Speed Control of Parking Assist System for Electrified Vehicle

Parking assist systems which relieve burden of drivers have been put into practice in the world. Mitsubishi Electric has also been developing several technologies to realize the system, where our products such as sonar (ultrasonic sensor), electric power steering (EPS), a motor, and an inverter are used. In the parking assist system, peripheral environment of the vehicle in a parking lot is detected with our sonar sensors and determine whether or not there is a parking space available. Estimation of the position and the attitude of the vehicle is also carried out. On the basis of the detection and the estimation, a smooth and efficient path to drive and park the vehicle is generated with an optimization technique. In particular, this paper focuses on a drive control for electrified vehicles to track the reference trajectory at a desired speed given from the assist system. Taking advantages of features of the motor, which has high-speed responses and generates precise and large torque even at a low speed, the automatic parking can be achieved in a smooth and exact way. In the case the vehicle deviates from the reference trajectory because of disturbances and uncertainties, our simple controller can recover the vehicle there. Vibration characteristics of the powertrain of the vehicle are also considered in the derivation of the controller. This paper shows the design procedure and effectiveness of the proposed method.