| The permanent magnet (PM) spherical motor can realize multiple-DOF motion. Itgreatly simplifies the mechanical structure and improves the response and positioningaccuracy of transmission systems. Therefore, it becomes a new research hotspot inPM motor field. However, related technologies in this branch are not mature, most ofwhich are still in theoretical stage.This paper proposes a PM spherical motor with a new structure and builds itsfinite element model. The electromagnetic forces between the PM poles and the coilsat different positions are analyzed. Based on the above, the rotation torque of PMspherical motor is obtained.In this paper, a synthesis method of magnetic levitation force in PM sphericalmotor is presented and Lorentz force is utilized to produce at the same time rotationtorque and levitation force. As there is no direct contact between the stator and rotor,it overcomes the adverse impact of friction torque.Then the equation of levitationforce control is established. The required magnetic levitation force can be synthesizedby controlling the stator currents. Simulation model is constructed; furthermore therelationships between coil currents and magnetic levitation force when there is noeccentric deviation are studied. The results show that the synthesis method oflevitation force is feasible and can provide a basis for control system design.In this paper, hysteresis current control method is applied to the permanentmagnet spherical motor. Conventional hysteresis current control method has manyadvantages such as fast response speed and simple hardware structures, however, itshysteresis switching frequency cannot be stabilized, this paper proposes a newring-width-prediction method to stabilize the frequency.This paper also introduces a hardware experimental platform which is built upbased on TMS320F2812DSP and the major components of hardware circuit areshown. By this hardware platform, the PM spherical motor can realize smoothrotation. |
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