Research On Key Technology Of Digital Torque Wrench

Intelligent assembly is an important part of intelligent manufacturing.Threaded connection is widely used in mechanical assembly.To ensure the reliability of threaded connections,torque wrenches provide preload for threaded connections.At present,there are still many deficiencies in data transmission and torque measurement error compensation of torque wrench in the market.The data transmission of torque wrench is mainly wired,with poor real-time transmission,low integration degree and inability to integrate with MES.Aiming at the above problems,this paper studies the key technologies of torque error compensation and data transmission.Develop a torque wrench lower computer system with torque measurement,LCD display,over-torque warning,bluetooth transmission and error compensation functions,and develop a data transmission system integrated with MES.The following studies were specifically carried out:First of all,the stress concentration and structure of torque wrench lever greater quality problem,the ANSYS finite element simulation and optimization design,by reducing lever lever slot width decreased in slot region of stress concentration phenomenon,stress and deformation distribution and 45 steel is quite but material density smaller carbon fiber as the arm rod material,make the torque wrench lighter.Secondly,the data transmission system is divided into three layers for research.The bottom layer is the lower computer system of torque wrench.Based on STM8L152C6 microprocessor,data acquisition,EEPROM storage,over-torque warning,torque display,bluetooth transmission,error compensation and calibration of measurement parameters are realized.The middle layer is a handheld terminal APP,which USES Android standard API to drive CCD,WIFI and bluetooth modules to realize bar code identification and wireless transmission.The top layer includes database and upper computer software,database management and real-time data transmission functions based on MySQL,data query and error analysis functions based on Eclipse,and an integrated interface with MES.Finally,the zero drift error is compensated by software de-zeroing method,and the torque wrench is calibrated by piecewise interpolation method and least square method respectively.Based on the idea of envelope interpolation compensation,a piecewise interpolation method is proposed to compensate mechanical hysteresis error.Through the experimental verification,the software zero-removing method and piecewise interpolation method have obvious effects on the compensation of zero-point error and mechanical hysteresis error.The torque wrench calibrated by the least square method has higher measurement accuracy and smaller error fluctuation.The verification experiment of torque wrench verifies that the lower machine system designed in this paper meets the design requirements in terms of function and precision.The data transmission system design is reasonable,the upper computer software function satisfies the design request,the man-machine interaction is good.It provides some reference for the future development of torque wrench towards more integration and intelligence.