Ball Mill Modular Permanent Magnet Direct Drive Motor Sensorless Control

At this stage,the drive system of the ball mill is still mainly composed of three-phase asynchronous machine,reducer and large and small gears.Due to its lengthy transmission chain,this traditional driving method has the disadvantages of low transmission efficiency,frequent maintenance,difficulty in starting and speed regulation,such as large size,etc.In view of the above problems,this project uses a low-speed and high-torque permanent magnet synchronous motor to directly drive the roller of the ball mill,cancels the deceleration link,and uses the frequency converter to start,stop and adjust the speed.This paper mainly studies the direct drive system of the ball mill,analyzes the control method of the motor and designs the control system.The main research contents are as follows:First of all,the drive motor of the ball mill should be studied,and the motor scheme design should be carried out in combination with the low-speed and high-torque characteristics of the ball mill load,and the general design rules of the direct-drive permanent magnet motor for ball mills should be summarized.The direct drive permanent magnet motor designed in this paper has a special structure,and the stator adopts a modular design,and each module is an independent unit motor.According to the given speed,power and rated voltage of the ball mill motor to be transformed,the size of the direct drive motor is estimated,and the electromagnetic scheme of the undivided motor and the modular motor is determined.The finite element models of the unblocked motor and the modular motor are established,and the rationality of the stator modular permanent magnet motor is verified through simulation analysis and comparison.The permanent magnet motor can use the sensor to obtain the position information of the rotor,but in the design of this paper,the installation space of the sensor is limited,the installation concentricity is difficult to guarantee,and it is also affected by vibration and dust during operation.Based on the above factors,the control method of the motor adopts the sensorless vector control,and the high frequency voltage signal injection method is used to realize the sensorless control at low speed.The principle and application of the rotating high frequency voltage injection method and the pulse vibration high frequency voltage injection method are expounded,and their advantages and disadvantages are compared and analyzed.The vector control adopts PI regulator,and the vector control model based on PI regulator is established and analyzed by simulation.Obtaining the position information of the rotor is very important for sensorless control.In this paper,a PI regulator is used to construct a PLL system.Finally,a sensorless vector control simulation model based on PLL-based pulse-vibration high-frequency voltage signal injection is established to prove the accuracy and feasibility of the sensorless control method.The collaborative control of the modular permanent magnet motor is studied to provide a theoretical basis for the subsequent control scheme of the drive system.Combined with a certain equipment manufacturing enterprise in Henan,a direct drive motor prototype with a rated power of 80 k W and a rated speed of 27r/min has been developed.In order to complete the prototype test experiment of the modular motor,the control system is designed,and the system composition includes the host computer（computer touch screen）,PLC controller,frequency converter and modular motor.Synchronous control of modular motors is accomplished by writing Lab VIEW programs and PLC control programs.Through the verification test,the feasibility of the control system and the correctness of the proposed study are proved,and the research on the permanent magnet direct drive system of the ball mill has certain reference value.