Research On Control System Of Large Electric Torque-fixed Tightening Wrench For Bolt

Electric power tower belongs to the space truss structure,it mostly adopts Angle steel of Q235 and Q345 material as its components,which are connected by bolts.The quality of bolt tightening directly determines the reliability of electric power tower structure.At present,the large bolts of electric power tower is fastened by electric tightening tools.The output torque range of electric tightening tools is limited and the accuracy is low,which is difficult to meet the needs of power grid construction condition.Due to the limited output torque range and low accuracy of electric tightening tools in China,it is difficult to meet the needs of power grid construction.The electric power tower appears the bolt over-tightened and under-tightened,even collapses and so on,which cause huge economic loss.Therefore,the development of a large electric torque-fixed tightening wrench for bolt is of great significance to China's power grid construction and other projects.This article compares existing bolt tightening schemes and bolt tightening tools.Aiming at the problems of small torque range and low accuracy of bolt tightening tools in China,a bolt tightening scheme based on the speed difference of the series motor was proposed through the study of the mechanical characteristics of the series motor.And the mathematical model of control system of electric torque-fixed tightening wrench for bolt is established.The control system of large electric torque-fixed tightening wrench for bolt adopts modular design idea,and PIC16F877A is selected as the control chip.The system is mainly composed of main controller module,signal acquisition module,motor drive module,man-machine interaction module,power supply module,system protection module and communication module.According to the functional requirements of the system,the selection of each module and the design of electrical schematic diagram were completed.On the basis of system hardware,the overall design scheme of control system software is determined.The software design of system calibration,speed signal acquisition and processing,full-wave controllable phase-shift voltage regulation,motor soft start,liquid crystal drive,key interruption,A/D signal acquisition,E~2PROM data reading and writing,and upper computer interface are completed.In addition,a sliding filter algorithm is used to perform digital filtering of the sampled data.In order to get the calibration equations of the system,a torque detection platform was built.The multi-group experimental data of the speed difference of the series motor and the corresponding output torque were collected.The least square method is used for quadratic fitting and linear fitting of experimental data.By comparing the determinable coefficient R~2,the quadratic fitting result is used as the system's calibration equation.The experimental platform test shows that the control system of large electric torque-fixed tightening wrench for bolt developed by this project runs stably and the tightening effect is reliable.The output range of torque is 1200-4000 N×mand the system error is less than±4%.The system meets the design requirements,it has been mass produced and put into the market.