JPH11257981A - Navigation system and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a navigation system in which stoppage of a vehicle is detected accurately. SOLUTION: A sensor section 1 comprises an angular speed sensor 1a and an acceleration sensor 1b for detecting angular speed and acceleration of a vehicle in a specified direction. A navigation system 20 receives signals from the sensor section 1 through an input means 20a. The navigation system 20 comprises means 20c for setting the reference value of output signal, means 20d for setting a threshold value as a reference for making a decision whether a vehicle is stopping or not, means 20e for calculating the difference between the reference value from the means 20c and an output signal received from the input means 20a, means 20f for making a decision that the vehicle is stopping if the calculated difference 15 smaller than the threshold value, and means 20g for correcting a processing means 20b when a decision that the vehicle is stopping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a navigation device and a recording medium, and more particularly to a navigation device and a navigation device for detecting a current position and attitude of a vehicle by referring to a signal output from a sensor unit having an acceleration sensor or an angular velocity sensor. The present invention relates to a computer-readable recording medium on which a program for causing a computer to execute such processing is recorded.

[0002]

2. Description of the Related Art For example, in a navigation device represented by a car navigation system, a current position and a posture of a vehicle are detected by referring to output signals from an acceleration sensor and an angular velocity sensor, and a CD is provided in accordance with the detection result. -ROM (Compac
t Disk-Read Only Memory) is configured to appropriately process map information and display it on a display device.

FIG. 12 is a block diagram showing a configuration example of such a conventional navigation device. In FIG. 1, the sensor unit 1 includes an angular velocity sensor 1a for detecting an angular velocity and an acceleration sensor 1b for detecting an acceleration.

The arithmetic processing unit 2 refers to the output signal of the sensor unit 1 to detect a current position of the vehicle (hereinafter abbreviated as a current position) and a current state (hereinafter abbreviated as a current state). I do. Then, of the map information stored in the storage device 3, a map of an area corresponding to the current position is obtained, processed as appropriate, and output to the display device 4 for display.

[0005] The storage device 3 is composed of, for example, a CD-ROM drive, and stores map information, programs executed by the arithmetic processing unit 2, and the like. The display device 4 is, for example, an LCD (Liquid Crystal).
Display) and an arithmetic processing unit 2
And displays, for example, road information and the like.

[0006]

However, in such a conventional navigation device, the arithmetic processing unit 2 calculates the variation error component included in the output of the sensor, the mounting attitude of the navigation device to the vehicle, and the like. A situation has occurred in which the current position and the current attitude include an error.

As a method for canceling an error contained in a signal output from such a sensor, for example, a method as shown in FIG. 13 has been proposed. When this flowchart is started, the following processing is executed. [S1] The processing unit 2 receives an output signal from the sensor unit 1. [S2] The arithmetic processing unit 2 determines whether or not the vehicle is stopped. If the vehicle is stopped, the process proceeds to step S3; otherwise, the process proceeds to step S4. [S3] The arithmetic processing unit 2 corrects the output signal of the sensor. [S4] The arithmetic processing unit 2 performs a normal process (a process of displaying a map according to a signal from the sensor unit 1).

According to such processing, when the vehicle is stopped (when the output of the sensor unit 1 is stable), an error component (for example, a fluctuation error or an offset due to the mounting posture of the sensor unit 1) is generated. Component, etc.), and the output signal of the sensor can be corrected.

Incidentally, in order to execute such a process, it is necessary to accurately determine whether or not the vehicle is stopped. However, it is very difficult to make such a determination accurately, and the accuracy has been extremely low.

Therefore, a method of making such a determination using a vehicle speed pulse detected by a vehicle speed sensor has been proposed. However, in order to use the vehicle speed pulse from the vehicle speed sensor, it is necessary to connect the navigation device and the vehicle speed sensor, so that there is a problem that the operation of mounting the navigation device becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and reliably detects a stopped state of a vehicle without complicating an attaching operation, and detects an error included in an output signal of a sensor unit. It is an object of the present invention to provide a navigation device that can be removed.

[0012]

According to the present invention, in order to solve the above-mentioned problems, a navigation apparatus for detecting a current position or attitude of a vehicle by referring to a signal output from a sensor unit having an acceleration sensor or an angular velocity sensor. An input unit for inputting an output signal of the sensor unit; an arithmetic processing unit for obtaining a current position and a posture of the vehicle by predetermined arithmetic processing from an output signal of the sensor unit input to the input unit; Reference value setting means for setting a reference value of the output signal of the sensor, threshold setting means for setting a threshold value of the output signal of the sensor unit, and a signal value of the output signal of the sensor unit input to the input unit at an arbitrary time Difference calculating means for calculating a difference between the difference value and the reference value; determining means for determining whether a difference value obtained by the difference calculating means is smaller than the threshold value; If it is determined that the difference value is smaller than the threshold value by means comprises a calibration means for the vehicle calibrating the processing means as being in a stopped state,
The navigation device is provided with:

The input means inputs an output signal of the sensor section. The arithmetic processing means obtains the current position and posture of the vehicle by predetermined arithmetic processing from the output signal of the sensor section input to the input means. The reference value setting means sets a reference value of the output signal of the sensor unit. The threshold setting means sets a threshold of the output signal of the sensor unit. The difference calculation means calculates a difference between a signal value at an arbitrary time of the output signal of the sensor unit input to the input means and a reference value. The determining means determines whether or not the difference value obtained by the difference calculating means is smaller than a threshold. When the determining unit determines that the difference value is smaller than the threshold, the calibrating unit calibrates the arithmetic processing unit assuming that the vehicle is in a stopped state.

For example, the input means inputs an output signal of a sensor unit having an angular velocity sensor or an acceleration sensor.
The arithmetic processing means obtains the current position of the vehicle and the current attitude of the vehicle by predetermined arithmetic processing from the output signal of the sensor section input to the input means. The reference value setting means sets a reference value that is the center of a change in the signal value of the output signal of the sensor unit. The threshold setting unit sets a threshold used when determining whether or not the vehicle is stopped based on an output signal of the sensor unit. The difference calculation means calculates a difference between a signal value at an arbitrary time of the output signal of the sensor unit input to the input means and a reference value. The determining means determines whether or not the difference value obtained by the difference calculating means is smaller than a threshold. The calibration unit determines that the vehicle is in a stopped state when the determination unit determines that the difference value is smaller than the threshold,
Calibrate the processing means to remove the effect of the fluctuation error contained in the output signal of the sensor unit

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of an embodiment of the present invention.

In FIG. 1, the sensor unit 1 includes an angular velocity sensor 1a and an acceleration sensor 1b.
In this figure, one angular velocity sensor 1a and one acceleration sensor 1b are shown for simplicity, but actually the traveling direction (X direction), the yaw direction (Y direction), and the pitch direction of the vehicle One set of sensors is provided for each (Z direction).

FIG. 2 is a diagram showing the relationship between the traveling direction of the vehicle and the X, Y, and Z axes. As shown in this figure, the direction parallel to the traveling direction of the vehicle is the X-axis direction. The direction orthogonal to the traveling direction of the vehicle and horizontal to the ground is the Y-axis direction. Further, a direction perpendicular to the traveling direction of the vehicle and perpendicular to the ground is defined as a Z-axis direction.

FIG. 3 shows the X, Y and Z axes and the angular velocity sensor 1.
FIG. 6 is a diagram illustrating a relationship between the detection amount and a detection amount detected by the acceleration sensor 1b. For example, an acceleration sensor in the X-axis direction detects the acceleration αx. The angular velocity sensor in the X-axis direction detects the angular velocity ωx.

That is, the detection amount of each sensor is defined as follows. αx: acceleration parallel to the X axis αy: acceleration parallel to the Y axis αz: acceleration parallel to the Z axis ωx: angular velocity of rotational motion along the X axis ωy: to the Y axis Angular velocity of rotational movement along the axis ωz angular velocity of rotational movement along the Z-axis The angular velocity and acceleration in the respective axial directions detected in this manner are supplied to the navigation device 20 as output signals of the sensor unit 1. Is done.

The navigation device 20 includes an input unit 20a, an arithmetic processing unit 20b, a reference value setting unit 20c, and a threshold value setting unit 2.
0d, difference calculating means 20e, determining means 20f,
It comprises a calibration means 20g, calculates the current position and current state of the vehicle with reference to the output signal of the sensor unit 1, acquires the corresponding map information from the storage device 3, and outputs it to the display device 4 for display. When the vehicle is stopped, a correction process for an error included in the output of the sensor unit 1 is performed.

The storage device 3 is constituted by, for example, a CD-ROM drive or the like, and stores map information, programs executed by the navigation device 20, and the like. The display device 4 is configured by, for example, an LCD or the like.
While displaying the map read from the storage device 3,
For example, road information is displayed.

Next, the navigation device 20 will be described in detail. The input unit 20a inputs an output signal of the sensor unit 1. The arithmetic processing unit 20b calculates the current position and the current state of the vehicle with reference to the output signal of the sensor unit 1 supplied from the input unit 20a, reads a map of an area corresponding to the current position from the storage device 3, After performing processing such as appropriate rotation in the direction corresponding to the current state, the data is supplied to the display device 4 for display.

The reference value setting means 20c sets a reference value of the output signal of the sensor unit 1. That is, the output signal of the sensor unit 1 is a signal that varies with time as shown in FIG. 4 (in this figure, the horizontal axis represents time, and the time t0
To t12 indicate sample points). The vertical axis corresponds to the output signal Vout. As can be seen from this figure, the amplitude of the output signal is small when the vehicle is stopped, and is large while the vehicle is running. As described above, the output signal Vou constantly fluctuates, but repeatedly oscillates around a predetermined voltage, and the central voltage value is the reference value Vref.

The threshold value setting means 20d calculates the threshold value Δ shown in FIG.
Set Vthresh. The details of this threshold will be described later. The difference calculation means 20 e
The difference between the reference value Vref supplied from c and the output signal Vout of the sensor unit 1 supplied from the input means 20a is obtained and supplied to the determination means 20f.

The determination means 20f compares the difference value calculated by the difference calculation means 20e with the threshold value ΔVthresh set by the threshold value setting means 20d, and determines whether the difference value is smaller than the threshold value.

The calibrating means 20g calibrates the arithmetic processing means 20b when the determining means 20f determines that the difference value is smaller than the threshold value. That is, when the difference value is smaller than the threshold value, it is determined that the vehicle is stopped, and the error included in the output signal from the sensor unit 1 input to the arithmetic processing unit 20b is removed. Perform a calibration process.

Next, an example of processing executed in the embodiment shown in FIG. 1 will be described with reference to FIG.
This processing is based on the output signal Vout of the sensor unit 1 and the reference value Vref.
Is calculated, and if the difference value is smaller than the threshold value ΔVthresh, it is determined that the vehicle is stopped and the arithmetic processing means 20b is calibrated.

When this flowchart is executed, the following processing is executed. [S21] The reference value setting means 20c sets the reference value Vref.

Since the reference value must be set for each sensor, the reference value setting means 20c sets a total of six reference values. [S22] The threshold value setting unit 20d sets a threshold value ΔVthresh.

Since the threshold value also needs to be set for each sensor, the threshold value setting means 20d sets a total of six threshold values. [S23] The input unit 20a outputs the output signal V of the sensor unit 1.
Enter out. [S24] The difference calculation unit 20e subtracts the reference value Vref from the output signal Vout of the sensor unit 1, and calculates a difference value ΔV. [S25] The determination unit 20f determines whether the absolute value of the difference value ΔV is smaller than a threshold value ΔVthresh, and as a result,
When it is determined that the absolute value of the difference value ΔV is smaller than the threshold value ΔVthresh, the process proceeds to step S26, and otherwise, the process proceeds to step S27. [S26] The calibrating unit 20g executes the calibration process of the arithmetic processing unit 20b to remove the error component included in the output signal of the sensor unit 1, assuming that the vehicle is currently stopped. [S27] The arithmetic processing means 20b performs normal processing. That is, the arithmetic processing unit 20b refers to the output signal of the sensor unit 1, calculates the current position and the current state of the vehicle, reads a map corresponding to the situation from the storage unit 3, and reads the map corresponding to the situation.
To be displayed.

According to the above-described processing, it is possible to accurately determine that the vehicle is stopped, so that the error component of the output signal from the sensor unit 1 can be corrected without fail.

In the above-described determination method, for example, as shown in FIG. 6, noise generated from the sensor unit 1 or other circuits or minute noise of the vehicle even when the vehicle is stopped. When the signal value of the output signal exceeds the threshold value ΔVthresh reflecting the vibration (in the example of FIG. 6, at time t5
And at t9), it was difficult to make an accurate determination.

Therefore, in order to cope with such a case, when the absolute value of the difference value ΔV is smaller than the threshold value ΔVthresh, the “number of equivalent samples” in which the value is incremented is defined. As shown in the lower part of FIG. 6, the “equivalent sample number” (Nsame) increases in portions other than the times t5 and t9. Therefore, during the time t0 to t12, the value of the equivalent sample number Nsame increases from the initial value 0 to the value 10. Therefore, after a predetermined period (time t0 to t12 in this example) has elapsed, if the number of equivalent samples is larger than the value 10, for example, it is determined that the vehicle is stopped, so that the vehicle is suddenly stopped. It is possible to eliminate the influence of noise or the like.

FIG. 7 shows the output signal of the sensor unit 1 of the running vehicle and the number of equivalent samples obtained by the same method. In this example, since the output signal of the sensor unit 1 exceeds the threshold value at most of the sample points, the number of equivalent samples is three. Therefore, according to the same criterion as described above, in this example, it is determined that the vehicle is running.

Next, FIG. 8 shows a flowchart for executing the above processing. When this flowchart is started, the following processing is executed. [S41] The threshold value setting unit 20d sets a threshold value ΔVthresh. [S42] The determination means 20f determines whether or not the stop determination sample number Nst
Set op.

For example, the number Nstop of samples for judging stop is set to a value of 1
Set to 0. [S43] The reference value setting means 20c sets the reference value Vref. [S44] The determination means 20f initializes the timer T to a value of 0. [S45] The determination means 20f initializes the number of equivalent samples Nsame to a value of 0. [S46] The input means 20a outputs the output signal V of the sensor unit 1.
Enter out. [S47] The difference calculation means 20e calculates a difference value ΔV by subtracting the reference value Vre from the output signal Vout of the sensor unit 1. [S48] If the absolute value of the difference value ΔV is smaller than the threshold value ΔVthresh, the determination unit 20f proceeds to step S49. Otherwise, the process skips step S49 and proceeds to step S50. [S49] The determination unit 20f increments the value of the equivalent sample number Nsame by one. [S50] The determination means 20f increments the value of the timer T by one. [S51] The determination means 20f determines that the value of the timer T is Tsamp
It is determined whether the value is larger than the value of (number of samples). If the value is larger, the process proceeds to step S52; otherwise, the process returns to step S46.

In the example shown in FIG. 7, the value of the number of samples Tsamp is 12. [S52] The determination means 20f determines whether or not the equivalent sample number Nsame is larger than the stop determination sample number Nstop.
Otherwise, the process proceeds to step S54. [S53] The calibration means 20g performs a calibration process of the arithmetic processing means 20b. [S54] The arithmetic processing means 20b performs normal processing.

According to the above processing, the number of equivalent samples Nsa
When me is larger than the stop determination sample number Nstop, it is determined that the vehicle is stopped.
Even when the output signal of the sensor unit 1 includes sudden noise, it is possible to accurately determine the stop state of the vehicle.

Incidentally, the threshold value ΔVthresh is
And other circuit characteristics (such as noise characteristics) can be determined in advance (at the time of device design). However, since the reference value Vref changes depending on the state of attachment of the navigation device 20 to the vehicle, it is difficult to set an appropriate value in advance at the time of design. Therefore, this reference value Vre
f must be set appropriately after installation. Therefore,
Hereinafter, a method of setting the reference value Vref will be described.

FIG. 9 is a diagram for explaining a method of setting the reference value Vref. As shown in this drawing, for example, it is assumed that the output signal Vout of the sensor unit 1 at time t1 is temporarily set to the reference value Vref. In that case, the range of the threshold ΔVthresh based on the reference voltage Vref is:
This is far from the range in which the output signal of the sensor unit 1 fluctuates.

Therefore, as shown in FIG. 10, the output signal is sampled within a predetermined time, and the change in the signal value is the smallest among the sampled output signals as compared with the immediately preceding sample point. The output signal is referenced to the reference voltage Vre
Set to f.

In this example, since the change between time t2 and time t3 is the smallest, for example, the signal value of the output signal at time t2 is set to Vref. Note that the signal value of the output signal at time t3 may be set to the reference value Vref.

FIG. 11 is an example of a flowchart for executing the above processing. When this flowchart is started, the following processing is executed. [S61] The determination means 20f initializes a variable i for counting the number of times of processing to a value 0. [S62] The input unit 20a outputs the output signal V of the sensor unit 1.
Enter out. [S63] The determination unit 20f receives the output signal Vout of the sensor unit 1 via the difference calculation unit 20e, and stores the signal value in the array V as the i-th element. [S64] The determination means 20f increments the value of the variable i by one. [S65] If the value of the variable i is larger than 12, the procedure proceeds to step S66. Otherwise, the procedure returns to step S62, and repeats the same processing as described above. [S66] The determination unit 20f sets a variable i for counting the number of times of processing to a value of 1. [S67] The determination unit 20f outputs the output signal V of the sensor unit 1.
An appropriate value (= 1000) is set to the variable ΔVmin that stores the minimum change value of out. It should be noted that this value uses a value that cannot normally occur. [S68] The determination unit 20f subtracts the (i−1) -th element from the i-th element of the array V in which the output signal is stored, and stores the absolute value of the obtained value as a change value. Variable Δ
Substitute V. [S69] If the value of ΔV obtained in step S68 is smaller than the minimum change value ΔVmin, the determination unit 20f proceeds to step S70, otherwise proceeds to step S72. [S70] The determination means 20f updates the value of ΔVmin with the value of ΔV.

As a result, the smallest change value in the processing up to that point is stored in ΔVmin. [S71] The determination unit 20f substitutes the value (i-1) for the variable n that stores the sample point having the minimum change value. [S72] The determination means 20f increments the value of the variable i by one. [S73] The determination unit 20f proceeds to step S74 when the value of the variable i is larger than 12, otherwise returns to step S68 and repeats the same processing as described above. [S74] The determination unit 20f sets the value V [n] of the n-th element (the output signal having the smallest change value) of the array V as the reference value Vref.

That is, the judgment means 20f is the difference calculation means 2
The value of V [n] is supplied to the reference value setting means 20c via 0e and stored. According to the above-described processing, an appropriate reference value Vref can be set according to the output signal of the sensor unit 1. Therefore, for example, an optimum reference value can be obtained regardless of the installation state in the vehicle. it can. as a result,
It is possible to accurately detect the stop state of the vehicle.

In the above embodiment, the reference value Vre
As the value f, the signal value output first among the two sample points whose change is the smallest is adopted, but the signal value output later may be adopted. In that case, in step S71, the value of the variable i may be substituted for the variable n.

Alternatively, the average value of the two output signals may be calculated and used as the reference value Vref.
In that case, in step S74, (V [n] +
V [n + 1]) / 2 may be used as the reference value Vref.

The above processing functions can be realized by a computer. In that case, the processing content of the function that the navigation device should have is described in a program recorded on a computer-readable recording medium,
By running this program on a computer,
The above processing is implemented by a computer. Examples of the computer-readable recording medium include a magnetic recording device and a semiconductor memory.

For distribution to the market, a CD-ROM
(Compact Disk Read Only Memory) or a program stored in a portable recording medium such as a floppy disk and distributed, or stored in a storage device of a computer connected via a network and transferred to another computer via the network You can also. When the program is executed by the computer, the program may be stored in a hard disk device or the like in the computer, loaded into the main memory, and executed.

[0050]

As described above, according to the present invention, the input means inputs the output signal of the sensor section, and the arithmetic processing means includes:
From the output signal of the sensor section input to the input section, the current position and orientation of the vehicle are obtained by arithmetic processing, the reference value setting section sets a reference value of the output signal of the sensor section, and the threshold setting section includes the sensor section The threshold value of the output signal is set, the difference calculation means obtains the difference between the signal value and the reference value at an arbitrary time of the output signal from the sensor unit input from the input means,
The determining means determines that the difference value obtained by the difference calculating means is
It is determined whether or not the difference value is smaller than the threshold value. When the difference value is determined by the determination means to be smaller than the threshold value, the calibration means calibrates the arithmetic processing means assuming that the vehicle is in a stopped state. Therefore, it is possible to accurately determine that the vehicle is stopped, and it is possible to reliably remove an error component included in an output signal from the sensor unit.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an embodiment of the present invention.

2 is a diagram showing a relationship between a traveling direction of a vehicle on which the navigation device shown in FIG. 1 is mounted and each axial direction.

FIG. 3 is a diagram illustrating a relationship between X, Y, and Z axes and detection amounts detected by an angular velocity sensor or an acceleration sensor.

FIG. 4 is a diagram showing a temporal change of an output signal of a sensor unit shown in FIG. 1 during running and during stopping.

FIG. 5 is a flowchart illustrating an example of a process for detecting stop of the vehicle, which is executed in the embodiment shown in FIG. 1;

FIG. 6 is a diagram showing a temporal change of an output signal of a sensor unit when the vehicle stops.

FIG. 7 is a diagram illustrating a temporal change of an output signal of a sensor unit during traveling of the vehicle.

FIG. 8 is a flowchart illustrating another example of a process for detecting stop of the vehicle, which is executed in the embodiment shown in FIG. 1;

FIG. 9 is a diagram showing a case where an output signal at time t1 is used as a reference value.

FIG. 10 is a diagram showing a case where an output signal at time t2 is used as a reference value.

FIG. 11 is a flowchart illustrating an example of a process for setting a reference value.

FIG. 12 is a block diagram illustrating a configuration example of a conventional navigation device.

13 is a flowchart illustrating an example of a process for canceling an error included in a signal output from a sensor in the conventional navigation device shown in FIG.

[Explanation of symbols]

1 ... sensor part, 1a ... angular velocity sensor, 1b ...
Acceleration sensor, 3… storage device, 4… display device,
20 navigation device, 20a input means, 20b
... arithmetic processing means, 20c ... reference value setting means, 20
d: threshold setting means, 20e: difference calculating means, 2
0f: determination means, 20g: calibration means

Claims (5)

[Claims] 1. A navigation device for detecting a current position and a posture of a vehicle with reference to a signal output from a sensor unit having an acceleration sensor or an angular velocity sensor, comprising: an input unit for inputting an output signal of the sensor unit; From a signal output from the sensor unit input to the input unit, an arithmetic processing unit that obtains the current position and posture of the vehicle by a predetermined arithmetic process, a reference value setting unit that sets a reference value of the output signal of the sensor unit, Threshold value setting means for setting a threshold value of the output signal of the sensor unit, difference calculating means for calculating a difference between a signal value at an arbitrary time of the output signal of the sensor unit input to the input means and the reference value, Determining means for determining whether a difference value obtained by the difference calculating means is smaller than the threshold; and determining that the difference value is smaller than the threshold by the determining means. Been the case, the navigation apparatus characterized by having a calibration means for the vehicle calibrating the processing means as being in a stopped state. 2. The computer according to claim 2, wherein the calibration unit determines that the vehicle is in a stopped state when the determination unit determines that the difference value is smaller than the threshold value a predetermined number of times or more within a predetermined time. 2. The navigation device according to claim 1, wherein the means is calibrated. 3. The reference value setting means samples an output signal of the sensor section over a predetermined period, extracts a sampling value having the smallest variation from two consecutive sampling values, and calculates a sampling value of those sampling values. 2. The navigation device according to claim 1, wherein one of the reference voltages is used as the reference voltage. 4. The reference value setting means samples the output signal of the sensor section over a predetermined period, extracts a sample value having the smallest change from two consecutive sampled values, and extracts the sampled value of the sampled value. The navigation device according to claim 1, wherein an average value is used as the reference voltage. 5. A computer-readable recording medium in which a program for performing a navigation process for detecting a current position and an attitude of a vehicle with reference to a signal output from a sensor unit having an acceleration sensor or an angular velocity sensor is provided. An input unit for inputting an output signal of the sensor unit; an arithmetic processing unit for obtaining a current position and a posture of the vehicle by predetermined arithmetic processing from an output signal of the sensor unit input to the input unit; an output of the sensor unit Reference value setting means for setting a reference value of a signal; threshold value setting means for setting a threshold value of an output signal of the sensor unit; a signal value of the output signal of the sensor unit input to the input unit at an arbitrary time and the reference value Difference calculating means for calculating a difference between the difference calculation means and a difference value obtained by the difference calculating means. Determining means for determining that the difference value is smaller than the threshold value, determining that the vehicle is in a stopped state, and calibrating the arithmetic processing means; A computer-readable recording medium on which is recorded.