Research On Improvement Of Electromagnetic Properties And Control Strategy Of Motorized Spindle Cells

Motorized spindle cell is a key component of high-speed CNC machine tools and its operating characteristics determines the machining quality of the machine tools. The main problems of motorized spindle in running are the temperature rise caused by electromagnetic loss and the vibration of the interaction of the magnetic field. Moreover, the power of motorized spindle is supplied by inverter and its output voltage (current) is non-sinusoidal with harmonics, resulting in a series of harmonic effects. The harmonic effects influence the performance and service life of the motorized spindle. Therefore, it is necessary to study the electromagnetic characteristics of the motorized spindle under inverter supply. In addition, the operation characteristics of the motorized spindle relate closely to the control system and high-performance electric spindle needs to match the high performance control system. So it is necessary to improve the performance of the control system. On the basis of the deep analysis of the electromagnetic loss, electromagnetic vibration and direct torque control strategy, the methods to improve the electromagnetic characteristics and the control strategy of the motorized spindle are studied in this paper. The main works and conclusions are summarized as follows:The influence of the power form and load and shaft materials on the electromagnetic loss is researched based on the finite element in order to reveal the essence of electromagnetic loss. Loading and measuring the load applied on a high speed motorized spindle in the non-machining state is an important issue in performance evaluation of high speed motorized spindle. A new method is developed through connection mode to make the loading possible in the experiment. The influence of the load and shaft materials on the efficiency and electromagnetic loss of the motorized spindle is further researched using that device. The simulation and experimental results show that applying the ceramic material to the shaft of the motorized spindle may reduce the electromagnetic loss effectively.The influence of the power form, load and shaft materials on the electromagnetic vibration is researched by the simulation and experiments in order to reveal the essence of electromagnetic vibration. The results show that the vibration speed of ceramic motorized spindle is smaller than the metal motorized spindle through the comparison of two kinds of motorized spindle under the same structural parameters. The influence of length and eccentricity of air-gap on the performance of the ceramic motorized spindle is further researched through simulation and experiment. It is pointed out that the bigger the air gap is, the smaller the vibration and noise of motorized spindle are. But at the same time, the efficiency of motorized spindle is reduced. Air-gap eccentricity results in unilateral magnetic force in motorized spindle and the deformation of the ceramic motorized spindle is smaller than the metal motorized spindle under unilateral magnetic force.A direct torque control spindle simulation model is established based on dynamic model of the motorized spindle and direct torque control principle, in order to analyze the influence of variation of stator resistance on performance of direct torque control. The main factors of influence the variation of stator resistance is analyzed in theory. The stator resistance under cold and hot conditions is measured by means of reference on the national test standards for motor parameter and the influence of stator current, operating frequency and temperature on the stator resistance is analyzed.A hybrid intelligent stator resistance identification strategy is proposed based on artificial neural network (ANN) and Case-Based Reasoning (CBR). A model for the stator resistance identification is established based on ANN-CBR. By comparing the recognition results and experimental results, it shows that the method fits for non-linear characteristics of the stator resistance identification problem with higher recognition accuracy.This thesis proposes the effective method to improve the running characteristics of motorized spindle based on study of the electromagnetic characteristics and direct torque control strategy. A basis is provided for the application of new material on motorized spindle and the theoretical foundation is established for the application of hybrid intelligent method in control system of motorized spindle.