Abstract
Keywords - parking assist, automatic steering, generating a route, clothoid curve, similar expansion
Abstract - In 2003, we were the first in the world to mass-produce an automatic steering type reverse parking assist system (Intelligent Parking Assist, or IPA). This system alleviates the burden placed on the driver and helps ensure safety by allowing the driver to concentrate on safety verification and vehicle speed control.
This paper describes two important route generation strategies that we have developed to achieve this system and it explains their effectiveness.
The first strategy we developed is the route generation strategy. An analysis of the operations performed by drivers showed that the use of a clothoid curve is effective for the vehicle to easily trace a smooth route as the steering wheel is turned. By means of this clothoid curve, we established a basic strategy that generated a route adaptable to the characteristics of the vehicle and the performance of the automatic steering actuator. We also developed an algorithm for accurately generating a target route that allows a vehicle to be guided by automatic steering to a target location specified by the driver, regardless of the starting position.
The second strategy is the method of recalculating the route to secure parking accuracy. Under the guidance of automatic steering, the vehicle may fail to trace the target route generated in the starting position because of transient delays in the steering due to factors such as tire condition and load variation. These can cause an error in parking. In order to minimize such parking errors, the vehicle must automatically be rerouted from its position to the target position. While assistance is in progress, however, the system may generate a target route that includes non-negligible errors due to the effects of the vehicle steering angle, if the above-mentioned route generation method is directly applied. We overcame this problem by developing an algorithm capable of precisely recalculating the route.
As a result of these route generation strategies, we achieved an automatic steering type reverse parking assist system that guarantees high-accuracy parking and comfortable steering.