text: 1. Field of the Invention
  The present invention relates to an obstacle detection system for motor vehicle and, in particular, to an obstacle detection system for a motor vehicle which detects an obstacle ahead of the motor vehicle in order to avoid contact with the obstacle.
  2. Description of the Related Art
  The conventional obstacle detection system for a motor vehicle includes means for estimating a course on which the vehicle is supposed to travel based on the driving conditions of the vehicle, such as a steering angle and/or a vehicle speed. The obstacle detection system can detect the obstacle ahead with which the vehicle has a high possibility of contacting, with high accuracy, by using a radar device scanning a wide scope and picking up only the information of the obstacle on the course estimated by the above estimating means among the information obtained by the radar device. Such conventional obstacle detection system for a motor vehicle is disclosed in, for example, Japanese Patent Publication No. 51-7892.
  The above-mentioned obstacle detection system detects the obstacle ahead only if it is located on the course estimated, since the system judges that vehicle has the highest possibility of contacting with the obstacle on this course. Thus, when detecting the obstacle on the course, the obstacle detecting system informs the driver of this fact so that the driver operates the vehicle while taking care to avoid the obstacle ahead. On the contrary, when the obstacle on the course is not detected, the driver still operates the vehicle on the course knowing of no obstacle on the course.
  However, the above-mentioned conventional obstacle detection system does not detect an obstacle on another course located just outside of the course estimated. It should be noted that the vehicle has the second highest possibility of contacting with the obstacle located on the outside course though the vehicle has the highest possibility of contact with the obstacle on the course estimated. Further, the conventional detection system does not detect a vehicle traveling in front of the vehicle as the obstacle when the vehicle traveling in front of the vehicle moves toward the outside course from the course estimated. As a result, since the driver operates the vehicle with little consideration of the obstacle existing on the outside course, the driver's operations for avoiding the contact with the obstacle are delayed. Such driver's operation includes an operation of having a necessary distance between the vehicle and the obstacle ahead, an operation of reducing the vehicle speed, a steering operation and the like. The delay of the driver's operations for avoiding the contact with the obstacle is a problem to be solved.
  On the other hand, a conventional vehicle control system is also disclosed in, for example, Japanese Patent Laid-Open No. 1-197133. The vehicle control system is used to have the vehicle travel with safety. The vehicle control system includes means for controlling the vehicle, so as to follow the specific vehicle traveling ahead, based on the traveling conditions of these two vehicles. Since the vehicle with the vehicle control system is automatically controlled so as to follow the vehicle traveling ahead, the vehicle can travel, with safety, keeping the necessary distance between the vehicle and the vehicle traveling ahead as long as the vehicle ahead travels with safety.
  However, the vehicle with the vehicle control system has a possibility of following the vehicle traveling ahead even when the vehicle ahead travels with no safety. Further, the vehicle control system generally does not include the device for detecting an obstacle located ahead. Therefore, if the obstacle exists ahead or the vehicle to be followed becomes an obstacle, a rapid operation for avoiding contact with the obstacle could not be carried out. Moreover, even where the vehicle to be followed travels ahead with safety, the vehicle could not follow the vehicle traveling ahead when the vehicle ahead moves toward the course located at the outside of the course on which the vehicle ahead was traveling previously. When the vehicle to be followed becomes an obstacle, even if the vehicle control system includes the device for detecting the obstacle ahead, the detection device could not detect the obstacle ahead when the vehicle ahead moves toward the outside course.