| According to the national emission requirements for diesel vehicles,we use SCR aftertreatment technology to reduce NOx emissions.The electric geared urea supply pump in the SCR aftertreatment system plays a decisive role in the injection pressure and injection accuracy of the aqueous urea solution,and the electric motor in the urea supply pump provides the injection pressure for the urea pump.The controlling of the motor to be able to reach the target pressure of the urea pump and the back pumping of the urea pump when the car is stopped is the key to the research in this paper.Brushless DC motors are selected as the urea pump drive motors in this paper.Brushless DC motors have low losses,higher efficiency and longer service life,and are inherently smaller,better sealed and more corrosion resistant.The brushless DC motor basically meets the functional and drive control requirements of the new geared urea supply pump for SCR catalytic converters in diesel engine aftertreatment systems,so the brushless DC motor is selected as the drive motor for the urea pump.Target pressure of the supply pump meets the requirements of the SCR post-processor.The main work of the thesis is as follows.1.Firstly,the basic structure of the brushless DC motor and its driving method and the working principle of the brushless DC motor are briefly analysed.With a full understanding and analysis of the brushless DC motor,the mathematical models of the three-phase winding phase voltage equation,the motor output electromagnetic torque equation and the motor motion equation are established using its working principle and complete the mathematical model of the overall brushless DC motor.2.Study the fuzzy control algorithm of the brushless DC motor based on the operating characteristics of the urea supply pump.A brief introduction and analysis about the working characteristics,control principle and parameter adjustment methods of the traditional PID control algorithm is given,followed by a brief introduction of the control principle,control structure,design steps and control parameter adjustment principles of the fuzzy PID control algorithm,and finally simulation experiments are carried out.The simulation experiments firstly design the fuzzy controller in the MATLAB command window,followed by the fuzzy controller in the MATLAB/ In the simulation experiments,the fuzzy controller is first designed in the MATLAB command window,then the simulation model of the brushless DC motor and its speed control system is built on the MATLAB/Simulink platform,then the electromagnetic torque waveforms and speed waveforms of the brushless DC motor are compared between the fuzzy PID control and the traditional PID control in two operating modes,and finally the control performance of the fuzzy PID control and the traditional PID control is compared and analysed.The superiority of fuzzy PID control algorithm for speed control.Complete the control algorithm design part of the motor drive control system.3.3.Design the hardware circuit of the motor drive control system.The S32K142 is selected as the main control chip for the hardware circuit of the control system and the advantages of this control chip are briefly explained.This is followed by the design of the three-phase full-bridge inverter circuit and the Hall signal circuit responsible for the real-time detection of the motor rotor position.4.Brushless DC motor speed test and urea pump pressure test on the urea pump test rig.The results of the testing and analysis are used to verify the feasibility of the motor drive control system.5.Finally,a summary and reflection on the research content of this paper is presented,and a research outlook on the brushless DC motor and its drive control strategy is proposed. |
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