CN108734847A - A kind of bank note thickness measuring method and device based on 3-axis acceleration sensor - Google Patents

Abstract

The invention discloses a banknote thickness measurement method and device based on a three-axis acceleration sensor. plate, extended bearings, and three-axis accelerometer. When working, the banknote passes through the gap between the driving wheel shaft and the passive thickness measuring wheel shaft, and the passive thickness measuring wheel shaft is jacked up at the moment the banknote passes through, and the vibration is transmitted to the extended bearing at the end, and then transmitted to the thickness measuring wheel shaft. On the upper part of the mounting plate, since the triaxial acceleration sensor is installed on the upper part, therefore, the slight vibration of the passive thickness measuring wheel shaft can be directly transmitted to the triaxial acceleration sensor, by receiving the signal on the triaxial acceleration sensor and according to the present invention. The thickness measurement method of each banknote can be processed, and the thickness value and corresponding vibration law of each banknote can be obtained.

Description

A banknote thickness measurement method and device based on a three-axis acceleration sensor

technical field

The invention relates to the field of banknote sorting machines, in particular to a method and device for measuring the thickness of banknotes based on a three-axis acceleration sensor.

Background technique

With the continuous development of scientific and technological progress, banknote sorting machines, as indispensable banknote sorting equipment for banks and financial companies, are used more and more widely. In recent years, counterfeit and counterfeit banknotes have frequently appeared in China. Banks have continuously increased their requirements for banknote sorting. The detection of tape on the surface of banknotes has become an essential function of sorting machines. As a key structural component of the sorting machine, the banknote thickness measuring device has seriously restricted the development of the sorting machine due to its immature domestic technology.

In the existing thickness measurement technology, there are infrared thickness measurement, ultrasonic thickness measurement and Hall thickness measurement. Infrared thickness measurement is easily affected by stains on the surface of banknotes, and the detection effect on non-reflective banknote adhesions is not satisfactory, resulting in misjudgment of the thickness of banknotes. Ultrasonic thickness measurement has very high requirements on the structure, and it is necessary to ensure the smooth passage of banknotes. For banknotes running at high speed, it is difficult to ensure the stability of banknotes in mass production. The principle of Hall thickness measurement is to sense the change of the magnetic field to judge the thickness of banknotes. Since the bearings and elastic wheels are all metal structures, it is easy to be magnetized to interfere with the Hall sensor.

There is a banknote thickness measuring device in the prior art, such as patent application number: 201620182548.7, application date: March 10, 2016, patent name: banknote thickness measuring device, the application discloses a device that uses eddy current coils as the detection original Banknote thickness measuring device, the device detects the change of the gap between the metal sheet and the eddy current coil caused by the displacement of the movable end of the passive thickness measuring wheel, so that the impedance and inductance of the eddy current coil end change to judge the thickness of the banknote, thereby improving Measurement accuracy and anti-interference ability. This application has improved the measurement accuracy and anti-interference ability of the banknote thickness measuring device to a certain extent, but the application still cannot suppress the rapid vibration of the thickness measuring device, especially when the banknote hits the upper and lower rollers of the thickness measuring device, it will cause large vibrations. The eddy current sensor cannot measure the thickness of the banknote at the initial stage of passing the banknote, which makes the thickness measuring device have errors when detecting whether the front end of the banknote is pasted with adhesive tape or has abnormal thickness problems such as folded corners.

Therefore, the prior art needs to be further improved and perfected.

Contents of the invention

The object of the present invention is to overcome the deficiencies of the prior art and provide a banknote thickness measurement method based on a three-axis acceleration sensor with simple operation and high recognition accuracy.

Another object of the present invention is to overcome the shortcomings of the prior art and provide a device based on the above thickness measuring method.

The object of the present invention is achieved through the following technical solutions:

A banknote thickness measurement method based on a triaxial acceleration sensor, the cover thickness measurement method mainly includes the following steps:

Step S1: Install the three-axis acceleration sensor on the upper left corner of the extension axis, and set the measured X-axis to be the vertical downward direction of the vertical note-out axis, the Y-axis to be the vertical direction of the note-out axis to the left, and the Z-axis to be parallel Inward direction of the banknote output axis.

Step S2: The system is powered on, and the three-axis acceleration sensors measure the acceleration of the three axes respectively, and are connected to the data acquisition card. Make corrections.

Step S3: During measurement, the piezoelectric element in the triaxial acceleration sensor generates a piezoelectric constant when subjected to an external force F:

Formula 1:

Formula 2 can be obtained from the above formula: Q=d*F, where Q is the amount of charge, d is the piezoelectric constant, and F is the force received; combine the above formula with Newton's second law formula 3: F=m*a to get Formula 4: Q=d*m*a, where d and m are fixed values after the piezoelectric ceramic material and mass block of the acceleration sensor are determined, and Q and a are linearly related, and the three-axis acceleration can be obtained by measuring the charge Q The acceleration value of the sensor.

Step S4: The three-axis acceleration sensor transmits the measured value in the form of analog voltage to the data acquisition card after filtering, and the data acquisition card performs AD conversion on the analog value and outputs it to the computer for processing.

Step S5: Start the computer, initialize the parameters of the computer, set the D/A output data to 0, and ensure that the piezoelectric driver has no excitation voltage signal in the initial state.

Step S6: Formula 5 is obtained from Formula 4: In order to avoid the interference of the high-frequency signal on the sensor, the result is low-pass filtered, and the acceleration formula 6 is obtained: ai is the sampling value of the acceleration value at time i.

Step S7: Integrating Formula 6 to obtain Formula 7: Δt is the time difference between two samples.

Step S8: Integrate formula 7 to obtain displacement formula 8: where vi is the sampled value of velocity at time i.

Step S9: Repeat the banknote test several times, and adjust the control parameters repeatedly according to the observation of the vibration effect and the analysis of the stored data, and then calculate the displacement of the banknote output axis, and send it out through the wireless communication module to detect whether the banknote is pasted Sticky paper and its location.

As a preferred solution of the present invention, in order to improve the accuracy of measurement, the vibration generated when the thickness measuring device rotates makes the output voltage of the acceleration sensor fluctuate slightly up and down at 1.2V when no banknote passes through the banknote delivery shaft; When the banknotes are on the shaft, the banknotes are squeezed out of the banknote shaft, so that the banknote output shaft drives the acceleration sensor to vibrate up and down, thereby converting the physical signal into an electrical signal, and the peaks between adjacent ones are basically the same.

As a preferred solution of the present invention, in order to make the thickness measurement system work more stable and reliable, the parameter initialization in the step S5 of the present invention includes the initial value setting of the control algorithm parameters, the corresponding initial value, control address and driver of the data acquisition card. mode setting.

As a preferred solution of the present invention, in order to further improve the sensitivity and measurement accuracy of the thickness measuring system, the three-axis acceleration sensor of the present invention adopts a model of ADXL327 three-axis acceleration sensor, which has a large measurement range, high sensitivity, wide bandwidth, and is sensitive to temperature. The impact is small, the cost is low, and the thickness measurement requirements can be well met.

As a preferred solution of the present invention, the data acquisition card is an Agilent data acquisition card. Compared with other data acquisition cards, Agilent data acquisition cards have more models and stable performance. It uses a general-purpose rather than proprietary standard high-speed USB2.0 interface, which is easy to connect, plug and play, and bundled with Keysight Modular Instruments MeasurementManger software , can quickly set up and perform data processing. In addition, it is also compatible with a variety of application software development environments with little interference.

As a preferred solution of the present invention, since the installation position of the thickness measuring device will be inclined during the installation process or after long-term operation, resulting in inaccurate measurement accuracy, the present invention has deviations in the installation of the three-axis acceleration sensor or deformation due to aging When the installation position is tilted, the X-axis of the three-axis acceleration sensor is no longer parallel to the direction of the gravitational acceleration. At this time, the acceleration measured by the X-axis is only a component of the acceleration of the active thickness measuring wheel. The included angle between them is θ, the output of the X-axis is A _XOUT , the output of the Y-axis is A _YOUT , and the output of the Z-axis is A _OUTZ , then the calculation formula of the included angle θ is Equation 9:

According to the included angle θ, the actual acceleration A of the up and down movement of the active thickness measuring wheel can be deduced as formula 10:

Integrating Equation 10 yields Equation 11: Δt is the time difference between two samples; and then integrate the formula 11, the displacement formula 12 can be obtained: Where v _i is the sampled value of velocity at time i. The above design or adjustment can well deal with this situation, so as to ensure that the requirement of higher measurement accuracy is met.

Another object of the present invention is achieved through the following technical solutions:

A banknote thickness measuring device based on a three-axis acceleration sensor, the thickness measuring device mainly includes a base body, a circuit board, a driving wheel shaft, a passive thickness measuring wheel shaft, a thickness measuring bracket, a metal sheet, an eddy current coil, a thickness measuring installation plate, and an extended bearing , and a three-axis acceleration sensor for measuring the vibration law of the passive thickness measuring wheel axle. The active wheel shaft is located below the passive thickness measuring wheel shaft, arranged parallel to the passive thickness measuring wheel shaft, and frictionally connected with the passive thickness measuring wheel shaft. The base body is fixed and located on one side of the passive thickness measuring wheel shaft; the passive thickness measuring wheel shaft is set on the thickness measuring bracket, and the thickness measuring bracket is installed on the base body and connected to the base body in rotation. One end of the metal sheet is fixed on the base, and the other end abuts on the thickness measuring support, and is driven to vibrate up and down by the thickness measuring support. The eddy current coil is defined above the metal sheet and is electrically connected to the circuit board, and the circuit board detects the distance between it and the metal sheet.

Specifically, the thickness measurement mounting plate is provided with a connection hole for connecting the passive thickness measurement wheel axle and a slot for easy vibration measurement. The expansion bearing is installed in the connection hole, and the end of the passive thickness measuring wheel shaft is inserted into the connection hole, and is connected with the thickness measurement installation plate through the expansion bearing, and the vibration during measurement is transmitted to the thickness measurement installation plate. The slot extends from one edge of the thickness measuring mounting plate to the other side to divide the thickness measuring mounting plate into an upper part for measurement and a lower part for installation, and the upper part and the lower part are not completely divided. The slot does not go through the thickness measuring installation plate. The triaxial acceleration sensor is arranged on the upper part of the thickness measuring installation board and is electrically connected with the circuit board. When working, the banknote passes through the gap between the driving wheel shaft and the passive thickness measuring wheel shaft, and the passive thickness measuring wheel shaft is jacked up at the moment the banknote passes through, and the vibration is transmitted to the extended bearing at the end, and then transmitted to the thickness measuring wheel On the upper part of the mounting plate, since the three-axis acceleration sensor is installed on the upper part, the slight vibration of the passive thickness measuring wheel shaft can be directly transmitted to the three-axis acceleration sensor. By receiving and processing the signals on the three-axis acceleration sensor, it can be obtained The thickness value of each banknote and the corresponding vibration law.

Further, in order to obtain a more accurate vibration law, thereby improving the measurement accuracy, the lower part of the thickness measuring installation plate of the present invention is also provided with a second triaxial acceleration sensor for improving measurement accuracy, and the second triaxial acceleration sensor is arranged on the The lower corner is electrically connected to the circuit board.

As a preferred solution of the present invention, in order to amplify and react finer vibrations to the triaxial acceleration sensor located at the end, the triaxial acceleration sensor of the present invention is arranged on the upper corner of the thickness measuring installation plate.

The working process and principle of the present invention are as follows: when working, the banknote passes through the gap between the driving wheel shaft and the passive thickness measuring wheel shaft, and the passive thickness measuring wheel shaft is lifted up at the moment the banknote passes through, and the vibration is transmitted to the On the extended bearing, it is transmitted to the upper part of the thickness measuring installation plate. Since the triaxial acceleration sensor is installed on the upper part, the slight vibration of the passive thickness measuring wheel shaft can be directly transmitted to the triaxial acceleration sensor. By receiving the triaxial acceleration sensor The signal on the banknote is processed according to the thickness measurement method provided by the present invention, and the thickness value and corresponding vibration law of each banknote can be obtained. Use the acceleration sensor to detect the vibration of the banknote output shaft when the banknote passes through the banknote, and judge whether the thickness of the banknote is abnormal according to its vibration law. It can detect whether the adhesive tape is pasted on the banknote or there are abnormal thickness problems such as folded corners, and even determine the position of the adhesive tape and small size, simple operation and low cost, expanding the application range of the three-axis acceleration sensor.

Compared with the prior art, the present invention also has the following advantages:

(1) The three-axis acceleration sensor provided by the present invention has the advantages of wide frequency band, small mass, convenient installation, less wiring, and compact structure. The reasonable arrangement scheme of the three-axis acceleration sensor is combined with the filtering algorithm to realize the output of the thickness measuring device. The measurement of the vibration displacement of the banknote shaft greatly improves the accuracy of the thickness measuring device.

(2) The banknote thickness measurement method based on the three-axis acceleration sensor provided by the present invention combines the eddy current detection element with the acceleration sensor, utilizes the eddy current coil as the detection element, and detects the displacement generated by the movable end of the passive thickness measurement wheel. The gap between the metal sheet and the eddy current coil changes, so that the impedance and inductance of the eddy current coil change to judge the thickness of the banknote, thereby improving the thickness measurement accuracy and anti-interference ability of the thickness measuring device, and the acceleration sensor ensures the initial banknote passing. The stability and accuracy of banknote thickness measurement.

(3) The banknote thickness measurement method based on the three-axis acceleration sensor provided by the present invention adopts that the original components do not respond to the magnetic field of the environment, and external magnetic interference will not affect the normal measurement of the thickness.

(4) The banknote thickness measurement method based on the three-axis acceleration sensor provided by the present invention adopts the installation method of the three-axis acceleration sensor of the extended bearing, which eliminates the displacement measurement error caused by the incomplete parallelism between the upper and lower axes of the acceleration sensor and the acceleration of gravity, and can be greatly improved. Improve the calculation accuracy of the displacement and ensure the accuracy of the thickness measuring device

Description of drawings

Fig. 1 is a schematic structural diagram of a banknote thickness measuring device based on a three-axis acceleration sensor provided by the present invention.

Fig. 2 is a schematic diagram of the installation of the triaxial acceleration sensor provided by the present invention.

Fig. 3 is a schematic diagram of three-axis standard positions of the three-axis acceleration sensor provided by the present invention.

Fig. 4 is a schematic diagram when the three-axis acceleration sensor provided by the present invention is tilted.

Fig. 5 is a flow chart of processing acceleration sensor data provided by the present invention.

Explanation of the labels in the above-mentioned accompanying drawings:

1-seat body, 2-driving axle, 3-passive thickness measuring axle, 4-thickness measuring bracket, 5-metal sheet, 6-thickness measuring mounting plate, 7-extended bearing, 8-triaxial acceleration sensor.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear and definite, the present invention will be further described below with reference to the accompanying drawings and examples.

Example 1:

As shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5, the present invention discloses a banknote thickness measurement method based on a three-axis acceleration sensor. The cover thickness measurement method mainly includes the following steps:

Step S1: install the three-axis acceleration sensor 8 on the upper left corner of the extension axis, and set the measured X-axis to be the vertical downward direction of the vertical note-out axis, the Y-axis to be the vertical direction of the note-out axis to the left, and the Z-axis to be Parallel to the inner direction of the banknote output axis.

Step S2: The system is powered on, and the three-axis acceleration sensor 8 measures the acceleration of the three axes respectively, and is connected with the data acquisition card. After calculation, the inclination angle when the thickness measuring device is installed is obtained. Acceleration is corrected.

Step S3: During measurement, the piezoelectric element in the triaxial acceleration sensor 8 generates a piezoelectric constant when subjected to an external force F:

Formula 1:

Formula 2 can be obtained from the above formula: Q=d*F, where Q is the amount of charge, d is the piezoelectric constant, and F is the force received; combine the above formula with Newton's second law formula 3: F=m*a to get Formula 4: Q=d*m*a, where d and m are fixed values after the piezoelectric ceramic material and mass block of the acceleration sensor are determined, and Q and a are linearly related, and the three-axis acceleration can be obtained by measuring the charge Q Acceleration value of sensor 8.

Step S4: The three-axis acceleration sensor 8 transmits the measured value in the form of analog voltage to the data acquisition card after filtering, and the data acquisition card performs AD conversion on the analog value and outputs it to the computer for processing.

Step S5: Start the computer, initialize the parameters of the computer, set the D/A output data to 0, and ensure that the piezoelectric driver has no excitation voltage signal in the initial state.

Step S6: Formula 5 is obtained from Formula 4: In order to avoid the interference of the high-frequency signal on the sensor, the result is low-pass filtered, and the acceleration formula 6 is obtained: ai is the sampling value of the acceleration value at time i.

Step S7: Integrating Formula 6 to obtain Formula 7: Δt is the time difference between two samples.

Step S8: Integrate formula 7 to obtain displacement formula 8: where vi is the sampled value of velocity at time i.

Step S9: Repeat the banknote test several times, and adjust the control parameters repeatedly according to the observation of the vibration effect and the analysis of the stored data, and then calculate the displacement of the banknote output axis, and send it out through the wireless communication module to detect whether the banknote is pasted Sticky paper and its location.

As a preferred solution of the present invention, in order to improve the accuracy of measurement, the vibration generated when the thickness measuring device rotates makes the output voltage of the acceleration sensor fluctuate slightly up and down at 1.2V when no banknote passes through the banknote delivery shaft; When the banknotes are on the shaft, the banknotes are squeezed out of the banknote shaft, so that the banknote output shaft drives the acceleration sensor to vibrate up and down, thereby converting the physical signal into an electrical signal, and the peaks between adjacent ones are basically the same.

As a preferred solution of the present invention, in order to make the thickness measurement system work more stable and reliable, the parameter initialization in the step S5 of the present invention includes the initial value setting of the control algorithm parameters, the corresponding initial value, control address and driver of the data acquisition card. mode setting.

As a preferred solution of the present invention, in order to further improve the sensitivity and measurement accuracy of the thickness measuring system, the three-axis acceleration sensor 8 of the present invention adopts the model as the ADXL327 three-axis acceleration sensor, which has a large measurement range, high sensitivity, and wide bandwidth. The influence of temperature is small, the cost is low, and it can well meet the requirements of thickness measurement.

As a preferred solution of the present invention, the data acquisition card is an Agilent data acquisition card. Compared with other data acquisition cards, Agilent data acquisition cards have more models and stable performance. It uses a general-purpose rather than proprietary standard high-speed USB2.0 interface, which is easy to connect, plug and play, and bundled with Keysight Modular Instruments MeasurementManger software , can quickly set up and perform data processing. In addition, it is also compatible with a variety of application software development environments with little interference.

As a preferred solution of the present invention, since the installation position of the thickness measuring device will be tilted during installation or after long-term operation, resulting in inaccurate measurement accuracy, the present invention may deviate in the installation of the triaxial acceleration sensor 8 or appear due to aging. When the installation position is tilted due to deformation, the X-axis of the triaxial acceleration sensor 8 is no longer parallel to the direction of the gravitational acceleration. At this time, the acceleration measured by the X-axis is only a component of the acceleration of the up-and-down movement of the active thickness measuring wheel. The included angle between the gravitational accelerations is θ, the output of the X-axis is A _XOUT , the output of the Y-axis is A _YOUT , and the output of the Z-axis is A _OUTZ , then the calculation formula of the included angle θ is Equation 9:

According to the included angle θ, the actual acceleration A of the up and down movement of the active thickness measuring wheel can be deduced as formula 10:

Integrating Equation 10 yields Equation 11: Δt is the time difference between two samples; and then integrate the formula 11, the displacement formula 12 can be obtained: Where v _i is the sampled value of velocity at time i. The above design or adjustment can well deal with this situation, so as to ensure that the requirement of higher measurement accuracy is met.

Another object of the present invention is achieved through the following technical solutions:

A banknote thickness measuring device based on a three-axis acceleration sensor, the thickness measuring device mainly includes a base body 1, a circuit board, a driving wheel shaft 2, a passive thickness measuring wheel shaft 3, a thickness measuring bracket 4, a metal sheet 5, an eddy current coil, a thickness measuring The mounting plate 6, the extended bearing 7, and the triaxial acceleration sensor 8 used to measure the vibration law of the passive thickness measuring wheel shaft 3. The active wheel shaft 2 is located below the passive thickness measuring wheel shaft 3 , is arranged parallel to the passive thickness measuring wheel shaft 3 , and is frictionally connected with the passive thickness measuring wheel shaft 3 . The base body 1 is fixedly arranged on one side of the passive thickness measuring wheel shaft 3; the passive thickness measuring wheel shaft 3 is arranged on the thickness measuring bracket 4, and the thickness measuring bracket 4 is installed on the base body 1 and rotates with the base body 1 connect. One end of the metal sheet 5 is fixed on the base body 1, and the other end abuts on the thickness measuring support 4, and is driven by the thickness measuring support 4 to vibrate up and down. The eddy current coil is defined above the metal sheet 5 and electrically connected to the circuit board, and the distance between the eddy current coil and the metal sheet 5 is detected by the circuit board.

Specifically, the thickness measuring mounting plate 6 is provided with a connection hole for connecting the passive thickness measuring wheel axle 3 and a slot for easy vibration measurement. The expansion bearing 7 is installed in the connection hole, the end of the passive thickness measuring wheel shaft 3 is inserted into the connection hole, and is connected with the thickness measurement installation plate 6 through the expansion bearing 7, and the vibration during measurement is transmitted to the thickness measurement installation plate 6 . The slot extends from one edge of the thickness measuring mounting plate 6 to the other side to divide the thickness measuring mounting plate 6 into an upper part for measurement and a lower part for installation, and the upper part and the lower part are not completely divided . The slot does not go through the thickness measuring mounting plate 6 . The triaxial acceleration sensor 8 is arranged on the upper part of the thickness measuring installation plate 6 and is electrically connected with the circuit board. When working, the banknote passes through the gap between the driving wheel shaft 2 and the passive thickness measuring wheel shaft 3, and the passive thickness measuring wheel shaft 3 is lifted up at the moment the banknote passes through, and the vibration is transmitted to the expansion bearing 7 at the end, so that It is transmitted to the upper part of the thickness measuring installation plate 6. Since the triaxial acceleration sensor 8 is installed on the upper part, the slight vibration of the passive thickness measuring wheel shaft 3 can be directly transmitted to the triaxial acceleration sensor 8. By receiving the triaxial acceleration sensor 8 The signal on the banknote is processed and the thickness value of each banknote and the corresponding vibration law can be obtained.

Further, in order to obtain more accurate vibration rules, thereby improving measurement accuracy, the lower part of the thickness measuring mounting plate 6 of the present invention is also provided with a second triaxial acceleration sensor 8 for improving measurement accuracy, and the second triaxial acceleration sensor 8 is arranged on the corner of the lower part, and is electrically connected with the circuit board.

As a preferred solution of the present invention, in order to amplify and react finer vibrations to the triaxial acceleration sensor 8 located at the end, the triaxial acceleration sensor 8 of the present invention is arranged on the upper corner of the thickness measuring installation plate 6 .

The working process and principle of the present invention are: when working, the banknote passes through the gap between the driving wheel shaft 2 and the passive thickness measuring wheel shaft 3, and the passive thickness measuring wheel shaft 3 is lifted up at the moment the banknote passes through, and the vibration is transmitted to the The extended bearing 7 at the end is transmitted to the upper part of the thickness measuring installation plate 6. Since the triaxial acceleration sensor 8 is installed on the upper part, the slight vibration of the passive thickness measuring wheel shaft 3 can be directly transmitted to the triaxial acceleration sensor 8 Above, by receiving the signal from the triaxial acceleration sensor 8 and processing it according to the thickness measuring method provided by the present invention, the thickness value and corresponding vibration law of each banknote can be obtained. Use the acceleration sensor to detect the vibration of the banknote output shaft when the banknote passes through the banknote, and judge whether the thickness of the banknote is abnormal according to its vibration law. It can detect whether the adhesive tape is pasted on the banknote or there are abnormal thickness problems such as folded corners, and even determine the position of the adhesive tape and small in size, simple in operation and low in cost, expanding the application range of the three-axis acceleration sensor 8 .

Example 2:

A banknote thickness measuring device includes a base body 1, a circuit board, and at least two thickness measuring mechanisms, the thickness measuring mechanism includes a driving wheel, a passive thickness measuring wheel, a thickness measuring wheel bracket and a metal sheet 5, and the circuit board is located on the The upper part of the base, the rotating end of the thickness measuring wheel bracket is pivotally connected to the movable end of the thickness measuring wheel bracket, and the circuit board is provided with an eddy current coil corresponding to the metal sheet 5 of each thickness measuring mechanism, and the metal sheet 5 is provided with On the frame and between the eddy current coil and the thickness measuring wheel bracket, the first end of the metal sheet 5 is arranged on the frame, the second end of the metal sheet 5 abuts against the movable end of the thickness measuring wheel bracket and Located below the eddy current coil, the driving wheel is arranged on one side of the passive thickness measuring wheel and is driven by friction with the passive thickness measuring wheel. The gap between the driving wheel and the passive thickness measuring wheel is the paper passing gap.

The device is composed of a battery, a power module, a three-axis acceleration sensor 8, a data acquisition card, a wireless communication module, and a computer. The battery and the power supply module generate the power required by the whole device. The three-axis acceleration sensor 8 measures the acceleration of three axes. The data acquisition card collects and corrects the acceleration data and transmits the data to the computer through the wireless communication module. The data is corrected and the displacement is calculated to detect the authenticity of the banknote.

The installation position of this device is shown in Figure 2. The thickness measuring mechanical structure is made up of acceleration sensor and expansion shaft, and expansion bearing 7 is fixed on the banknote counter by screw. When banknotes enter the banknote-discharging shaft, the banknote-discharging shaft extrudes the expansion bearing 7 to drive the acceleration sensor to move. By analyzing the change law of the output voltage of the acceleration sensor, it can be detected whether there is abnormality in the thickness of the banknote.

The concrete operation process of banknote thickness measuring method provided by the present invention is as follows:

1) The present invention uses a battery to power the device, the battery is connected to the power supply board, and the power supply module generates stable voltage and supplies power to the acceleration sensor, data acquisition card and wireless communication module.

2) Acceleration is subsequently collected and banknote passing test is carried out. The device measures the acceleration of three axes through the triaxial acceleration sensor 8, and outputs the acceleration to the data acquisition card in the form of analog quantity.

3) The acceleration sensor used in this device is ADXL327. The sensor is a single-chip three-axis sensor produced by American AD Company. The measurement range is ±2.5g, and it can withstand 1000g vibration shock. The chip can measure acceleration in three directions at the same time, which is suitable for static and dynamic acceleration measurement. The Xout, Yout and Zout pins of the chip are the acceleration outputs of the X-axis, Y-axis and Z-axis respectively, where the X-axis is used to measure the acceleration in the up-down direction, the Y-axis is used to measure the acceleration in the left-right direction, and the Z-axis is used for Acceleration in the front-back direction is measured. In this circuit, the ADXL327 power supply voltage Vs is 3.3V, and the sensitivity is 462mV/g. When the measured value is 0g, the output voltage value is Vs/2, which is 1.65V. When the acceleration changes, the output voltage of the corresponding axis changes. Therefore, by measuring the output voltage of a certain axis, the acceleration of the axis can be calculated.

4) The output of the three-axis acceleration sensor 8 is sent to the data acquisition card in the form of voltage analog quantity, and the data acquisition card performs AD conversion on the input analog quantity, and uses digital quantity to represent the magnitude of the acceleration.

5) When the thickness measuring mechanism is working, the piezoelectric element in the triaxial acceleration sensor 8 will generate a piezoelectric constant after being subjected to an external force F:

Therefore, the charge Q=d*F(2);

Where Q is the amount of charge, d is the piezoelectric constant, and F is the force received. The force received by the acceleration sensor in the device of the present invention is mainly the inertial force generated by the mass block vibrating with the banknote output shaft. According to Newton's second law F=m*a(3);

The inertial force is equal to the mass multiplied by the acceleration, and the formula (2) (3) can be combined to obtain Q=d*m*a (4); where d and m are determined after the piezoelectric ceramic material of the acceleration sensor and the mass block are determined Fixed value. Therefore, within the measurable range of the sensor, Q and a have a linear relationship, and the acceleration value can be represented by the charge Q.

6) Utilize the computer to obtain the vibration information, and the output of the triaxial acceleration sensor 8 is a voltage signal, as can be seen from formula (4) In order to avoid the interference of the high-frequency signal on the sensor, the result is low-pass filtered to obtain the acceleration ai is the acceleration sampling value at time i.

7) After expressing the speed in digital form, calculate the angle between the X-axis of the acceleration sensor and the acceleration of gravity, and use the angle to correct the acceleration output by the X-axis. When the device is installed correctly and without any deformation, the directions of the X-axis, Y-axis and Z-axis of the acceleration sensor are shown in Figure 3. The X-axis is in the opposite direction to the gravitational acceleration and is used to measure the acceleration in the up-down direction of the active thickness measuring wheel; the Y-axis is used to measure the acceleration in the left-right direction; the Z-axis is used to measure the acceleration in the front-back direction. At this time, the output of the X axis is the acceleration of the active thickness measuring wheel moving up and down.

8) When the installation of the device is deviated or deformed due to aging, the device may be tilted, and the X-axis of the acceleration sensor is no longer parallel to the direction of the acceleration of gravity. At this time, the acceleration measured by the X-axis is only the up-and-down motion acceleration of the active thickness measuring wheel a component of . As shown in Figure 4. Let the angle between the X-axis and the acceleration of gravity be θ, the output of the X-axis is AXOUT, the output of the Y-axis is AYOUT, and the output of the Z-axis is AOUTZ, then the angle θ is:

According to the angle θ, the actual acceleration A of the up and down motion of the active thickness measuring wheel can be deduced as:

9) Through the correction of the X-axis acceleration, the actual acceleration of the up and down movement of the active thickness measuring wheel can be calculated. The upper and lower dead points are the two extreme values of the acceleration, and the motion period of the active thickness measuring wheel can be found out by judging the extreme values . The displacement of the active thickness measuring wheel in a cycle can be calculated by the quadratic integral of the acceleration in a cycle.

10) Integrate formula (8), namely Δt is the time difference between two samples.

11) Integrate the formula (9) to get the displacement formula where vi is the sampled value of velocity at time i.

12) Use MATLAB to process the output signal of the acceleration sensor, as shown in Figure 5. When no banknotes pass through the banknote output shaft, the vibration generated when the thickness measuring device rotates causes the output voltage of the acceleration sensor to fluctuate slightly around 1.2V; when there are banknotes passing through the banknote output shaft, the banknotes are backlogged on the banknote output shaft, so that the banknote output shaft drives the acceleration The sensor vibrates up and down, thereby converting the physical signal into an electrical signal, and the peaks of adjacent waves are basically the same.

13) Repeat the banknote passing test several times, and adjust the control parameters repeatedly according to the observation of the vibration effect and the analysis of the stored data.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (9)

1. a kind of bank note thickness measuring method based on 3-axis acceleration sensor, which is characterized in that include the following steps：

Step S1：3-axis acceleration sensor is mounted on to the upper left corner of extended axis, and the X-axis of setting measurement is vertical cash dispenser axis Vertically downward direction, Y-axis are the horizontal left direction of vertical cash dispenser axis, and Z axis is to be parallel to cash dispenser axis inward direction；

Step S2：System electrification, three 3-axis acceleration sensors respectively measure the acceleration of three axial directions, and and data Capture card connects, and angle of inclination when measuring thickness device installation is obtained after calculating, while repairing to the acceleration of cash dispenser axis Just；

Step S3：When measurement, it is normal that the piezoelectric element in 3-axis acceleration sensor generates piezoelectricity when by applied external force F Number：

Formula 1：

Formula 2 as available from the above equation：Q=d*F, wherein Q are the quantity of electric charge, and d is piezoelectric constant, and F is the power being subject to；By above formula and newton Second law formula 3：F=m*a is combined and is obtained formula 4：The piezoelectric ceramics material of Q=d*m*a, wherein d and m in acceleration transducer Material and mass block are fixed values after determining, obtain Q and a is in a linear relationship, can obtain 3-axis acceleration by measuring charge Q The acceleration value of sensor；

Step S4：3-axis acceleration sensor by measured value in the form of analog voltage it is filtered after be conveyed to data collecting card, Analog quantity is AD converted by data collecting card, and is exported to computer disposal；

Step S5：Start computer, and parameter initialization is carried out to computer, sets D/A output datas as 0, it is ensured that initial shape State piezoelectric actuator is without driving voltage signal；

Step S6：Formula 5 is obtained by formula 4：To avoid interference of the high-frequency signal to sensor, result is carried out low Pass filter obtains Acceleration Formula 6：Ai samples for i moment acceleration values Value；

Step S7：Integral is carried out to formula 6 and obtains formula 7：Δ t is two Time difference between secondary sampling；

Step S8：Formula 7 is integrated, displacement formula 8 can be obtained：Wherein Vi is the sampled value of i moment speed；

Step S9：Repeat crosses paper money to test several times, and according to the observation of vibrating effect and storage data analysis, adjusts repeatedly Control parameter, then the displacement for obtaining cash dispenser axis is calculated, module is sent out by radio communication, detects whether bank note is pasted with this Gummed paper and its position.

2. the bank note thickness measuring method according to claim 1 based on 3-axis acceleration sensor, which is characterized in that when not having When bank note passes through cash dispenser axis, the vibration that measuring thickness device generates when rotating keeps acceleration transducer output voltage small size above or below 1.2V Fluctuation；When there is bank note to pass through cash dispenser axis, bank note squeezes cash dispenser axis, and cash dispenser axis is made to drive acceleration transducer up-down vibration, from And physical signal is converted into electric signal, it is adjacent between wave crest it is essentially identical.

3. the bank note thickness measuring method according to claim 1 based on 3-axis acceleration sensor, which is characterized in that the step Parameter initialization in rapid S5 includes the initial value setting of control algolithm parameter, the corresponding initial value of data collecting card, control ground The setting of location and type of drive.

4. the bank note thickness measuring method according to claim 1 based on 3-axis acceleration sensor, which is characterized in that described three Axle acceleration sensor uses model ADXL327 3-axis acceleration sensors.

5. the bank note thickness measuring method according to claim 1 based on 3-axis acceleration sensor, which is characterized in that the number Agilent data collecting card is used according to capture card.

6. the bank note thickness measuring method according to claim 1 based on 3-axis acceleration sensor, which is characterized in that when three axis Caused by the installation of acceleration transducer deviation occurs or deformation occurs aging when installation site run-off the straight, three axis add The X-axis of velocity sensor and acceleration of gravity direction are no longer parallel, and the acceleration that X-axis is surveyed at this time is only on active thickness measuring wheel The one-component of lower acceleration of motion, if the angle between X-axis and acceleration of gravity is θ, the output of X-axis is A_XOUT, Y-axis output For A_YOUT, Z axis output is A_OUTZ, then the calculation formula of angle theta is formula 9：

The actual acceleration A that the up and down motion of active thickness measuring wheel can be released according to angle theta is formula 10：

Integral is carried out to formula 10 and obtains formula 11：Time differences of the Δ t between double sampling；It is right again Formula 11 is integrated, and displacement formula 12 can be obtained：Wherein v_iIt is the i moment The sampled value of speed.

7. a kind of banknote thickness gauge based on 3-axis acceleration sensor, which is characterized in that including pedestal, circuit board, active Wheel shaft, passive thickness measuring wheel shaft, thickness measuring bracket, sheet metal, eddy current coil, thickness measuring mounting plate, extension bearing and 3-axis acceleration Sensor；The drive sprocket axle is located at below passive thickness measuring wheel shaft, is arranged in parallel with passive thickness measuring wheel shaft, and with passive thickness measuring wheel Axis frictional connection；The pedestal fixed setting, is located at the side of passive thickness measuring wheel shaft；The passive thickness measuring wheel shaft is arranged in thickness measuring On holder, the thickness measuring bracket is mounted on pedestal, is rotatablely connected with pedestal；One end of the sheet metal is fixed on pedestal, The other end is connected on thickness measuring bracket, its up-down vibration is driven by thickness measuring bracket；The eddy current coil regulation is in the upper of sheet metal Side, and circuit board electrical connection, by its spacing between sheet metal of circuit board detecting；

The thickness measuring mounting plate is equipped with the connecting hole for connecting passive thickness measuring wheel shaft and the fluting convenient for measurement vibration； The extension bearing is mounted in connecting hole, and the end of the passive thickness measuring wheel shaft is inserted into connecting hole, by extend bearing with Thickness measuring mounting plate connects, and vibration when measuring is passed to thickness measuring mounting plate；One side edge of the fluting from thickness measuring mounting plate Extend to the other side and thickness measuring mounting plate is divided into the top for measurement and the lower part for installation；It is described fluting and not through Thickness measuring mounting plate；The 3-axis acceleration sensor is arranged on the top of thickness measuring mounting plate, and and circuit board electrical connection.

8. the banknote thickness gauge according to claim 7 based on 3-axis acceleration sensor, which is characterized in that the survey Thick mounting plate lower part is additionally provided with the second 3-axis acceleration sensor for improving measurement accuracy, and second 3-axis acceleration passes Sensor is arranged on the corner of lower part, with circuit board electrical connection.

9. the banknote thickness gauge according to claim 7 based on 3-axis acceleration sensor, which is characterized in that described three Axle acceleration sensor is arranged in the upper corner of thickness measuring mounting plate.