Research And Design On Automatic Obstacle Avoidance System

The ability to avoid the obstacles automatically measures the intellectualiztion of robots, as well as guarante safe travel for intelligent vehicles. Effective algorithm is the core of this ability. Traditional control algorithms always rely on accurate mathematical models of the controlled object and integrity environment information. So they are not quite satisfying, while the control process is relatively complex, or mathematical models are difficult to gain.During this thesis, the obstacle avoidance system was studied and designed. It could be divided into four parts: Information Gathering Module, Central Processing Module, Controlling Module and Controlled Object. Information Gathering Module was composed by ultrasonic distance measuring system and differential GPS system. They were used to measure the distances between obstacles and controlled object and to realize self-positioning. Datas were sent to upper compouter through serial interface and processed in Central Processing Module.Control signal was sent to Controlling Module. Brushless motor and steering component changed the steering angle in order to avoid obstacles.Fuzzy Logic Control theory was introduced in algorithm designing.The whole obstacle avoidance process was divided into two main behaivor patterns——goal seeking and obstacle avoidance.These two behavior patterns could be mutully shifted under certain conditions. Fuzzy controllers of each behaviour pattern were established. Step length was controlled by steering angle to decelerate during curving. Hypotesized aim method was used to avoid typical traps. The simulation platform of obstacle avoidance was developped and to testify the validity of the algorithm.Software and hardware design for ultrasonic distance measuring system were completed based on AT89C51 for Information Gathering Module. Measuring difference was computated to be±2%. Differential GPS was used to make up the insufficiency in circumstance detecting. Meanwhile, the theory of Global Positioning System, the process of signal receiving and processing were introduced.Brushless motor and Electricl Power Assisted Steering were chosen to compose the Implementing Module.The intelligent concept vehicle was taken as the controlled object to carry out experiments under real circumstances.The results of the experiments matched the simulation process and improved the significance of the whole system.