| Summary: | 碩士 === 國立屏東科技大學 === 機械工程技術研究所 === 86 ===
This project is to study the application of fuzzy control theory on differential brake steer system. The purpose of a differential brake steer system is that when a vehicle deviates from road direction, it applies different braking force on left and right wheels to generate a countering torque, and consedquently, to correct the direction of the vehicle.
This research uses a two degree of freedom bicycle model to simulate the dynamics of a vehicle. The dynamics model also contains brake system dynamics, which features ABS (anti - skid braking system) system with the characteristics of saturation.
In the project, classical PID control and fuzzy control theories are used to design the differential brake steer control system. The performances are compared. The inputs to the system are: (1) lateral deviation of the vehicle gravity center from the road center, (2) changing rate of the deviation, and the outputs from the controllers are the braking forces at each tire. The PID controller design is based on two D. O. F. model. The gains of the controller is tuned according to the required performance of the system. For the fuzzy controller, fuzzy theorem is used to develop appropriate fuzzy matrix to adjust parameters to improve the transient and steady - state behaviors. Beside the inputs stated above, predicted deviation of the vehicle future path from road profile is also used in fuzzy controller to see its contribution.
In this research, effects of different factors on the performances of the system are investigated. These factors include: (1) steering wheel deviation, (2) heading angles deviation of the vehicle, and (3) lateral deviation of the vehicle. The results of the simulations reveal that the steering can be corrected by the system successfully, under permissible safety range.
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