Research On A Compact And Active Three-dimensional Uniform Magnetic Field Compensation System

The use of magnetic field distribution characteristics for non-destructive testing of vehicle metal parts and similar mechanical parts has many advantages compared with traditional testing methods,but some certain requirements for the surrounding magnetic field environment are required.The zero magnetic field environment can minimize the influence of the earth magnetic field and other interference magnetic fields,and provide a better working environment for the above detection methods.Therefore,it is deeply significant to build a zero magnetic field environment efficiently and flexibly.At present,the main means to achieve a zero magnetic field environment are passive shielding and active compensation.Compared with the passive shields,the active compensation has the characteristics of light weight and controllable volume by using compensation coils.Therefore,the study on active compensation technology has high theoretical and experimental value and significance.This thesis designs and builds a compact three-dimensional uniform magnetic field active compensation system.Cosine coil(cosθ)and Lee-Whiting coil are used as the main compensation coils to make the most efficient use of space.A novel 6-DOF manipulator combined with compensation coil is explored to make the system realize the automatic compensation of environmental magnetic field more flexibly.The magnetic field distribution characteristics of the two kinds of coils in space were analyzed theoretically.A three-dimensional coil was developed by using non-magnetic materials and the uniform magnetic field of longitudinal Z axis and transverse X and Y axis was realized.Combined with three-dimensional motion control platform,current control module,HMC5883 L three-axis magnetic field sensor and other devices,a compact uniform magnetic field active compensation system is built.Combined with the forward/inverse kinematics algorithm of the manipulator and the spatial trajectory planning strategy and on the premise of ensuring the effect of magnetic field compensation,the robot arm is used to control the position of coils,which can effectively improve the flexibility and adaptability of the system.The effects of sensor scanning speed,ambient noise and test rod thickness on the magnetic field measurement results are tested.The uniformity of the magnetic field in the system and the effect of active compensation were analyzed.The results show that when the ambient noise is less than 17 d B,the scanning speed of the sensor is 9 mm/s and the thickness of the scanning rod of the sensor is 4mm,the magnetic field test efficiency is high and the influence of vibration on the experimental results is minimal.In a cylindrical test space with a length of 16 cm and a diameter of 3.0 cm,the magnetic field in the central area of the system space is close to zero.The error of the area within 1% of the magnetic field deviation rate is less than4.5% compared with the theoretical calculation.The system achieves the goal of generating a uniform magnetic field and automatically compensating for the environmental magnetic field,while simplifying the experimental device and controlling the cost.It has great reference value in many fields,such as material defect detection of vehicle mechanical parts based on zero magnetic field environment,magnetic field characteristic analysis of metal materials,and measurement of electrocardiogram and electroencephalogram.