Research On Magnetic-thermal Coupling Characteristics Of High Overload Motors In Robot Joint

Permanent magnet synchronous motors have become the most common drive motors for quadruped robot joints due to their excellent performance,superb interference,compact size,low weight and small fluctuations.As robotics advances and the performance requirements of permanent magnet synchronous motors increase,traditional motor designs are no longer applicable.However,there is little research on how to optimize the design of motor stator and rotor parameters to achieve high performance output for such motors with the same size limitation.The torque overload capacity and load torque fluctuation of permanent magnet synchronous motor are analyzed.Starting from the basic formula of electromagnetic torque and voltage equation of the motor,the main reasons affecting the motor torque overload capability are analyzed,and the key parameters affecting the motor torque overload capability are obtained as cross-axis and straight-axis reactance,back-EMF and core magnetic saturation degree.By changing the structural parameters of stator and rotor,the effects of different tooth width,slot width,permanent magnet thickness and pole arc coefficient on the torque overload capacity of permanent magnet synchronous motor are analyzed;from the basic principle of torque fluctuation,the main components of torque fluctuation are slot torque and ripple torque at load,combined with the method of freezing magnetic permeability,the effects of different tooth width,slot width,permanent magnet thickness and pole arc coefficient on The effect of different tooth width,slot width,permanent magnet thicknesses and pole arc coefficient on motor torque fluctuations is analyzed in conjunction with the frozen permeability method.A quadruped robot joint high overload motor was designed.The influence of three parameters on the performance of the motor,namely,the pole-slot combination,the stator inner diameter and the air gap,is analyzed in detail.The final design of the motor is determined by comprehensive analysis of each parameter.A two-dimensional model of the motor is established,and the simulation calculation of the motor under different loads is carried out by the finite element method to obtain the waveforms of key parameters,such as no-load back-EMF,air gap magnetic density and output torque,etc.The overload capacity of the motor and the torque fluctuation under overload conditions are also calculated to verify the rationality of the designed motor.The temperature rise simulation calculation of the motor under different loads is carried out.The density,thermal conductivity,specific heat capacity and volume of each material are accurately calculated by building a three-dimensional model of the motor and simplifying the windings and so on,and the heat dissipation coefficient and heat generation rate of the motor are accurately estimated according to the different load conditions.The steady-state temperature field and transient temperature field simulations are carried out for different load conditions of the motor to prove that the temperature rise of each part of the designed motor is within the required range.By building an experimental platform and connecting experimental equipment,the prototype is tested systematically,and the obtained data are compared with the simulation experimental results to verify the rationality of the prototype design.