Research On Well Logging Permanent Magnet Brushless DC Motor Drive System Based On Fuzzy Logic

In view of performance requirements in extreme work environment for the permanent magnet Brushless DC motor applied to well logging, fuzzy fractional order PID control algorithm is adopted to improve the performance of the well logging drive system, which is analyzed through simulation and experiments. Hardware circuits and software program are designed to realize relevant functions to make sure the motor can drive the logging instruments to operate reliably in the underground environment.First, in order to improve the control performance, fractional order PID control strategy is applied to well logging motor drive system, and the order of every link of PID regulator is extended from integer to fraction. The transfer function of the well logging Brushless DC motor is given, on the basis of which the characteristics of integration order and differentiation order are analyzed. Under the SIMULINK environment, a double closed-loop Brushless DC motor drive simulation model is established, and the performance of fractional order PID controller and integer PID controller are compared. The simulation results show that fractional order PID control algorithm is more flexible, which can improve the stability and dynamic response ability of the well logging drive system.Second, in order to make the motor operate more smoothly in the well logging environment, fuzzy logic theory is applied to the motor drive system to improve its adaptability, and fuzzy inference rules are determined according to the characteristics of every part of the fractional order PID controller. By using MATLAB fuzzy logic toolbox, we design the fuzzification part and defuzzification part of the controller, and this fuzzy controller is applied to adjust the parameter of fractional order PID controller in the speed loop of the well logging motor drive system. The simulation results show that fuzzy fractional order PID control strategy can efficiently improve the dynamic performance and robustness of the well logging drive system.On the basis of well logging Brushless motor, hardware circuits are given to achieve the functions required by the drive system, the hardware parts include DSP main processing unit, rotor position acquisition unit, current sampling unit, logic level conversion unit, main circuit MOSFET power driven unit and instruction communication unit. Based on the hardware parts, software system is also given, which is composed of AD sampling module, soft starting module, logic commutation module, 485 instruction communication module, digital fuzzy PID module, etc.Finally, the motor drive system applied to well logging is tested by experiments. The results of the experiments show that this system can realize the function of communicating with upper computer, and the fuzzy control strategy can improve the performance of the well logging drive system. This motor drive system is compatible with the other parts of the logging instruments to realize required functions.