Research On TCS Dynamometer Test-bed For A Rear-Drive Vehicle

With the development of automobile industry, more and more demands to vehicle active safety performance are taken into account. When vehicle starts or accelerates on the soft road or the road with low coefficient of friction, the wheels will slip excessively because of the low adhesion that the road surface provides. It causes the longitudinal and lateral adhesions to further reduce. And the vehicle stability,handling and acceleration will greatly reduce. Traction control system (TCS) is coming to be a popular feature on many vehicles because it can prevent the driven wheels from slip during vehicle accelerates especially when vehicle starts,accelerates or corners and improve vehicle's acceleration stability and handling. The research on TCS has been experienced for several decades. Since the first electric TCS was equipped on vehicle in 1985, TCS has been widely used. Nowadays, TCS has grown into the multiple function electric system that monitored by sensors, administrated by micro-processors and executed by actuators. TCS are equipped on more and more automobiles. But researches on traction control technology are in commencement phase in China, which mainly focusing on the researches on controllers. With the development of Hardware-in-the-loop (HILL), the cost of researches on controllers is lower, and the period of researches is reducing. The HILL has played an important part in the exploitation of Automobile electronic system, especially in the researches on TCS. This paper is a part of the program 'Research on Traction Control System of Light Off-Road Vehicle', and design the TCS dynamometer Test-bed for a rear-drive vehicle. There are six chapters in the dissertation. In Chapter One, the function and the construction of vehicle traction control system are introduced; the history of the TCS, its control methods and its present status are discussed. Meanwhile the difficulties in researches on TCS and function of HILL are discussed also. the contents of the dissertation are put forward. In Chapter Two, the TCS dynamometer Test-bed for a rear-drive vehicle is established. In this section the hardware scheme of Test-bed are discussed. including the scheme of sensors(wheel-speed sensor, throttle position sensor, brake pressure sensor), electronic throttle and hydraulic control unit are chosen or design. And the choice of dynamometer system for the test-bed are discussed also. In Chapter Three, the scheme of torque control for AC vector dynamometer are studied. In this section the control logic of and the theory of torque control for AC vector dynamometer are discussed, the constant simulated scheme and the dynamic simulated scheme of road resistance force for AC vector dynamometer are put forward. And test studies are made on low-μ-road, split-μ-road under the constant control of AC vector dynamometer. In chapter four, the control strategy and control algorithm of TCS are studied. The methods of throttle PID control and the brake threshold control which we adopted in test-bed are introduced. For PID control, set the target slip ratio, then calculate the actual slip ratio from the vehicle dynamic models, according to their difference design the control rules and control engine acceleration pedal open so as to regulate the engine output torque. Sequentially make the value of driven slip ratio are around or equal to the target slip ratio. For brake threshold control, Since active brake can control wheels independently and isn't suitable for continuous work, brake control are only used on split-μroad. regards the difference of driven-wheel slip ratio threshold and rotate acceleration as second threshold. and simulate several operating modes. And the results show that if the threshold can be chosen reasonably, TCS can effectively improve the driving ability of automobile. In chapter five, the test study for the Hardware-in-the-loop simulator for traction control system. In this section the control algorithm, sensors, actuators on test-bed are validated. Chapter Six is the summary and conclusion of the dissertation. The following conclusions can be derived from the simulation study and the test study of TCS. (1) the simulation results indicate that the throttle PID control algorithm and the brake threshold control algorithm can prevent excess spin of driven wheel effectively and improve traction, stability, controllability, and...