| Voice coil actuators(VCAs) are special electrical machines which operate only within a range of stroke lengths or angles. Compared with traditional electrical machines,VCAs have many outstanding advantages, such as small volume, direct driving without gears, high precision and low inertia, and so used for driving light weight and low inertia loads. VCAs can be classified into single magnetic circuit VCAs and dual magnetic circuit VCAs from the aspect of magnetic circuit structure, or linear VCAs(LVCAs) and rotary VCAs(RVCAs) from the aspect of motion type. Dual magnetic circuit RVCAs are the main research objects of the thesis, which are commonly used for precision servo drive systems working within limited angle range in some areas such as aerospace.With finite element analysis software(Maxwell), the relation between peak parameters and rotor parameters, the principle and restraining measures of both electric damping and armature reaction are analyzed detailedly. In addition, an experimental motor is made to conduct experimental study.At present, most studies relating to VCAs focus on electromagnetic design and stator parameter optimization, while the influence of rotor parameter on motor performance is neglected. In this paper, analytical expressions of RVCAs’ peak torque and peak loss are derived based on simplified magnetic circuit models, and influences of wire diameter and equivalent coil area on peak torque and peak loss are also analyzed. Especially, two unique influences of installing dimension and environment temperature for this type motor are researched as well. Finally, several effective measures of improving RVCAs’ peak torques are summarized.Articles relating to electric damping effect are rare. In this paper, principles of electric damping effect in both single and dual magnetic circuit RVCAs were analyzed.Through theoretical derivation, the analytical expressions of damping force were obtained, and then verified by finite elements analysis. It is proved that the electric damping of single magnetic circuit RVCAs is caused by different magnet polarities, while that of dual magnetic circuit RVCAs is caused by different magnetic field layers or magnetic field margin effect. The electric damping magnitude caused by different magnetic field layers is nearly 30 times greater than that caused by magnetic field margin effect. With ANSYS Workbench, it is verified that rotor frame made in aluminium alloy has better thermal and mechanical performance that that made in polyimide. For rotor frame made in aluminium alloy, a horizontal slit makes deformation increase by 4.24%, while a vertical slit makes deformation increase by 5 times, which should be avoided.The armature reaction of RVCAs is also studied in this paper. Base on magnetic circuit analysis, structures with parted magnetizer boards are proposed to mitigate armature reaction, and compared with traditional structures with holes on magnetizer boards.According to the finite element analysis, the air gap flux density of parted top and bottom magnetizer boards structure is the most uniform. In addition, a structure with magnets in the gaps on top and bottom magnetizer boards are also proposed to improve torque and compensate for the decrease of air gap flux density caused by gaps. Then gap width and the height of magnets in the gaps are further optimized so that air gap flux density becomes more flat.Finally, an experimental motor is made. Peak indicators, voltages between different rotor arms, and peak torques when rotor stands in different position are all tested. The experimental results match with the results of theoretical and simulation analyses, which proves the correctness of the aforementioned analytical approaches. |
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