Research On Direct Drive System Of External Rotor PMSM For Textile Double Twister

Traditionally,the double twister is driven by asynchronous motor with belt,which has the disadvantages of high energy consumption,uneven rotation speed of each spindle and inflexible production.Compared with it,using permanent magnet motor with belt is more energy-saving,but it still can not avoid the inherent defects of this transmission mode.The electric spindle double twister uses a low-power external rotor permanent magnet motor to drive each spindle directly,which can reduce the transmission chain and improve the yarn product quality.However,the cost of the transmission system increases after direct drive,which also puts forward higher requirements for the stability of the output torque.This paper focuses on the direct drive system of external rotor permanent magnet motor for double twister.The main research contents are as follows:The permanent magnet motor direct drive system is used to replace the original mechanical transmission system,and the average value of motor output torque and torque fluctuation are optimized under the selected optimal pole slot coordination.Through the analytical method,it is analyzed that the parameter factors significantly affecting the optimization objective are pole arc coefficient,air gap length,permanent magnet thickness,stator slot depth and stator slot width,and then the mathematical relationship between the optimization objective and each optimization variable is fitted by the response surface method,then the Pareto front of the optimization problem is obtained by evolutionary algorithm,and the global optimal solution is objectively selected by TOPSIS method.After the verification of finite element calculation,an external rotor permanent magnet motor for electric spindle double twister which can replace asynchronous machine and belt is finally determined.The outer rotor motor for double twister has high working frequency and large stator iron consumption.Due to the outer rotor structure,the heat source is located in the middle of the motor,so it is difficult to dissipate heat.This paper calculates the loss of each part of the motor,analyzes the temperature of each part of the motor by using the equivalent heat network method under the determined natural air cooling conditions,and explores the relationship between the temperature rise of micro outer rotor motor and heat load,and verify that the permanent magnet will not have irreversible demagnetization at the rated working point.The linear speed of the outer rotor motor studied in this paper is high,and the mechanical strength of the rotor is analyzed.The double twister works in the dirty environment with cotton lint flying,which may affect the sensor signal transmission.Based on this working condition,the position free control strategy of permanent magnet motor based on id = 0 is studied,and an improved sliding mode observer using sigmoid function instead of symbolic function to weaken chattering is proposed.A three-stage speed control scheme is designed,which uses I / f full load starting at low speed,current drop method for switching,and improved sliding mode observer for angle estimation at medium speed.The simulation results show that the motor speed is stable without impact,and can better suppress chattering and have stronger stability.