Research On Control Strategy And System Of Motor-Drive Exhaust Gas Re-Circulation Valve

Exhaust gas recirculation technology is an effective measure to reduce NOx emissions in vehicle exhaust,and it is the main technical means to cope with my country’s increasingly strict emission regulations.Under higher emission requirements,the EGR(Exhaust Gas Re-circulation,EGR)valve,as the core control component in the exhaust gas recirculation system,needs to have higher control precision,faster response speed and stability.In this thesis,the EGR valve driven by the finite angle torque motor is taken as the research object,and the control strategy and system research of the EGR valve is carried out.The main research work includes follows.(1)The EGR rate control requirements of the exhaust gas recirculation system under different application conditions are analyzed;based on the basic structure of the EGR valve driven by the limited angle torque motor,its system model is established.(2)Based on the EGR valve system model,a design scheme of the control system including "position closed loop and current closed loop" is proposed.The control model under the above structure is proposed,and the corresponding software module is designed based on the model;the control hardware unit is designed,including the minimum system of the controller,sensor and signal processing,motor drive and communication interface circuit.(3)A torque nonlinear compensation method based on BP neural network is proposed,which solves the inherent torque fluctuation problem of finite-angle torque motors.The output nonlinear mechanism of finite-angle torque motor is analyzed,and the output characteristics of cogging torque fluctuation and armature effect are described;a feedforward compensation method based on BP neural network is proposed,and an offline learning platform is further built to realize the motor "Offline learning and online compensation" of nonlinear characteristics,experimental data show that the method proposed in this thesis can reduce the output torque deviation from 0.09 N·m to less than 0.03 N·m.(4)The performance test platform of EGR valve is independently developed,and the experimental research on the performance of EGR valve is carried out based on the test platform.The static and dynamic parameters of the EGR valve under different winding turns and air gaps are studied,and the optimal working point of the test sample is defined.The innovation of this thesis is that a method of "offline learning and online compensation" is proposed,which solves the inherent torque fluctuation problem of limited-angle torque motors,and further proposes a compensation algorithm based on BP neural network and an offline learning mechanism.EGR technology can not only effectively reduce the content of nitrogen oxides in automobile exhaust,but also has the advantages of low cost and less requirements for engine changes.The research in this thesis provides an effective solution for the high-performance EGR valve system,which has certain practical application value;it plays a certain role in improving the level of fuel vehicle engine technology,reducing emissions and protecting the environment.