JP2000356647A - Method and device for detecting offset error of acceleration sensor, present position detection device for vehicle, and navigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make properly detectable an offset error specific to a sensor such as an acceleration sensor used for detecting a present position by self-contained navigation calculation and not requiring wiring to an ECU. SOLUTION: A general expression of an output value S of an acceleration sensor is S=α+gsinθ+εS. Because a travel direction acceleration α is α=0 in a halting state of a vehicle, the output value S1 of the acceleration sensor measured according to measurement indication is S1=gsinθ+εS1 (S150). Then, an output value S2 of the acceleration sensor measured according to second measurement indication inputted in a state that the vehicle is halted with the vehicle back to front at the same position is S2=-gsinθ+εS2 (S180). The offset errors εS1, εS2 are values intrinsic to the sensor, and are constant regardless of a road surface condition. Accordingly, because εS1=εS2=εS is assumed, S1+S2=2εS is gotten. Hence, a mean value (S1+S2)/2 of the sensor output values S1, S2 is equal to the offset error εS (S190).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting an offset error of a sensor used for detecting a current position by, for example, a self-contained navigation calculation, and further based on a sensor output value corrected based on the detected offset error. The present invention relates to a technology for detecting a current position and performing navigation.

[0002]

2. Description of the Related Art There is known a navigation device which displays a current position of a vehicle as it travels along with a road map on a display, sets an appropriate route from a current position to a destination, and provides route guidance. And contributes to a smoother drive.

In displaying such a current position of a vehicle and providing route guidance, it is fundamental to detect the current position of the vehicle. In the current position detection for the vehicle, for example, dead reckoning navigation calculation is performed using the azimuth change amount calculated based on the output value from the gyroscope and the moving distance calculated based on the output value from the vehicle speed sensor. What you do is known as basic technology.

A vehicle speed sensor extracts a speed signal such as a vehicle speed pulse. When a navigation device is retrofitted to a vehicle, wiring work is required and a burden is imposed on a user. Also, depending on the type of vehicle, wiring may not be possible due to design problems.
Since wiring work is performed for U (electronic control device), the risk of malfunction of the ECU cannot be eliminated.

[0005] Therefore, as a means for calculating the moving distance without requiring wiring to the ECU, it is conceivable to use an acceleration sensor or a gyro sensor for detecting acceleration in the vehicle traveling direction. However, since the zero point of an acceleration sensor or a gyro sensor fluctuates due to an external factor such as a temporal change or a temperature change, the sensor output includes an error. In particular, the acceleration sensor is used when the vehicle is running uphill.
Since the traveling direction component of the gravitational acceleration of the earth is detected, a situation in which the acceleration cannot be accurately detected is likely to occur. When the output value of the acceleration sensor or the gyro sensor includes an error as described above, the error is also included in the moving distance and the moving direction of the vehicle calculated using the output value. Since this error is cumulatively calculated, the error also accumulates with the length of the traveling time of the vehicle, and has a problem that the error cannot be ignored.

The invention described in Japanese Patent Application Laid-Open No. 9-96535 for solving these problems calculates a pitch angle from an output value of an acceleration sensor when the vehicle acceleration is zero, and advances the pitch angle. It is used to correct directional acceleration. Further, in the invention described in Japanese Patent Application Laid-Open No. 8-327378, an angular velocity sensor that calculates a pitch angle direction velocity of a vehicle when the vehicle is traveling by calculating a front-back direction inclination angle of a road surface from a gravity component applied in a vehicle front-rear direction when the vehicle is stopped. By integrating the detection signal, the change in the inclination angle of the road surface is calculated,
It is disclosed that the influence of the gravitational acceleration component on the detection signal of the acceleration sensor is removed.

[0007]

However, in the methods disclosed in the prior art, the influence of the inclination angle of the road surface may be eliminated, but the offset error (zero point output value) inherent in the acceleration sensor is not eliminated. Can not.

Accordingly, the present invention provides a method and apparatus for appropriately detecting an inherent offset error of a sensor, such as an acceleration sensor, which is used for detecting a current position by self-contained navigation calculation and does not require wiring to an ECU. The purpose is to provide. It is another object of the present invention to provide a device and a navigation device for detecting a current position based on a sensor output value corrected based on the detected offset error.

[0009]

Means for Solving the Problems and Effects of the Invention

(1) Regarding Claims 1 and 2 The invention according to claim 1 is a method for detecting an offset error of an acceleration sensor used in a current position detecting device for a vehicle. The general formula of the output value S of the acceleration sensor is the following formula 1
a. S = α + g sin θ + εS Equation 1a where α: acceleration in the traveling direction of the vehicle parallel to the road surface g: gravitational acceleration θ: inclination angle of the road surface εS: offset error of the acceleration sensor This acceleration sensor is used for a vehicle current position detecting device. For example, the speed is obtained by integrating the output value (acceleration) of the acceleration sensor, and the moving distance is obtained by further integrating the output value (acceleration). In this case, the terms other than α in the above equation 1a become errors when the true speed and the moving distance are obtained.
Since θ changes according to the road surface condition, it is necessary to separately calculate the inclination angle of the road surface. However, εS is a value unique to the sensor and does not change depending on the road surface condition.

Therefore, an offset error is detected in the following procedure. It acquires output values S ₁ of the acceleration sensor in a state where the vehicle is stopped. When the vehicle is stopped, the acceleration α in the traveling direction of the vehicle parallel to the road surface is 0, and the offset error in this case is εS
_{When 1} is set, the above equation 1a is represented as the following equation 1b. S ₁ = g sin θ + εS ₁ Expression 1b Next, the output value S ₂ of the acceleration sensor is acquired in a state where the vehicle is stopped at the same position after being inverted by 180 degrees. Since the inclination of the road surface is the same (θ is equal) as in the above case, if the offset error in this case is εS ₂ , it is expressed as the following equation 1c. S ₂ = −g sin θ + εS ₂ Expression 1c Then, the average value of the two acquired sensor output values S ₁ and S ₂ is calculated, and the average value is detected as an offset error. Here, the point that the average value of the sensor output values S ₁ and S ₂ can be an offset error will be described.

When the above equations 1b and 1c are added, the following equation 1 is obtained.
It can be deformed like e. S ₁ + S ₂ = εS ₁ + εS ₂ Equation 1d The offset errors εS ₁ and εS ₂ are values unique to the sensor as described above, and are constant depending on the road surface condition. Therefore, εS ₁ = εS ₂ = εS may be set.

Therefore, the above equation 1d is transformed into the following equation 1e. S ₁ + S ₂ = 2εS Equation 1e Therefore, the offset error εS is expressed as the following equation 1f. εS = (S ₁ + S ₂ ) / 2 Equation 1f Since the offset error εS of the acceleration sensor obtained as in Equation 1f is basically invariable, it only needs to be carried out once after mounting on the vehicle. . It should be noted that “basically unchanged” is because, for example, a slight change may occur due to a change over time. If you take that into account,
The operation may be performed again after an appropriate period has elapsed.

A second aspect of the present invention is an example of an apparatus for implementing the offset error detecting method according to the first aspect. The device includes command input means for inputting a sensor output value acquisition command from a user. This may be provided as an operation switch near the driver's seat of the vehicle. When a liquid crystal display device or the like is used for navigation or television image display, a so-called touch panel may be provided so that input can be performed by touching the screen with a finger or the like.

[0014] Then, the first obtaining means, based on the obtained command has been made via the command input means in a state where the vehicle is stopped, to obtain the output values S ₁ of the acceleration sensor. Further, the second acquisition unit may be configured to respond to the acquisition command issued through the command input unit in a state where the vehicle is turned 180 degrees at the same position and stopped after the output value S ₁ is acquired by the first acquisition unit. based acquires an output value S ₂ of the acceleration sensor. That is, the user obtains the output value S by the first acquisition unit.
_{After 1} is obtained, the vehicle is set at 180deg at the same position.
Invert and stop. After that, an acquisition command is input.

[0015] The average value calculating means comprises a first and a second.
, The two sensor output values S ₁ ,
It calculates an average value of S _2, an average value thereof was calculated to offset errors. With this configuration, even if an acceleration sensor that does not require wiring to the ECU is used to detect the current position by the self-contained navigation calculation, the offset error unique to the sensor can be appropriately detected. If the correction is performed based on the error, the problem that the error is accumulated and the error becomes so large that it cannot be ignored can be solved.

(2) Claims 3 and 4 The invention according to claim 3 is a method for detecting an offset error of an acceleration sensor used in a current position detecting device for a vehicle. The present invention relates to a method of detecting an offset error of a two-axis acceleration sensor whose detection axis is inclined at an arbitrary angle with respect to a vertical axis of a vehicle.

Here, consider a two-axis acceleration sensor in which the first and second detection axes are inclined by 45 deg in directions opposite to each other with respect to the vertical axis of the vehicle. That is, assuming that the first detection axis is inclined 45 degrees from the vertical axis of the vehicle, the second detection axis is inclined -45 degrees from the vertical axis of the vehicle. In the following description, it is assumed that the direction of the first detection axis is positive.

In this case, a general expression of the output value S ₁ of the acceleration sensor based on the first detection axis and the output value S ₂ of the acceleration sensor based on the second detection axis is expressed by the following expression 2a. _{S 1 = αcos (π / 4} ) + gcos {(π / 4) -θ} + εS 1 S 2 = -αcos (π / 4) + gcos {(π / 4) + θ} + εS 2 ...... Formula 2a where, alpha: Acceleration in the traveling direction of the vehicle parallel to the road surface g: gravitational acceleration θ: inclination angle of the road surface εS ₁ : offset error of the acceleration sensor due to the first detection axis εS ₂ : offset error of the acceleration sensor due to the second detection axis , The offset error εS ₁ ,
εS ₂ is detected.

With the vehicle stopped, an output value S ₁ of the acceleration sensor based on the first detection axis and an output value S ₂ of the acceleration sensor based on the second detection axis are obtained. When the vehicle is stopped, the acceleration α in the traveling direction of the vehicle parallel to the road surface is 0, and thus the above equation 2a in this case is expressed as the following equation 2b. S ₁ = g cos {(π / 4) −θ} + εS ₁ S ₂ = g cos {(π / 4) + θ} + εS ₂ Equation 2b Then, when this equation 2b is modified, the following equation 2c is obtained. . (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² [cos {(π / 4) −θ} ² + cos {(π / 4) + θ} ² ] = g ² [{cos ( π / 4) cosθ + sin (π / 4) sinθ｝ ² + {cos (π / 4) cosθ−sin (π / 4) sinθ} ² ] = g ² [2 {cos (π / 4) cosθ} ² +2 { sin (π / 4) sin θ} ² ] = g ² (cos ² θ + sin ² θ) = g ² Equation 2c (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² Is the center coordinate (εS ₁ , εS ₂ ) on the S ₁ , S ₂ plane.
And a circle of radius g.

Accordingly, the output value S ₁ of the acceleration sensor based on the first detection axis and the output value S ₂ of the acceleration sensor based on the second detection axis are located on the circle represented by the above equation. . Therefore, a set of output values (S ₁ , S ₂ )
Are obtained for at least three different sets, and assuming a center coordinate (S ₁ , S ₂ ) and a circle having a radius g on the S ₁ and S ₂ planes corresponding to each set, the intersection coordinates of the circles are The center coordinates (εS ₁ , εS ₂ ) in the above-described equation of the circle. Thus, the offset errors εS ₁ and εS ₂ of the first and second detection axes can be detected.

The "three different sets" are the output values S ₁ ,
Means that the S ₂ itself is different. That is, if they are not different, at least three different circles cannot be assumed,
This is because their intersection is not uniquely determined. In the above description, a two-axis acceleration sensor in which the first and second detection axes are inclined by 45 deg and -45 deg with respect to the vertical axis of the vehicle, respectively, is assumed. Even if it is an axis acceleration sensor, 45de
If g and -45 deg components are considered, the same can be applied. In other words, even if the angle is arbitrary, if the mounting angle is known,
Since it is easy to calculate the 45 deg component in the case of the first detection axis and the −45 deg component in the case of the second detection axis, the calculated output value component (45 deg)
The same process may be performed using the g component and the −45 deg component).

However, in the case of two axes, it is common to mount the first and second detection axes at an angle of 45 deg and -45 deg with respect to the vertical axis of the vehicle, respectively, as assumed above. So, in fact,
In many cases, the output value can be used as it is without calculating the component, and the processing load does not increase.

The invention described in claim 4 is an example of a device for implementing the offset error detection method described in claim 3. The device determines a stop state of the vehicle based on a change in the output value of the acceleration sensor. When the vehicle is in the stop state, the output value of the acceleration sensor by the first detection axis is 45d.
acquires -45deg component S ₂ of the output value of the acceleration sensor according to eg component S ₁ and the second detection axis. Then, at least three different sets of output value components (S ₁ , S ₂ ) are acquired, and the center coordinates (S ₁ , S ₂ ) and the radius g on the S ₁ , S ₂ plane corresponding to each set are obtained. Draw a circle. Note that it is not necessary to draw this drawing so that a human can visually recognize it, and it is sufficient to draw the drawing on a memory, for example. And
The intersection coordinates (εS ₁ , εS ₂ ) of these circles are calculated. As described above, if at least three different circles are drawn, their intersections are unambiguously determined. Therefore, their intersection coordinates (εS ₁ , εS ₂ ) are set to the offset errors εS ₁ , εS ₂ .

(3) Claims 5 and 6 In claims 3 and 4 described above, a set of output value components (S
₁, S_Two) For at least three different sets, corresponding to each set
And S₁, S_TwoCenter coordinates on the plane (S₁ , S_Two )
Assuming a circle with radius g
(ΕS₁, ΕS_Two), The first and second inspections
Outer axis offset error εS₁, ΕS_TwoIs a technique for detecting
Was. However, in practice, the set of output value components (S₁, S_Two)
Does not take extremely different values, and measurement errors
Exist, so that multiple circles do not intersect at one point
Is also conceivable. Therefore, such a measurement error
Offset error of the first and second detection axes even when added
εS₁, ΕS_TwoClaim 5 shows a method for detecting
Things are conceivable. That is, a set of output value components
(S ₁, S_Two) For at least three different sets
Same as claim 5 described above, but thereafter,
At least three sets of output value components S₁, S_TwoApproximation on a plane
A circle tangent to a straight line, with at least three sets of output values
Assuming a circle of radius g with the center of gravity as the point of contact,
The center coordinate is (εS₁, ΕS_Two) By seeking
1, offset error εS of the second detection axis₁, ΕS_TwoDetect
You do it.

For example, a straight line approximated by the least square method or the like is used as the approximate straight line, and the center of gravity is used as the contact point. An example of a specific obtaining method will be described. A straight line approximated by the least squares method from at least three sets of output value components is defined as axis 1. A straight line passing through the center of gravity of at least three sets of output value components and orthogonal to the axis 1 is defined as an axis 2.

The initial value of the center coordinates (εS ₁ , εS ₂ ) of the circle is (0,0). From the initial value, the center of the circle is moved in the direction of axis 1 by the bisection method, and the center that minimizes the sum of the distances between the circle and at least three sets of output value components is searched. The center of the circle is moved in the direction of the axis 2 by the bisection method from the center obtained above, and a center that minimizes the sum of the distances between the circle and at least three sets of output value components is searched.

The center coordinates (εS ₁ , εS ₂ ) of the circle are set as offset errors εS ₁ , εS ₂ of the first and second detection axes. The invention described in claim 6 is an example of an apparatus for performing the offset error detection method described in claim 5.
The device determines a stop state of the vehicle based on a change in an output value of the acceleration sensor. When the vehicle is in a stop state, the apparatus detects a 45 deg component S ₁ of the output value of the acceleration sensor by the first detection axis and a second detection axis. -45d of the output value of the acceleration sensor due to
to get eg component S _2. Then, a set of output value components (S
₁ , S ₂ ) for at least three different sets, and a circle having a tangent to an approximate straight line on the S ₁ , S ₂ plane of at least three sets of output value components, and at least three sets of output value components Assuming a circle having a radius g having the center of gravity as a contact point, the center coordinates (εS ₁ , εS ₂ ) of the circle are calculated. The center coordinates (εS ₁ , εS ₂ ) become offset errors εS ₁ , εS _{2 of} the first and second detection axes.

(4) Regarding Claim 7 The invention according to claim 7 is a vehicle current position detection device provided with the offset error detection device according to any one of claims 2, 4, and 6. The current position detection device for a vehicle of the present invention, a direction sensor that outputs a signal according to the amount of change in direction of the vehicle,
An acceleration sensor that outputs a signal corresponding to the acceleration applied to the vehicle, wherein the relative position calculation means calculates the azimuth change amount calculated based on the output value of the azimuth sensor and the output value of the acceleration sensor. It is assumed that the self-contained navigation calculation is performed using the moving distance to calculate the relative current position of the vehicle.

The offset error detecting device according to claim 2 or 4, and a correcting means for correcting the output value of the acceleration sensor based on the offset error of the acceleration sensor detected by the offset error detecting device. I have. Then, the relative position calculating means performs the self-contained navigation calculation using the moving distance calculated based on the output value of the acceleration sensor corrected by the correcting means.

With this configuration, even if an acceleration sensor that does not require wiring to the ECU is used to detect the current position by the self-contained navigation calculation, the offset error inherent in the sensor can be properly detected and corrected. Therefore, it is possible to solve the problem that the error is accumulated and the error becomes so large that it cannot be ignored and accurate current position detection becomes impossible.

(5) Claim 8 By the way, in order to obtain the moving distance for detecting the current position by the self-contained navigation calculation, a method of obtaining the acceleration in the traveling direction of the vehicle and integrating it twice can be adopted. However, as can be seen from the above description, in addition to the above-described offset error of the acceleration sensor, the output value of the acceleration sensor includes an error (g sin θ) caused by the inclination angle of the road surface.
) Exists. Therefore, in order to eliminate the influence of the inclination angle and obtain the true traveling direction acceleration (α), a sensor for detecting the inclination angle of the road surface is required. Since this sensor includes a pitch rate sensor, a vehicle current position detecting device as described in claim 6 can be employed.

That is, in addition to the structure described in claim 7,
Further, a pitch rate sensor that outputs a signal corresponding to the angular velocity in the pitch direction of the vehicle, a stop determination unit that determines a stop state of the vehicle, and when the stop determination unit determines that the vehicle is in a stop state, An output value at the time of stop for obtaining an output value of the pitch rate sensor, and an output value obtained by the output value at the time of stop is set as an offset error of the pitch rate sensor, and the output value of the pitch rate sensor is determined based on the offset error. A road surface inclination angle is calculated based on the output value of the pitch rate sensor and the output value of the acceleration sensor corrected by the correction unit, and the influence of the road surface inclination angle is removed from the output value of the acceleration sensor. It has a removing means.

Although the pitch angle is obtained by integrating the output of the pitch rate sensor, this pitch angle is not an absolute angle but only a relatively changed angle. On the other hand, the road surface inclination angle obtained from the output value of the acceleration sensor is a value when the vehicle is stopped. Therefore, by adding the pitch angle obtained from the output value of the pitch rate sensor based on the road surface inclination angle θ when the vehicle is stopped, the road surface inclination angle can be detected at an arbitrary timing in the running vehicle. It is.

As described above, the pitch rate sensor can be used to obtain the true traveling direction acceleration (α) by eliminating the influence of the inclination angle on the output value of the acceleration sensor. Therefore, there is a problem that when the offset error is accumulated, the error becomes so large that it cannot be ignored. Therefore, as in the case of the above-described acceleration sensor, it is necessary to detect the offset error and correct the output value of the pitch rate sensor.

Therefore, the output value of the pitch rate sensor constructed by mounting the angular velocity sensor for detecting the vehicle pitch direction is acquired in a stopped state of the vehicle, and the acquired output value is detected as an offset error. The general formula of the output value J of the angular velocity sensor is expressed by the following formula 3a. J = ω + εJ Expression 3a where ω: angular velocity εJ: offset error of the acceleration sensor And, while the vehicle is stopped, ω = 0, so the output value J during the stop
= ΩJ is the offset error.

Therefore, the removing means calculates the road surface inclination angle based on the output value of the pitch rate sensor and the output value of the acceleration sensor corrected by the correction means, and determines the influence of the road surface inclination angle from the output value of the acceleration sensor. If it is removed, the influence of the inclination angle θ of the road surface during the output value S = α + g sin θ corrected by the offset error of the acceleration sensor can be removed, and a true acceleration in the traveling direction of the vehicle can be obtained. Therefore, it can contribute to the realization of accurate detection of the current position.

(6) Claim 9 From the viewpoint of accurate detection of the current position, the following configuration may be adopted. That is, according to a ninth aspect of the present invention, in the vehicle current position detecting device according to the seventh or eighth aspect, a radio wave for receiving a radio wave for radio navigation and outputting an absolute current position and a traveling direction of the vehicle. The relative current position calculated by the receiver and the relative position calculating means is
The current position correcting means for correcting based on the output value from the radio wave receiver is provided.

In this case, a typical radio wave for radio navigation is a radio wave from a GPS satellite, but the absolute position information based on the radio wave from the GPS satellite needs to assume an error of about 100 m. is there. Therefore, in order to improve the accuracy of position detection, it is necessary to increase the accuracy of the relative current position itself calculated by the self-contained navigation calculation, so that the influence of the offset error of the acceleration sensor and the pitch rate sensor described above is eliminated. This is very useful for detecting the current position of the vehicle.

(7) Claims 10 and 11 By the way, it is conceivable to perform various processes using the vehicle current position detected by the vehicle current position detecting device described above. For example, as set forth in claim 10, a vehicle current position detecting device according to any one of claims 7 to 9, a map data storage unit storing map data including road map data, and a vehicle current position detecting device Map display means for reading out road map data around the current position of the vehicle detected from the map data storage means and displaying it as a road map, and displaying the current position of the vehicle on the road map in an identifiable manner. It can also be realized as a navigation device.

According to another aspect of the present invention, there is provided the navigation apparatus according to the tenth aspect, further comprising a route and a vehicle to a preset destination on the road map displayed on the map display means. Display the current position of the vehicle detected by the current position detection device for identification,
In consideration of the relationship between the route to the destination and the current position of the vehicle, the present invention can be realized as a navigation device including route guidance means for performing predetermined route guidance.

(8) Others A function for realizing the above-described method of detecting the offset error of the acceleration sensor, the method of detecting the offset error of the pitch rate sensor, and the relative position detecting means of the current position detecting device in a computer system. Can be provided, for example, as a program started on the computer system side. For such a program,
For example, floppy disk, magneto-optical disk, CD-
It can be used by recording it on a computer-readable recording medium such as a ROM or a hard disk, loading it into a computer system as needed, and starting up. Alternatively, the program may be recorded in a ROM or a backup RAM as a computer-readable recording medium, and the ROM or the backup RAM may be incorporated in a computer system and used.

[0042]

Embodiments of the present invention will be described below with reference to the drawings. It is needless to say that the embodiments of the present invention are not limited to the following examples, and can take various forms as long as they belong to the technical scope of the present invention.

[First Embodiment] FIG. 1 is a block diagram showing the overall configuration of a navigation device 1 according to the first embodiment. The navigation device 1 according to the present embodiment is configured as a so-called car navigation system mounted on a vehicle, a position detector 12 for detecting a current position of the vehicle, and a wireless telephone line for collecting various road traffic information. Communication device 18 for performing data communication with the information distribution center 4 via the
, An external information input / output device 19, an operation switch group 20 for inputting various commands to the device, and a remote control terminal (not shown) ), A display screen is embedded in an instrument panel (instrument panel), and a map display screen is displayed in addition to a display such as a speedometer and a tachometer. A display device 26 for performing various displays such as a TV and a TV screen, and various processes are executed in response to inputs from a position detector 12, an operation switch group 20, a data input device 22, and a remote controller (not shown). An external information input / output device 19, an external memory 24, and a navigation control circuit 30 for controlling the display device 26 are provided. Here, the position detector 12 is a GPS (Global Positioning System).
m) which receives the transmitted radio wave from the artificial satellite via the GPS antenna and detects the position, direction, speed, etc. of the vehicle
And outputs a detection signal corresponding to the angular velocity of the rotational motion applied to the vehicle, comprising an S receiver 12a and an "azimuth sensor".
12b, and an acceleration sensor 12c for detecting acceleration in the front-rear direction of the vehicle
And a pitch rate sensor 12d for detecting an angle (hereinafter, referred to as a "pitch angle") inclined in a pitch operation direction of the vehicle.

Among them, the acceleration sensor 12c is a so-called one-axis acceleration sensor, and as shown in FIG. 3, its sensitivity direction is set to be positive in the traveling direction (forward direction) of the vehicle. . Further, the pitch rate sensor 12d of the present embodiment has an angular velocity sensor attached for detecting the pitch angle direction.

The communication device 18 is a wireless telephone device 18 such as a portable telephone or a car telephone which can be connected to a public telephone network.
a, and in accordance with a command from the navigation control circuit 30, a connection is established with the information distribution center, which is an external information source, in a predetermined procedure via the wireless telephone device 18a.
And a modem 18b that encodes data from 0 into a form that can be transmitted via the wireless telephone device 18a and decodes data input via the wireless telephone device 18a into a form that can be processed by the control circuit 30. Have.

On the other hand, the external information input / output device 19 receives an FM broadcast signal via a radio antenna (not shown), or receives a VICS (Vehicle Information) disposed near a road.
ion and Communication System) Receives a radio beacon signal and an optical beacon signal from a fixed station for service. The received information is sent to the navigation control circuit 30 for processing. In addition, information can be transmitted to the outside.

Next, as the operation switch group 20, a touch switch integrally formed with the display device 26 and set on a display screen or a mechanical key switch provided around the display device 26 is used. The map data input device 22 is a device for inputting various data including so-called map matching data, map data, and landmark data for improving the accuracy of position detection. As a storage medium, a CD-ROM or a DVD
In general, other media such as a memory card may be used.

The display device 26 is a color display device.
On the display screen, the vehicle current position mark input from the position detector 12, the map data input from the map data input device 22, and a guidance route to be displayed on a map can be displayed in a superimposed manner. it can. As the display device 26, for example, a CRT, a liquid crystal display, a plasma display, or the like may be used.

The navigation control circuit 30 is configured as a normal computer, and has a well-known CPU and RO inside.
M, RAM, I / O and bus lines for connecting these components are provided. And the GPS receiver 12a,
Based on the output from the gyroscope 12b, the acceleration sensor 12c, and the pitch rate sensor 12d, data for performing dead reckoning such as the current position and the traveling direction of the vehicle is calculated.

When the navigation device 1 inputs the position of the destination from a remote control sensor 21 through a remote control terminal (hereinafter, referred to as a remote control) (not shown) or an operation switch group 20, the navigation device 1 changes the current position to the current position. It also has a so-called route guidance function that automatically selects an optimal route to the destination and forms and displays a guidance route. As a technique for automatically setting the optimum route, a technique such as the Dijkstra method is known. It should be noted that, instead of such a route guidance to the destination, a process of simply displaying the current position of the vehicle on a map is always performed. In other words, in an unfamiliar area, a kind of navigating function will be exhibited even if only the current position of the vehicle is known.

Therefore, the current position detector 5 shown in FIG.
0 and the navigation execution unit 70
This is realized as the processing of FIG. Among these, the current position detecting section 50 is measured by the offset error measuring section 51 for measuring the offset error (εS) of the acceleration sensor 12c based on the detection signal from the acceleration sensor 12c and the offset error measuring section 51. Offset error storage unit 5 for storing the offset error (εS)
2 and the offset error (ε) of the pitch rate sensor 12d based on the detection signal from the pitch rate sensor 12d.
J) is provided, and an offset error storage unit 62 for storing the offset error (εJ) measured by the offset error measurement unit 61 is provided. In addition, the stop determination unit 53, the inclination angle calculation unit 54, the vehicle speed calculation unit 55, the movement distance calculation unit 56, the relative position calculation unit 57, the position calculation unit 58, and the gyroscope 12b An azimuth change amount calculation unit 65 that calculates an azimuth change amount based on the detection signal of
An absolute position calculator 67 for calculating an absolute position based on GPS positioning data obtained from the GPS receiver 12a.

The stop judging section 53 judges whether or not the vehicle is stopped based on the detection signal from the acceleration sensor 12c, and outputs the judgment result to the two offset error measuring sections 51 and 61, Angle calculation unit 54 and vehicle speed calculation unit 5
5 and output. The two offset error measuring units 51 and 61 measure the offset error (εS) of the acceleration sensor 12c and the offset error (εJ) of the pitch rate sensor 12d with reference to the stop determination result from the stop determination unit 53, respectively. I do. This processing will be described later.

On the other hand, the inclination angle calculation section 54 is based on the detection signal from the acceleration sensor 12c and the detection signal from the pitch rate sensor 12d, and also refers to the stop determination result from the stop determination section 53 to determine whether the vehicle is present. The inclination angle (θ) of the traveling road surface is calculated. That is, the acceleration sensor 12c
Output values from the vehicle are parallel to the road surface in the traveling direction acceleration α, the gravitational acceleration g, the road surface inclination angle θ, and the acceleration sensor 1
S = α + g sin θ + using offset error εS of 2c
It is expressed as εS. Since the offset error (εS) is stored in the offset error storage unit 52, S−εS is subtracted from the output value S from the acceleration sensor 12c.
= Α + g sin θ. Here, when the vehicle is stopped, α = 0, so the input value (S−εS) to the inclination angle calculation unit 54 is gsinθ. Therefore, the value of the road surface inclination angle θ can be obtained. In addition, this road surface inclination angle θ
Is a value when the vehicle is stopped. Therefore,
The output from the pitch rate sensor 12d is used to determine the road surface inclination angle θ when the vehicle is running. That is, the pitch angle is obtained by integrating the output of the pitch rate sensor 12d, but this pitch angle is not an absolute angle but an angle that has relatively changed. Therefore, by adding the pitch angle obtained by integrating the output of the pitch rate sensor 12d to the value at the time of stopping obtained from the output value of the acceleration sensor 12c, the actual road surface inclination angle can be detected in the running vehicle. can do.

The vehicle speed calculation unit 55 is based on the value (S−εS) obtained by correcting the output S from the acceleration sensor 12c and the road surface inclination angle (θ) calculated by the inclination angle operation unit 54.
The vehicle speed V is also referred to by referring to the stop determination result from the stop determination unit 53.
Is calculated. Then, the moving distance calculator 56 calculates the moving distance based on the vehicle speed V calculated by the vehicle speed calculator 55. The determination result from the stop determination unit 53 is also input to the vehicle speed calculation unit 55 because the vehicle speed is 0 when the vehicle is stopped, and it is not necessary to perform the vehicle speed calculation. That is, no extra calculation is performed.

The relative position calculator 57 is provided with a moving distance calculator 5
The relative position of the vehicle is calculated based on the moving distance calculated in 6 and the azimuth change amount calculated in the azimuth change amount calculation unit 65. Then, the position calculation unit 58 corrects the relative position of the vehicle calculated by the relative position calculation unit 57 based on the absolute position of the vehicle calculated by the absolute position calculation unit 67,
Navigation execution unit 7 as the final vehicle current position
Output to 0.

Next, a description will be given of a measurement process in the offset error measuring section 51 for measuring an offset error (εS) of the acceleration sensor 12c. As described above, the acceleration sensor 12c of the present embodiment has one inspection axis, and FIG.
It is assumed that the traveling direction of the vehicle matches the sensitivity direction of the acceleration sensor 12c as shown in FIG. The fact that the traveling direction of the vehicle coincides with the sensitivity direction of the acceleration sensor 12c means that the inspection axis of the acceleration sensor 12c is arranged along the vertical direction of the vehicle.

FIG. 4 is a flowchart showing a processing procedure executed when measuring the offset error (εS) of the acceleration sensor 12c. A description will be given along this flowchart. First, in the first step S110, an input from a user is received. This receives an input from a remote control sensor 21 via a remote controller (not shown) or an operation switch group 20. Then, it is determined whether or not the input indicates the error measurement mode (S
120), if the error measurement mode is instructed (S12)
0: YES), proceeds to S130 and waits for the first measurement instruction from the user.

The user stops the vehicle at a predetermined place, and inputs a measurement instruction in that state. As described above, the input may be made from the operation switch group 20 or the like. In the case of the presence of the the first measurement instruction (S140: YES), the routine proceeds to S150, and measures the output values S ₁ of the acceleration sensor 12c at that time, temporarily stored.

Thereafter, the flow shifts to S160, and waits for a second measurement instruction from the user. Prior to the second measurement instruction, the user stops the vehicle by inverting the vehicle by 180 degrees at the same position. That is, the vehicle is stopped by reversing the front and rear. In this state, a second measurement instruction is input. As described above, the input may be made from the operation switch group 20 or the like. When the second measurement instruction is issued (S170: YE
S), the operation proceeds to S180, and measures the output value S ₂ of the acceleration sensor 12c at that time, temporarily stored.

Then, the flow shifts to S190, where the two sensor output values S ₁ , S1 measured and stored in S150 and S180 are stored.
An offset error (.epsilon.s) calculates the average value of S _2. By calculating in this way, the offset error (εS)
A description will be given of points that can be obtained.

The output value S of the acceleration sensor 12c in this case is
Is represented by the above-described expression 1a. That is, S
= Α + g sin θ + εS. Since the sensor output value S ₁ measured in S 150 is a value at the time of stopping, the acceleration α in the traveling direction of the vehicle parallel to the road surface is 0, and the offset error in this case is εS _1. It is represented as That is, S ₁ = g sin θ + εS ₁ .

On the other hand, the sensor output value S ₂ measured in S180 is an output value in a state where the vehicle is stopped at the same position after being inverted by 180 degrees. Road slope (θ)
Are the same, the offset error in this case is εS ₂
Then, it is expressed as the above-described expression 1c. That is,
S ₂ = −g sin θ + εS ₂

Then, when these two output values S ₁ and S ₂ are added, the above equation 1e is obtained. That is, S ₁
+ S ₂ = εS ₁ + εS ₂ Offset error εS ₁ , ε
S ₂ is unchanged by is road conditions a sensor-specific values as described above. Therefore, εS ₁ = εS ₂ = ε
S may be used.

Therefore, it can be transformed into S ₁ + S ₂ = 2εS,
If both sides are divided by 2, the offset error εS is expressed as in the above-mentioned expression 1f. That is, εS = (S ₁ + S ₂ ) / 2
Becomes This is an average value of the sensor output values S ₁ and S ₂ . In this way, the offset error (εS) of the acceleration sensor 12c can be obtained. However, since the offset error εS is basically unchanged, it is only necessary to carry out the offset error once after the vehicle is mounted on the vehicle. It should be noted that “basically unchanged” is because, for example, a slight change may occur due to a change over time. If you take that into account,
The operation may be performed again after an appropriate period has elapsed.

The offset error (εS) thus measured is stored in the offset error storage section 52 and is subtracted from the output value (S) from the acceleration sensor 12c. That is, the offset error (εS) is corrected from the output value (S) of the acceleration sensor 12c.

Next, an offset error measuring section 61 for measuring an offset error (εJ) of the pitch rate sensor 12d.
Will be described. The pitch rate sensor 12d of the present embodiment is configured by attaching an angular velocity sensor for detecting a vehicle pitch direction. The general formula of the output value J of the angular velocity sensor is expressed as J = ω + εJ using the angular velocity ω and the offset error εJ. Since ω = 0 when the vehicle is stopped, the output value J = ωJ during the stop is an offset error.

Therefore, the offset error measuring section 61
Measures the output J = ωJ from the pitch rate sensor 12d when the stop determination unit 53 determines that the vehicle is in the stop state, and stores the output J = ωJ in the offset error (εJ) storage unit 62. Thereafter, a value corrected by subtracting the offset error εJ from the output value J of the pitch rate sensor 12d is output to the inclination angle calculation unit 54.

As described above, in the navigation device 1 of this embodiment, since the acceleration sensor 12c used for detecting the current position does not require wiring to the ECU, the acceleration sensor 12c for extracting a speed signal such as a vehicle speed pulse is used. In contrast, even when retrofitting the vehicle, wiring work is not required, and there is no burden on the user. In addition, depending on the type of vehicle, wiring may not be possible due to design problems, and wiring work may be performed on an ECU (electronic control device). Therefore, the risk of malfunction of the ECU cannot be eliminated. Therefore, there is an advantage of using the acceleration sensor 12c which does not require such wiring to the ECU.

In the prior art using the acceleration sensor, the influence of the inclination angle of the road surface may be eliminated, but the offset error (zero point output value) inherent in the acceleration sensor cannot be eliminated. In the case of the present embodiment, the offset error inherent to the acceleration sensor 12c can be appropriately detected. Further, the pitch rate sensor 12d can also appropriately detect the offset error unique to the sensor.

Therefore, if the correction is made based on the offset error, it is possible to appropriately solve the problem that the error is cumulatively calculated and becomes an error that cannot be ignored. Further, by using the output value thus corrected, the vehicle speed calculation, the moving distance calculation, and the relative position calculation performed using the output value can be appropriately performed. That is, it is possible to solve the problem that the error is accumulated and the error is so large that it cannot be ignored, and the current position cannot be accurately detected.

[Second Embodiment] In the first embodiment described above,
It is assumed that the acceleration sensor 12c has only one detection axis. However, if the acceleration sensor 12c has two detection axes, the offset error (εS) can be detected as follows. It should be noted that since the configuration of the device when applied is the same as that of the first embodiment shown in FIGS.

Here, as shown in FIG. 5, the two detection axes are 45 deg in opposite directions with respect to the vertical axis of the vehicle.
Consider a two-axis acceleration sensor that is only tilted. That is,
Assuming that the first detection axis is inclined by 45 degrees with respect to the vertical axis of the vehicle, the second detection axis is -4 degrees from the vertical axis of the vehicle.
This means that it is inclined by 5 degrees. In the following description, the first
Is assumed to be positive.

In this case, the general expression of the output value S ₁ of the acceleration sensor based on the first detection axis and the output value S ₂ of the acceleration sensor based on the second detection axis is expressed by the following equation. _{S 1 = αcos (π / 4} ) + gcos {(π / 4) -θ} + εS 1 S 2 = -αcos (π / 4) + gcos {(π / 4) + θ} + εS 2 So, first stop the vehicle state, and acquires the output value S ₂ of the acceleration sensor by the output value S ₁ and the second detection axis of the acceleration sensor according to the first detection axis. When the vehicle is stopped, the acceleration α in the traveling direction of the vehicle parallel to the road surface is 0, so that the vehicle is deformed as in the following expression. S ₁ = g cos {(π / 4) −θ} + εS ₁ S ₂ = g cos {(π / 4) + θ} + εS _{2 When} this equation is modified, the following equation is obtained. (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² [cos {(π / 4) −θ} ² + cos {(π / 4) + θ} ² ] = g ² [{cos ( π / 4) cosθ + sin (π / 4) sinθ｝ ² + {cos (π / 4) cosθ−sin (π / 4) sinθ} ² ] = g ² [2 {cos (π / 4) cosθ} ² +2 { sin (π / 4) sin θ} ² ] = g ² (cos ² θ + sin ² θ) = g ² This (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² As shown in FIG. 6, this is an equation of a circle having a center coordinate (εS ₁ , εS ₂ ) and a radius g on the S ₁ , S ₂ plane. Thus, the output value S ₁ of the acceleration sensor based on the first detection axis and the output value S ₂ of the acceleration sensor based on the second detection axis
Will be located on the circle represented by the above equation.

Therefore, as shown in FIG. 7, three sets of output values (S ₁₁ , S ₂₁ ), (S ₁₂ , S ₂₂ ), and (S ₁₃ , S ₂₃ ) are obtained and are set on the S ₁ , S ₂ plane. At each output value (S ₁₁ ,
A circle having a radius g having the center coordinates (S ₁ , S ₂ ) with (S ₂₁ ), (S ₁₂ , S ₂₂ ), and (S ₁₃ , S ₂₃ ) is drawn on a memory, for example. In FIG. 7, each circle is indicated by a broken line. FIG.
In order to facilitate understanding, three sets of output values (S
₁₁ , S ₂₁ ), (S ₁₂ , S ₂₂ ), and (S ₁₃ , S ₂₃ ) are differentiated so that the three circles can be clearly distinguished. Actually, these three sets of output values (S ₁₁ , S ₂₁ ), (S ₁₂ ,
_{S 22), (S 13,} S 23) it is more close values.

In this way, the intersection of these three circles
The coordinates are the center coordinates (ε
S₁, ΕS_Two). Note that three sets of output values (S₁₁,
S_{twenty one}), (S ₁₂, S_{twenty two}), (S₁₃, S_{twenty three}) Is the output value
Are themselves different (that is, the coordinates themselves are different)
Means that. If these are not different, at least 3
Three different circles cannot be assumed, and their intersection is uniquely defined.
Because it does not fit.

Thus, the offset errors εS ₁ and εS ₂ of the first and second detection axes can be detected. In the case of the first embodiment, the act of reversing the direction of the vehicle at the same place is indispensable, but in the case of the second embodiment, it is only necessary to obtain the information when the vehicle is stopped. To reduce.

In the above description, the first and second detection axes are each 45 degrees with respect to the vertical axis of the vehicle.
Although a two-axis acceleration sensor inclined by deg and −45 deg is assumed, a two-axis acceleration sensor having other inclinations can be similarly applied in consideration of the 45 deg and −45 deg components. That is, even if the angle is an arbitrary angle, if the mounting angle is known, the 45 deg component is used in the case of the first detection axis, and -45 in the case of the second detection axis.
Since the deg component can be easily calculated, a similar process may be performed using the calculated output value components (45 deg component, -45 deg component).

[Third Embodiment] In the above-described second embodiment,
Represents three sets of output values (S₁₁,
S_{twenty one}), (S₁₂, S_{twenty two}), (S₁₃, S_{twenty three}Get each)
S corresponding to the set₁, S_TwoCenter coordinates on the plane (S₁ ,
S_Two ) And a circle of radius g, and the intersection of these circles
If the coordinates are (εS₁, ΕS_Two), The first,
Offset error εS of second detection axis₁, ΕS_TwoDetect
The method was adopted. However, as described in the description regarding FIG.
As shown in FIG. 7, three sets of output values are used for easy understanding.
(S₁₁, S _{twenty one}), (S₁₂, S_{twenty two}), (S₁₃, S_{twenty three}) Difference
To make the distinction between the three circles clear.
Therefore, actually, these three sets of output values (S₁₁, S_{twenty one}),
(S ₁₂, S_{twenty two}), (S₁₃, S_{twenty three}) Is closer
You. Also, because there are measurement errors, etc., multiple circles
It is possible that they do not intersect.

Therefore, in the third embodiment, the following method is used to detect the offset errors εS ₁ and εS ₂ of the first and second detection axes even when such a measurement error occurs. It was adopted. That is, a set of output value components (S
₁ , S ₂ ) for at least three different sets, and a circle having a tangent to an approximate straight line on the S ₁ , S ₂ plane of the at least three sets of output value components, and at least three sets of output value components Assuming a circle having a radius g having a contact point at, and determining the center coordinates of the circle (εS ₁ , εS ₂ ), the offset errors εS ₁ , εS ₂ of the first and second detection axes are detected. It is.

Here, an example of a specific method of obtaining the value will be described. A straight line approximated by the least squares method from at least three sets of output value components is defined as axis 1. A straight line passing through the center of gravity of at least three sets of output value components and orthogonal to the axis 1 is defined as an axis 2.

The initial value of the center coordinates (εS ₁ , εS ₂ ) of the circle is (0,0). From the initial value, the center of the circle is moved in the direction of axis 1 by the bisection method, and the center that minimizes the sum of the distances between the circle and at least three sets of output value components is searched. The center of the circle is moved in the direction of the axis 2 by the bisection method from the center obtained above, and a center that minimizes the sum of the distances between the circle and at least three sets of output value components is searched.

The center coordinates (εS ₁ , εS ₂ ) of this circle are set as offset errors εS ₁ , εS ₂ of the first and second detection axes. [Others] (1) Although the above-described embodiment is implemented as the navigation device 1, the present invention can be applied to a device that executes processing other than navigation using the detected current position.

(2) Further, in the above-described embodiment, the relative position obtained based on the calculated azimuth change amount and the moving distance,
Although the dead reckoning calculation of the current position of the vehicle is performed based on the absolute position obtained based on the GPS positioning information, the current position of the vehicle may be corrected by a map matching process. The correction by the map matching is to compare the travel locus of the vehicle, which is calculated based on dead reckoning, to the current position with road information based on map data to perform position estimation.

(3) The gyroscope 12b is an example of a direction sensor. For example, a gyroscope 12b that obtains a direction by accumulating a steering angle of a vehicle obtained from a geomagnetism or a rotation difference between left and right steered wheels and the like is used. You may.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a navigation device as an embodiment of the present invention.

FIG. 2 is a functional block diagram of a current position detection unit.

FIG. 3 is an explanatory diagram illustrating a sensitivity direction and the like of a uniaxial acceleration sensor.

FIG. 4 is a flowchart showing a procedure for measuring an offset error of the acceleration sensor.

FIG. 5 is an explanatory diagram showing a mounting state of an acceleration sensor according to a second embodiment having two inspection axes.

FIG. 6 is a diagram for explaining a method of measuring an offset error of the acceleration sensor according to the second embodiment.

FIG. 7 is a diagram for explaining a method of measuring an offset error of the acceleration sensor according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Navigation apparatus 4 ... Information distribution center 12 ... Position detector 12a ... GPS receiver 12b ... Gyroscope 12c ... Acceleration sensor 12d ... Pitch rate sensor 18 ... Communication apparatus 18a ... Wireless telephone apparatus 18b ... Modem 19 ... External information input Output device 20 ... Operation switch group 21 ... Remote control sensor 22 ... Map data input device 24 ... External memory 26 ... Display device 30 ... Navi control circuit 50 ... Current position detection unit 51 ... Offset error measurement unit 52 ... Offset error storage unit 53 ... Stop judging part 54 ... Inclination angle calculating part 55 ... Vehicle speed calculating part 56 ... Movement distance calculating part 57 ... Relative position calculating part 58 ... Position calculating part 61 ... Offset error measuring part 62 ... Offset error storing part 65 ... Azimuth change amount calculating part 67: absolute position calculation unit 70: navigation execution unit

Continued on the front page (72) Inventor Yoshiyuki Matsubara 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Masayuki Takami 1-1-1, Showa-cho, Kariya City, Aichi Prefecture F-term in Denso Corporation (Reference) 2F029 AA02 AB01 AB07 AB09 AC01 AC02 AC04 AD03 2F105 AA02 BB08 BB17

Claims (11)

[Claims] 1. A offset error detecting method of an acceleration sensor used in the current position detecting device for a vehicle, obtains the output values S ₁ of the acceleration sensor in a state of stopping the vehicle, then the vehicle and characterized in that the output value S ₂ of the acceleration sensor obtained in a stopped state by 180deg inverted to detect the acquired two sensor output values S _1, the average value of S ₂ as an offset error in the same position Method for detecting an offset error of an acceleration sensor. 2. An offset error detecting device for an acceleration sensor used in a current position detecting device for a vehicle, comprising: command input means for inputting a sensor output value obtaining command from a user; and stopping the vehicle. based on the command input means obtains a command has been made via the state, the first acquisition means for acquiring output values S ₁ of the acceleration sensor, after the output values S ₁ is acquired by the first acquisition means ,
Based on the acquisition command it has been made via the command input means in a state of stopping by 180deg inverted in the same position the vehicle, a second acquisition means for acquiring the output value S ₂ of the acceleration sensor, the first And average value calculating means for calculating an average value of the two sensor output values S ₁ and S ₂ obtained by the second obtaining means. The average value calculated by the average value calculating means is defined as an offset error and An offset error detection device for an acceleration sensor. 3. A method for detecting a current position of a vehicle, comprising the steps of:
And the second two detection axes are at an arbitrary angle with respect to the vertical axis of the vehicle.
Offset error detection of a two-axis tilted acceleration sensor
The method according to claim 1, wherein the first detection axis is used while the vehicle is stopped.
45 deg from the vehicle vertical axis of the output value of the acceleration sensor
45 deg component S in the inclined direction₁ And the second
Whether the output value of the acceleration sensor by the detection axis is the vertical axis of the vehicle
-45 deg component S in the -45 deg tilt direction
_Two And an output of the acceleration sensor based on the first and second detection axes.
45 deg component S of value ₁ , -45deg component S_Two Off
Set error is εS₁, ΕS_TwoAnd the gravitational acceleration is g
If (S₁-ΕS₁)^Two+ (S_Two-ΕS_Two)^Two= G^Two 
Is established based on the relationship of
(S₁, S_Two) For at least three different sets, and
Correspondingly S₁, S_TwoCenter coordinates on the plane (S₁, S_Two)
And a circle of radius g, the intersection coordinates of these circles are
(ΕS₁, ΕS_Two), Based on the first, the first
2 offset error εS of the detection axis₁, ΕS_TwoCan detect
Method of detecting offset error of acceleration sensor characterized by
Law. 4. A vehicle according to claim 1, wherein said first position detection device is used for a vehicle current position detection device.
And an offset error detection device for a two-axis acceleration sensor in which a second two detection axes are inclined at an arbitrary angle with respect to a vertical axis of the vehicle, wherein the vehicle is stopped based on a change in an output value of the acceleration sensor. And a 45 deg component of the output value of the acceleration sensor by the first detection axis inclined by 45 deg from the vehicle vertical axis when the stop determination means determines that the vehicle is in a stopped state. S ₁ and -45deg inclined -45deg the vehicle vertical axis of the output values of the acceleration sensor according to the second detection axis
Acquisition means for acquiring component S _2, the first and 45deg component of the second output value of the acceleration sensor according to the detection axis, respectively .epsilon.s ₁ Offset Error -45deg components, .epsilon.s _2, the gravitational acceleration is g In this case, based on the relationship of (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² being established, the set of output value components (S ₁ , S ₂ ) is obtained by the acquisition unit. For at least three different sets, and S ₁ , S ₂ corresponding to each set
Intersection coordinate calculating means for drawing a circle having center coordinates (S ₁ , S ₂ ) and a radius g on a plane and calculating intersection coordinates (εS ₁ , εS ₂ ) of the plurality of circles. An offset error detecting device for an acceleration sensor, wherein the intersection coordinates (εS ₁ , εS ₂ ) calculated by the calculating means are set as the offset errors εS ₁ , εS _{2 of} the first and second detection axes. 5. A vehicle according to claim 1, which is used in a vehicle current position detecting device.
And the second two detection axes are at an arbitrary angle with respect to the vertical axis of the vehicle.
Offset error detection of a two-axis tilted acceleration sensor
The method according to claim 1, wherein the first detection axis is used while the vehicle is stopped.
45 deg from the vehicle vertical axis of the output value of the acceleration sensor
45 deg component S in the inclined direction₁ And the second
Whether the output value of the acceleration sensor by the detection axis is the vertical axis of the vehicle
-45 deg component S in the -45 deg tilt direction
_Two And an output of the acceleration sensor based on the first and second detection axes.
45 deg component S of value ₁ , -45deg component S_Two Off
Set error is εS₁, ΕS_TwoAnd the gravitational acceleration is g
If (S₁-ΕS₁)^Two+ (S_Two-ΕS_Two)^Two= G^Two 
Is established based on the relationship of
(S₁, S_Two) For at least three different sets,
S of three sets of output value components₁, S_TwoApproximate straight line on the plane
A tangent circle, with the center of gravity of three sets of output value components
Assuming a circle having a radius g, the center coordinate of the circle is (εS
₁, ΕS_Two), The first and second inspections are performed.
Outer axis offset error εS₁, ΕS_TwoSpecially to detect
A method for detecting an offset error of an acceleration sensor. 6. A first position detecting device for use in a vehicle current position detecting device, comprising:
And an offset error detection device for a two-axis acceleration sensor in which a second two detection axes are inclined at an arbitrary angle with respect to a vertical axis of the vehicle, wherein the vehicle is stopped based on a change in an output value of the acceleration sensor. And a 45 deg component of the output value of the acceleration sensor by the first detection axis inclined by 45 deg from the vehicle vertical axis when the stop determination means determines that the vehicle is in a stopped state. S ₁ and -45deg inclined -45deg the vehicle vertical axis of the output values of the acceleration sensor according to the second detection axis
Acquisition means for acquiring component S _2, the first and 45deg component of the second output value of the acceleration sensor according to the detection axis, respectively .epsilon.s ₁ Offset Error -45deg components, .epsilon.s _2, the gravitational acceleration is g In this case, based on the relationship (S ₁ −εS ₁ ) ² + (S ₂ −εS ₂ ) ² = g ² being established, the set of output value components (S ₁ ,
S ₂ ) are obtained for at least three different sets, and the at least three sets of output value components are circles whose tangents are approximate straight lines on the S ₁ and S ₂ planes, and the centroids of at least three sets of output value components are assuming a circle of radius g of the contact, the center coordinates (εS _1, εS ₂₎ of the circle and a center coordinate calculating means for calculating, said center coordinates center coordinates calculated by calculation means (.epsilon.s ₁ , ΕS ₂ ) as offset errors εS ₁ , εS _{2 of} the first and second detection axes. 7. An azimuth sensor for outputting a signal corresponding to an amount of azimuth change of the vehicle, an acceleration sensor for outputting a signal corresponding to an acceleration applied to the vehicle, and an azimuth change calculated based on an output value of the azimuth sensor Relative position calculating means for performing self-contained navigation calculation using the amount and the moving distance calculated based on the output value of the acceleration sensor, and calculating a relative current position of the vehicle. An offset error detecting device according to any one of claims 2, 4 and 6, and a correcting means for correcting an output value of the acceleration sensor based on an offset error of the acceleration sensor detected by the offset error detecting device. The relative position calculation means uses the movement distance calculated based on the output value of the acceleration sensor corrected by the correction means, The vehicle current position detecting device characterized by performing the navigation operation. 8. A current position detecting device for a vehicle according to claim 7, further comprising: a pitch rate sensor for outputting a signal corresponding to an angular velocity of the vehicle in a pitch direction; A stop output value obtaining means for obtaining an output value of the pitch rate sensor when the stop determining means determines that the vehicle is in a stopped state; and an output value obtained by the stop output value obtaining means. Is an offset error of the pitch rate sensor, and a correcting means for correcting an output value of the pitch rate sensor based on the offset error; and an output value of the pitch rate sensor and an output of the acceleration sensor corrected by the correcting means. Removing means for calculating the road surface inclination angle based on the value, and removing the influence of the road surface inclination angle from the output value of the acceleration sensor. Dual-purpose current position detection device. 9. The current position detecting device for a vehicle according to claim 7, further comprising: a radio wave receiver that receives a radio wave for radio wave navigation and outputs an absolute current position and a traveling direction of the vehicle. A current position correction device for correcting the relative current position calculated by the relative position calculation device based on an output value from the radio wave receiver. 10. A current position detecting device for a vehicle according to claim 7, a map data storage means storing map data including road map data, and a current position detecting device for a vehicle. Map display means for reading out the road map data around the current position of the vehicle from the map data storage means and displaying the read data as a road map, and displaying the current position of the vehicle on the road map in an identifiable manner. A featured navigation device. 11. The navigation device according to claim 10, further comprising: a route to a preset destination and a current position detected by the vehicle on the road map displayed on the map display means. A navigation device comprising: a route guidance unit that displays a current position of a vehicle so as to be identifiable and performs predetermined route guidance in consideration of a relationship between the route to the destination and the current position of the vehicle.