| Permanent magnet linear servo motor (PMLSM) has the advantages of simple structure, small size, light weight, high thrust density, high efficiency, good controllability and stable and reliable operation. Thus it has gradually become the mainstream of the linear servo motor. However, how to improve the thrust density and weaken the thrust ripple have been two important contents in the research field of PMLSM. The studies of two commonly used PMLSM structures are carried out about the two issues in this paper. One is double-side air-cored PMLSM (DAPMLSM) which is suitable for light loads, rapid response, high precision requirements, and another is unilateral water-cooled PMLSM which is suitable for high-load, high-thrust occasions.Firstly, based on the equivalent magnetization intensity (EMI) method, the unified hierarchical linear model is established for PMLSM magnetic field and thrust analytical calculation. It is suitable for permanent magnet with different shapes and distribution, different AC or DC armature currents and different winding distributions.Secondly, the electromagnetic design of DAPMLSM is studied. Analytical expression of no-load air-gap magnetic field is obtained based on EMI. One simplified and unified method for other shapes PM is introduced, through dividing PM to rectangular segments and then superposing. The selection principles of motor parameters are given after analysis. Intelligent algorithm is introduced to optimize the no-load flux density waveform, effectively reducing the thrust fluctuations and improving the servo performance. The larger transverse end-effect of DAPMLSM will affect the air-gap magnetic field, no-load back EMF and thrust. Thus a flux leakage coffeient is defined to evaluate the end-effect, and it is influenced by the transverse length of the motor, the height of the air-gap and the height of. PM Experiments of the prototype verify the credibility of the analytical model and finite element analysis.Thirdly, the electromagnetic design of unilateral water-cooled PMLSM is studied. The magnetic field distribution characteristic at the end of the primary is obtained. The detent force is reduced through comprehensive use of various methods after the source analysis. Based on the established linear motors platform, reciprocating motion characteristics under no-load and load conditions are measured. The results indicate the motor has good servo performance.The final studies mainly focus on its thermal characteristics and reasonable cooling system design to improve its electromagnetic load and thrust density. Based on the loss calculation results, a three-dimensional model coupling temperature field and pipe flow is established. It calculates fast and could comprehensive consider the heat source modification, the thermal contact resistances, heat transfer between the primary and the secondary, water flow and its cooling effect on the temperature distribution in the motor. The thermal characteristics of the usual and the water-cooled motor in different conditions are studied. The obtianed maximum permissible load current and the maximum operating time provide guidance for the motor drive. The parameters selection methods and the design principles of the water-cooling system are provided for the guidance of PMLSM water-cooling system design. Because for the additional water-cooling system, the maximum thrust density is improved2.6times with the same temperature rise limits. It indicates the drive ability of PMLSM is greatly improved. Air-insulated isolation and precise cooling system are added to the linear servo system to reduce the temperature of the working platform, reduce the thermal deformation of machine components and to ensure the servo machining accuracy. The experimental results and temperature analysis match well, verfiying the correctness of temperature analytical methods and conclusions. |
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