Research On Rotation Angle Measurement Of Spherical Joint Based On Spherical Head Stereo Coding

Precision spherical joint is a spherical pair to realize three degrees of freedom rotary motion.It is widely used in robot,machine tool,automobile chassis,high-end medical equipment,aerospace equipment,marine engineering equipment,ships and other fields.In order to realize measurement of three-dimensional rotation direction and rotation angle of precision spherical joint,and solve the problem that it is difficult for spherical joint to know its own motion state and rotation pose in real time,a new measurement scheme based on pseudo-random coding strategy was proposed.According to the principle of pseudo-random code,the three-dimensional coding is designed on the ball head,and then the coding is recognized by eddy current sensor array.When the probe sweeps the ball head,the continuously changing output signal corresponding to the shape characteristics of the ball head is obtained.The model relationship between the sensor output signal combination and the ball hinge rotation angle is established by neural network algorithm,the recognition of rotation direction and measurement of rotation angle are realized.In the early stage,eddy current method was used to measure the two-dimensional rotary precision of ball head,but the resolution and precision are low,which can not meet the actual needs of precision engineering.This paper is a promotion,expansion and new attempt on this basis.In view of the shortcomings and limitations of the existing eddy current methods,this paper has carried out in-depth research in the following aspects: Based on the principle of pseudo-random coding,three-dimensional coding was designed and implemented in the ball head,and the uniqueness of three-dimensional coding at any position on the ball head was ensured through the reasonable configuration of the size of the spherical pattern and the depth of the groove,thus forming the absolute coding;The best matching mode of the sensor and the ball head surface morphology features was determined by simulation analysis and experimental testing;The original artificial neural network algorithm was improved to reconstruct the fitting relationship between the eddy current sensor measurement value and the ball hinge rotation angle value;The eddy current calibration device was redesigned and developed,and the measurement of the rotation angle of the original sample machine around the spherical hinge rod was added,so as to realize the measurement of the three-dimensional rotation angle.The experimental results show that in the case of single axis measurement,the mean square deviations of the rotation angles around the three axes are 2?34??6?47? and 12?44? respectively,and in the three axis combined measurement,the mean square deviations of the rotation angles around the three axes are 22?32??25?58? and 30?17? respectively.