Development Of Electronic Control Unit For Air Spring

More and more application of air suspension are presented in automotive suspension system due to their performances. In the paper, two-degree-of-freedom vibration model of air suspension is built and stiffness adjustment theory and control characteristic of air suspension are discussed. On the basis, electronic control unit for air spring is developed.This paper discussed that the driving smoothness may be improved by altering stiffness of air spring. In the course of developing the hardware system, the circuits diagram is finished by the mean of EDA software. On the basis of analyzing function of hardware circuit, choose the AT89C51 as single chip microprocessor. Filter and amplifier circuit, sample and hold circuit, Analog-to-Digital conversion circuit, watchdog circuit, out port control circuit and power supply circuit were designed. In the course of software development, structure and modular design method is adopted in the principle of reliability and practice. With complex nonlinear of vehicle control system, variable parameter fuzzy-PID control algorithm was designed without mathematical precise model. Applying fuzzy control theory, it adjust parameters of increment PID algorithm on-line for efficiently controlling stiffness of air spring by altering ah" pressure in the air spring.This control unit take stiffness parameter of air spring as control value and acceleration in vertical vibration is looked as aim value. The control unit can processes electrical signal of acceleration measured by accelerometer in order to obtain altering trend of stiffness parameter of air spring. Air pressure can be changed by switching on and off valve so that stiffness parameter can may be continuously altered. Single frequency excitation experiments show that the control unit for air spring can efficiently alter stiffness parameter according to connected acceleration signal in vertical vibration and the driving smoothness is improved. It has some advantages, such as ability of anti-interference, fast response, high stability and reliability ,small size, low price.