Integrated Design Of Spherical Joint Rotation Angle Measurement System

Precision spherical joint is a kind of spherical motion mechanism which can rotate in any direction in space.It has been widely used in industrial equipment and parallel mechanism such as robot,parallel mechanism,measuring instrument and so on.However,there is still a lack of high-precision measurement method for the real-time detection of its spatial rotation angle.Accurate acquisition of its spatial rotation angle is helpful for motion error prediction analysis,feedback and attitude control of application equipment.After several years of research and experience accumulation,our team has proposed two kinds of measurement methods based on magnetic effect and eddy current effect respectively.The nonlinear model relationship between the measured physical quantity and the rotation angle is established by using the measurement data and supplemented with artificial neural network or equivalent magnetic charge method.The main research content of this paper is to improve the system integration of the spherical joint angle measurement scheme based on the magnetic effect,the measurement system is integrated,intelligent and portable while ensuring the measurement accuracy,which is prepared for the future productization and application.The main contents include:through simulation and experimental testing,the design of data acquisition circuit based on STM32F407 has been completed,including the design and development of sensor constant current source power supply circuit,analog signal amplification and filtering circuit,analog-to-digital conversion circuit and Bluetooth communication circuit;the RBF artificial neural network model is embedded into the STM32 through C language programming to calculate the angle in real time,and the calculation results are transmitted to the USB serial port or Bluetooth module to realize the real time display of the spherical joint space rotation angle;the experimental platform was built to test and verify the integrated angle measurement system,complete the experimental data processing and error source analysis.The experimental results show that: the measuring system is within ±20° rotation range of the spherical joint,the mean square error of angle ? is 29?43?,the mean square error of angle ? is 26?8?,which realizes the basic function of measurement within ±20°;when ? and ? are in the rotation range of -20°?0°,the mean square error of angle ? is 10'47 ",and the mean square error of angle ? is 4'8",which indicates that the measurement system has high measurement accuracy in a small angle of rotation range.Compared with the existing technical scheme,this scheme realizes the integration of signal acquisition and processing circuit,and the sensor data can be directly calculated by RBF artificial neural network in STM32.While meeting the measurement accuracy and speed,the space occupied by the measurement system is greatly reduced,which is convenient for integrated assembly in the reserved space of the spherical joint base.The goal of integration,intelligence and portability of the measurement system is initially realized,and the manufacturing cost is greatly reduced.