Research On Embedded Position Detection Method Of The Servo Motor Based The Time Grating Sensing Technology

Since the 21 st century,China’s industrial automation has entered a new stage.Alternating current(AC)servo control has been the mainstream of mechanical automatic control system and is developing rapidly in the direction of integration and intelligence.However,as a basic component of automatic control,few servo motor integrated with the key position detection technology.Thus,how to embed into the motor to detect the position in the full speed range and without destroy the structure of the motor,which is the research direction to solve the problem of position detection of servo motor.The embedded time grating sensor was developed by the author’s research group.It takes advantage of the characteristics of time grating sensor such as structural flexibility and realize measurement equal diversion only use mechanical equalization.The transmission parts(gears,worm gears)and moving parts(bearings)of the electromechanical system are taken as part of the sensor.That breaks the traditional model of installing displacement sensors in coaxial and solves the detection problem in special conditions such as lager and hollow.In this context,study the embedded position detection of the mechanical drive components,which is typically represented by servo motor.Integrated the position sensor with the servo motor body has the advantage of tighten the motor structure and reduce the detection cost.The main contents and innovations of the paper are as follows:(1)Aiming at the traditional detection method of separates the position detection sensor from the motor body,based on the idea of embedded time grating position detection and the structure of motor with the equalizing slot and equalizing permanent magnet,two embedded time grating sensing methods based on coil winding and magnetic sensor are proposed which integrated the motor and detection technology together.In order to construct the moving coordinate system of time grating,the construction methods and the models of various embedded time grating traveling waves with two,three,or multiplexing standing waves are proposed.In the process of derivation,the signal compensation model of "time compensation space" is proposed,and the key technologies to realize embedded position detection are the modeling and decoupling of space magnetic field and the design of position sensing unit.(2)In view of the complex magnetic field environment inside the motor,athree-dimensional magnetic field decoupling method is proposed and the models are building from the end and axial direction.Based on the layered region method,the analytical models are established to solve the differential region of the end-face field when stator and rotor acting alone or together.Based on Biosavart’s law and simplified permanent magnet model,the analytical model is established to solve the axial space magnetic field.Besides,the result of the finite element simulation and the experimental tests prove that the end-face magnetic field distribution meeting the test demand when it is far away from the rotor and positive to the air gap.(3)Aiming at the different structure types of rotor and magnetic sensor,single group and multi-group sensing units are designed respectively.In order to solve the difficult problem of filtering the spatial harmonics whose frequency is changed with rotational speed,the inverse and in-phase harmonic sensor array optimization design is proposed to avoid the complex filtering technology;In order to solve the problem that the number of poles in the motor body is limit,based on the time grating position solution model,the optimal design of sensor array with different frequency space doubling is proposed to improve position detection performance from the sensor source.(4)Develop a prototype of servo motor with position detection function,and design an experimental system to collect test data.Based on the sensing mechanism,analyzed the source of error and built mathematical model,the error correction from signal compensation and data processing are proposed to further improve the detection accuracy.The result of the performance test show that the stability of the proposed method is 9.2″,repetition error is 11.4″,and the precision is within ±10′ in the speed range of 200 rpm.(5)The new method of embedded time grating position detection based on magnetic sensor has been successfully extended to the position detection of the permanent magnet linear motor,the design of active and passive angle displacement sensor.The scheme design,modeling simulation and experimental research are discussed,respectively.In summary,the embedded position detection method is easy to integrate with the measured system,which makes the measured object both as the device and as a part of the sensor,and converts the randomness added by the coaxial mounting sensor into the system error which exist between sensor components and easy to control or eliminate.This paper applied the embedded position detection method into the motor,which provides the possibility for position detection in the narrow space,and opens up a new idea of the integrated detection.The fusion of time grating technology providesguarantee for high precision and high resolution.At the same time,this method opens up a new direction for the diversification of time grating sensors.Under the trend of intelligent measurement and control and integration of servo system,this method has a broad application prospect.