The Research On Zero Error Compensation Method Of Electronic Balance

The electronic balance is a key weighing equipment in many fields such as trade settlement,quality inspection management,production chemical industry,etc.Under the influence of many factors such as weighing sensor manufacturing process,temperature,creep and weighing circuit,the strain-gauge electronic balance results in zero-point error,which leads to the decrease of weighing accuracy.On the other hand,the zero-point error of electronic balance is complicated,and various error factors are related to each other.The zero-point tracking method used in existing projects has obvious defects,and the compensation effect needs to be further improved.Therefore,in order to make up for the shortcomings of the zero-point error compensation methods of strain-gauge electronic balances,the following research is carried out:This thesis introduced research status and development trend of electronic balances,expounded the existing zero-point error compensation methods of strain-gauge electronic balances and the shortcomings,analyzed the weighing principle and zeropoint error generation mechanism of strain-gauge electronic balances in detail,and pointed out the background of the research.This thesis proposed an electronic balance zero-point error compensation method based on the Autostep-LMS adaptive filter.Firstly,based on the principle of linear adaptive filter,the zero-point error compensation method of electronic balance is constructed.Secondly,after comparing and analyzing the performance of the adaptive filtering algorithm,the Autostep-LMS algorithm without adjusting step size control parameters is selected to adjust the adaptive filter structure.The simulation results show that Autostep-LMS algorithm has fast convergence speed and small steady-state error.The application of the compensation method to electronic balance shows that the method has good online compensation effect.This thesis proposed an electronic balance zero-point error compensation method based on the BP neural network adaptive filter.The structure of neural network adaptive filter and BP algorithm are introduced,and the zero-point error compensation method of electronic balance is constructed based on BP neural network adaptive filter.The experimental results show that the online compensation of zero-point error of the electronic balance with this method has good online compensation effect.This thesis designed an electronic balance weighing system based on STM32F407 microprocessor.The hardware circuits such as conditioning circuit,analog-to-digital conversion circuit,information processing unit and communication interface circuit are designed,and the detailed parameter of conditioning circuit are given.The system software design is completed,including the system main program,signal acquisition subprogram,zero error compensation subprogram and so on.According to the "JJG 1036-2008 Electronic Balance Verification Regulations",the repeatability error,loading and unloading indication error of the electronic balance based on Autostep-LMS zero-point error compensation method and BP neural network zero-point error compensation method are tested respectively.The experimental results show that the repeatability error of electronic balance based on Autostep-LMS compensation method is less than 2.5 mg,and the indication error of loading and unloading is less than 1.7 mg;the repeatability error of electronic balance based on BP neural network is less than 1.7 mg,and the indication error of loading and unloading is less than 1.4 mg.All the indexes of the two electronic balance systems meet the standard of II accuracy balance.