Development of intelligent braking system.

摘要

A new braking control system, the intelligent braking system, is developed in this thesis. The intelligent braking system consists of two parts. The first part is the intelligent warning system. It is designed to alert the driver when the vehicle is approaching a dangerous situation. Those dangerous circumstances may be caused by changes in pavement condition, road geometry, traffic flow, and so on. The intelligent warning system will utilize the information of the expected stopping distance and the available stopping distance to judge whether the driver is in danger. The second part of the intelligent braking system is the braking and steering control system. It is designed to be activated by a warning signal and help the driver control the vehicle, especially when braking is combined with steering.; The objective of the proposed intelligent braking system is to warn the vehicle operator of impending dangerous conditions and help the driver stop the vehicle more efficiently. There are three important contributions in the thesis.; First, a relatively simple and easy to implement method for measuring a sliding braking coefficient between vehicle tires and road surface is proposed for use in the braking system. Compared with the ASTM E 274 method, the accelerometer-based method is very promising. Combining the vehicle speed sensor and wheel speed sensor, the accelerometer-based method can provide an accurate measurement of the tire-pavement coefficient of friction.; Second, the fuzzy logic is used in the intelligent warning system to determine the sliding braking coefficient. The sliding braking coefficient is the coefficient of friction that exists when the wheels are locked during braking. Because of the characteristic of the fuzzy logic, the intelligent warning system provides a simple and reliable algorithm. It is the first time that the fuzzy logic has been used to solve such a problem.; Third, a new methodology is developed and applied in the control algorithm for vehicle braking combined with steering. Obviously, it is more difficult for the driver to stop the vehicle when braking and turning at the same time. On the other hand, rollover accidents usually happen when a vehicle is turning or changing lanes. The braking and steering control system applies the optimal control theory to assist the driver in stopping the vehicle. The algorithm shows good control on the vehicle lateral and yaw motion and it is easy to implement in a vehicle. The methodology proposed in this thesis investigates the relation between the longitudinal velocity, lateral velocity, and the yaw angular velocity. It is very important when the vehicle lateral and yaw stability are considered.; Compared with the existing braking systems, the intelligent braking system can alert the driver in advance and help the driver control the vehicle. It is possible for the intelligent braking system to reduce the number of accidents that happen because of the driver's inattentiveness or inexperience.