Research Of Position Detection Method For Three DOF Permanent Magnetic Spherical Motor Based On Rotary Encoder

Permanent magnet spherical motor is a new multi-dimensional motor, which has many features such as simple structure, light weight, small size, relatively simple control. Compared to conventional motor, it can effectively simplify the complexity of the structure and improve static and dynamic performance of the system in movement of the three-dimensional space. In this paper, A new three-DOF spherical motor is analyzed and researched which is based on the analysis of the development of multi-DOF motor. Kinetic model suitable for the motor is established and proposed. In the basis of the research and the analysis of the kinetic model and the three DOF position detection device based on the rail structure of the rotary encoder, PD control strategy based on the position detection get simulated and verified.The main work of this paper includes the following specific areas:(1)a three-DOF spherical permanent magnet motor is proposed, Its structure, torque and motion characteristics are analyzed. The spherical permanent magnet motor stator poles are made of two layers of24coils and its rotor poles are made of four layers of40permanent magnets. On the basis of the analysis of the magnetic force between a single pair of stator and rotor pole, the relationship between torque and angle about a pair of stator and rotor pole are fitted. Combined with permanent magnet spherical motor rotor position parameters the expression of the synthetic torque of the motor is derived.(2) Kinematic model of single rigid body elaborates the transformation of the three-dimensional rotating coordinate. By rotating the three axes successively, It was verified that it is more suitable to describe the motor rotor position using X-Y-Z Euler angles. According to two kinds of the rail structure of the rotary encoder which is used for position detection, it forward kinematic analysis and inverse kinematics analysis provides a theoretical basis for three DOF position detection(3) By means of simulating the detection of the rotor position by the analysis of single DOF movement, two DOF movement and three DOF movement, the relationship between spherical motor rotor position and the encoder gets the similarities and differences between the two rail structure. The rotation matrix T is simulated for solving the stator position of spherical permanent magnet motor in space(4) the kinetic model of spherical permanent magnet motor is solved by analyzed the relationship between magnetic field, torque and current in the coil. By dynamic modeling the motor using Maltlab, the motion control system based on PD control about spherical permanent magnet motor is established, which Analyses the change about location tracking, position tracking error, torque control and the impact of the delay on the PD measuring system. It provides the basis for in-depth study of the spherical motor.The work is supported by the National Natural Science Foundation of China (51100771,51307001), the National Science Research Key Program of Anhui Provincial Education Department (KJ2013A012) and Anhui Provincial Science Foundation (1308085QE82).