Basic Research Of Position Detection Method For A Novel3-DOF Deflection Type PM Motor

With the development of the motors from the19th century, the extensive and in-depthresearch of the conventional one-dimensional motor drive mechanism has been carried outby scholars from various countries. However, with the developing trends of themechanical automation and intelligence complication, the requirements of motiontechnology devices by the actuators are not needed to be performed only confined in asingle-degree-of-freedom (DOF) movement direction. Therefore, the motors which canrealize multi-DOF motions have become the research targets of domestic and foreignscientific researchers. As the future tends of the motors to be lightweight and miniaturized,the materials play a decisive role. Currently, with many magnetic materials ferrite, alnico,NdFeB rare earth permanent magnets (PM) and others emerged and due to the PM madeactuators’ appealing characteristics of small size, light weight, simple structure andconvenient operation, etc., the large size and operating heavily motors are graduallyreplaced by the PM motors. Therefore, the multi-DOF PM motors have caught intensiveresearch attention recently in the field of special motors.In this background, a novel3-DOF deflection type PM motor is proposed. On thebasis of referring the various structures of multi-DOF PM motors and their positiondetecting systems, this paper further proposes a new position detect technique for the3-DOF deflection type PM motor with double-layer stator coils and single-layer drum typerotor structure. Based on the analysis of domestic and abroad situations of multi-DOFmotor and its position detection technique, fundamental researches such as modeling themagnetic field, introducing the algorithm and the experimental facilities design have beenconducted on the novel3-DOF deflection type PM motor which is small size, newstructure and easy to control. This main works of this paper mainly contain followingaspects in detail:1) On the basis of a brief introduction of the structure and size of a novel3-DOFdeflection type PM motor, a detailed description for the operation principles of3-DOFmotions are presented. Due to the position detection technology is achieved by measurethe angles of the rotor from detecting device, to achieve a clear relationship between therotation angles and the rotor magnetic field, the transformation of the stator and rotorcoordinates is introduced. Furthermore, the two parameters spatial with forward and inversion models of the magnetic field analysis are illustrated, which can be taken asconceptual basis for the modeling part of detection.2) According to the material properties and structure of the PM, this paper adoptsdistributed multipole (DMP) model for characterizing the equivalent magnetic field modelof the rotor PM. Based on the brief introduction of the basic theory of magnetic field, theDMP equivalent transformation of both cylindrical PM and multi-layer coil are carried outand simplified equivalent DMP models are established. At the same time, the Matlaboptimization toolbox is used to validate the established model and the validation resultsshow the effectiveness of the model.3) According to the DMP model theory, the position detection system model of themotor has been proposed, and the methods and principles of using linear hall sensors tomeasure magnetic field of the PM are introduced. Simultaneously, the polynomialapproximation to the relationship between the magnetic field of motion and the angles ofrotation is analyzed and studied, and then the simulations to the forward and inversionmodels of the detection system are implemented respectively, with the simulation resultsand error validating the reasonableness of this method.4) After detailed discussions and analysis of motor’s magnetic field and detectionsystem, the experimental platform for the position detection system of the motor based onlinear hall sensor has been built. The experimental study of using traditional multi-pointmeasurement method with gauss meter to detect rotor position is addressed in detail, andthe results of experimental studies are compared with the results of analysis model.Meanwhile, a preliminary experimental study for the automatic detection method based onthe potion sensors are carried out, whose core element is the STM32F103BT6in ARMseries. Experimental results show that the measured rotor positions and rotation angles bythe multi-point measuring method using the gauss meter are in accordance with theanalysis results, which proves the designed program can achieve the position detection ofmotor; on the other hand, the preliminary experimental results of automatic detectionbased on the position sensors prove the rationality of the system and at present thein-depth study of the system is still in progress.