KR20100126922A - Earth magnetic sensing apparatus, install method thereof, and vehicle movement detecting method using the same - Google Patents

Abstract

PURPOSE: An earth magnetic sensing apparatus, an install method thereof, and a vehicle movement detecting method using the same are provided to perform an initial operation without an additional switch on the outside of a case. CONSTITUTION: A terrestrial magnetism sensor(10) senses the terrestrial magnetism which is varied according to the movement of a vehicle. The terrestrial magnetism sensor includes a closed case and a vibration sensor. The vibration sensor is arranged inside the case. An amplifier(20) amplifies the output of the terrestrial magnetism sensor. A comparator(50) compares amplified terrestrial magnetism and with a reference signal and outputs an interrupt signal. A controller(60) senses the movement of the vehicles and outputs a digitized offset control value. A first digital-analog converter(27) changes the digitized offset control value into an analog value.

Description

Geomagnetic sensor device, installation method thereof and vehicle movement detection method {EARTH MAGNETIC SENSING APPARATUS, INSTALL METHOD THEREOF, AND VEHICLE MOVEMENT DETECTING METHOD USING THE SAME}

The present invention relates to a geomagnetic sensor device buried beneath the surface layer, an installation method thereof, and a vehicle movement detection method using the same, and more particularly, by providing a sensor for converting vibrations transmitted into an enclosed case into electrical energy. The present invention relates to a geomagnetic sensor device that performs initialization by using an output signal generated and maintains an idle state in a normal state, and then switches to an operation state only when entering a vehicle, an installation method thereof, and a vehicle movement detection method using the same.

In order to detect the information of the vehicle passing through the road, various vehicle detection devices such as loop detectors, image detectors, ultrasonic detectors, microwave detectors, and laser detectors have been used.

The loop detector is the most widely used detection device. It detects the occupancy of the vehicle by applying an oscillation signal to the roof coil embedded on the road surface and detecting a change in the magnetic field when there is a metallic object on the road surface. The loop detector is most widely used as a vehicle occupancy sensor because it has a low price and stable performance regardless of environmental conditions, despite the disadvantage that it is more vulnerable to cutting during road construction than the ultrasonic and imaging methods. Loop detectors install one or a pair per lane and use oscillating waves of different frequencies to prevent errors caused by magnetic fields induced in adjacent loop coils. As mentioned above, the loop detector has been adopted in most cases in Korea because the detection information is more reliable and cheaper to install than other types of detectors, but the following disadvantages are pointed out.

-The loop detector is affected by the inductance change depending on the pavement of the road and the materials used. Therefore, there is a remarkable difference in performance depending on the absence of construction failure and the shape and size of the detector. That is, there are many cases where it is impossible to collect and collect erroneous data due to moisture or disconnection of the loop detector due to careless construction.

-It is necessary to control traffic flow during installation.

-Deterioration of detector performance due to road damage and deterioration of detector performance due to deformation of pavement. On-site installation is the most detectable method on the market, but no comprehensive verification has been done.

-In case of general national highways, the failure status of loop detectors is increasing by year, with 48 places in 1999, 49 places in 2000, 127 places in 2001, and 140 places in 2002. As the cause of the failure, the failure caused by road damage and disconnection is increasing very rapidly, and the suspension of operation due to the road pavement construction is also increasing.

-For highways, there is a cost for repairing damage and fault detectors once a year for one loop detector. It takes about 2 ~ 3 weeks from the service order of the roof detector to repair and the police consultation according to the selection of maintenance company and the road blockage.The damage and the failure of the loop detector are mostly caused by the lanes. For lanes where information is not collected, traffic information is provided by referring to the information of adjacent lanes.

-As it is buried on the road surface, it causes troubles over time such as damage by vehicles or natural corrosion (about 2 years of loop sensor durability if no loop break occurs).

-According to the internal data of the operation of unmanned enforcement equipment of the National Police Agency, it is estimated that the sensor breakage occurs about twice a year, which is expected to be about 20-30%.

As described above, the loop detector embeds the roof coil over a fairly wide ground, making installation and maintenance difficult, high frequency of breakage, and low speed vehicle detection. In particular, due to road changes in Korea, where asphalt is mostly asphalt, irregularities are generated due to temperature changes, and the breakage rate is high.

The image sensor is a method of recognizing a distribution of pixel values of a region to be detected in advance and determining whether to enter a vehicle by changing pixel values when the vehicle enters. In case of young ginseng detector, it is a non-embedded type, and the application cases are increasing recently because of the relative merits of the inconvenience of installation work and difficulty of maintenance of buried type such as loop detector. In addition, unlike other detectors, there is an advantage that the administrator can check with the naked eye, so if the performance improvement such as resolution is supported, it is expected to be developed in the future. However, the result of image detector analysis has been pointed out that it is very sensitive to changes in climatic conditions and environment, such as deterioration of discrimination performance due to sudden changes in light quantity during rainy weather and sunset, and requires periodic maintenance because the lens needs to be cleaned. In other words, one installation cost is relatively very expensive.

Ultrasonic sensors are sensitive to climate and surrounding environment, and the detection area is conical, so there is no directivity. Microwave detectors are mainly used to obtain vehicle speed information, but they are expensive to install and require specialists for maintenance. Laser detectors require periodic maintenance for oscillator tuning, and expensive equipment to obtain accurate information.

Recently, a traffic information collection system using a geomagnetic sensor device using a geomagnetic sensor has been developed to overcome such disadvantages, which is relatively easy to install and provides accurate traffic information in real time by detecting accurate vehicle movement. It is known. Since the geomagnetic sensor is usually buried at a lower position than the road surface, the case must be sealed to protect it from moisture, etc. from the outside, and the initial setting is required depending on the installation position at the initial installation.

1 is a block diagram of a conventional geomagnetic sensor device for detecting a vehicle movement. The conventional geomagnetic sensor device is an amplifier 20, a comparator 50, a control unit 65, an external exposure switch 75, a transceiver consisting of a geomagnetic sensor 10, resistors R1 and R2, and an OP amplifier. ), The power supply unit 90 and the case 100. At least two switches are attached to the conventional geomagnetic sensor device, one of which is an external exposure switch 75 and the other is a first variable resistance control switch 30 for setting an offset of the amplifier 20. In addition, the second variable resistance control switch 40 may be further provided to adjust the comparison value CMP of the comparator 50. The installation and operation of the conventional geomagnetic sensor device will be briefly described. The conventional geomagnetic sensor device activates the external exposure switch 75 on before it is buried under the road surface. The geomagnetic sensor device starts operation by the external exposure switch 75, and the geomagnetic value measured by the magnetic sensor 10 is amplified by the amplifier 20 and compared with the reference value by the comparator 50. The calculation is performed by the controller 69 and then output to the transceiver 80. The installer checks the geomagnetic value output from the transceiver unit 80 using a separate external device while adjusting the first variable resistance control switch 30 and the second variable resistance control switch 40 from the transceiver unit 80. Check if the geomagnetism value output reaches the desired output value. When the desired output value is reached, the installation of the geomagnetic sensor device is completed by fixing the first variable resistance control switch 30 and the second variable resistance control switch 40 and embedding the conventional geomagnetic sensor device in a hole previously formed under the road surface. .

However, since the conventional geomagnetic sensor device uses an external exposure switch 75, it is vulnerable to leakage when buried under the road surface. In addition, since the offset value of the amplifier and the comparator must be set before the geomagnetic sensor device is buried, it may be set to include an error from the offset and the comparison value required at the buried position, which may cause the geomagnetic sensor malfunction. have. This may cause a very serious measurement error in the reality of using the amplifier 20 by amplifying the output of the geomagnetic sensor 10 to about 100 times the value. A bigger problem is that when the geomagnetic sensor device is used for a long time, a drift occurs when the geomagnetic sensor 10 self-saturates and a small change occurs in the output value. In order to compensate for this, the offset applied to the amplifier must be corrected in real time. . However, the conventional geomagnetic sensor device has a problem that cannot be corrected after setting the fixed value once because the variable resistor is used to correct the offset applied to the amplifier.

An important part of the practical application of another realistic geomagnetic sensor device to a road or parking system is to reduce power consumption, but conventional geomagnetic sensor devices have no means for efficiently reducing power consumption.

The present invention is to solve the above problems, it is possible to start the initial operation without installing a separate switch to the outside of the case, the geomagnetic sensor device can be set to the offset value of the amplifier after placing the buried device An object of the present invention is to provide a geomagnetic sensor device, an installation method thereof, and a vehicle movement detection method using the same.

Another object of the present invention is to provide a geomagnetic sensor device capable of compensating for an offset value applied to an amplifier in real time in a draft generated in the geomagnetic sensor periodically during an initial operation or a period when a vehicle is not detected. Furthermore, an object of the present invention is to provide a geomagnetic sensor device capable of reducing operation power consumption by installing a vibration sensor inside a case, an installation method thereof, and a vehicle movement detection method using the same.

The object of the present invention can be achieved by a geomagnetic sensor device comprising a sealed case and a vibration sensor provided in the case in the geomagnetic sensor device for detecting the geomagnetism changes according to the movement of the vehicle.

Still another object of the present invention is to provide a vibration sensor in a sealed case and install a geomagnetic sensor embedded below the road surface, the first step of providing a hole for inserting the geomagnetic sensor by digging below the road surface; The geomagnetic sensor device is inserted into the provided hole, and the geomagnetic sensor installation method includes a second step of applying vibration to a case of the geomagnetic sensor device and a third step of embedding the geomagnetic sensor device. .

Still another object of the present invention is to provide a vibration sensor inside a sealed case and to detect whether the vehicle moves by using a geomagnetic sensor device embedded below a road surface, the method comprising: detecting vibration applied to the geomagnetic sensor device; A first step, a second step of operating the geomagnetic sensor when vibration is detected in the first step, and a third step of detecting whether the vehicle moves from the geomagnetism output from the geomagnetic sensor Achievable by the method.

The geomagnetic sensor device according to the present invention has a self-calibration function, so that the initial installation is easy and the offset value can be corrected in real time even during use, so that the post-management is convenient. The geomagnetic sensor device according to the present invention can correct the draft of the geomagnetic sensor that changes according to the temperature and the surrounding environment in real time, so that the vehicle movement can be detected more accurately.

In addition, the geomagnetic sensor device according to the present invention is easy to install by installing a vibration sensor inside the case and can prevent the moisture even when buried under the road surface to improve the reliability of the product, in particular after the initialization of the geomagnetic sensor and the amplifier The offset value can be set to minimize measurement errors.

By applying the vibration sensor, the geomagnetic sensor device of the present invention can be easily switched from an idle state to an operating state by using the vibration sensed when the vehicle enters the vehicle. Can be reduced.

Hereinafter, the advantages, features and preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram of a geomagnetic sensor device according to the present invention. The geomagnetism sensor device according to the present invention includes a geomagnetism sensor 10, an amplifier 20 composed of resistors R1 and R2 and an OP amplifier, an analog-to-digital converter (hereinafter referred to as 'ADC'), a first digital- Analog converter 27 (hereinafter referred to as 'first DAC'), second digital-to-analog converter (hereinafter referred to as 'second DAC'), comparator 50, control unit 60, vibration sensor 70, Consists of the transceiver 80, the power supply unit 90 and the case 100. The geomagnetic sensor 10 is a sensor for measuring the geomagnetism, and in the present invention, a geomagnetic sensor of the company H was used and a sensor that outputs 1.65 mV in a 0.5 gauss environment when a 3.3V driving voltage is applied.

The amplifier 20 is a circuit for outputting the amplified geomagnetic sensor signal by amplifying the geomagnetic sensor value output from the geomagnetic sensor 10. For example, the amplifier 20 includes two resistors R1 and R2 and an OP amplifier. An offset signal was applied as an amplification reference signal to the '+' terminal of the amplifier OP amplifier, and connected to the output terminal of the geomagnetic sensor 10 to the '-' terminal. Therefore, the amplifier 20 amplifies and outputs the geomagnetic sensor value input based on the offset value. If the offset value applied as the reference signal of the amplifier 20 has a fixed value, the geomagnetic sensor 10 is caused by a draft phenomenon in which the geomagnetic sensor 10 is slightly changed in the sensing output value over time. The distortion signal output from the sensing signal is saturated in the OP amplifier of the amplifier 20 appears. Accordingly, in the present invention, the first DAC 27 provides an offset value that can be continuously changed while being corrected in real time through the control unit in order to prevent the amplified signal from being saturated.

The comparator 50 compares the amplified geomagnetic sensor signal with a comparison value CMP, which is a reference signal, and outputs a 'high' value when the geomagnetic sensor signal has a higher value than the comparison value CMP, and when it is low, 'low' A value is output and this output is input to the control unit 60. The comparison value CMP is used as a threshold for determining whether the vehicle passes. The 'high' signal output from the comparator 50 is also used as an interrupt signal for changing the control unit 60 from an idle state to an operation state. The comparison value CMP output from the controller 60 is applied to the '-' terminal of the comparator through the second DAC 57, and the output signal of the amplifier 20 is connected to the '+' terminal.

The controller 60 receives the amplified geomagnetic sensor signal, which is an output signal of the amplifier 20, through the ADC 25, and compares the 'amplified geomagnetic sensor signal' stored in an internal memory or a separate external memory, and the like. The comparison value is used to calculate the offset signal applied to the amplifier 20 and the comparison value CMP applied to the comparator 50, and a series of applying the same through the first DAC 27 and the second DAC 57. Take control. In addition, since the control unit 60 can be changed to the operation mode from the idle state in response to the interrupt signal input from the comparator 50, there is an advantage to save the power of the geomagnetic sensor device.

The power supply unit 90 usually uses a dry battery as a device for supplying power to each circuit component. The vibration sensor 70 detects a vibration applied to the case 100, converts the vibration into an electrical signal, and applies the vibration signal to the controller 60, and typically uses a piezo sensor. When the geomagnetic sensor device of the present invention is put into a hole formed in advance below the road surface and the shock is applied to the sealed case body, the shock is detected by the vibration sensor 70 and generates an interrupt signal to the control unit 60, This interrupt signal initializes the geomagnetic sensor. In addition, the geomagnetism sensor device of the present invention in the normal state while maintaining a rest state is buried under the road surface and the vibration generated when the vehicle approaches by the vibration sensor 70, using the detection signal geomagnetic It is possible to reduce power consumption by switching some components of the sensor device to an operational state.

The transceiver 80 transmits the measured geomagnetic value to an external device and also receives a control or data signal input from the external device. The transceiver 80 may be configured in any form of wired or wireless.

The case 100 is for protecting the internal components safely when the geomagnetic sensor device is embedded below the road surface. Since it is buried under the surface of the road, internal components must be safely protected even in weather conditions such as rain, snow, and freezing in winter. The geomagnetic sensor device of the present invention is characterized in that no component is exposed to the outside of the case and all components are installed inside the sealed case.

As described above, in the present invention, the geomagnetic sensor of the company H operated at 3.3V is used. As seen from the output terminal of the amplifier 10, as shown in FIG. When the amplified geomagnetic sensor signal is outputted, it is ideal because the same operation width is guaranteed in the up and down direction based on 1.65V. In other words, the voltage applied to the '-' terminal of the amplifier 10 is ideally applied so that the output value of the amplifier 10 swings with respect to the intermediate value of 1.65V.

Offset setting

As described above, the geomagnetic sensor 10 used by the inventor of the present invention is a geomagnetic sensor of the H company, the offset is ± 0.5mV / V, the operating voltage is 3.3V. When the 3.3V voltage is applied to the geomagnetic sensor 10 after being initialized as a set trigger, 0.5mV / V × 3.3V = 1.65mV is output. Since the amplifier 20 used in the present invention has amplification capacity of 500 times, the geomagnetic sensor output amplified by the amplifier 20 has an offset of 1,65 mV × 500 = 0.825 V, and the waveform at this time is shown in FIG. same as a)

When the offset is set to 0.825V as shown in Fig. 3 (a), the saturation is more likely to occur when the amplified output of the geomagnetic sensor swings below 0.825V. Therefore, in order to prevent the amplified output of the geomagnetic sensor from saturation, it is necessary to adjust the offset to be 1.6V as shown in FIG.

Therefore, when the controller 60 calculates the offset adjustment value as shown in Equation 1, the offset adjustment value becomes 1.6-0.825 = 0.775V.

Offset Adjustment = Reference Amplified Geomagnetic Sensor Signal-Amplified Geomagnetic Sensor Signal

The inventor of the present invention uses a 12-bit first DAC 27, and thus has an adjustment value of 0.8 mV per bit, and thus converts it to a digitized offset adjustment value of 775 mV / 0.8 mV = 968 and then converts it to a first DAC 27. ), The amplified offset of the geomagnetic sensor 10 is adjusted to be 1.6V. The first DAC 27 continues to maintain the same value until a new value is applied from the controller 60.

Offset correction

After the offset is set to the initial value and the geomagnetic sensor 10 is embedded, a method of automatically compensating the offset when a geomagnetic draft is generated according to the temperature due to an increase in temperature will be described. When the temperature rises, the sensing signal output from the geomagnetic sensor 10 changes, so the offset must be newly set.

At room temperature (25 ℃), if 3.3V voltage is applied after initialization with set trigger, 0.5mV / V × 3.3V = 1.65mV should be output, but after the temperature rises, the geomagnetic sensor 10 Assume that the output voltage is 1.8mV higher than 1.65mV. In other words, assume that as much as 0.15 mV of temperature drift has occurred. Since the amplifier 20 used in the present invention has amplification capacity of 500 times, the geomagnetic sensor output amplified by the amplifier 20 has an offset of 1,8 mV × 500 = 0.9V. When the offset adjustment value is calculated according to Equation 1, since the reference amplified geomagnetic sensor signal (1.6V)-amplified geomagnetic sensor signal (0.9V) is calculated as 0.7V and uses the 12-bit first DAC 27, Since there is an adjustment value of 0.8 mV per bit, a digital value of 700 mV / 0.8 mV = 875 is applied to the first DAC 27 to adjust the amplified offset of the geomagnetic sensor 10 to be 1.6 V. Therefore, in the normal case, a digital value of '968' is applied to the first DAC 27, but a digital value of '875' is applied to the first DAC 27 to compensate for the temperature drift, and thus a bias voltage after amplification ( 1.6V) can be achieved.

Comparison ( CMP ) Set

The H geomagnetic sensor 10 used in the present invention has a characteristic of 1mV / V / Gauss, in the case of Korea, it is known that approximately 0.5 gauss is detected in the usual geomagnetic. Applying this, a change of 1mV / V / Gauss × 3.3V × 0.5 Gauss = 1.65mV occurs. When this signal passes through the 500 times amplifier 20, a signal change of 1.65 mV x 500 = 825 mV occurs. Assuming that about 50% of the 825mV of the amplified geomagnetic sensor signal variation is a threshold for judging whether the vehicle is traveling, the comparison value is 1.6V + (825mV / 2) = about 2.0V. ) Should be set. If the second DAC 57 of 12 bits is used, it is 0.8mV per bit, so it is digitized to a digital value of 2V / 0.0008V = 2500, and then applied to the second DAC 27 output buffer to detect the comparison output of the sensor. Set to '1'. That is, when the amplified geomagnetic sensor signal value as shown in Figure 4 exceeds 2.0V, the comparator 50 applies a '1' (high) signal to the controller 60 to determine that the vehicle is passing, and amplified When the geomagnetic sensor signal value does not exceed 2.0V, the comparator 50 determines that the vehicle is not passing by applying a '0' (low) signal to the controller 60.

Hereinafter, an operation flow of the controller will be described using a flowchart. 5 is a flowchart of a sensor unit initialization routine of the geomagnetic sensor device according to the present invention. The geomagnetic sensor 10, the A / D converter 25, the first D / A converter 27, the second D / A converter 57, and the sensor control signal are initialized (ST401). Initialization of the geomagnetic sensor 10 proceeds by degaussing by first applying a magnetic field in one direction and then applying a magnetic field in the opposite direction. An Ad_value, which is an A / D converted value of the amplified geomagnetic sensor signal output from the amplifier 20, is input to the controller 60, and it is determined whether the Ad_value is the same as the stored amplified reference offset signal (ST 403). If the Ad_value is the same as the stored amplified reference offset signal as a result of the determination of step ST403, the process does not need to change the offset signal, so the process moves to step ST415 and ends.

If it is determined in step ST403 that Ad_value is not the same as the stored amplified reference offset signal, it is determined whether the Ad_value value is being changed (ST405). The change of the Ad_value indicates that the vehicle is passing around the geomagnetic sensor 10 or the situation affecting the geomagnetism is being generated, and thus the section in which the Ad_value does not change is identified. If it is determined that Ad_value does not change, it is used to determine a new digitized offset adjustment value to be applied to the amplifier 20 (ST407). The method of calculating the new digitized offset adjustment value is the same as described above. That is, the offset adjustment value is calculated from the 'amplified geomagnetism sensor signal-amplified geomagnetism sensor signal' according to Equation 1, digitized according to the number of bits of the first DAC 27 using the same, and then counted. The offset adjustment value is applied to the first DAC 27.

The determined converted offset adjustment value is applied to the first DAC 27 to apply the offset value of the amplifier 20 (ST409). After the new reference value is applied to the amplifier 20 and the comparator 50, the A / D conversion value Ad_value of the geomagnetic sensor signal amplified by the amplifier 20 is determined (ST411), and it is determined whether the Ad_value value is an allowed value. If it is determined (ST413), and if the allowable value, the offset reference value setting is terminated (ST415). If the Ad_value value is not an allowable value, the operation is performed again from step ST407.

Of course, various modifications are possible in the flow of FIG. 5. For example, in the embodiment of FIG. 5, if Ad_value is compared with a previously set "reference amplification geomagnetic sensor signal" and does not match, the reference value setting flow of FIG. 5 is performed. In this way, with a slight modification, the Ad_value value is read at regular intervals, and this count is counted only if the Ad_value value that is repeatedly identified is the same, and the Ad_value value is determined only when the number of counters exceeds a certain threshold. And thereafter there may be a way to proceed with the flow.

6 is a flowchart illustrating the overall operation of the geomagnetic sensor device according to the present invention. The geomagnetic sensor device is placed in a previously prepared hole in the lower part of the road surface (ST601), and then an impact is applied to the outer surface of the sealed case (ST602). The vibration sensor 70 is operated by the impact applied to the outer surface of the case, and the output of the vibration sensor is applied to the control unit 60 as an interrupt signal to execute the sensor initialization routine shown in FIG. 5 (ST603). The geomagnetic sensor device according to the present invention has an advantage of operating the geomagnetic sensor device by operating a vibration sensor therein without attaching a separate switch outside the sealed case 100. Next, the installation of the geomagnetic sensor device is completed.

After performing the geomagnetic sensor initialization routine, the peripheral circuit power is turned off and the control unit 60 is maintained at the idle state (ST605). Here, the peripheral circuit is a component except for the power supply unit 90, the vibration sensor 70, and the control unit 60. In the embodiment of FIG. 2, the geomagnetic sensor 10, the amplifier 20, the comparator 50, and the A / D converter (25), the first DAC 27, the second DAC 57 and the transceiver 80.

The control unit 60 checks whether the vibration sensor 70 operates while maintaining the idle state (ST607). Operation of the vibration sensor 70 means that an object causing vibration passes near the buried geomagnetic sensor device. When the vibration sensor 70 operates, the power of the peripheral circuit is turned on (ST609). At this time, the control unit 60 is converted to an operation state for a while to supply power to the peripheral circuit, and after the power is supplied to the peripheral circuit to be switched back to the idle state to minimize power consumption.

If the geomagnetic sensor 10 is always kept on, significant power consumption occurs. Currently known geomagnetic sensor 10 is known to consume a current of several tens mA in operation. As the power supply unit 90 installed inside the sealed case 100, it is assumed that a battery uses 2,500 mA as a battery capacity, and the geomagnetic sensor 10 consumes 3.3 mA per hour. The conventional geomagnetic sensor device without the vibration sensor 70 should always turn on the geomagnetic sensor 10, so the available time is calculated as '2500 / 3.3 = 758 hours' and can be used for about a month. In order to solve this problem, the geomagnetic sensor device of the present invention is provided with a vibration sensor and by maintaining the geomagnetic sensor 10 in an off state in general, by presenting a method of turning on the geomagnetic sensor 10 only when the vibration sensor is operated. The power consumption can be reduced.

It is determined whether there is a next vehicle entry (ST611). If it is determined that the step S611 is not entering the vehicle, the sensor initialization routine of the step ST603 is performed. Whether the vehicle enters the top of the geomagnetic sensor device is determined by whether the comparator 50 outputs an interrupt signal, and when an interrupt is generated, the vehicle 60 detects that the vehicle is entering and switches the control unit 60 to an operating state. It transmits to the transceiver 80 (ST613). As described above, the transceiver 80 may be transmitted by wire or wireless. Next, the A / D converted signal value Ad_value of the geomagnetic sensor signal amplified by the amplifier 20 is determined (ST615). It is determined whether Ad_value has a value larger than the comparison value CMP (ST617). If the Ad_value is greater than the comparison value, it means that the vehicle stays around the geomagnetic sensor. If the Ad_value is not greater than the comparison value, it means that the vehicle has passed completely. Therefore, the comparison value at step ST513 may be determined as a margin that can detect that the vehicle is not around the geomagnetic sensor. If the Ad_value has a value not greater than the comparison value CMP in step ST617, a passing completion signal indicating that the vehicle has passed is transmitted to the external device through the transceiver (ST619), and the peripheral circuit is turned off and the controller is idle ( ST605).

In the present invention, when the vibration sensor 70 does not operate, the power of the peripheral circuit is kept in the off state and the control unit 60 is kept in the rest state. Thereafter, when the vibration sensor 70 operates in step ST607, only the peripheral circuit is kept in the off state, the control unit 60 is still in the idle state, and the control unit 60 only when an interrupt signal is generated in the comparator 50. The power consumption is minimized by switching from the idle state to the operating state.

In a practical embodiment, among the components of the geomagnetic sensor device shown in FIG. 2, the ADC 25, the comparator 50, the first DAC 27, the second DAC 57, and the controller 60 may be a single Texas Instruments. 4) implemented.

The present invention described above is not limited to the above-described embodiments and drawings, and various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those who have knowledge.

1 is a block diagram of a conventional geomagnetic sensor device for detecting a vehicle movement.

Figure 2 is a circuit diagram of a geomagnetic sensor device according to the present invention.

Figure 3 is an example showing the amplifier output waveform of the geomagnetic sensor device according to the present invention.

Figure 4 is a waveform diagram for explaining the output signal to the input waveform of the comparator of the geomagnetic sensor device according to the present invention.

5 is a flowchart illustrating an amplifier offset changing routine when a draft occurs in the geomagnetic sensor in the geomagnetic sensor device according to the present invention.

6 is an operation flowchart of the geomagnetic sensor device according to the present invention.

***** Brief description of the main symbols on the drawing *****

10: geomagnetic sensor 20: amplifier

25: analog-to-digital converter 27: first digital-to-analog converter

30: variable resistor for offset value adjustment 40: variable resistor for comparison signal adjustment

50: comparator 57: second digital-to-analog converter

60: control unit

Claims (7)

In the geomagnetic sensor device for detecting the geomagnetic changes according to the movement of the vehicle, Sealed case; And Geomagnetic sensor device comprising a vibration sensor provided in the case. The method of claim 1, Inside the case Geomagnetic sensor for detecting the geomagnetic; An amplifier configured to output an amplified geomagnetic sensor signal by amplifying the geomagnetic sensor output signal using an offset value as a reference signal; A comparator for comparing the amplified geomagnetic sensor signal with the comparison signal using a comparison value as a reference signal and outputting an interrupt signal; The vehicle detects the movement of the vehicle according to the interrupt signal, compares the amplified geomagnetic sensor signal with a stored reference amplified geomagnetic sensor signal, calculates an offset adjustment value that is a difference value between quantum values, and counts the calculated offset values. A control unit for outputting an adjustment value; And And a first digital-to-analog converter for converting the digitized offset adjustment value output from the controller into an analog signal and then applying the offset signal of the amplifier. 3. The method of claim 2, The output signal of the amplifier is input to the control unit using an analog-to-digital converter, the control unit provides a quantized comparison value, converts the digitized comparison value input from the control unit into an analog of the comparator And a second digital-to-analog converter for inputting the reference signal. 3. The method of claim 2, And the control unit operates the geomagnetic sensor from an off state to an on state when an electrical signal is output from the vibration sensor. As a method of installing a geomagnetic sensor embedded in the sealed case and buried beneath the road surface, A first step of digging a lower surface of the road to provide a hole for the geomagnetic sensor; Inserting a geomagnetic sensor device into the prepared hole and applying vibration to a case of the geomagnetic sensor device; And And a third step of embedding the geomagnetic sensor device. A method of detecting whether a vehicle moves by using a vibration sensor in a sealed case and using a geomagnetic sensor device embedded below a road surface, Detecting a vibration applied to the geomagnetic sensor device; A second step of operating the geomagnetic sensor when vibration is detected in the first step; And And a third step of detecting whether the vehicle moves from the geomagnetism output from the geomagnetic sensor. The method of claim 6, The third step is A third step of amplifying a signal output from the geomagnetic sensor; And And comparing the amplified signal with the comparison signal to determine whether the vehicle enters the vehicle.

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