| The research of vehicle electronic stability control system (ESC) is focus andcentral issue of vehicle dynamic control. The function of ESC includes anti-lockedbraking system (ABS), traction control system (TCS) and active yaw control (AYC). Inorder to make vehicle moves as driver’s wish, when the vehicle drives, ESC Monitorsvehicle driving status to adjust engine torque or brake pressure due to the differencebetween the actual state of motion of the vehicle and driver’s expect state of motion.The critical function of ESC hydraulic control unit (HCU) is that how to apply thebrake actively. This thesis studies the hydraulic circuit of the active brake system,analyzes the working principle of the power source-piston pump, and designs theparameters of relevant components in the hydraulic circuit of the active brake system.On the basis, the pressure drop as a result of the suction orifice effect has been reducedand a vacuum of0.5bar has been achieved in the inlet of the piston pump. After that,the function of active brake can be achieved.In order to study the dynamic of ESC-HCU and match hardware parameter afterESC manufacturing, This thesis establishes a simulation platform of ESC-HCU inwhich the choice of orifice diameter of inlet and outlet valve, the optimization of thepiston pump flow, the design of volume of accumulator are considered. Nevertheless,this thesis analyzes the influence of these parameters to the rate of pressure increasingand pressure decreasing which is the basis for ESC hardware match.In ESC, the two-status-two-way high-speed on/off valve is used to build up, holdor reduce the brake pressure. Traditional research of high-speed on/off valve in controlof pulse width modulation (PWM) concentrated in low frequency of10-100Hz. Thisthesis studies the proportion function of high-speed on/off valve in control of highfrequency of2~4kHz. This thesis establishes a high-speed on/off valve simulationmodel which is in control of PWM of2~4kHz modulation frequency inMATLAB-Simulink, and analyzes the proportion function of high-speed on/off valve indifferent duty cycle of the control of PWM. Nevertheless, a further study on influenceof different parameters to enlarge the control rage is discussed. By change the coilnumber, spring stiffness and seat angle, the ESC can control the rate of buildingpressure and limit the system pressure. After the sample of the designed ESC being manufactured, hardware in loop testand a test in actual vehicle are carried out. The result verifies the function of activebrake can be achieved and the rate of building pressure can be controlled by changingthe orifice diameter of inlet and outlet valve, piston pump flow and volume ofaccumulator. Nevertheless, the application of high-speed on/off valve in pressure-limitvalve in control of high frequency PWM verifies the proportion function of high-speedon/off valve and the influence of different parameters to the control rage. |
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