Magnetic Field Optimization And Rotor Orientation Measurement Of A PM Spherical Motor

A PM spherical motor is electromagnetism-based multi-degree-of-freedomactuator with novel structure and operation principle. The kind of motor present itsunique advantages and potential prospect in engineering application. However, thereis also distinct diversity with the spherical motor in magnetic field distribution, toqueand control methods, if compared with conventional electric motor. At present, thestudy on the spherical motor is in the early stage of exploration. The advancement inthe electromagnetism design, analysis and motion control of the motor can not meetthe requirement of practical application and intensive study is required.The thesis presents a novel design concept of PM spherical motor with Halbacharray on rotor surface and the structure and operational principle are given. Theanalytical model of the magnetic field for the spherical rotor with Halbach arraymagnet is established with the spherical harmonic theory and the fundamental andharmonic of the magnetic field is analyzed. The effect of the magnet structureparameters and material property on the magnetic field distribution is analyzed.To obtain ideal magnetic field distribution and make the best of magnetic material,the analytical model of magnetic field of PM spherical motor in air gap is used toestablish the mathematics model for pole shape optimization of PM spherical rotorwith Halbach array which take the fundamental percentage and magnetic materialvolume as objective functions. Particle swarm algorithm is used to perform the multiobject optimization and the optimization schemes are obtained. The optimizationresult is presented.The analytical toque model of PM spherical motor for individual hollow windingin the air gap magnetic field is established according to Lorentz law. The effect of thewinding structure parameters and air gap width on the toque is analyzed. The resultanttoque model for multi windings is established on the basis of above analysis. Thetoque resultant algorithm for multi windings based on the principle of minimumenergy and grouping of dividing the windings into three groups orthogonal to eachother along equivalent spinning axis.An optics-based orientation sensor for spherical rotor is presented for the closeloop control of spherical motor. The sensor uses two ring detectors to detect thelongitude and latitudes on rotor surface. The intersection points obtained are used to compute ZYZ angle of rotor. The static characteristics of the sensor are deduced andthe performance parameters are analyzed. The sensor is verified experimentally.According to the motion of PM spherical motor, the forward and inversekinematics model and the Jacobi formula are deduced. On this basis, Lagrangeequation is used to establish the dynamics model for PM spherical motor.Higher-degree polynomial algorithm and linear interpolation algorithm of trajectoryplanning are presented and verified with simulation methods.