Design And Research Of Electronically Controlled VGT Control System And Its Actuator

Turbocharging technology is currently an effective way to improve performance,fuel economy and emissions of internal combustion engines.However,internal combustion engines matched with conventional turbochargers face the problems such as insufficient torque at low speed,slow transient response and poor economy under partial load.Variable geometry turbocharger(VGT)can effectively solve the problems above,therefore it has drawn attention at home and abroad.This dissertation focus on the research and design of a variable geometry turbocharger control system.Firstly,the control strategy of VGT system under different operating conditions is analyzed.To cope with the poor responsiveness of the closed-loop control strategy of boost pressure,a direct control method for the guide vanes that control VGT flow geometry is proposed.To obtain desirable boost pressure through the control of the vane position,the pattern of VGT vane position under different conditions was analyzed.In order to improve the stability and reliability of the system,a closed-loop feedback control of the vane position is adopted.A set of DC motor-driven,small-sized,light-weighted VGT actuator system has been analyzed and designed.Secondly,the working principle of VGT actuator is analyzed,and the simulation model of actuator control system is established in MATLAB / Simulink environment,focusing on the working process of DC motor.Based on the PID control,the relationship among motor angular position,motor speed and armature current is analyzed.The influence of different control parameters on system performance is studied.Finally,the hardware and software of VGT electronic control system are designed,which includes the selection of controller,sensors,drivers and other chips,the design and debugging of power supply circuit,drive circuit and digital signal processing circuit and the development of control software based on Freescale’s MC9S12XS128 microcontroller.Experiments have been carried out to verify the VGT actuator control system.Results showed that the system functions well under different forms of input signals.These works laid the foundation for VGT turbocharging control system.