Research On The Limited Angle Torque Motor And Its Characteristics

Limited angle torque motor(LATM)can directly move back and forth in a limited angle without any intermediate transmission mechanism.It has the advantages of higher power density,ordinary mechanism,ordinary control mode and high reliability.Therefore,it is widely used in the complex control field of defense and medical.The existing series products of LATM are mostly ring wound type,but the motor with this structure has the disadvantage of low torque density.Although the torque density of cogging type LATM is higher,the nonlinear torque characteristic caused by magnetic circuit saturation results in smaller operating range and the cogging effect results in larger torque fluctuation in constant torque range.In this thesis,taking the surface semi-inserted LATM of the stator tooth groove as the concentrated winding structure as an example,the electromagnetic mechanism,constant torque range,the relationship between electromagnetic torque,magnetic chain and current as well as rotor position angle,current and rotor position angle,and the comparison with conventional cogging structure are analyzed.In this paper,based on the analysis of the magnetic circuit structure and electromagnetic mechanism of the LATM,an structure scheme with the ratio of insertion depth to thickness of permanent magnet of 1/2 is provided.And through the classical magnetic circuit method,the analytical formula of electromagnetic torque is derived.And according to this structure,the finite element method is used for numerical simulation,Simulation results show that,using this mechanism,the torque fluctuation in the constant torque range can be reduced obviously,and the linearity of torque characteristic is good,which can meet the engineering requirements.The magnetic field subdomain mathematical model of the surface semi-inserted LATM is established,And based on this model,a method is provided to estimate the constant torque range of the surface semi-inserted LATM.In order to verify the correctness of the established model,this paper uses the numerical calculation of mathematical model and the finite element calculation of electromagnetic field in the motor for the no-load,load characteristics and constant torque range of the motor.The consistency between the two results is good,which shows that the provided magnetic field sub domain mathematical model and constant torque interval estimation method are correct and reasonable.Based on the finite element simulation models of the surface semi-inserted LATM,analysis of the relationship between the motor magnetic chain and electromagnetic torque and the current and rotor position angle,and the temperature-up characteristics of the motor within the constant torque range.It is concluded that the magnitude of the current value has almost no effect on the flux of the motor,but the flux of the motor changes linearly with the rotor position angle;the electromagnetic torque increases linearly with the increase of the current value during the constant torque period;and the motor can operate safely under rated conditions.The simulation model of conventional 4-pole 24-slot surface semi-inserted LATM is established,its electromagnetic characteristics are analyzed by the finite element method,and contrast with a concentrated winding structure.The results show that the constant speed range of the surface semi-inserted LATM with concentrated winding structure is larger than that of the conventional cogging type,and the cogging effect has little effect on the constant torque range,but the torque fluctuation value is larger than that of the conventional cogging type.