Research On The Key Technologies Of Eddy Current Intelligent Spherical Joint Rotation Angle Measurement

Precision spherical joint is a three-degree-of-freedom low-pair motion mechanism,which has been widely applied in robots,parallel mechanisms,medical equipment and other industrial fields on account of its flexible movement,compact structure,high load capacity.In order to improve the motion accuracy of the equipment and obtain spherical joint motion state and rotation position in real time,based on the existing measurement methods of magnetic effect,the project team developed a rotation angle measurement method of spherical joint based on Eddy current sensor.The basic principle is to construct the geometric shape characteristics on the surface of the ball head,and embed the Eddy current sensor in the ball socket.When the ball head rotates,When the ball head rotates,the relative position change of the probe and the shape characteristics will cause the characteristic change of sensor measurement signal.The model relationship between the output signal combination of the sensor and the rotation angle of the spherical joint is established by the neural network algorithm.Although the feasibility of the scheme has been verified by the previous research and results,there are some shortcomings,such as the poor repeatability of eddy current sensor data collection,the unreasonable sensor matching scheme and so on,which affect and limit the measurement accuracy and range.In view of these problems,this paper further improves the measurement methods,and improves the measurement accuracy and performance.The main work of this paper includes:Using simulation analysis and experimental test to determine the best matching scheme of the sensor and the ball head surface shape characteristics,upgrading the design scheme of the prototype machine;The fitting relationship between the measured value of Eddy current sensor and the rotation angle of spherical joint is reconstructed by improving the artificial neural network algorithm;The eddy current angle measurement prototype is redesigned and the relevant experiments are carried out;the high-precision angle calibration device is used to evaluate the experimental measurement results and analyze the measurement accuracy,resolution and range of the prototype.The simulation results of the improved eddy current spherical joint prototype show that:In the range of ±20°,the mean square error of angle ? is 19'39",the mean square error of angle ? is 14'50";In the range of ±12°,the mean square error of angle ? is 8'43",the mean square error of angle ? is 8'55";In the actual experiment of the prototype,the mean square error of angle ? is 21'17",the mean square error of angle ? is 25'14".And ?in the measurement range of 5°?20°,? in the measurement range of 4°?20°,the mean square error of angle ? reaches 7'5",and the measurement mean square error of angle? reaches 5'26".Compared with the original eddy current angle measurement scheme,the improved eddy current intelligent spherical joint realizes the rotation angle measurement within the range of ±20°,and shows a higher measurement accuracy in the rotation angle of a small area,which proves that this design scheme has certain advantages in improving the angle measurement function of the spherical joint,and is expected to be further researched and applied.