Development Of Electronic Control Unit For Air Suspension With Axuiliary Chamber Based On Fuzzy Control

More and more application of air suspensions are presented in automotive suspension system due to their performances. The paper is based on the one-quarter vehicle vibration model of air suspension system with auxiliary chamber and stiffness adjustment theory and control characteristic of air suspension are discussed. On the basis, an electronic control unit for air suspension is developed. In the paper, with complex nonlinear of vehicle air suspension control system, fuzzy control theory without mathematical precise model was applied to design the air suspension controller.The main parts of the air suspension is air spring, the dynamic character of the air suspension systems with auxiliary chamber is interrelated observably to the size of the throttle orifice and the pressure of the gas of the spring.This control unit take stiffness parameter of air spring as control value, and acceleration in vertical vibration is looked as aim value. The electronic unit of the air suspension can processes electrical signal of acceleration measured by accelerometer in order to obtain altering trend of stiffness parameter of the air suspension, the signals from MCU were tranmitted to the step motor driver. The size of the throttle orfice can be changed by the valve drived by the step motor, so that stiffness parameter can be continuously altered, and the driving smoothness is improved.The core of the paper is the designing of the fuzzy controller. In the course of developing the hardware system, the circuits diagram and print circuit board are finished by the mean of Protel software. On the basis of analyzing function of hardware circuit, choosing AT89C55 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 and step motor driving circuit, display circuit, etc. During the design of the outer-ring circuit, the expandability and the generality of the controller have been considered, so that it can be suitable for many other applications. The software is programmed by C51. In the course of software development, structure and modular design...