Research On High-speed Banknote Thickness Measurement System Based On Beam Kinematics Analysis

With the large circulation of the RMB,counterfeit currency and altered coins are also appearing in large numbers.In order to identify the difference between this type of banknote and the real banknote very effectively,the thickness measurement of the banknote becomes a very important technique for the money detector and the clearing machine.However,in most banks in China,the point detectors and the sorting machines all use the mechanical thickness measurement system structure,that is,the eddy current sensor is used to detect the small displacement change of the shrapnel(cantilever beam)during the banknote transfer process.However,due to the complexity of the mechanical structure transmission of the thickness measurement system and the vibration of the machine itself,it is easy to cause the inaccuracy of the eddy current sensor thickness measurement.Therefore,it is impossible to fully recognize the problem of counterfeit currency and abnormal thickness of the coin that is currently common in banks.In order to find out the reason for the accuracy of the banknote thickness measurement of the mechanical thickness measurement system,and then optimize the mechanical structure of the mechanical thickness measurement system,it is urgent to study the displacement change of the shrapnel in the high-speed motion transmission process.This paper mainly uses the mechanical thickness measurement system in the banknote sorting machine as the research object,which is divided into the following two contents:(1)Analysis and Research on Thickness Transfer Process of Banknotes Based on Mechanical Thickness Measurement SystemIn order to clearly understand the thickness measurement inaccuracy caused by mechanical transmission during the thickness measurement transfer,it is necessary to analyze the working state of the key components(such as rocker arm and shrapnel)in the mechanical thickness measurement system during the banknote transfer process.In this paper,the mechanical thickness measurement system of the sorting machine is taken as the research object.The working state of the rocker arm mechanism,the shrapnel and the eddy current sensor during the transfer of the banknote is analyzed in detail,and the mechanical thickness measurement system is also established.The mathematical model and thecorresponding transfer function are derived;the mathematical model of the cantilever beam(shrap)is established and the corresponding deflection curve formula is derived;Establish a mathematical model of the beam(shrap)and derive the corresponding formula of the deflection curve.The combination of the two models of the theoretical deflection curve of the beam during the transfer of banknotes(2)Observing the motion state of key components of the thickness measurement system during the paper currency transfer process based on high-speed cameraIn order to analyze the inaccuracy of the thickness measurement of the key components of the mechanical thickness measurement system.In this paper,the mechanical thickness measurement system of the sorting machine is used as the research object.Under the same banknote thickness,the displacement curve of the beam(shrap)under the static(low speed)is obtained by using the high-speed camera and combined with the motion analysis software.The high-speed camera captures and combines the motion analysis software to obtain the beam force point and the displacement of the rocker arm contact point in the vertical direction under dynamic(high speed);use the high-speed camera to capture the movement of the beam and the movement of the rocker under the high-speed banknote thickness measurement The motion analysis software was used to obtain the relevant data,and the displacement-speed-acceleration image was drawn using matlab.Data processing and conclusion: the vertical displacement of the contact point between the shrapnel and the rocker arm is 0.071 mm under the thickness of a banknote of 0.09mm;the maximum vertical displacement of the beam under the static force is 0.063mm;the stress of the beam is obtained in the experiment.The vertical displacement is up to 0.064 mm.It can be seen that the theoretical and actual displacement of the static lower beam stress point is different from the actual displacement by 0.008 mm,and the absolute error degree is 11.27%.The layout of the eddy current sensor has a great influence on the banknote thickness measurement;the relative position of the low-speed and high-speed lower beam stress points The error is 0.001 mm,which shows that the small vibration of the beam has a great influence on the detection of the eddy current sensor.Using a high-speed camera to observe whether the beam and the rocker arm are separated,the conclusion is that during the process of banknotes,the rocker arm and the beam have a short separation,resulting in inaccurate thickness measurement,which is used to optimize the mechanical thickness measurement system solid foundation.