JP2001280984A - Method and device for correcting gain error of acceleration sensor, device for detecting present position for vehicle, and navigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of appropriately correcting a gain error irrespective of correction of an offset error of an acceleration sensor (a G sensor). SOLUTION: A gain correction factor K is determined by the following expression; K=[T2(Vn-Vn-1)-T1(Vn-1-Vn-2)].(αn-αn-1).T1.T2. Because the gain correction factor K is determined from a ratio of a differential of acceleration determined from an output of the G sensor T2(Vn-Vn-1)-T1(Vn-1-Vn-2) and a differential of acceleration determined from a GPS velocity, (αn-αn-1).T1.T2, the differential of the acceleration is taken and the offset error is negated even when the offset error is included in an output from the acceleration sensor. Thereby, the gain correction factor K is determined without considering the offset error, and there is no need to wait for execution of offset correction so that correction timing is not delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for correcting a gain error of an acceleration sensor used in a current position detecting device for a vehicle.

[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.

Therefore, as means for calculating the moving distance without the need for wiring to the ECU, an acceleration sensor for detecting acceleration in the traveling direction of the vehicle is used, and the output (ie, acceleration) from the acceleration sensor is double integrated. There is a method of calculating the distance by using a distance. However, since the sensitivity surface of the acceleration sensor is not always mounted perpendicular to the traveling direction, when the acceleration sensor is mounted at an angle θ with respect to the vertical surface, detection is performed by a multiple of cos θ. The acceleration will be small. This is called a gain error. That is, if a gain error occurs due to a difference in the attached angle, an error occurs in the distance obtained based on the output of the acceleration sensor.

[0006] Even when the output from the acceleration sensor is deviated as described above, in order to be able to calculate the speed and the distance with high accuracy, the speed and the distance are obtained when the vehicle is stopped or running at a constant speed. Japanese Patent Laid-Open No. Hei 10-30 discloses a technology in which an offset is corrected by an average of the output of an acceleration sensor, and a gain error is corrected by a ratio between speed data obtained from the output of the acceleration sensor and speed data obtained by GPS positioning.
No. 7032.

[0007]

However, in the case of the method disclosed in the prior art, since the speed data obtained from the output of the acceleration sensor (specifically, by integrating the output acceleration) is used, Only after the offset was corrected could the gain error be corrected. That is,
As a premise, a configuration for obtaining an offset error is required, and gain correction cannot be performed unless offset correction is performed, so that the correction timing is delayed.

Accordingly, an object of the present invention is to provide a technique capable of appropriately correcting a gain error regardless of correction of an offset error of an acceleration sensor.

[0009]

According to a first aspect of the present invention, there is provided a gain error correction method for correcting a gain error of an acceleration sensor used in a current position detecting device for a vehicle, based on an output of the acceleration sensor based on an output of the acceleration sensor. For the difference,
The ratio of the difference between the accelerations calculated using the GPS speed is used as a gain correction coefficient, and the output of the acceleration sensor is corrected using the gain correction coefficient.

In the method described in the above-mentioned conventional publication, the gain error is corrected by the ratio between the speed data obtained from the output of the acceleration sensor and the speed data obtained by the GPS positioning. Correction could not be performed, and the timing at which correction could be performed was delayed. On the other hand, in the method of the present invention, the gain correction coefficient is obtained from the ratio of the difference between the accelerations (the amount of change in the acceleration). Even if the acceleration includes an offset error, the offset error is canceled because the difference between the accelerations is calculated. Therefore, a correction coefficient can be obtained without considering the presence or absence of an offset error. Therefore, a configuration for obtaining the offset error is unnecessary, and needless to say, the execution of the offset correction need not be waited, and the correction timing is not delayed.

The invention described in claim 2 is an example of a device for realizing the gain error correction method described in claim 1, and the above-described effect can be exhibited in this gain error correction device. By the way, as a specific method when the correction coefficient calculation means calculates the gain correction coefficient, for example, the method described in claims 3 and 4 can be considered.

First, in the case of claim 3, the correction coefficient calculating means calculates the gain correction coefficient K by the following equation. K = [T ₂ (V _n −V _n−1 ) −T ₁ (V _n−1 −V _n−2 )} / (α _n −
α _n−1 ) · T ₁ · T _{2 In} this case, the difference (V _n −V _n−1 ) of the GPS speed V _n ,
Since the time intervals T ₁ and T ₂ corresponding to (V _n−1 −V _n−2 ) are used, it is possible to correct even when the reception intervals of the satellite radio waves from the GPS satellites are not constant.

Further, in the case of claim 4, the correction coefficient calculating means calculates the gain correction coefficient K by the following equation. K = If _{(V n + V n-2} -2 · V n-1) / (α n -α n-1) · T This is because the reception interval T of the GPS electric wave is assumed to be constant Actually, it is preferable to use after determining that the reception interval is constant.

Considering the calculation of the gain correction coefficient K by the formulas shown in claims 3 and 4, the formula in claim 4 has higher accuracy, but cannot be used unless the reception interval is constant. There is a possibility that the state where the correction coefficient K itself does not exist continues for a long time. On the other hand, the expression of claim 3 allows the case where the accuracy is low, but has an advantage that the gain correction coefficient can be set early because it can be used even if the reception interval is not constant.

Therefore, instead of using each of them in a fixed manner, a method as claimed in claim 5, which makes use of the advantages of both, can also be adopted. That is, the formula shown in claim 3 is used for a predetermined number of times after the reception from the GPS satellite is started, and thereafter, the formula shown in claim 4 is used. The intention is as follows. By using the expression of claim 3, the gain correction coefficient can be set for the first predetermined number of times even if the precision is low. This prevents a situation in which the gain correction coefficient itself does not exist. However, after that, it is better to update to a high-precision one, so that after a predetermined number of times, only the high-precision gain correction coefficient is calculated using the expression of claim 4. Thus, it is considered that the gain error can be more appropriately corrected as a whole.

On the other hand, when calculating the gain correction coefficient,
Even if it can be calculated theoretically, it may be calculated only when the condition shown in claim 6 is satisfied. The condition is that at least one of three conditions is satisfied: the GPS speed is equal to or more than a certain value, the GPS acceleration as a change amount of the GPS speed is equal to or more than a certain value, and the change amount of the GPS acceleration is equal to or more than a certain value. With regard to, since the accuracy of the GPS speed obtained by GPS positioning becomes relatively lower as the speed itself becomes slower, it is intended to improve the accuracy by using only the GPS speed of a certain value or more. With regard to, since the error becomes relatively large when the change amount of the GPS speed is small, the effect of the error is intended to be reduced by using only the speed change amount equal to or more than a certain value. Also, as to the error, if the amount of change in acceleration is small, the error will be relatively large. Therefore, in this case, the effect of the error is intended to be reduced by using only the amount of change in acceleration equal to or more than a certain value.

Note that, although these methods have some effects even when one of the conditions (1) to (4) is employed, the effects are further enhanced when a plurality of conditions are used in combination. The condition set forth in claim 6 takes into account the effects of poor accuracy and errors caused by using the GPS speed obtained by GPS positioning, but considers the effects caused by mounting errors of the acceleration sensor itself. In consideration of this, the calculation may be performed only when the condition shown in claim 7 is satisfied. That is, the gain correction coefficient is calculated only when the angular velocity detected by the angular velocity sensor is equal to or less than a certain value.

The intention to adopt this condition is as follows. Normally, if the mounting angle of the acceleration sensor has an error θ in the yaw direction of the vehicle, it should be smaller than the true acceleration by a factor of cos θ, but when the vehicle is turning, a lateral acceleration component occurs. Since the acceleration sensor outputs a value obtained by adding the component, an accurate correction coefficient cannot be calculated. Therefore, it is better to correct in a situation where the vehicle is traveling straight, and ideally, the lateral acceleration is zero.
, That is, it is preferable to calculate only when the vehicle is in a straight traveling state. However, in practice, the lateral acceleration is completely zero.
Is unlikely to occur. Therefore, taking into account a threshold value that allows a small lateral acceleration generated when the vehicle is traveling straight in normal driving, the gain correction coefficient is calculated only when the angular velocity is equal to or less than a certain value. To do so.

As the gain correction coefficient used for correction by the correction means, for example, it is possible to use an average value of the latest calculated predetermined number of gain correction coefficients. In this way, stable gain correction can be performed. On the other hand, a vehicle current position detecting device according to a ninth aspect includes an azimuth sensor that outputs a signal corresponding to an amount of change in the azimuth of the vehicle, and an acceleration sensor that outputs a signal corresponding to acceleration applied to the vehicle. , The relative position calculating means,
It is assumed that the self-contained navigation calculation is performed using the direction change amount calculated based on the output value of the direction sensor and the moving distance calculated based on the output value of the acceleration sensor to calculate the relative current position of the vehicle. And The gain error correction device according to any one of claims 2 to 8 described above, wherein the relative position calculation means calculates the movement distance calculated based on the output value of the acceleration sensor corrected by the gain error correction device. It is used to perform self-contained navigation calculation.

In the vehicle current position detecting device according to the present invention, since the gain error correcting device has a GPS receiver, the relative position calculated by the relative position calculating means is provided. Naturally, the correct current position can be corrected based on the absolute position information received by the GPS receiver. However, it is necessary to assume that an error of about 100 m occurs in the absolute position information by the radio wave from the GPS satellite. Therefore, in order to improve the accuracy of the position detection, it is necessary to increase the accuracy of the relative current position itself calculated by the self-contained navigation calculation, and thus it is necessary to eliminate the influence of the gain error of the acceleration sensor described above. Must be very useful for detecting the current position of the vehicle.

It is conceivable that various processes are performed using the current vehicle position detected by the current vehicle position detecting device. For example, a current position detecting device for a vehicle, map data storage means storing map data including road map data, and road map data around a current position of the vehicle detected by the current position detecting device for a vehicle are converted into map data. The present invention can also be realized as a navigation device including a map display unit that reads out from the storage unit and displays the current position of the vehicle on the road map while displaying the road map as a road map (claim 11). Further, on the road map displayed on the map display means, a route to a preset destination and a current position of the vehicle detected by the current position detection device for a vehicle are identifiably displayed, and a route to the destination is displayed. The present invention can also be realized as a navigation device including route guidance means for performing a predetermined route guidance in consideration of the relationship with the current position of the vehicle (claim 12).

Further, the above-described method of correcting the gain error of the acceleration sensor and the function of realizing the relative position detecting means and the current position correcting means of the current position detecting device in the computer system are activated on the computer system side, for example. It can be provided as a program to do. In the case of such a program, for example, a floppy (registered trademark) disk, a magneto-optical disk, a CD-RO
It can be used by recording it on a computer-readable recording medium such as a hard disk 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.

[0023]

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 apparatus 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), a display such as a speedometer and a tachometer, and a map display screen. 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 (Glob)
al Positioning System) receives the transmitted radio wave from the satellite via the GPS antenna,
A GPS receiver 12a for detecting a speed or the like, a gyroscope 12b for outputting a detection signal corresponding to an angular velocity of a rotational motion applied to the vehicle, and corresponding to an "angular velocity sensor" and an "azimuth sensor"; An acceleration sensor 12c for detecting acceleration in the front-rear direction.

The acceleration sensor 12c is a so-called one-axis acceleration sensor, and its sensitivity direction is set to be positive in the traveling direction (forward direction) of the vehicle. The communication device 18 includes a wireless telephone device 18a such as a mobile phone or a car telephone that can be connected to a public telephone network, and a wireless telephone device 18 according to a command from the navigation control circuit 30.
a, a connection with an information distribution center, which is an external information source, is made in accordance with a predetermined procedure, and data from the navigation control circuit 30 is encoded into a form that can be transmitted via the wireless telephone device 18a. And a modem 18b for decoding data input via the device 18a into a form that can be processed by the control circuit 30.

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 outputs from the gyroscope 12b and the acceleration sensor 12c, data for performing dead reckoning such as the current position and traveling direction of the vehicle is calculated.

When the navigation device 1 inputs the position of the destination from a remote control sensor 21 via a remote control terminal (hereinafter, referred to as a remote controller) (not shown) or the 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 them, the current position detection unit 50 calculates a gain correction coefficient for correcting a gain error of the acceleration sensor 12c based on the detection signal from the acceleration sensor 12c and the GPS speed obtained from the GPS receiver 12a. A coefficient calculation unit 41 and a gain correction coefficient storage unit 42 for storing the calculated gain correction coefficient are provided. In addition, the offset error measuring unit 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 measured by the offset error measuring unit 51 (ΕS), an offset error storage unit 52, a stop determination unit 53, a vehicle speed calculation unit 55, and a movement distance calculation unit 56.
A relative position calculator 57, a position calculator 58, an azimuth change calculator 65 for calculating an azimuth change based on a detection signal from the gyroscope 12b, and a GPS receiver 12
a) an absolute position calculating section 67 for calculating an absolute position based on the GPS positioning data obtained from a.

The stop judging section 53 judges whether or not the vehicle is stopped based on the detection signal from the acceleration sensor 12c.
1 to the offset error measuring unit 51 and the vehicle speed calculating unit 55. Then, the offset error measurement unit 51 also measures the offset error (εS) of the acceleration sensor 12c with reference to the stop determination result from the stop determination unit 53. This offset error (εS) is stored in the offset error storage unit 52 and is used as follows. That is, the acceleration sensor 1
The output value from the acceleration sensor 12c is represented by S = α + εS using the acceleration α in the traveling direction of the vehicle parallel to the road surface and the offset error εS of the acceleration sensor 12c.
By subtracting the offset error εS from the output value S from, S−εS = α.

On the other hand, the gain correction coefficient K calculated by the gain correction coefficient calculation section 41 and stored in the gain correction coefficient storage section 42 is used as follows. That is, the above-described traveling direction acceleration α (= S−εS) is multiplied by the gain correction coefficient K to obtain α × K. And this corrected value is
The result is output to the stop determination unit 53 and the vehicle speed calculation unit 55 described above. The details of the correction of the gain error will be described later.

The vehicle speed calculation unit 55 is based on a value (S−εS) × K obtained by correcting an offset error and a gain error with respect to the output S from the acceleration sensor 12c, and a stop determination result from the stop determination unit 53. The vehicle speed V is calculated with reference to FIG. Then, the moving distance calculation unit 56 includes a vehicle speed calculation unit 55
The moving distance is calculated based on the vehicle speed V calculated in.
Note that the determination result from the stop determination unit 53 is the vehicle speed calculation unit 55
Is also input that the vehicle speed is 0 when stopped.
This is because there is no need to calculate the vehicle speed. That is, no extra calculation is performed.

The relative position calculating section 57 corresponds to “relative position calculating means”, and is based on the moving distance calculated by the moving distance calculating section 56 and the azimuth change amount calculated by the azimuth change amount calculating section 65. , And calculate the relative position of the vehicle. The position calculating unit 58 corresponds to “current position correcting means”, and calculates the relative position of the vehicle calculated by the relative position calculating unit 57 based on the absolute position of the vehicle calculated by the absolute position calculating unit 67. And outputs it to the navigation execution unit 70 as the final current position of the vehicle.

Next, a process for correcting a gain error of the acceleration sensor 12c will be described. FIG. 3 is a flowchart showing a processing procedure executed when calculating a gain correction coefficient for correcting a gain error of the acceleration sensor 12c. This process is executed by the gain correction coefficient calculation unit 41.

In the first step S110 in FIG. 3, it is determined whether or not the vehicle is running. This determination is made based on the determination result by the stop determination unit 51. Then, when the vehicle is traveling (S110: YES), the process proceeds to S120, but when the vehicle is not traveling (S110: NO), the present process is terminated as it is. As described above, based on the determination result from the stop determination unit 53, the vehicle speed is 0 when the vehicle is stopped,
This is because it is not necessary to perform a gain correction operation.

In the following S120 to S160, it is determined whether the calculation of the gain correction coefficient K in S170 is possible or not. In order to understand the substantial meaning of this determination,
Since it is better to know the calculation content of the gain correction coefficient K in 170, the process in S170 will be described first.

In S170, a gain correction coefficient K is calculated based on the following equation (1). K = [T ₂ (V _n −V _n−1 ) −T ₁ (V _n−1 −V _n−2 )} / (α _n −α _n−1 ) · T ₁ · T ₂ ... [Equation 1] Here, K: gain correction coefficient of the acceleration sensor V _n : GPS speed measured at the nth position α _n : Obtained from the output of the acceleration sensor from the time when the GPS speed was measured at the (n−1) th position to the time when the nth position was measured Average acceleration T ₁ : Time interval from the time when the GPS speed is measured at the (n−1) th position to the time when the nth position is measured T ₂ : From the time at which the GPS speed is measured at the (n−2) th position to n−
Time interval until the time when the first positioning is performed This equation 1 is based on the assumption that the following equations 2 and 3 are satisfied (equation 2 ×
T ₂ ) − (Equation 3 × T ₁ ) to obtain K. V _n = K (α _n −εα) · T ₁ + V _n-1 (Equation 2) V _n-1 = K (α _n-1 −εα) · T ₂ + V _n-2 (Equation 3) In Equations 2 and 3, εα is an offset error of the acceleration sensor 12c.

Here, the meaning of Equation 1 will be considered.
Equation 1 can be transformed into Equation 4 below. K = [T ₂ (V _n −V _n−1 ) −T ₁ (V _n−1 −V _n−2 )} / (α _n −α _n−1 ) · T ₁ · T ₂ = [(V _n −V _n−1 ) / T ₁ − (V _n−1 −V _n−2 ) / T ₂ ｝ / (α _n −α _n−1 ) = (β _n −β _n−1 ) / (α _n − alpha _n-1) ... [equation 4] where, K: gain correction coefficient for the acceleration sensor V _n: n-th GPS velocity alpha _n and positioning: the positioning of the n-th from the time that the positioning of the GPS velocity n-1 th Average acceleration obtained from the output of the acceleration sensor until the time β _n : Average acceleration obtained from the GPS speed from the time when the GPS speed is measured at the (n−1) th position to the time when the GPS speed is measured at the nth position T ₁ : GPS speed the n-1 th time from positioning the time to the time that the positioning of the n-th interval T _2: n-from the time that the positioning of the GPS speed n-2 th
Time interval until the time when the first positioning is performed As can be seen from Expression 4, the ratio of the acceleration difference (acceleration change amount) is used as the gain correction coefficient K.

Now, the condition determination in S120 to S160 will be described. First, in S120, the positioning state of the GPS receiver 12a is determined. Specifically, it is determined whether or not the positioning data (GPS speed in this case) for the past three times has been obtained. This is because the calculation formula of the gain correction coefficient K shown in the above-described formula 1 cannot be calculated unless the past three GPS speeds have been obtained. Accordingly, if the GPS speeds for the past three times have been obtained (S120: YES), the process proceeds to S130, but if not (S120: NO), this process is terminated.

This step S120 is a precondition for calculating the gain correction coefficient K, that is, the calculation itself cannot be performed unless this condition is satisfied. That is, it is determined whether the gain correction coefficient can be calculated.
On the other hand, in the following S130 to S150, even if the gain correction coefficient can be calculated, the calculation of the gain correction coefficient is performed in order to eliminate the influence of the inaccuracy and the error caused by using the GPS speed. Are permitted to be executed.

First, in S130, it is determined whether or not the GPS speed is equal to or higher than a predetermined value (for example, 3 m / s).
If the speed is equal to or more than the predetermined value (S130: YES), S1
40, and if less than the predetermined value (S130: N
O), the process is terminated as it is. The meaning of this condition is
It is as follows. GPS velocity V _n obtained by the GPS positioning, the speed itself becomes slow because the relatively accuracy is poor, it is intended to improve the accuracy so as to use only the GPS velocity V _n of the predetermined value or more.

[0045] In S140, GPS speed GPS acceleration is the change amount of V _n is determined whether the whether a predetermined value (e.g., 1 m / s ²⁾ above, if the GPS acceleration is a predetermined value or more (S140: YES ), The process proceeds to S150, and if the value is less than the predetermined value (S140: NO), the present process is terminated as it is. The meaning of this condition is as follows. GPS speed V
_If the change amount of _n is small, the error becomes relatively large, so
It is intended to reduce the influence of the error by using only the speed change amount equal to or more than a certain value.

In S150, it is determined whether or not the amount of change in the GPS acceleration is equal to or more than a certain value (for example, 1 m / s ² ).
50: YES), the process proceeds to S160, and if it is less than the predetermined value (S150: NO), the present process is terminated as it is. The meaning of this condition is as follows. The amount of change in acceleration corresponds to (β _n −β _n-1 ) of the numerator in the above equation 4, but if the amount of change in acceleration is small, the error also becomes relatively large. It is intended to reduce the influence of the error by using only the acceleration change amount described above.

The "change amount" in S140 and S150 is not determined by the sign, but is determined by its absolute value. These steps S130 to S150 are conditions for eliminating the influence of inaccuracy and errors caused by the use of the GPS speed. On the other hand, in the next step S160, the mounting errors of the acceleration sensor 12c itself are reduced. This is a condition that takes into account the resulting effects. Specifically, the gyroscope 12b
It is determined whether or not the angular velocity detected at is equal to or less than a certain value (for example, 1 rad / s). If the angular velocity is equal to or more than the certain value (S160: YES), the process proceeds to S170. S160: NO), this process ends as it is.

The purpose of this condition determination is as follows. Originally, if the mounting angle of the acceleration sensor 12c has an error θ in the yaw direction of the vehicle, it should be smaller than the true acceleration by cos θ times. That is, if the true acceleration is α, αcos θ is output. However, when the vehicle is in a turning state, a lateral acceleration component occurs,
Since the acceleration sensor 12c outputs a value to which the component is added, it is impossible to calculate an accurate gain correction coefficient K. Therefore, it is better to correct in a situation where the vehicle is traveling straight, and ideally, it is preferable to calculate only when the lateral acceleration is 0, that is, when the vehicle is in a completely straight traveling state. However, in practice, a situation where the lateral acceleration is completely zero is unlikely to occur. Therefore, in consideration of a threshold value that allows a small lateral acceleration that occurs when the vehicle is traveling straight in normal driving, if the angular velocity is equal to or less than a predetermined value (S
160: YES), the gain correction coefficient K in S170 is calculated.

When the gain correction coefficient K has been calculated in S170, it is temporarily stored, and in S180, it is determined whether or not the latest n or more gain correction coefficients K have been calculated and stored. to decide. If only less than n gain correction coefficients K have been calculated and stored (S1
80: NO), this process ends as it is. On the other hand, if n or more gain correction coefficients K have been calculated and stored (S
180: YES), the latest n gain correction coefficients K
Is the final gain correction coefficient K (S19).
0). The final gain correction coefficient K is stored in the gain correction coefficient storage unit 42 and is used for correcting the output of the acceleration sensor 12c.

As described above, in the navigation device 1 of the present embodiment, since the acceleration sensor 12c used for detecting the current position does not require wiring to the ECU, a vehicle speed sensor for extracting a speed signal such as a vehicle speed pulse is provided. 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 offset is corrected in order to correct the gain error by the ratio between the speed data obtained from the output of the acceleration sensor and the speed data obtained by the GPS positioning. Otherwise, the gain error cannot be corrected, and the timing at which the correction can be performed is delayed. In the case of the present embodiment, such a disadvantage does not occur. That is, since the gain correction coefficient K is obtained from the ratio of the difference of acceleration (the amount of change in acceleration), even if the output value from the acceleration sensor 12c includes the offset error ε, the difference between the accelerations is obtained. Therefore, the offset error εS is eliminated. As described above, Equation 1 used for calculating the gain correction coefficient K in S170 in FIG. 3 is (Equation 2 × T ₂ ) − (Equation 3)
× T ₁ ). Equations 2 and 3 show the offset error ε
S is included. However, by taking the difference between the accelerations, the offset error εS is eliminated. Therefore, the gain correction coefficient K can be obtained without considering the presence or absence of the offset error εS. That is, there is no need to wait for the execution of the offset correction, and the correction timing is not delayed.

Further, if the output value thus corrected is used, a vehicle speed calculation performed using the output value,
The calculation of the moving distance and the calculation of the relative position can be appropriately performed. [Second Embodiment] The second embodiment is different from S170 of FIG.
Is obtained by changing the equation used for calculating the gain correction coefficient K to the following equation 5. _{K = (V n + V n} -2 -2 · V n-1) / (α n -α n-1) · T ... [ Equation 5] This Equation 1, given the establishment of the following formula 6,7 Equation 6 is obtained by calculating K from Equation 7. V _n = K (α _n −εα) · T + V _n−1 (Equation 6) V _n-1 = K (α _n−1 −εα) · T + V _n-2 (Equation 7) 7 is an offset error of the acceleration sensor 12c.

Here, the meaning of Equation 5 will be considered.
Equation 5 can be modified as in Equation 8 below. _{K = (V n + V n} -2 -2 · V n-1) / (α n -α n-1) · T = [(V n -V n-1) / T- (V n-1 -V _n−2 ) / T｝ / (α _n −α _n−1 ) = (β _n −β _n−1 ) / (α _n −α _n−1 ) where K is the gain of the acceleration sensor. correction factor V _n: GPS speed and positioning the n-th alpha _n: average acceleration obtained from the acceleration sensor output during the period from the time that the positioning of the GPS velocity (n-1) th to the time that the positioning of the n-th beta _n: GPS velocity Is the average acceleration obtained from the GPS speed between the time when the position is measured at the (n−1) th position and the time when the position is measured at the nth position. T: Positioning interval of the GPS speed As can be seen from Expression 8, in the case of the second embodiment, In this case, the ratio of the acceleration difference (acceleration change amount) is used as the gain correction coefficient K. However, when using Equation 5, the positioning interval T needs to be constant. Therefore,
In S120 in FIG. 3, it is determined whether the positioning interval T is constant in addition to whether the GPS speeds for the past three times have been obtained. This determination is specifically performed as follows. That is, this time (n), last time (n-1), two times before (n-
2) GPS times Tn, Tn-1, Tn-2 received respectively
ΔT1 = Tn−Tn−1, ΔT2 = Tn−1−Tn−2
It is determined whether ΔT1 = ΔT2.

In the case of Expression 5 used in the second embodiment, it is considered that the gain correction coefficient K can be obtained with high accuracy because the positioning interval T is constant. Third Embodiment Regarding the calculation of the gain correction coefficient K, Equation 1 is used in the first embodiment, and Equation 5 is used in the second embodiment. When examining these equations, equation 5 has higher accuracy, but cannot be used unless the positioning interval is constant, so that a state in which the gain correction coefficient K itself does not exist may continue for a long time. On the other hand, Equation 1 allows a case where the accuracy is relatively low, but can be used even if the positioning interval is not constant, and therefore has the advantage that the gain correction coefficient K can be set earlier.

Therefore, in the third embodiment, a method is proposed in which the two formulas for calculating the gain correction coefficient K are not fixedly used but take advantage of both. Specifically, between S120 and S130 in the flowchart of FIG. 3, S121, S123, S125, and S1 shown in FIG.
Insert 27 four steps. It will be described in order.

At S121, to which the operation proceeds when the determination at S120 is affirmative, it is determined whether or not within the first Y times from the start of the GPS positioning. If it is within Y times (S121: YES), the above-described equation 1 is unconditionally adopted (S123). As a result, the calculation of the gain correction coefficient K in S170 of FIG. 3 can be performed without the positioning interval being constant, and even if the accuracy is relatively low, the gain correction coefficient K can be set for the time being. In addition, it is possible to prevent a situation where the gain correction coefficient itself does not exist.

On the other hand, if the positioning has exceeded the first Y times (S121: NO), the flow shifts to S125 to determine whether the positioning interval is constant. As described in the second embodiment, this corresponds to the GPS time T received at the latest three times, ie, this time (n), last time (n-1), and last time (n-2).
ΔT1 = Tn−Tn−1, ΔT for n, Tn−1 and Tn−2
Assuming that 2 = Tn−1−Tn−2, it is determined whether ΔT1 = ΔT2. If ΔT1 = ΔT2 (S125:
YES), Equation 5 is adopted (S127). Thus, the gain correction coefficient K calculated in S170 of FIG.
Is more accurate.

If ΔT1 = ΔT2 is not satisfied (S1
25: NO), this process ends as it is. in this case,
The gain correction coefficient K calculated using Equation 1 or Δ
When T1 = ΔT2, the gain correction coefficient K calculated using Equation 5 is stored in the gain correction coefficient storage unit 42 (see FIG. 2), so that there is no particular problem regarding the correction. That is, it is only necessary to update the condition when the condition of ΔT1 = ΔT2 is satisfied and the accurate gain correction coefficient K can be newly calculated.

[Others] (1) In the above embodiment, S130 in the flowchart of FIG.
As shown in S160 to S160, the calculation is permitted only when all the four conditions are satisfied as the calculation permission condition of the gain correction coefficient. These conditions have a certain effect even if they are permitted when only one of them is satisfied, but the effect is more enhanced if two or more of the four conditions are used in combination.

(2) In the above embodiment, the navigation device 1
However, the present invention can be applied to an apparatus that executes processing other than navigation using the detected current position. (3) In the above embodiment, as shown in FIG. 2, the current position detection unit 50 includes the offset error measurement unit 51 and its storage unit 5.
2 is provided. It is not necessary to correct the offset error in order to correct the gain error, but it is assumed here that it is applied to the current position detection, and in order to obtain the distance, it is necessary to correct and integrate the offset error of the acceleration sensor output. There is. Therefore, if considered in terms of a gain error correction device, a configuration for correcting an offset error is not required. In addition, considering the current position detecting unit 50 as a unit as in the embodiment, these configurations (51, 52) are necessary, but the above-described inconvenience that the gain error cannot be corrected without waiting for the offset error to be corrected. Does not occur in the case of the present embodiment.

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart illustrating a procedure for calculating a gain correction coefficient.

FIG. 4 is a flowchart illustrating a part of a procedure for calculating a gain correction coefficient in a third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Navigation device 4 ... Information distribution center 12 ... Position detector 12a ... GPS receiver 12b ... Gyroscope 12c ... Acceleration sensor 18 ... Communication device 18a ... Wireless telephone device 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 Navigation control circuit 41 Gain correction coefficient calculation unit 42 Gain correction coefficient storage unit 50 Current position detection unit 51 Offset error measurement unit 52: Offset error storage unit 53: Stop determination unit 55: Vehicle speed calculation unit 56: Moving distance calculation unit 57: Relative position calculation unit 58: Position calculation unit 65: Azimuth change amount calculation unit 67: Absolute position calculation unit 70: Execute navigation Department

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F029 AA02 AB07 AB09 AC02 AC14 AD01 5H180 AA01 FF04 FF05 FF07 FF22 FF27 FF32 KK06 9A001 JJ77 JZ11 KK37

Claims (12)

[Claims] 1. A method for correcting a gain error of an acceleration sensor used in a current position detecting device for a vehicle, the method comprising: calculating a gain error based on a satellite radio wave received from a GPS satellite with respect to a difference between an acceleration calculated based on an output of the acceleration sensor. The ratio of the difference between the accelerations calculated using the obtained GPS speed, which is the absolute speed of the vehicle, is used as a gain correction coefficient, and the output of the acceleration sensor is corrected using the gain correction coefficient. Gain error correction method. 2. A gain error correction device for an acceleration sensor used in a current position detection device for a vehicle, wherein the GPS reception device receives a satellite wave from a GPS satellite and outputs a GPS speed that is an absolute speed of the vehicle. Correction coefficient calculating means for calculating, as a gain correction coefficient, a ratio of an acceleration difference calculated using a GPS speed output from the GPS receiver to a difference between accelerations calculated based on the output of the acceleration sensor. A correction means for correcting the output of the acceleration sensor using the gain correction coefficient calculated by the correction coefficient calculation means. 3. The gain error correction device for an acceleration sensor according to claim 2, wherein said correction coefficient calculation means calculates said gain correction coefficient by the following equation. . K = [T ₂ (V _n −V _n−1 ) −T ₁ (V _n−1 −V _n−2 )} / (α _n −
_{α n-1) · T 1} · T 2 where, K: gain correction coefficient for the acceleration sensor V _n: GPS speed and positioning the n-th alpha _n: positioning the n-th from the time that the positioning of the GPS velocity n-1 th the average acceleration T was obtained from the acceleration sensor output until time _1: time interval from the time that the positioning of the GPS velocity (n-1) th to the time that the positioning of the n-th T _2: the GPS velocity (n-2) th to N- from the time of positioning
Time interval until the first positioning time 4. A gain error correction device for an acceleration sensor according to claim 2, wherein said correction coefficient calculation means calculates said gain correction coefficient by the following equation. . _{K = (V n + V n} -2 -2 · V n-1) / (α n -α n-1) · T where, K: gain correction coefficient for the acceleration sensor V _n: GPS velocity alpha that positioning the n-th _n : average acceleration obtained from the output of the acceleration sensor from the time when the GPS speed is measured at the (n-1) th position to the time when the nth position is measured. T: GPS radio wave reception interval 5. The gain error correction device for an acceleration sensor according to claim 2, wherein the correction coefficient calculating means calculates the gain correction coefficient a predetermined number of times after starting reception from a GPS satellite. A gain error correction device for an acceleration sensor, wherein the following formula is used, and thereafter the formula shown in claim 4 is used. 6. The gain error correction device for an acceleration sensor according to claim 2, wherein said correction coefficient calculating means determines that the GPS speed is equal to or higher than a predetermined value.
If the GPS acceleration, which is the amount of change in PS speed, is equal to or greater than a certain
A gain error correction device for an acceleration sensor, wherein the gain correction coefficient is calculated only when at least one of three conditions that a change amount of a PS acceleration is equal to or more than a certain value is satisfied. 7. The gain error correction device for an acceleration sensor according to claim 2, further comprising: an angular velocity sensor that outputs a signal corresponding to each rotation speed of the vehicle. A gain error correction device for an acceleration sensor, wherein the gain correction coefficient is calculated only when the angular velocity detected by the angular velocity sensor is equal to or less than a predetermined value. 8. The gain error correction device for an acceleration sensor according to claim 2, wherein said correction coefficient calculation means is capable of calculating an average value of the latest calculated predetermined number of gain correction coefficients. The correction means corrects an output of the acceleration sensor using an average value of the gain correction coefficient, and a gain error correction device for the acceleration sensor. 9. 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. Further, the apparatus further includes a gain error correction device according to any one of claims 2 to 8, wherein the relative position calculation means calculates a movement distance calculated based on an output value of the acceleration sensor corrected by the gain error correction device. A current position detecting device for a vehicle, wherein the self-contained navigation calculation is performed using the current position detecting device. 10. The current position detecting device for a vehicle according to claim 9, further comprising: correcting a relative current position calculated by said relative position calculating means based on an output value from said GPS receiver. A current position detecting device for a vehicle, comprising: a position correcting unit. 11. A vehicle current position detecting device according to claim 9 or 10, a map data storage means storing map data including road map data, and a vehicle detected by said vehicle current position detecting device. Map display means for reading 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. Navigation device. 12. The navigation device according to claim 11, 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.