JPH04346024A - Method and apparatus for detecting bearing - Google Patents

Abstract

PURPOSE:To detect the correct bearing by updating an offset value appropriately and excluding the effect of the drift of the offset even if a vehicle continues to run for a long time. CONSTITUTION:The bearing of a vehicle is detected by correcting the output of a gyroscope 1 with an offset value stored in an offset memory 11. A position detecting part 3 estimates the present position of the vehicle by a dead reckoning method and the like. When the vehicle continuously runs for a specified time, each link bearing at the present positions of the vehicle before and after this period is read from a road map memory 5. The difference between the link bearings is made to be the first bearing-change amount. In the position detecting part 3, the values after the offset correction for the outputs of the gyroscope 1 during the period corresponding to the first bearing-change amount are accumulated. The accumulated value is made to be the second bearing- change amount. 11. The new offset value is computed based on the first bearing- change amount and the second bearing-change amount. The new offset value is stored in the offset memory 11.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a direction detection method and a direction detection method for detecting the direction of a moving body such as a vehicle using a turning angular velocity sensor such as an optical fiber gyro, a mechanical gyro, a vibration gyro, or a gas rate gyro. It is related to the device.

0002

2. Description of the Related Art Conventionally, turning angular velocity sensors have been widely used in moving objects such as vehicles, aircraft, and ships to detect a predetermined orientation such as the direction of movement of the moving objects. The output signal from this turning angular velocity sensor is subjected to appropriate processing to calculate the amount of azimuth change Δθ that occurs as the vehicle moves.
is determined at every predetermined sampling period to create current orientation data of a vehicle, etc.

[0003] The current orientation θ of a vehicle, etc. is determined by the orientation θ0 obtained at the time of sampling the previous orientation change amount Δθ, and
Using the direction change amount Δθ, θ=θ0 +Δθ
・・・
... (1) Obtained as follows. The current orientation θ obtained in this manner is used for calculating the current position of a vehicle, etc. That is, for example, the east-west direction component Δx (=
ΔL× cosθ) and the north-south direction component Δy (=ΔL× s
inθ) is obtained. By adding each component of this vehicle movement amount to each component of the previous vehicle position data (Px', Py'), the current vehicle position data (Px, Py') is added.
Py) is obtained. Such a technique for detecting the position of a moving object is called dead reckoning navigation or the like.

However, with turning angular velocity sensors, even when the sensor output should be zero, such as when the vehicle is stopped or traveling in a straight line, there is a tendency for some offset output to occur due to the effects of temperature and humidity. . Unlike general noise components caused by vehicle vibrations, this offset output cannot be removed even by detection for a sufficiently long period of time, and has the property of being accumulated over time. When this offset output is accumulated, the detected current orientation θ includes a large error, making detection of the current position of the vehicle inaccurate.

In order to solve this problem, it has been proposed in the past to subtract the offset output from the sensor output to detect the current orientation θ. For example, the special public service in 1988
No. 39360 discloses a technique that utilizes the fact that the output of a turning angular velocity sensor during a period when a vehicle is stopped at a traffic light or the like is an offset itself. That is,
Offset correction is realized by detecting an offset from the output of the turning angular velocity sensor while the vehicle is stopped and subtracting the detected offset from the output of the turning angular velocity sensor while the vehicle is running. Also, for example,
3-182519 discloses a technique for performing similar offset correction using the output of a turning angular velocity sensor during straight travel. In this disclosed technique, it is identified from the road map data that the road on which the vehicle is traveling is a straight road, and the offset is detected based on the output of a turning angular velocity sensor while the vehicle is traveling on the straight road.

[0006]

However, the offset of the turning angular velocity sensor has the property of drifting due to changes in temperature and humidity, regardless of whether the vehicle is stationary or moving. Therefore, even if the output of the turning angular velocity sensor while driving is corrected using a fixed offset value determined while stopped or while driving in a straight line, the value after offset correction may contain an error due to the above-mentioned drift. become.

[0007] When a vehicle frequently stops or frequently runs on a straight road, the offset value used for correction can be updated while the drift is small, so the above problem is relatively rare. If the time from when the vehicle starts to when it stops is long, such as when driving in a It becomes inaccurate.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an azimuth detection method and an azimuth detection device that solve the above-mentioned technical problems and that enable accurate azimuth detection by effectively performing offset correction of a turning angular velocity sensor. That's true.

[0009]

Means for Solving the Problems and Operations FIG. 1 is a block diagram showing the basic configuration of a direction detection device to which the direction detection method of the present invention is applied. This direction detection device is mounted on a vehicle or other moving object to detect the direction of the moving object, and includes a turning angular velocity sensor 21 that detects the turning angular velocity of the moving object, and a turning angular velocity sensor 21 that is included in the output of this turning angular velocity sensor 21. The vehicle is equipped with a correction means 22 for correcting the offset that has been generated, and the direction of the moving object is detected based on the output of the correction means 22.

The offset contained in the output of the turning angular velocity sensor 21 varies over time due to the influence of temperature, humidity, and other factors. Therefore, the offset value, which is the correction amount in the correction means 22, is updated by the offset update means 23. In order to update the offset value, a current position detecting means 24 that detects the current position of the mobile object, and a link that connects nodes that are predetermined coordinate positions on the map and corresponds to a route along which the mobile object can travel; and a map memory 25 that stores, for each link, a link direction that is a direction unique to each link when a mobile object moves along the link. Detection of the current position by the current position detection means 24 is performed by any method, for example, by using a value obtained by offset-correcting the output of the turning angular velocity sensor 21 by the correction means 22, and an output of a speed sensor or the like that detects the speed of the moving object. Based on this, it may be performed by so-called dead reckoning. In addition, GPS (Global Positioning)
System) The current position of the moving body may be detected by measuring the propagation delay time of radio waves from the satellite.

The current position information detected by the current position detecting means 24 is given to the determining means 27. This determination means 2
7 determines that a matching state exists when the trajectory of the detected position by the current position detecting means 24 has a predetermined correlation with any link stored in the map memory 25. That is, a matching state is determined when the detected current position and the link in the map data match well. The link orientation of the link corresponding to the current position at the time when the determining means 27 determines the matching state is stored in the first storage means 31 as a first orientation.

On the other hand, the movement/stop determination means 28 determines whether the moving object is moving or stopped. This determination result is given to the offset updating means 23 as well as to the moving time measuring means 29 which measures the time during which the moving body is continuously moving. The travel time measuring means 29 is also given the determination result by the determining means 27. The travel time measuring means 29 starts measuring after the first direction is stored in the first storage means 31, and when the moving/stopping determining means 28 determines that the moving body is moving, and the determining means 27 As long as it is determined that a matching state exists, the measurement of the moving time of the moving object is continued, and when the measured moving time reaches a predetermined time, a write command is given to the second storage means 32 from the line 30. As a result, in the second storage means 32, the link orientation of the link corresponding to the current position at that time is stored as the second orientation.

If the moving object stops or the matching state is no longer determined before the moving time measuring means 29 measures the predetermined time, the moving time measuring means 29
The measurement time will be reset. Note that the first storage means 3
The first and second storage means 32 may be configured using separate memory devices, or may be configured using different storage areas of the same memory device.

The first orientation and the second orientation stored in the first storage means 31 and the second storage means, respectively, are provided to the first orientation change amount detection means 41. The first azimuth change amount detecting means 41 determines the first azimuth change amount from, for example, the difference between the first azimuth and the second azimuth. On the other hand, the output of the correction means 22 is transmitted to the second direction change amount detection means 4.
It is given to 2. This second direction change detection means 4
2, by accumulating the output of the correction means 22, the first
A second azimuth change amount corresponding to the azimuth change amount is detected. That is, the second azimuth change amount detection means 42 starts accumulating the output of the correction means 22 at the timing when the first storage means 31 memorizes the first azimuth, and the second storage means 32 The accumulation is stopped at the timing of storing , and the accumulated value at that time is provided to the offset updating means 23 as the second azimuth change amount. Since the output of the correction means 22 is the output of the turning angular velocity sensor 21 after offset correction, its cumulative value becomes the azimuth change amount.

The offset updating means 23 calculates a new offset value based on the first and second azimuth change amounts given from the first azimuth change amount detection means 41 and the second azimuth change amount detection means 42, respectively. calculate. Since the first azimuth variation is determined based on the link azimuth in the matching state, this first azimuth variation is extremely close to the true value. On the other hand, since the second azimuth change amount is the cumulative output of the turning angular velocity sensor 21 after offset correction, it is the cumulative amount of offset drift that occurred during driving. Therefore, for example, by subtracting the first azimuth change amount from the second azimuth change amount, the cumulative value of the offset drift amount can be determined. If the amount of offset drift is known from this cumulative value, a new offset value can be determined based on this. This new offset value is provided to the correction means 22 via line 35. After updating the offset value, a signal from line 37 causes the first storage means 31 and the second storage means 3 to be
2 are cleared.

Note that the second azimuth change amount detection means 42 may accumulate the output of the turning angular velocity sensor 21 as it is before offset correction. In this case, the detected second azimuth change amount is the true azimuth change amount plus an offset including the offset drift amount. Therefore, for example, by subtracting the first azimuth change amount from the second azimuth change amount, the cumulative value of the offset including the offset drift amount can be determined, and a new offset value can be determined based on this.

Since the cumulative value detected by the second azimuth change detection means 41 is accumulated over a predetermined time measured by the travel time measuring means 29, it is determined that the amount of offset drift due to, for example, vibration of the moving object is not detected. Other noise components are canceled out by long-term accumulation. This allows the offset value to be determined accurately. Note that when the moving/stopping determining means 28 determines that the moving body is stopped, the offset updating means 23 updates the line 3.
The offset value may be updated based on the output of the correction means 22 given from 6. That is, since the output of the correction means 22 when the moving body is stopped is the offset drift amount itself, a new offset value can be determined based on this. When the moving body stops in this way, updating the offset value based on the output of the correction means 22 is a more direct and accurate method of determining the offset value than determining the offset value using the link direction. This is because it can be done. Such updating of the offset value during stoppage can also be performed based on the direct output of the turning angular velocity sensor 21 before offset correction. That is, since the output of the turning angular velocity sensor 21 while the vehicle is stopped is the offset itself, a new offset value can be obtained based on this.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples will be explained in detail below with reference to the accompanying drawings showing examples. FIG. 2 is a block diagram showing the basic configuration of a navigation device for implementing a vehicle direction detection method according to an embodiment of the present invention. This navigation device is used mounted on a vehicle, which is a moving object, and includes a gyro 1 which is a turning angular velocity sensor that detects the turning angular velocity of the vehicle, and a vehicle speed sensor 2 which detects the speed of the vehicle by detecting the rotational speed of the wheels. The position detection unit 3, which has these outputs, estimates the current position of the vehicle by so-called dead reckoning navigation or the like. An offset memory 11 that stores the offset value included in the output of the gyro 1 is connected to the position detection unit 3, and the current position is estimated using a value corrected by subtracting the offset value from the output of the gyro 1. is used. The position detection unit 3 includes a CPU (not shown), etc.
It has a memory 15 that functions as a work area and a continuous running counter 16 for measuring the continuous running time of the vehicle. Various types of gyros can be used as the gyro 1, such as an optical fiber gyro, a mechanical gyro, a vibration gyro, and a gas rate gyro.

Estimated position data representing the current position detected by the position detection section 3 is given to a control section 4 composed of a CPU (central processing unit) or the like. The control unit 4 is a CD-RO
A road map of the area corresponding to the estimated position data is read out from a road map memory 5 made up of an M, etc. via a memory drive 6, and the estimated position is displayed together with this road map on a display unit 7 such as a CRT. A console 8 equipped with a key input section and the like is provided in conjunction with the display section 7, and various instruction input operations can be performed. From the position detection unit 3, along with the estimated position data, direction data representing the traveling direction of the vehicle (hereinafter referred to as "vehicle direction") is also transmitted.
The information is given to the control section 4, and the direction of the vehicle is also displayed on the display section 7 at the same time.

The position detection in the position detecting section 3 is performed by the above-mentioned dead reckoning, and by matching the estimated position obtained by this dead reckoning with the road map read out from the road map memory 5 via the memory drive 6. This is done in combination with the matching method. This map matching method is a technology that corrects the estimated position to the position on the road map by utilizing the fact that the current position of the vehicle is always one point on the road.

The road map memory 5 stores road data consisting of combinations of nodes and links. A node is a predetermined coordinate position on a road map, and is set at a branch point, a bend in a road, or the like. Further, a link corresponds to a road connecting nodes, and in principle, a vehicle can only take a coordinate position on this link. Road data consists of node data and link data. The node data consists of the node number and the address of the link connected to the node, and the link data includes the link number, the addresses of the start and end nodes of the link, the distance of the link, and the direction in which the vehicle passes through the link. It consists of direction, road type, etc. In this embodiment, using the above link direction, the gyro 1
The offset value for offset correction is updated as appropriate.

The detection of the direction of the vehicle by the position detecting section 3 will be described in detail below. The direction of the vehicle is detected solely based on the output of the gyro 1, as described above. The output of the gyro 1 includes an offset that is an output when the turning angular velocity of the vehicle is zero. This offset value is stored in the offset memory 11, and the position detection unit 3 performs offset correction by subtracting the offset stored in the offset 11 from the output of the gyro 3, and uses the value obtained as a result of this offset correction. By accumulating, the amount of change in direction of the vehicle is detected. Therefore, by giving the initial direction from the console 8, etc.,
The direction of the vehicle will be detected.

On the other hand, since the offset value has the property of drifting due to changes in temperature and humidity, if a constant offset value stored in the offset memory 11 is always used, the error due to the above drift will accumulate. This causes a large error in the detected direction. Therefore, it is necessary to appropriately detect a correct offset value with the drift amount corrected, and perform offset correction using this new offset value. It is preferable that such offset value updates be performed at as short time intervals as possible; if a constant offset value is used for a long period of time, a large error may occur in the detected orientation.

When the vehicle stops at a traffic light, etc., the true turning angular velocity during this stop is zero, so the output of the gyro 1 during this stop is set to the previous offset value OF(N-1).
The value corrected by is the offset drift amount ΔOF itself. Therefore, each time the vehicle stops, the position detection unit 3 detects the offset drift amount ΔOF based on the offset-corrected output of the gyro 1, and calculates a new offset value O by correcting this offset drift amount ΔOF.
F(N) is determined and the value stored in the offset memory 11 is updated to the new offset value OF(N).

On the other hand, when the vehicle is traveling on a highway or the like, the continuous traveling time of the vehicle becomes long, so it is necessary to update the offset value to a new value even while the vehicle is traveling. FIG. 3 is a flowchart for explaining processing for updating the offset value when the continuous running time becomes long. The position detection unit 3 includes a CPU and the like therein, and correction of the offset value is realized by software processing. In step s1, it is determined whether the vehicle is running based on the output of the vehicle speed sensor 2, and if the vehicle has stopped, the process returns after step s12, and the offset value when the vehicle has stopped is determined. Update processing is performed.

In step s2, the degree of correlation between the trajectory of the estimated vehicle position detected by dead reckoning or the like and links in the vicinity of this estimated position is calculated. Then, it is determined whether there is a link having a predetermined correlation and therefore a matching state exists in which the link and the trajectory of the estimated position match well. If there is no matching state, the process returns after the process of step s12.

If it is determined in step s2 that a matching state exists, the count value C of the continuous running counter 16 is incremented in step s3. That is, the continuous running counter 16 performs a counting operation only when the vehicle is running and in the matching state.In step s4, it is determined whether the count value C of the continuous running counter 16 is 1. . If the count value C is 1, in step s5, the link direction of the link corresponding to the current position of the vehicle at that time is stored in a predetermined storage area of the memory 15 inside the position detection unit 3 as the first direction d1. be done. If the count value C is a value other than 1, the process advances to step s6.

In step s6, the output of the gyro 1 is accumulated. This accumulated output of the gyro 1 has been subjected to offset correction based on the offset value stored in the offset memory 11. In step s7,
It is determined whether the count value C of the continuous running counter 16 is equal to a predetermined value M corresponding to a predetermined time T (for example, 300 seconds). If the count value C of the continuous running counter 16 is not the predetermined value M, the process returns and the operations from step s1 are repeated. Further, if the count value C is equal to the predetermined value M, the process proceeds to step s8.

In step s8, the link direction of the link corresponding to the current position of the vehicle at that time is stored in the memory 15 inside the position detecting section 3 as the second direction d2. Through the processing of steps s1 to s7, the second orientation d2 is determined by the fact that after the first orientation d1 is stored, the vehicle continuously travels for a predetermined period of time T, and the matching state is maintained during this period. It will be remembered only if it continues.

At step s9, the first detected orientation d2 stored at step s5 is subtracted from the second orientation d2 stored at step s8, thereby determining the difference in orientation detected at the time interval of the predetermined time T. Desired. This value becomes the amount of change in direction ΔD1 of the vehicle at the time interval of the predetermined time T. This azimuth change amount ΔD1 corresponds to the first azimuth change amount. This first direction change amount ΔD1 is based on the accurately determined link direction, and the link is selected based on the estimated position in the matching state, so it is a highly accurate value. .

On the other hand, the integrated value of the output of the gyro 1 after offset correction during the predetermined time interval T becomes the second azimuth change amount ΔD2. This second azimuth change amount ΔD2 includes an integrated value Σ of the offset drift amount ΔOF due to changes in humidity, temperature, and the like. On the other hand, by accumulating the offset-corrected output of the gyro 1 over a period of time equal to or longer than the predetermined time T, noise components caused by vibrations while the vehicle is running are almost canceled out. Therefore, the difference between the second azimuth variation ΔD2 obtained by accumulating the values after the offset correction of the output of the gyro 1 and the first azimuth variation ΔD1 obtained based on the link azimuth is determined by the predetermined time T. It corresponds to the integrated value Σ of the drift amount ΔOF in the time interval of .

It is preferable that the offset value OF be updated at as short a time interval as possible, and for this purpose, it is necessary to make the predetermined time T as short as possible. However, when considering the removal of noise caused by vibrations during running, it is appropriate to select the predetermined time T to be about 300 seconds as described above. In step s10, the above two azimuth changes Δ
An integrated value Σ of the drift amount ΔOF is obtained from D1 and ΔD2, and the drift amount ΔOF is further calculated based on this integrated value Σ. As shown in FIG. 4, this drift amount ΔOF is calculated based on the assumption that the offset drift amount ΔOF at the time of the previous offset value correction (time t1) is zero, and from this point on, the offset drift amount ΔOF is proportional to the passage of time. This is done on the assumption that the value increases monotonically. That is, since the integrated value Σ corresponds to the area of the shaded region in FIG. 4, the offset drift amount ΔOF is calculated based on the following equation (2).

[0033]

[Math 1]

In equation (2), t represents time, time t1 is the time when the link direction is first stored in step s5, and time t2 is the time when the link direction is stored second in step s9. This is the time when the direction was memorized. The time interval ΔT is equal to the predetermined time T described above. From the above equation (2), the offset drift amount ΔOF can be obtained from the following equation (3).

[0035]

[Math 2]

In step s11, offset memory 1
1, the previous offset value OF(N-1) is read out, and a new offset value OF(N) is calculated based on this offset value OF(N-1). This new offset value OF(N) will be stored in the offset memory 11. New offset value OF(N)
is simply, OF(N) =OF(N-1
) +ΔOF
(4) However, in this embodiment, a new offset value OF(N) is calculated according to the following equation (5).

OF(N) = (1-K)・OF(N-1
) +K・(OF(N-1) +ΔOF)
However, 0≦K≦1.
(5) In this way, by applying a so-called filter to update the offset value OF, it is possible to update the offset value with higher certainty. That is, as described above, the offset value is updated on the assumption that the offset drift amount ΔOF changes linearly as shown in FIG.
The actual change in the offset drift amount ΔOF over time is complicated, and may exhibit changes as shown in FIG. 5, for example. Therefore, there may be a large difference between the true offset drift amount ΔOF and the offset drift amount ΔOF obtained according to the above equations (2) and (3). If you update the offset value OF using a calculated value that deviates greatly from the true value, the offset value OF may be updated to a value that is too large or conversely to a value that is too small each time the offset value is updated. The updating operation will be repeated. In such a situation, if matching with the map is no longer possible, offset correction will be performed using the incorrect offset value OF until the vehicle stops, resulting in a larger orientation detection error than if no processing was performed during continuous driving. There is a risk that this may occur.

Furthermore, since the offset value OF updated using the offset drift amount ΔOF that includes an error includes a large error, the offset value OF(N) that includes such a large error is updated. There is no guarantee that the next offset value OF(N+1) to be updated will be updated to the correct value. Therefore, by applying the filter as described above, it is possible to update the offset value with higher certainty.

As a result of a simulation conducted by the inventor of the present invention, it is considered that the value of K is approximately 0.4 to 0.6. When the value of K is set to 0.1 to 0.3, the update amount of the offset becomes small, so the effect of calibration during running becomes small. Also, set the value of K to 0.
If it is 7 or more, the offset value will become too large or too small, and the direction detection error will become larger.

After the offset value OF is updated in step s11, the count value C of the continuous running counter 16 is cleared in step s12, and the gyro 1
The integrated value of the output after offset correction is cleared. At the same time, the first and second orientations d1 and d2 stored in the memory 15 are cleared. As described above, according to this embodiment, when the vehicle continuously travels for a predetermined time T, the link direction read from the road map memory 5 is used to detect the amount of change in direction ΔD1 at the time interval of the predetermined time T. On the other hand, the output of the gyro 1 after offset correction is integrated to detect the azimuth change amount ΔD2. and,
An offset drift amount ΔOF is determined based on the two azimuth changes ΔD1 and ΔD2, and the offset value OF is updated using this offset drift amount ΔOF. In this way, even if the vehicle is running continuously for a long time, the offset value can be updated while the vehicle is running. For example, even when driving on a highway, the offset value can be updated based on the output of gyro 1. It is possible to prevent a large error from occurring in the detected direction of the vehicle. This results in
This can also contribute to improving the accuracy of detecting the position of the vehicle, and the current position of the vehicle and the direction of travel of the vehicle can be accurately displayed on the display 7. In addition, the above-mentioned Japanese Patent Application Publication No. 6
Unlike the prior art disclosed in Japanese Patent No. 3-182519, the offset value can be updated even when the vehicle is not traveling on a straight road.

However, when the vehicle stops, the offset value OF is updated based on the output of the gyro 1 at the time of this stop. This is because the offset value can be determined more directly and accurately than by determining the offset value using the link orientation. FIG. 6, FIG. 7, and FIG. 8 are diagrams showing test results by the inventor of the present invention. The test was conducted by driving continuously on a highway for about 50 minutes. FIG. 6 shows changes in the offset value OF over time. The predetermined time T is 300 seconds, and the constant K in equation (5) for updating the offset value is 0.5. Table 1 shows the azimuth change amount difference (difference between the first and second azimuth change amounts ΔD1 and ΔD2) and the newly determined offset value based on this azimuth change amount for each time interval.

[0042]

[Table 1]

FIG. 7 shows the difference between the azimuth detected by performing offset correction of the gyro output using the offset values sequentially updated as described above and the accurate azimuth measured in advance at each point on the road. (i.e. orientation error) over time is shown. From FIG. 7, it is understood that the azimuth error during continuous running for 50 minutes is suppressed to about 50 degrees. Table 2 shows the angular difference that occurred at each time interval of 300 seconds and the cumulative angular difference obtained by accumulating these angular differences. The orientation error depicted in FIG. 7 corresponds to the cumulative angular difference.

[0044]

[Table 2]

FIG. 8 shows the time change in the orientation error, which is the difference between the detected orientation based on the gyro output after offset correction and the previously measured orientation, when the offset value is not updated while driving on the expressway. It is shown. This figure 8
From this, it can be seen that if the offset value is not updated while the vehicle is running, an azimuth detection error of about 300 degrees will occur after 50 minutes of running. The angular difference and cumulative angular difference (corresponding to the azimuth error) at each time point corresponding to FIG. 8 are shown in Table 3 below.

[0046]

[Table 3]

Next, another embodiment of the present invention will be described. In the first embodiment described above, the output of the gyro 1 is offset-corrected, and the second azimuth change amount ΔD2 obtained by integrating the value after this offset correction is used as the first azimuth obtained based on the link azimuth. The offset drift amount ΔOF is calculated by comparing with the change amount ΔD1. In contrast, in this embodiment, the output of the gyro 1 before offset correction is integrated. The difference between the integrated value of the output of the gyro 1 before offset correction and the azimuth change amount ΔD1 calculated based on the link azimuth is the integrated value of the offset including the offset drift amount ΔOF. Therefore, for example, assuming that the offset drifts linearly over time as shown in FIG. 9, the integrated value S of the offset corresponds to the area of the shaded region in FIG. therefore,

[
0048

[Math 3]

Therefore, the new offset value OF(N
) is obtained from the above-mentioned integrated value S and the previous offset value OF(N-1) stored in the offset memory 11 by the following equation (7).

[0050]

[Math 4]

Even in this case, as in the case of the first embodiment, when the continuous running time reaches the predetermined time T, the offset value is updated to the correct value even while the vehicle is running. Therefore, the direction of the vehicle can be detected accurately. Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, an example was described in which the present invention is applied to a navigation device that detects the direction of a vehicle, but the present invention can be widely used to detect the direction of other moving bodies such as ships and aircraft. It is something. Various other changes can be made without departing from the gist of the invention.

[0052]

As described above, according to the azimuth detecting method and azimuth detecting device of the present invention, even when a moving object continues to move continuously for a long time, the offset included in the output of the turning angular velocity sensor can be reduced. The previous offset value can be updated to the correct offset value by appropriately detecting fluctuations in the offset value. Thereby, offset correction of the turning angular velocity sensor can be performed favorably, and orientation detection accuracy can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a direction detection device to which a direction detection method of the present invention is applied.

FIG. 2 is a block diagram showing the basic configuration of a navigation device to which a direction detection method according to an embodiment of the present invention is applied.

FIG. 3 is a flowchart for explaining an operation for updating an offset value.

FIG. 4 is a diagram for explaining a method of calculating an offset drift amount.

FIG. 5 is a diagram showing changes over time in an actual offset drift amount.

FIG. 6 is a diagram showing temporal changes in offset values in tests conducted by the inventor of the present invention.

FIG. 7 is a diagram showing changes in orientation error over time in tests conducted by the inventor of the present invention.

FIG. 8 is a diagram illustrating changes in orientation error over time when the prior art is applied.

FIG. 9 is a diagram for explaining a method of calculating an offset value.

[Explanation of symbols]

21 Turning angular velocity sensor 22 Correction means 23 Offset updating means 24 Current position detection means 25 Map memory 27 Determination means 28 Movement/stop determination means 29 Travel time measurement means 31 First storage means 32 Second storage means 41 First direction Change amount detection means 42 Second azimuth change amount detection means 1 Gyro (turning angular velocity sensor) 2 Vehicle speed sensor 3 Position detection section (current position detection means, correction means,
(determination means, first azimuth change amount detection means, second azimuth change amount detection means, offset update means) 4 Control section 5 Road map memory 11 Offset memory 15 Memory (first storage means, second storage means) 1
6 Continuous running counter

Claims (4)

[Claims] Claims 1. Direction detection that corrects an offset included in the output of a turning angular velocity sensor that detects the turning angular velocity of a moving object, and detects the heading of the moving object based on the output of the turning angular velocity sensor after this offset correction. In the method, the current position of the moving object is detected, and when the locus of the detected position and the link corresponding to the path along which the moving object can move have a predetermined correlation, a matching state is determined, and the matching state is determined. When it is determined that the link direction is the direction in which the moving body moves through each link, the link direction of the link corresponding to the detected current position is stored as the first direction, and this first direction is After the direction is memorized, it is determined whether the moving object has been moving continuously for a predetermined period of time, and it is determined that the moving object has been moving continuously for the predetermined period, and the matching state is maintained throughout this period. The link orientation of the link corresponding to the current position of the moving object at the time when it is determined that Detecting the cumulative value of the output of the turning angular velocity sensor after the offset correction or before the offset correction in a period corresponding to the first azimuth change amount as a second azimuth change amount;
An azimuth detection method characterized by updating an offset value for offset correction based on the first azimuth change amount and the second azimuth change amount. 2. Direction detection according to claim 1, wherein when the moving object stops, the offset value is updated based on the output of the turning angular velocity sensor before or after the offset correction while the moving object is stopped. Method. 3. A turning angular velocity sensor that detects the turning angular velocity of a moving body, and a correction means for correcting an offset included in the output of the turning angular velocity sensor, and based on the output of the correction means, the moving body In an orientation detection device that detects the orientation of a map, there are links that connect nodes that are predetermined coordinate positions on a map, and that correspond to routes along which a mobile object can move, as well as links that connect nodes that are predetermined coordinate positions on a map. A map memory that stores a link direction, which is a direction, for each link, a position detection means that detects the current position of a moving object, a trajectory of a detected position by this position detection means, and one of the links stored in the map memory. and determining means for determining that a matching state exists when there is a predetermined correlation between the
a first storage means for storing, as a first orientation, the link orientation corresponding to the current position of the mobile object at the time when the matching state is determined; means for determining whether the moving body has been continuously moving for a predetermined period of time; and a means for determining whether the movable object has been continuously moving for the predetermined period after storing the first direction, and the matching state is maintained for the period. a second storage means for storing, as a second orientation, the link orientation corresponding to the current position of the moving body at the time when it is determined that the moving object is continuing; a first azimuth change amount detection means for detecting the azimuth change amount; and an output of the correction means or the turning angular velocity sensor during a period corresponding to the first azimuth change amount detected by the first azimuth change amount detection means. a second azimuth change amount detection means for detecting the cumulative value of as a second azimuth change amount; and an offset value in the correction means is updated based on the first azimuth change amount and the second azimuth change amount. An azimuth detection device comprising: offset updating means. 4. A claim further comprising means for updating an offset value, when the moving object stops, based on the output of the turning angular velocity sensor or the output of the correcting means before the offset correction while the moving object is stopped. The direction detection device according to item 3.