The Design And Control Of Slice Type Permanent Magnet Bearingless Motor

Slice Type Permanent Magnet Bearingless Motor(SPMBLM) is a novel type of bearingless motor. Maintaining the basic characteristics of bearingless motor that it combines torque-output and self-levitation capabilities, SPMBLM may possibly achieve 5-freedom-degree-levitation due to its slice-like structure. And this unique structure would give rise to less cost in manufacturing and controlling, which endows it with the best industrial perspective among bearingless motors so far. This thesis focuses on the principle, design and control of the SPMBLM, which possesses significant theoretical value and engineering prospect and is organized as follows:Firstly, Based on the principles of the radial force rotor bears, the harmonics components of the magnetic field in the air-gap of a non-saliency beaingless motor is analyzed and in order to describe the radial suspension characteristics of a non-salient bearingless motor, the concept of space harmonics is redefined. Based on this new definition, a complete analytical expression of tradial force with the space harmonics effect considered is presented. The presented expression is validated by comparison of the field-circuit coupled method with the 2D Finite Element Analysis (FEA) method in detail and the possible magnitude error is also discussed further. These works offer a valuable guidance for the design of permanent magnet bearingless motor from the viewpoint of theoretical fundamentals.Secondly, some design considerations of a SPLBLM is proposed with the optimization method of the magnetic suspension system, the shape of rotor's permanent magnets, the distribution of suspension winding. included. The improved linear characteristics of the racial force and passive levitation charactoristics are both validated by 2D and 3D FEA.Thirdly, the rotor flux Field Orientation Control (FOC) is applied for the torque sub-system of this SPMBLM. Based on the torque sub-system FOC, an integrated mathematical model is established with both the torque and the suspension sub-system and all the coupling factors considered. A control strategy with eccentricity and torque current compensation scheme is suggested for the model. In addition, in order to improve the dynamic characteristics, an enhanced PID control algorithm is proposed for the rotor displace control. Simulation study of the SPMBLM verifies the feasibility and advantage of the control strategy when suspension system is under both electromagnetic and mechanical interferences.Finally, a digital SPMBLM controller based on the TM320LF2407 Digital Signal processor and the corresponding control program float chart is also presented with the major modules in detail. The static levitation of the SPMBLM in single radial freedom degree is experimented with this motor system.