Study On Electronic Throttle Valve Control Of Engine

Compared with the traditional mechanical throttle,electronic throttle control system has great benefit to improve the precision of control,accurately adjust the air,improve the air-fuel ratio and torque,to make modern car be green power,economic and environmental,safe and comfortable.Electronic throttle is a dynamic system with strong nonlinearity including static and dynamic nonlinearity.The difficulty of control lies in how to balance the dynamic performance requirements of electronic throttle control system in response speed,stability and control accuracy.In this paper,the static and dynamic feedback control structure is adopted.Among them,the static feedforward controller compensates the nonlinearity of spring and friction to improve the response speed of the system according to the calibration compensation voltage;dynamic feedback controller using a combination of linear PID approximation of nonlinear control to improve the stability and accuracy of system.In this paper,based on the hardware/software and bottom driver software of engine electronic control unit(ECU)in the laboratory,the control algorithm and the diagnosis strategy of electronic throttle had been modified.The main contributions in the article are as follows:(1)Design of position sensor signal processing and diagnosis software.Signal processing includes the signal collection,normalization and self-learning.The corresponding diagnosis software had been designed which divided into out of range diagnosis and correlation diagnosis in order to ensure the accuracy and correctness of electronic throttle position measurement,at the same time,determined the weighting factor according to the result of diagnosis in order to calculate the actual throttle position and the reference throttle position.Finally,the diagnosis software was verified by setting artificial fault.(2)Design of embedded control software.In order to improve the emission performance and driving stability,designed the filtering and rate limiting software of the desired position.In view of the nonlinearity caused by the return spring and friction of the electronic throttle valve,designed a control algorithm of feed-forward compensation and PID closed-loop feedback.Finally,the feed-forward and feedback control voltages were compounded into a complete motor control voltage and converted to a limited duty cycle to drive the motor.(3)Design of control performance diagnosis software.In order to ensure that theelectronic throttle control in the practical work of good performance,designed the dynamic throttle actuation diagnostic,steady state throttle actuation diagnostic,engine airflow actuation diagnostic and throttle return diagnostic software.The dynamic performance and throttle return diagnostic strategy was verified through experiment,which further improved the system stability and reliability.(4)Parameter tuning and experiment.The method of critical ratio was used to get the parameters of digital PID controller under different range of error to calculate the closed loop control voltage.Finally a comparison was made on the performance of large and small opening for the electronic throttle with and without nonlinear compensation by experiment.The results verified the improved dynamic performance of the proposed control algorithm in terms of shorter response and smaller steady-state error compared with the simple PID controller.In view of the overshoot phenomenon,the ramp response experiment was carried out based on the analysis of the reason and eliminated the overshoot which proved the necessity and feasibility of the filtering and rate limiting of desired position.