shows the potential to be integrated into automobiles.