Research On Concentrated Winding Limited Angle Torque Motor And Its Characteristics

Limited angle torque motor(LATM)without any complex intermediate transmission devices,can rotate within a limited angular range.It has many advantages,such as simple structure,high reliability,simple control and so on.Nowadays,the LATM products are mostly toroidally wound type,and the fatal drawback of low torque density makes it difficult to apply to the occasions where the volume and weight of motor are strictly limited.Although the slotted LATM has a higher torque density,there are prominent problems such as large cogging torque,severe magnetic field saturation and nonlinearity of the torque characteristic within its operation range.In this thesis,a concentrated winding LATM is put into focus,and the problems of mechanism,estimation method of constant torque range,operation characteristic and nonlinear magnetic circuit model have been studied.Aiming at the conventional slotted LATM,the magnetic circuit structure and mechanism are analyzed.On these basis,a concentrated winding LATM is proposed,and its electromagnetic torque is deduced by the magnetic equivalent circuit method.Based on the electromagnetic torque formula,the main dimensions of the motor are determined by taking full consideration of the given design requirements,and the LATM structure is optimized by finite element method(FEM).In order to further improve the torque density of the concentrated winding LATM,a pointed tooth-tip is proposed,and the comparison and verification of electromagnetic performance between the conventional parallel and the pointed tooth-tip are carried out by the prototype and experiment test.It is found that the torque performance of the latter increases by about 29 %.Using the Laplace's and Poisson's equations of the constant magnetic field,a magnetic field subdomain model for concentrated winding LATMs is established.Both no-load and load characteristics of LATMs are calculated by the model,and the magnetic field subdomain model is verified by FEM.In order to estimate the constant torque range of the concentrated winding LATM based on the magnetic field subfield model is proposed.Under the condition of the given current and torque ripple band,the constant torque range is obtained by the proposed method.The static torque measurement of the both prototypes with 4 poles/4 slots and 12 poles/12 slots are carried out,which validates the proposed estimation method.After analyzing the conventional mathematic model of the LATMs,the accurate mathematic model is proposed.Compared with the constant electromagnetic parameters such as torque coefficient,inductance in the conventional mathematical model,the proposed model can take full consideration of the torque coefficient,the flux and the inductance versus with the winding current and the rotor position.By using this model,the simulation method of position tracking characteristics of LATM is obtained.Compared with the traditional field-circuit coupling method,the computation efficient of the proposed method is much higher keeping with the same computation precision.A thermal circuit model for concentrated winding LATMs with is proposed to estimate the operating temperature of the machine.The operation experiment for the 4 poles/4 slots prototype are carried out to validate the position tracking characteristic and the estimation method of the temperature.Referring to the LATMs with cylinder stators and rotors,and symmetrical distribution of teeth,a rectangular LATM with asymmetric tooth is proposed.Based on the principle of magnetic circuit,a nonlinear magnetic circuit model of the rectangular LATM with asymmetric tooth is proposed,and the calculation results of the model are compared with the FEM.The nonlinear magnetic circuit model can consider fully the magnetic circuit saturation problem,and the calculation time is short.After preliminarily designing the novel LATM based on the nonlinear model,the shape of the teeth is optimized further by FEM.Finally,the rectangular LATM with asymmetric tooth is designed and manufactured.The experimental results indicates that the output torque of the rectangular LATM with asymmetric tooth is better than the LATM with cylinder stator.