Research On Over Load Thermal Field And Linear Sensor Magnetic Field Of Motors For Joint

Joints are the basis components of robot, whose performance has a direct impact on the reliability of the robot. Based on the operation characteristic of the robotic joint system, the drive motor for joints should have small size, high power density, low torque ripple, low inertia, wide speed range, high reliability and so on. Compare to other motors, permanent magnet synchronous machine which has excellent performances is widely used in the joint drive systems with high precision.Through researching the overall characteristic of the drive system for robotic joints, a high power density permanent magnet synchronous machine is designed and a linear hall sensor is used as the position detection components of motor in this paper. The simulation of motor's magnetic field is done using the FEM method. The magnetic field distribution of the motor is studied when motor is operating. The validity of the motor's design is demonstrated.Beacause of the asymmetry of rotor structure, the equation of motor is nonlinear time-varing equation. The d-q coordinate system is used to decoupling the equation, and the mathematical model is given in the d-q coordinate system. According to the different vector control methods, the mechanical and efficiency properties are analyzed in the Id=0 control mode and voltage control mode. Operating performance on the influence of control method is analyzed.Based on the characteristic of joint drive system, such as a wide range of load changes, high over load ability, normal operation under locked-rotor operation, steady-state and transient thermal field are analyzed when motor operates in the rated operation. Through changing the load, the change of temperature rise and overload ability are studied. At last, the temperature rise is analyzed when motor operates under locked-rotor operation.In order to acquire the position signal of motor during operation, not only the high precision linear hall sensor is required, but also the sinusoidal flux density is acquired. Through changing proportionality coefficient, the thickness of magnet and detection distance analyzes the sinusoidal magnetic field, and sinusoidal magnet is given under different pole pairs.