Development Of Electronic Control Unit For Air Suspension With Axuiliary Chamber

The paper is based on the one-quarter vehicle vibration model of air suspension system with auxiliary chamber, stiffness adjustment theory and control characteristic of air suspension were also discussed. A simulation model was built using Matlab as to be the excitation for white noise road surface, sine wave road surface and tooth wave road surface. Compared with passive suspension, we validated the usefulness of the optional control method and a control unit was developed.In the course of developing the hardware system, the circuits diagram and print circuit board were finished by Protel DXP 2004. On the basis of analyzing function of hardware circuit, choosing AT89C52 MCU as the core of the controller hardware, including filter and amplifier circuit, sample and hold circuit, Analog-to-Digital conversion circuit, out port control circuit etc.In the course of developing the software system, based on the former results we had got, self-adaptation control method without mathematical precise model was applied to design the air suspension controller.The Control unit took acceleration in vertical vibration as aim value , processed the vertical acceleration signal from acceleration transducer, had a FFT transform to get the adjusting tendency compared with the control rules we set before. Electronic valve was controlled to get or lose electric to adjust the pressure of air spring and the signals from MCU was transmitted to the step motor driver. The size of the throttle orifice can be changed by the valve.By the comparing the results of the suspension controlled and non-controlled, Single frequency excitation experiments show that the control unit can adjust the stiffness and damping based the acceleration signal measured to improve the driving smoothness. The test shows the result is ideal.