JP3582403B2 - Reader / writer for ID tag - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a handheld ID tag reader / writer that communicates with an ID tag provided on an object by radio waves to exchange data.
[0002]
[Problems to be solved by the invention]
For example, as a moving object identification system, there is a remote ID system using high-frequency radio waves. In this method, communication between a controller and an ID tag is performed by radio waves, and data of an ID tag at a remote position is read or data is written to the ID tag.
[0003]
Such a remote ID system is considered to be applied to various systems such as a delivery system, an inventory management system, and a sales system. As an example, there is a tallying system for a rotating sushi shop. The outline of this system is that the ID tag embedded in the plate on which sushi is placed records data such as the type of sushi, the time it was made, and the selling price. It collects them in places, communicates with the ID tags on those dishes, and obtains data from the ID tags to calculate the amount to be paid by the customer.
[0004]
In the case where the present invention is applied to such a totaling system, if the reader / writer communicating with the ID tag is of a fixed type, the total may be calculated by placing a plate in the communication area of the fixed type reader / writer. However, the fixed type reader / writer is inconvenient because the plate must be brought to that position. Therefore, a hand-held reader / writer has been considered in order to be able to easily perform the tallying on the table where the customer is sitting.
[0005]
In a hand-held reader / writer, a reader / writer body is usually held above a plate stacked on a table to perform a transmission / reception operation. However, since the operator usually does not recognize the number of dishes, it is difficult to confirm whether or not the operator has communicated with the ID tags of all the dishes. If the number of stacked dishes is 4 to 5, the operator can recognize the number of dishes, and if the number of ID tags that have communicated is displayed on the display unit, communication with the ID tags of all dishes is performed. You can immediately recognize whether you have done it. However, according to this method, when the number of dishes increases, the number of dishes cannot be recognized at a glance, so even if the display of the number of communicated ID tags is seen, it is not clear whether or not communication has been made with the ID tags of all dishes.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ID tag reader / writer capable of estimating the number of stacked objects.
[0007]
[Means for Solving the Problems]
When the ID tag reader / writer is brought close to the target object, the transmission antenna of the ID tag reader / writer and the reception antenna of the ID tag are electromagnetically coupled to each other, and a mutual induction action occurs therebetween. The inductance changes. The change in the inductance of the transmission antenna at this time changes according to the number of ID tags (antenna coils) on the other side to be electromagnetically coupled.
[0008]
Therefore, according to the first aspect of the present invention, when communicating with the ID tag, the inductance of the transmitting antenna is obtained, and the number of stacked objects is estimated using the inductance. Then, when the communication with the ID tag is completed, it is determined whether or not the number of the communicated ID tags is equal to the estimated number of stacked tags, and the determination result is notified. I do. Therefore, it is possible to recognize whether or not communication has been performed with the ID tags of all the objects in the stacked state.
[0009]
Further, when the transmitting antenna and the receiving antenna of the ID tag are electromagnetically coupled to each other and a mutual induction action occurs, the impedance of the transmitting antenna also changes. According to the second aspect of the present invention, since the impedance of the transmitting antenna is obtained and the number of stacked objects is estimated using both the inductance and the impedance of the transmitting antenna, the number of objects can be estimated more accurately.
[0010]
According to the third aspect of the present invention, the difference between the transmission frequency and the resonance frequency of the transmission antenna is obtained by detecting the phase difference between the signal waveforms at both ends of the coil constituting the transmission antenna. Since the resonance frequency of the transmission antenna is changed by changing the connection pattern of the correction capacitor so that the maximum resonance current flows through the transmission antenna, reading and writing to the ID tag can be performed in the resonance tuning state. It is possible to prevent a possible region from being narrowed. Further, the inductance of the transmission antenna can be easily obtained from the capacitance of the correction capacitor.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that this embodiment is applied to a tallying system for a revolving sushi restaurant. Here, the rotating sushi shop is a shop having the following system.
[0012]
A loop-shaped conveyor is provided in the store, and tables and seats are provided along the conveyor. Sushi is placed on a plate and transported to the audience by a conveyor. The customer takes the dish on which the favorite sushi is placed from among the dishes carried by the conveyor, and after eating, the dishes are sequentially stacked on the table. The shop places the sushi on a plate of a color or pattern corresponding to the selling price, so that the customer can know the approximate amount to be paid to the store from the type and the number of the stacked plates. After the meal, the clerk counts the number of plates by color or pattern, and determines the amount to be paid to the store.
[0013]
As shown in FIG. 7, the dish 1 on which sushi is placed is made of plastic such as ABS resin, and has an ID tag 2 embedded therein. As shown in FIG. 6, the ID tag 2 includes an antenna coil 3 for transmitting and receiving a radio signal, a resonance capacitor 4, a control IC 5, and a smoothing unit 6. The IC 5 and the smoothing section 6 are mounted on a printed wiring board 7.
[0014]
The control IC 5 is a one-chip semiconductor element constituting a rectifier 9, a modulator / demodulator 10, a memory 11, etc., in addition to an MPU (microprocessor unit) 8 as a control unit. Although not shown, the smoothing unit 6 has a smoothing capacitor, a Zener diode, and the like.
[0015]
The antenna coil 3 is connected in parallel with the resonance capacitor 4 to form a resonance circuit. When a predetermined high-frequency power radio signal is transmitted from a reader / writer, which is an external device, the antenna coil 3 receives the signal. And supplies it to the rectification unit 9. The rectifying unit 9 constitutes an operation power supply circuit together with the smoothing unit 6. The rectifying unit 9 rectifies an electric power radio signal transmitted from the resonance circuit, smoothes the electric power radio signal by the smoothing unit 6, and supplies a constant voltage DC power (operation electric power). ) And supply it to the MPU 8 and the like.
[0016]
A signal such as data transmitted from the reader / writer is transmitted while being superimposed on a power radio signal, and the signal is demodulated by the modem 10 and provided to the MPU 8. The MPU 8 operates according to an operation program stored in a ROM included in the memory unit 11, executes a process corresponding to a signal input from the modem unit 10, and erases received data from the EEPROM or the like included in the memory unit 11. The data is written to a possible non-volatile memory, or data is read from the memory unit 11, modulated by the modulation / demodulation unit 10, and transmitted as a radio signal from the antenna coil 3.
[0017]
As a reader / writer for an ID tag that communicates with the ID tag 2 on the plate 1, there is a hand-held reader / writer 12 shown in FIG. The hand-held reader / writer 12 is provided with a head 13b at the tip of an operation section 13a also serving as a grip section, and incorporates a battery 14 (see FIG. 5) as an operation power supply. The display unit 15 (see FIG. 5) made of liquid crystal is provided on the front side of the head 13b. The operation unit 13 is provided with, for example, a plurality of key switches 16. The key switches 16 are used to instruct operation contents and to input basic data necessary for totaling, for example, unit prices of the dishes 1 by type. It has become. The operation unit 13 is provided with a tallying key switch 17 for instructing a tallying process in addition to the key switches 16 described above.
[0018]
The hand-held reader / writer 12 includes a main controller 18 and a remote controller 19 (corresponding to read / write means and resonance frequency changing means) as shown in FIG. The main control unit 18 is connected to the key switch 16 group and the tallying key switch 17 via a switch circuit 20, and exchanges data with the display unit 15 and a higher-level device (for example, a personal computer). A communication unit 21 for exchanging information is connected. The switch circuit 20 transmits a signal corresponding to the operated key switch to the main control unit 18. The remote control unit 19 is in charge of data communication with the ID tag 2, and is connected to an antenna unit 22 for transmitting and receiving a radio signal to and from the ID tag 2, and a sounding unit 23 such as a buzzer. .
[0019]
FIG. 3 schematically shows the configuration of the main control unit 18 of the handheld reader / writer 12. As shown in FIG. 3, the main control unit 18 includes an MPU 24, a ROM 25 storing an operation program, a RAM 26 for temporarily storing data, a communication unit 27 for executing communication with the remote control unit 19, and the like. I have. The MPU 24 processes data and controls peripheral devices. The MPU 24 executes a process corresponding to a signal sent from the remote control unit 19 or the switch circuit 20, and also executes a process content or a process being executed. The result is displayed on the display unit 14.
[0020]
FIG. 4 schematically shows the configuration of the remote control unit 19. As shown in FIG. 4, the remote control unit 19 includes an MPU 28, a ROM 29 that stores an operation program and a database described later, a RAM 30 that temporarily stores data, a communication unit 31 that executes communication with the main control unit 18, The transmitting unit 33 includes a transmitting unit 33 connected to the transmitting antenna 32 of the antenna unit 22, a receiving unit 35 connected to the receiving antenna 34, and the like. The MPU 28 controls communication with the ID tag 2 and controls the sound generator 23. When communicating with the ID tag 2, first, the MPU 28 modulates the reference signal in the transmitter 33 and modulates the power for the power. The transmission signal is transmitted from the transmission antenna 32 as a radio signal, and then transmitted from the transmission antenna 32 after being modulated by the transmission unit 33 so that the data to be transmitted is superimposed on the power radio signal.
[0021]
The radio signal transmitted from the ID tag 2 is received by the receiving antenna 34, demodulated by the receiving unit 35, and discriminated as data. Then, the MPU 28 of the remote control unit 19 temporarily stores the data demodulated by the reception unit 35 in the RAM 30, and then transmits the data to the main control unit 18 via the communication unit 31. I have.
Here, the transmission antenna 32 and the reception antenna 34 are both formed of coils, and are disposed on the front side in the head 13b.
[0022]
Now, the transmission unit 33 of the remote control unit 19 has an automatic tuning function for automatically tuning the resonance frequency of the transmission antenna 32 to the frequency of the transmission signal. The automatic tuning function of the transmission unit 33 will be described below. I do.
[0023]
First, the principle of automatic tuning will be described.
In a series resonance circuit including a coil L, a capacitor C, and a resistor R (resistance of the coil L) as shown in FIG. 9, a voltage difference between both ends of the coil L (corresponding to the transmission antenna 32) becomes a transmission output. At the time of resonance tuning when the resonance frequency matches the resonance frequency, the maximum current flows through the series resonance circuit, and the transmission output becomes maximum. At this time, the signal waveforms at both ends of the coil L are 90 ° out of phase with the waveform of the transmission signal (see the solid line in FIG. 9). On the other hand, at the time of resonance non-tuning in which the frequency of the transmission signal and the resonance signal are shifted, the voltage difference between both ends of the coil L decreases as shown by the broken line in FIG. At this time, the phase shift of the signal waveform at both ends of the coil L is out of 90 °. For this reason, the transmission output from the coil L decreases as compared with the time of resonance tuning.
[0024]
FIG. 10 shows the relationship between the phase difference between the voltages across the coil L and the transmission output. In FIG. 10, it can be seen that the transmission output is maximum when the phase difference is 90 °, and that the transmission output decreases as the phase difference deviates from 90 °. Further, it can be seen that there is a correlation between the phase shift between both ends of the coil L and the transmission output (resonance current). Therefore, by adjusting the phase shift within the allowable range by changing the capacitance of the capacitor C, it is possible to realize automatic tuning in which the resonance frequency of the transmission antenna 32 is adjusted to the transmission frequency, and the resonance current (transmission output) is reduced. Adjustment can be made to be sufficient.
[0025]
FIG. 2 schematically shows the configuration of the transmission unit 33. In FIG. 2, the transmission circuit 36 of the transmission unit 33 is connected to the series resonance circuit 37 and the first level conversion circuit 38, and transmits a reference signal (transmission signal) of a predetermined frequency to the series resonance circuit 37 and the first level conversion circuit 38. The signal is output to the level conversion circuit 38. The series resonance circuit 37 is configured by connecting the transmission antenna 32 and the resonance capacitor circuit 39 in series.
[0026]
The resonance capacitor circuit 39 is configured by connecting a reference capacitor 40 and a correction circuit 41 in parallel, and the capacitance of the entire resonance capacitor circuit 39 is equal to the capacitance of the reference capacitor 40 and the correction circuit 41. Is the value obtained by adding the capacitance of The correction circuit 41 includes a plurality of first to n-th unit circuits 42 connected in parallel. One unit circuit 42 includes a capacitor 42a (corresponding to a correction capacitor) and a capacitor 42b (corresponding to a correction capacitor). ) Are connected in series, and a switch 42c is connected in parallel with the capacitor 42b. Therefore, the capacitance of the entire correction circuit 41 and the capacitance of the resonance capacitor circuit 39 are determined according to the on / off state of the switch 42c of each unit circuit 42.
[0027]
Here, if the capacitances of the capacitors 42a and 42b in each unit circuit 42 are set to the same capacitance, for example, 2C, the capacitance of the unit circuit 42 becomes C when the switch 42c is off, and the switch 42c In the ON state, the capacitance of the unit circuit 42 is 2C. Therefore, by turning on the switch 42, the capacitance of the unit circuit 42 can be increased from C to 2C by C.
[0028]
When the correction circuit 41 is composed of the first to sixth unit circuits 42, the capacitances of the capacitors 42a and 42b in the first to sixth unit circuits 42 are 64C, 32C, 16C, 8C, 4C, and 2C, respectively. Therefore, when the switches 42c of the first to sixth unit circuits 42 are independently turned on, the capacitance of the entire correction circuit 41 increases by 32C, 16C, 8C, 4C, 2c, and 1C. . This means that the capacitance of the entire correction circuit 41 can be adjusted in the range of 0 to 63C in units of 1C according to the combination pattern of the ON / OFF state of the switch 42c of each unit circuit 42.
[0029]
In this case, the correction circuit 41 is designed so that the series resonance circuit 37 is in resonance tuning with the switch 42c of the first unit circuit 42 being turned on. This is because the resonance frequency of the series resonance circuit 37 is set as a design value at the center of the adjustable frequency range of the correction circuit 41 so that the increase or decrease of the capacitance of the correction circuit 41 is corrected. This is for effective use.
[0030]
The voltage dividing circuit 43 is connected in parallel to the resonance capacitor circuit 39 having the above configuration. The voltage dividing circuit 43 includes a capacitor 43a and a capacitor 43b connected in series, and outputs a voltage level at a common connection point between the capacitors 43a and 42b to a second level conversion circuit 44. A circuit having a small capacitance is used so as not to affect the capacitance of the circuit 39.
[0031]
The first and second level conversion circuits 38 and 44 convert an input signal into a binary signal, and output the binary signal to an exclusive OR circuit 45.
The exclusive OR circuit 45 outputs the exclusive OR of the binary signals input from the first and second level conversion circuits 38 and 44 to the phase difference voltage conversion circuit 46. The exclusive OR circuit 45 outputs a phase difference signal indicating the phase difference between the reference signal from the transmission circuit 36 and the resonance signal of the series resonance circuit 37. If the phases of both signals do not match, the phase difference signal is output. And outputs a pulse-shaped phase difference signal indicating the magnitude and direction of the phase difference.
[0032]
The phase difference voltage conversion circuit 46 converts the phase difference signal output from the exclusive OR circuit 45 into a voltage indicating the phase difference and the phase difference direction, and converts the signal into a transmission tuning deviation determination circuit 47 (corresponding to a transmission tuning deviation obtaining means). Output to The transmission tuning deviation determination circuit 47 outputs the phase difference and the phase difference direction to the C (capacitor) on / off control circuit 48 (corresponding to the counting means) and the MPU 28 based on the voltage output from the phase difference voltage conversion circuit 46. Then, the C on / off control circuit 48 controls the on / off of the switch 42 c of the unit circuit 42 of the correction circuit 41 so that the signal phase difference between the two ends of the transmission antenna 32 becomes 90 ° so that the electrostatic capacitance of the series resonance circuit 37 becomes 90 °. Adjust capacity. Further, the MPU 28 determines whether or not frequency tuning has been performed based on a signal from the transmission tuning deviation determination circuit 47 (tuning determining means).
[0033]
Here, the inductance of the coil constituting the transmission antenna 32 changes due to the relationship between the transmission antenna 32 and the ID tag 2 electromagnetically coupled to the surrounding environment, and the impedance of the transmission antenna 32 changes accordingly. The inventor has determined that there is a certain relationship with the number of dishes 1 on which the inductance and the impedance are stacked.
[0034]
That is, FIGS. 11 and 12 show the results of experiments on the relationship between the number of stacked plates 1 and the inductance and impedance. According to FIGS. 11 and 12, there is a certain relationship between the number of stacked plates 1 and the inductance. However, for example, when the number of dishes 1 is two and seven, the values are 278 μH and 277 μH in the first test, 273 μH and 273 μH in the second test, and there is almost no difference.
[0035]
However, the relationship between the number of stacked plates 1 and the impedance is 12.5 Ω and 28.4 Ω in the first test when the number of plates 1 is 2 and 7 and 11 in the second test. There is a significant difference between 0.7Ω and 30.4Ω. From this, if the inductance and the impedance are known, the number of stacked plates 1 at that time can be estimated.
[0036]
Therefore, when the frequency tuning is completed, the MPU 28 obtains on / off information for each switch 42c of the resonance capacitor circuit 39 from the C on / off control circuit 48, and obtains the capacitance of the resonance capacitor circuit 39 from the on / off information. ing. The MPU 28 obtains information on current flowing through the transmission antenna 32 from a current sensor 49 provided on the transmission antenna 32. The MPU 28 obtains the inductance of the transmission antenna 32 based on the capacitance information, and obtains the current sensor 49 The impedance of the transmitting antenna 32 is obtained based on the current information from.
[0037]
On the other hand, the relationship between the number of stacked plates 1, the impedance, and the impedance is stored in a table in the ROM 29. Then, the MPU 28 obtains the number of stacked plates 1 from the calculated inductance and impedance and the data table stored in the ROM 29.
[0038]
Next, the operation of the above configuration will be described with reference to the flowchart shown in FIG. When the MPU 24 of the main control unit 18 enters the tallying routine of FIG. 1, it enters a state of monitoring whether or not the tallying key switch 17 is turned on (step S1). Now, in order to count the payment amount of the customer who has completed the meal, the hand-held reader / writer 12 is brought on the plate 1 stacked on the customer table as shown in FIG. It is assumed that the key switch 17 is operated while the front surface of the head 13b on which the receiving antenna 34 is disposed is brought into contact with the inner bottom surface of the top plate 1.
[0039]
Then, a signal corresponding to the tallying key switch 17 is input from the switch circuit 20 to the main control unit 18, and the MPU 24 decodes the signal input from the switch circuit 20. In this case, the input signal from the switch circuit 20 is a tally command signal ("YES" in step S1), which instructs communication with the ID tags 2 of all dishes 1 that the customer has finished eating. The MPU 24 of the main control unit 18 outputs a tally command to the remote control unit 19. Accordingly, the MPU 28 of the remote control unit 19 first applies a reference signal of a predetermined frequency to the transmission antenna 32 for measuring the number of sheets in order to communicate with the ID tag 2 (step S2).
[0040]
In other words, the MPU 28 controls the C on / off control circuit 48 to set only the switch 42c of the first unit circuit 42 of the correction circuit 41 to the on state, and the capacitance of the correction circuit 41 becomes the capacitance. The adjustment is made in the middle of the correctable range. Then, in this state, the transmission circuit 36 outputs a reference signal having a predetermined frequency. As a result, the series resonance circuit 37 is brought into a resonance state by the reference signal.
[0041]
Although the series resonance circuit 37 is designed to be in a resonance state (resonance tuning state) at the maximum current according to the output of the reference signal from the transmission circuit 36, the transmission antenna 32 of the handheld reader / writer 12 is The inductance changes depending on the number of stacked 1 (ID tags 2) and the like. Since the resonance frequency of the transmission antenna 32 is determined by the inductance and the resonance capacitor 41, the resonance frequency and the resonance current of the transmission antenna 32 change due to the change in the inductance.
[0042]
Then, the MPU 28 of the remote control unit 19 detects the signal phase difference between both ends of the transmission antenna 32 based on the determination result by the transmission tuning deviation determination circuit 47 of the transmission unit 33, and determines whether the phase difference is within the reference range. (Step S3; tuning determination means). At this time, when the phase difference between the reference signal and the resonance signal exceeds the allowable range, it is determined that the resonance signal is not in the resonance tuning state ("NO" in step S3), and a switching command is given to the C on / off control circuit 48. . As a result, the on / off pattern of the switch of the correction circuit 41 is switched in a short time, and the resonance frequency of the transmission antenna 32 approaches the frequency of the reference signal (step S4). Then, when the phase difference between both ends of the transmitting antenna 32 falls within a predetermined range, it is determined that resonance tuning has been achieved (“YES” in step S3), and the process proceeds to step S5.
[0043]
In step S5, the MPU 28 calculates the current capacitance value of the resonance capacitor circuit 39 from the on / off state of each switch 42c of the correction circuit 41 by the current C on / off control circuit 48, and then calculates the resonance capacitance. The inductance of the transmitting antenna 32 is calculated from the capacitance of the capacitor circuit 39 (Step S6; inductance obtaining means). Next, the MPU 28 detects a resonance current currently flowing from the current sensor 49 to the transmission antenna 32 (Step S7), and calculates an impedance of the transmission antenna 32 from the resonance current (Step S8; impedance obtaining means).
[0044]
Then, the MPU 28 searches the number of stacked dishes 1 with reference to the data table stored in the RAM 30 from the current inductance and impedance of the transmitting antenna 32, and stores the number in the RAM 30 as the estimated number. (Step S9).
[0045]
After estimating the number of stacked plates 1, the MPU 28 communicates with the ID tag 2 of the plate 1 (step S10). In communication with the ID tag 2, the reference signal is modulated by the transmitting unit 33 and transmitted as a power radio signal from the transmitting antenna 32, and the transmitting unit 33 modulates the data to be transmitted on the power signal. And transmits from the transmission antenna 32.
[0046]
Then, on the ID tag 2 side of the plate 1, the transmitted radio signal is received by the antenna coil 33, and the radio signal is rectified and smoothed by the rectifying unit 9 and the smoothing unit 6 to be converted into DC power of a constant power. It is supplied as a power supply for operation such as. When the power for operation is supplied, the MPU 8 of the ID tag 2 of each plate 1 starts operating and performs processing according to the content of the transmitted signal, in this case, the ID number of the plate 2 from the memory unit 1, An operation is performed in which data of two types or the like are read, modulated by the modulation / demodulation unit 10 and transmitted from the antenna coil 3. The radio signal transmitted from the ID tag 2 of each plate 1 is received by the receiving antenna 34 of the hand-held reader / writer body 12, the received signal is demodulated by the receiving unit 35, and the demodulated data is stored in the RAM 30. .
[0047]
In this way, the MPU 28 communicates with the ID tags 2 of the stacked dishes 1 and determines that the communication with the ID tags 2 of all the dishes 1 has been completed, and the MPU 28 proceeds to step S11 to perform communication. It is determined whether or not the number of the ID tags 2 matches the number data stored in the RAM 30 (match determination means).
[0048]
Here, it is determined that the communication with all the IDs 2 of the dishes 1 has been completed as follows. That is, when communicating with one ID tag 2, the MPU 28 stores the ID number of the ID tag 2 in the RAM. At this time, if the ID number has already been stored, the data is not stored in the RAM. When the number of communicated ID tags 2 increases, the ID number stored in the RAM also increases. However, when the ID tags 2 of all the stacked dishes 1 are communicated, the ID numbers stored in the RAM 30 are used in subsequent communication. No other numbers are lost. When this state continues for a predetermined time, the MPU 28 determines that communication with the ID tags 2 of all the dishes 1 has been completed.
[0049]
If the number of ID tags 2 with which the communication has been performed matches the number data stored in the RAM 30, the MPU 28 determines "YES" in step S11 and proceeds to step S12 to generate a sound. The control unit 23 causes the display unit 15 to perform a sounding operation (for example, a beeping sound) indicating that all communication has been completed, and notifies the main control unit 18 that communication has been completed normally, and causes the display unit 15 to display that communication has been completed. Subsequently, the MPU 24 of the main control unit 18 reads the type (price) and the number of each dish 1 stored in the RAM 30 via the MPU 28 of the remote control unit 19, and calculates the amount to be paid by the customer. This is stored in the RAM 26, and the processing ends.
[0050]
When it is determined that the communication with the ID tags 2 of all the dishes 1 has been completed as described above, and when the number of ID tags that have completed communication does not match the number data stored in the RAM 30, the MPU 28 In step S11, "NO" is determined, and the sound generation unit 23 is caused to perform a sound generation operation (for example, a beep, a beep, a beep sound) indicating that the estimated number and the communication number do not match, and the main control unit 18 also performs that operation. This is notified and displayed on the display unit 15. By this sounding and display, the user notices an abnormality, and when the number of stacked plates 1 is too large, the plate 1 is divided into two or a foreign object such as silver paper that blocks radio waves is left on the plate 1. If so, remove it. Then, the above operation is performed again.
[0051]
According to the present embodiment configured as described above, the number of stacked dishes 1 can be estimated based on the stacking height of the dishes 1, so that it is determined whether or not communication with all the dishes 1 has been completed. You can check. Moreover, since the number of plates 1 is estimated from the inductance and impedance of the transmission antenna 32, the number of plates can be estimated using the transmission unit 33 originally provided in the reader / writer 12. For this reason, in order to estimate the number of plates 1, for example, the stacked height of the plates 1 is measured by an ultrasonic distance measuring device, and the number of plates 1 is estimated from the stacked height. Does not require dedicated equipment.
[0052]
Further, in the present embodiment, the phase difference between the frequency of the reference signal and the frequency of the resonance signal of the series resonance circuit 37 is obtained by the automatic tuning function, and the correction circuit 41 is configured to maximize the resonance current based on the phase difference. Is adjusted, even if the resonance frequency of the series resonance circuit 37 deviates from the design value, the transmission area of the transmission antenna 32 can be narrowed without increasing the transmission output of the reference signal. Can be prevented, and data can be reliably read from the ID tag 2 of the stacked dishes 1. Then, since the inductance of the transmitting antenna 32 is obtained from the capacitance of the resonance capacitor circuit 39, the inductance of the transmitting antenna 32 can be easily obtained by using a component for automatic tuning.
[0053]
The present invention is not limited to the embodiment described above and shown in the drawings. For example, the present invention is not limited to the sushi plate 1, and may be variously modified and implemented without departing from the gist thereof. Can be.
[Brief description of the drawings]
FIG. 1 is a flowchart showing control contents of a tally operation in one embodiment of the present invention.
FIG. 2 is a circuit diagram showing a schematic electrical configuration of a transmission unit.
FIG. 3 is a block diagram showing an electrical configuration of a main control unit of the handheld reader / writer.
FIG. 4 is a block diagram showing an electrical configuration of the remote control unit.
FIG. 5 is a block diagram showing the overall electrical configuration of the handheld reader / writer;
FIG. 6 is a block diagram showing an electrical configuration of the ID tag.
FIG. 7 is a perspective view of a dish with a built-in ID tag.
FIG. 8 is a diagram showing a reading / writing state by a handheld reader / writer.
FIG. 9 is a circuit diagram and a signal waveform diagram for explaining a resonance state of the resonance circuit.
FIG. 10 is a diagram showing a relationship between a signal phase difference between both ends of a coil and a transmission output.
FIG. 11 is a diagram showing a relationship between the number of stacked plates and the inductance and impedance of the transmitting antenna.
FIG. 12 is the same graph.
[Explanation of symbols]
1 is a plate (object), 2 is an ID tag, 18 is a main control unit, 19 is a remote control unit (read / write unit, resonance frequency changing unit, inductance acquisition unit, impedance acquisition unit), 37 is a series resonance circuit, 32 Is a transmission unit, 33 is a transmission antenna, 39 is a resonance capacitor circuit, 47 is a transmission tuning deviation determination circuit (transmission tuning deviation obtaining means), and 48 is a capacitor on / off control circuit.

Claims (3)

An ID tag reader / writer including a read / write unit that reads / writes data from / to an ID tag attached to an object,
When communicating with the ID tag of the stacked object, an inductance obtaining unit that obtains an inductance of a transmitting antenna formed of a coil,
Estimating means for estimating the number of stacked objects based on the inductance obtained by the inductance obtaining means,
When communication with the ID tag is completed, the communication device includes a coincidence determination unit configured to determine whether the number of the ID tags that have communicated and the estimated number of stacks match,
An ID tag reader / writer configured to notify a result of the judgment by the coincidence judging means . Providing impedance detection means for determining the impedance of the transmitting antenna,
2. The ID tag reader according to claim 1, wherein the estimating unit estimates the number of stacked objects by using the inductance obtained by the inductance obtaining unit and the impedance obtained by the impedance obtaining unit. lighter. A resonance capacitor, which is constituted by a plurality of correction capacitors provided so as to exhibit different capacitances according to the connection pattern, and forms a series resonance circuit with the transmission antenna,
Transmission tuning deviation obtaining means for obtaining a deviation between a transmission frequency and a resonance frequency of the transmission antenna based on a phase difference between signal waveforms at both ends of a coil constituting the transmission antenna,
Resonance frequency changing means for changing the resonance frequency of the transmission antenna by changing the connection pattern of the correction capacitor so that the frequency shift determined by the resonance tuning shift obtaining means is within an allowable range,
3. The reader / writer for an ID tag according to claim 1, wherein the inductance obtaining unit obtains an inductance of the transmission antenna based on a capacitance of the correction capacitor.

Images