Study On Torque/Angle Composite Measuring Sensor For Rotary Joint

With the advancement of science and technology,the development of roboticsrelated technologies is mushrooming.The "Robot +" application action implementation plan proposes to double the density of robot development by 2025 compared to 2020.Whether it is collaborative robot arms or robots.Sensitive perception of torque and angle changes is required to provide accurate information back to the system.Due to space limitation,split torque sensors and rotary encoders are difficult to install and have complicated wiring,which increase the size of the robot’s joints and the cost.This paper designs an angle-torque composite measurement sensor to meet the need of industrial applications by studying the angle-torque composite measurement technology.The main work contents are as follows.(1)By analyzing the current torque and angle measurement scheme and the current status of research in detail,the measurement principle of torque and angle in this paper was based on the resistive strain effect of metals and Anisotropic magnetoresistive technology.(2)A new structure of angle-torque composite measurement sensor was proposed,and the structural design and optimization analysis of the composite sensor were completed.Structure of the torque measuring cross-shaped waist-shaped hole elastomer was optimized by using finite element analysis technology.The mechanical structure of the angle measuring part was designed with non-contact measurement,which facilitated the decoupling of angle measurement and torque measurement deformation and miniaturized structure of composite sensors.(3)The sensor hardware circuit was built based on the modular design concept,The angle measurement module and the torque measurement module were processed separately by dual processors.Two modules were communicated by RS485 bus.The final packaged angle and torque were transferred to IPC via bus.Force signal was converted to electrical signal based on Wheatstone full bridge circuit.The signal conditioning circuit design was completed,and some of the circuits were simulated and analyzed by Multism software.The magnetic angle element MT6813 was chosen to complete the hardware design of the high-precision angle measurement module.(4)The dual processors were programmed based on the Keil environment.The voltage signal was captured by using the processor’s on-board 12-bit ADC,and the voltages were converted to torque values through the formula.The communication between the processor and the angle chip were SPI,and the angle datas were read,which realized real-time acquisition of angle values.PVD function of the processor was used to set the voltage threshold,and the power-off memory function was realized.The communication between the dual processors was realized based on the RS485 bus method,and the angle measurement module transferred the data to the processor of the torque measurement module,and finally uploaded the data to the upper computer.(5)The sensor prototype was completed and the sensor test platform was built.The test experiments were conducted separately for the torque measurement module and the angle measurement module.Through rigorous test,the sensitivity of torque measurement is 46.902(m V/(N·m)),the linearity is 0.34%FS,the repeatability error is0.61%FS and the hysteresis is 0.12%FS.The angle measurement error is ± 0.33 °.The sensor designed in this paper achieves a torque-angle composite measurement function with compact structure and easy installation,which has good application value.