JPH04346023A - Method and apparatus for detecting bearing - Google Patents

Abstract

PURPOSE:To detect the correct bearing by updating the offset value appropriately and excluding the effect of the drift of the offset even if a vehicle continues to run for long time. CONSTITUTION:The bearing of a vehicle is detected by correcting the output of a gyroscope 1 with an offset value which is stored in an offset memory 11. When the vehicle continuously runs for specified time or longer, a position detecting part 3 obtains the first bearing-change amount based on the bearing information which is imparted from a GPS receiver 9. In the position detecting part 3, the value after the offset correction for the outputs of the gyroscope 1 during a period corresponding to the first bearing-change amount are accumulated. The accumulated value is made to be the second bearing-change amount. Furthermore, the position detecting part 3 computes the new offset value based on the first bearing-change amount and the second bearing-change amount and stores the new offset value into the offset memory 41.

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. For this reason, a certain offset value determined while stopped or while driving on a straight road,
Even if the output of the turning angular velocity sensor while the vehicle is running is corrected, the value after offset correction will contain an error due to the above-mentioned drift.

[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, azimuth detection means 25 is provided which receives radio waves from a predetermined artificial satellite 24 and detects the azimuth of the moving body. This direction detection means 25
For example, the direction may be detected by using the fluctuation in the frequency of the radio waves received from the artificial satellite 24 due to the Doppler effect caused by the movement of a mobile object, or the direction may be detected by other methods. It may be something you do.

[0011] The accuracy of azimuth detection by the azimuth detecting means 25 is determined by the accuracy determining means 26 as to whether or not it is higher than a predetermined accuracy. The accuracy determining means 26 makes the above determination based on, for example, the reception status of radio waves from the artificial satellite 24 and whether the output of the speed sensor 27 that detects the speed of the moving object is equal to or higher than a predetermined value. . That is, when azimuth detection using the Doppler effect is performed, changes in the reception frequency become more noticeable as the moving speed of the moving body increases, and the influence of errors can be eliminated and azimuth can be detected with high precision.

[0012] The output of the speed sensor 27 is given to movement/stop determination means 28, which determines whether the moving body is moving or stopped. This determination result is determined by the offset updating means 2.
In addition to being given to 3, it is also given to a moving time measuring means 29 that measures the time during which the moving body is continuously moving. When the accuracy determining means 26 determines that the detected orientation by the orientation detecting means 25 is equal to or higher than the predetermined orientation, the detected orientation at this time is stored in the first storage means 31 as the first detected orientation. After the first detection direction is stored in the first storage means 31, when a predetermined time is measured by the movement time measuring means 29, that is, when the moving body moves continuously for a predetermined time, After that, accuracy determination means 2
6 determines that the orientation detection accuracy of the orientation detection means 25 is equal to or higher than a predetermined value, the output of the orientation detection means 31 is stored in the second storage means 32 as the second detected orientation. Note that the first storage means 31 and the second storage means 32 may be configured using separate memory elements, or may be configured using different storage areas of the same memory element.

The first detection orientation and the second detection 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 detected azimuth and the second detected azimuth. On the other hand, the output of the correction means 22 is given to the second azimuth change amount detection means 42. The second azimuth change amount detection means 42 detects a second azimuth change amount corresponding to the first azimuth change amount by accumulating the output of the correction means 22. That is, the second direction change detection means 42 starts accumulating the output of the correction means 22 at the timing when the first storage means 31 stores the first detected direction, and the second storage means 32 starts accumulating the output of the correction means 22 at the timing when the first storage means 31 stores the first detected direction. The accumulation is stopped at the timing when the detected direction is memorized, and the cumulative value at that time is used as the second
is given to the offset updating means 23 as the 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 change amount is determined based on highly accurate detected azimuths detected at time intervals longer than a predetermined time measured by the travel time measuring means 29, this first azimuth change amount is true. The value is extremely close to that of . 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 period of time longer than the predetermined time measured by the travel time measuring means 29, it is possible to detect vibrations of the moving object. Noise components other than the offset drift amount 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 offset value based on the output of the correcting means 22 given from the line 36. Good too. 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, it is the artificial satellite 2 that updates the offset value based on the output of the correction means 22.
Rather than finding the offset value using radio waves from 4,
This is because the offset value can be determined directly and accurately. 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.

[0017]

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.

The position detection unit 3 provides the estimated position data as well as azimuth data representing the traveling direction of the vehicle (hereinafter referred to as “vehicle azimuth”) to the control unit 4, and the display unit 7 simultaneously displays the azimuth of the vehicle. Is displayed. The position detection unit 3 includes a GPS (Global Position
oning System) receiver 9 is connected. This GPS receiver 9 includes GPS satellites 10a to 10d that orbit in a predetermined orbit around the earth and emit time information, etc.
The current position of the vehicle is detected by measuring the propagation delay time of radio waves from the vehicle, and the detected position data is provided to the position detection unit 3. The GPS receiver 9 also provides the position detection section 3 with azimuth information indicating the azimuth of the vehicle. That is, when the vehicle moves, the GPS
The reception frequency of radio waves from the satellites 10a to 10d varies depending on the vehicle speed. Therefore, by monitoring the frequency of the received radio waves from each of the satellites 10a to 10d, the direction of the vehicle is detected, and the detected direction is provided to the position detecting section 3. Changes in the reception frequency due to the Doppler effect become more pronounced as the vehicle speed increases, so the faster the vehicle speed, the higher the direction detection accuracy becomes.

On the other hand, the GPS receiver 9 has four GPS
If radio waves from three of the satellites 10a to 10d can be received, so-called two-dimensional positioning excluding altitude is possible, and if radio waves from four satellites can be received, three-dimensional positioning including altitude is possible.
Dimensional positioning is possible. The GPS receiver 9 provides the position detection unit 3 with information indicating whether two-dimensional positioning, three-dimensional positioning is being performed, or whether any positioning is impossible. A state in which no positioning is possible means that only radio waves from two or fewer GPS satellites are received, such as when the vehicle is driving in the shadow of a building, or when radio waves from any of the satellites are received. This is a case where radio waves cannot be received.

[0021] 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 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, the direction of the vehicle is detected by giving the initial direction from the console 8 or the like, or by using the direction information given from the GPS receiver 9 as an initial value.

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 and updates the offset value when the vehicle has stopped. .

If the vehicle is running, in step s2, the direction information from the GPS receiver 9 is determined based on the information indicating the positioning accuracy from the GPS receiver 9 and the vehicle speed detected by the vehicle speed sensor 2. It is determined whether the accuracy is greater than or equal to a predetermined accuracy. This predetermined accuracy means that the GPS receiver 9 is performing three-dimensional positioning, and the vehicle speed is a predetermined value V.
It means the above. The reason why the vehicle speed is required to be equal to or higher than the predetermined value V is because the direction detection uses the Doppler effect as described above. Therefore, when the accuracy of the direction information is less than the predetermined accuracy, for example, when driving in a built-up area,
Due to poor reception of radio waves from S satellites 10a to 10d, 2
There are cases where only dimensional positioning is possible, cases where positioning is impossible, etc. Furthermore, if the vehicle speed detected by the vehicle speed sensor 2 is less than the predetermined value V, it is also determined that the accuracy is poor. If we consider offset correction while driving on a highway, the predetermined value V is, for example, 60 to 80 (km
/h) may be selected. For example, if the vehicle speed is 50 (
km/h), the direction detection error is about 6 degrees, and if the vehicle speed is 100 (km/h), the direction detection error is about 1 degree.

If it is determined in step s2 that the orientation detection accuracy is not higher than the predetermined accuracy, the process returns and the processing from step s1 is repeated. If it is determined in step s2 that the orientation detection accuracy is equal to or higher than the predetermined accuracy, then in step s3, the orientation information from the GPS receiver 9 is stored in the internal memory 15 of the position detection unit 3 as the first detected orientation d1. is stored in a predetermined storage area.

Next, in step s4, it is determined whether the vehicle is running, and if the vehicle is not running, step s1 is executed.
If the vehicle is running, the process proceeds to step s5, where a continuous running counter 1 for measuring continuous running time is counted.
The count value C of 6 is incremented. Then, 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, the continuous running counter 16
It is determined whether the count value C of is greater than or 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 less than the predetermined value M, the process returns to step s4, and if the count value C is greater than or equal to the predetermined value M, the process proceeds to step s8. In step s8, in the same manner as in step s2, it is determined whether the accuracy of the azimuth information from the GPS receiver 9 is greater than or equal to a predetermined accuracy, and if it is less than the predetermined accuracy, the process returns to step s4. .

[0030] In step s8, if it is determined that the accuracy of the direction information from the GPS receiver 9 is higher than a predetermined accuracy,
In step s9, the azimuth information from the GPS receiver 9 at this time is stored in a predetermined storage area of the memory 15 as the second detected azimuth d2. Also, the second detection direction d2
, the accumulation of the output of the gyro 1 (value after offset correction) is stopped.

[0031] Then, in step s10, step s
By subtracting the first detection orientation d2 stored in step s3 from the second detection orientation d1 stored in step 9, the difference between the orientations detected at time intervals longer than the predetermined time T is determined. This value becomes the amount of change in direction ΔD1 of the vehicle at a time interval longer than the predetermined time T. This azimuth change amount ΔD1 corresponds to the first azimuth change amount. This first azimuth change amount ΔD1 is a highly accurate value because it is based on the detected azimuth when the azimuth information from the GPS receiver 9 is highly accurate.

On the other hand, the integrated value of the output of the gyro 1 after offset correction in a time interval longer than the predetermined time T becomes the second azimuth change amount ΔD2. This second direction change amount ΔD2
includes the integrated value Σ of the offset drift amount ΔOF due to changes in humidity and temperature. 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 second azimuth change amount ΔD2 obtained by accumulating the value after offset correction of the output of the gyro 1 and the first azimuth change amount ΔD obtained from the azimuth information from the GPS receiver 9.
The difference from 1 corresponds to the integrated value Σ of the drift amount ΔOF in a time interval longer than the predetermined time T.

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 s11, the two orientation 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).

[0034]

[Math 1]

Note that in equation (2), t represents time, time t1 is the time when the direction information from the GPS receiver 9 is first stored in step s3, and time t2 is the time when the direction information from the GPS receiver 9 is first stored in step s3. This is the time when the orientation information is stored second in s9. The time interval ΔT is the time from when the continuous running counter 16 detects that the vehicle is in a continuous running state for a predetermined time T until the point in time when the direction detection accuracy is determined to be equal to or higher than the predetermined accuracy. , which is longer than the predetermined time T.

From the above equation (2), the offset drift amount ΔOF can be obtained from the following equation (3).

[0037]

[Math 2]

In step s12, 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, and the detection of the current position will be better than performing any processing during continuous driving. There is a risk that a large error may occur.

Furthermore, since the offset value OF updated using the offset drift amount ΔOF that includes an error will include a large error, it is updated based on the offset value OF(N) that includes such a large error. 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.

[0041] 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 s12, the count value C of the continuous travel counter 16 is cleared in step s13, and the gyro 1
The integrated value of the output after offset correction is cleared. At the same time, the first and second detection directions d1 and d2 stored in the memory 15 are cleared. As described above, according to this embodiment, when the vehicle is continuously traveling for a predetermined time T or longer, highly accurate azimuth information from the GPS receiver 9 is used to determine the azimuth at time intervals of the predetermined time T or longer. The amount of change ΔD1 is detected, and on the other hand, the output of the gyro 1 after offset correction is integrated to detect the amount of change ΔD2 in direction. Then, an offset drift amount ΔOF is determined based on the two azimuth change amounts 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 can also contribute to improving the accuracy of detecting the position of the vehicle, and the current position of the vehicle and the direction in which the vehicle is traveling can be accurately displayed on the display 7. Also,
The offset value can be updated even when the vehicle is not traveling on a straight road, unlike the prior art disclosed in Japanese Patent Application Laid-Open No. 63-182519.

However, when the vehicle stops, the offset value OF is updated based on the output of the gyro 1 at the time of the stop. This is because the offset can be determined more directly and accurately than by determining the offset value using the azimuth information from the GPS receiver 9. Next, other embodiments 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 Δ is obtained by integrating the value after this offset correction.
The offset drift amount ΔOF is calculated by comparing D2 with the first azimuth change amount ΔD1 obtained based on the azimuth information from the GPS receiver 9. In contrast, in this embodiment, the output of the gyro 1 before offset correction is integrated. The integrated value of the output of gyro 1 before this offset correction,
The difference from the azimuth change amount ΔD1 calculated from the azimuth information from the GPS receiver 9 becomes an integrated value of offsets including the offset drift amount ΔOF. Therefore, for example, assuming that the offset drifts linearly over time as shown in FIG. 6, the integrated value S of the offset corresponds to the area of the shaded region in FIG. therefore,

[0044]

[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).

[0046]

[Math 4]

Even in this case, as in the case of the first embodiment, when the continuous running time exceeds the predetermined time T, the offset value is updated to the correct value even while the vehicle is running. Thus, the direction of the vehicle can be accurately detected. 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.

[0048]

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 drawings]

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 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 Artificial satellite 25 Direction detection means 26 Accuracy judgment means 27 Speed sensor 28 Movement/stop judgment means 29 Travel time measurement means 31 First storage means 32 Second storage means 41 1 azimuth change amount detection means 42 2nd azimuth change amount detection means 1 Gyro (turning angular velocity sensor) 2 Vehicle speed sensor 3 Position detection section (correction means, accuracy determination means, first
4. Control unit 5. Road map memory 9. GPS receiver (direction detection means) 10a, 10.
b, 10c, 10d GPS satellite 11 Offset memory 15 Memory (first storage means, second storage means) 1
6 Continuous running counter

Claims (5)

[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 direction of a moving object is detected based on radio waves from a predetermined artificial satellite,
The detected direction based on the radio waves from the artificial satellite when this direction detection accuracy is higher than a predetermined precision is defined as the first detection direction, and after detecting this first detection direction, the moving object continues for a predetermined period of time. to determine whether the vehicle is moving,
Based on the radio waves from the artificial satellite after it has been determined that the moving object has been moving continuously for the predetermined period of time, and when the direction detection accuracy based on the radio waves from the artificial satellite is equal to or higher than the predetermined accuracy. The detected azimuth is a second detected azimuth, a first azimuth change amount is detected from the first detected azimuth and the second detected azimuth, and after the offset correction in a period corresponding to the first azimuth change amount. Alternatively, the cumulative value of the output of the turning angular velocity sensor before offset correction is detected as the second azimuth change amount, and the offset value for offset correction is updated based on the first azimuth change amount and the second azimuth change amount. A direction detection method characterized by: 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 A direction detection device for detecting the direction of a moving body includes a direction detection means for detecting the direction of a moving object based on radio waves from a predetermined artificial satellite, and a direction detection device that detects whether the direction detection accuracy of the direction detection means is higher than a predetermined accuracy. an accuracy determining means for determining; a first storage means for storing the detected orientation of the orientation detecting means when the orientation detection accuracy is equal to or higher than a predetermined accuracy as a first detected orientation; means for determining whether the moving body has been continuously moving for a predetermined time or more after the detection of the first detection direction; a second storage means for storing, as a second detection direction, the direction detected by the direction detection means when the direction detection accuracy is equal to or higher than a predetermined precision; a first azimuth change amount detection means for detecting a first azimuth change amount from the azimuth;
a second azimuth change amount detection that detects, as a second azimuth change amount, the cumulative value of the output of the correction means or the turning angular velocity sensor during a period corresponding to the first azimuth change amount detected by the azimuth change amount detection means; and offset updating means for updating an offset value in the correction means based on the first amount of change in direction and the second amount of change in direction. 4. The azimuth detecting means detects the azimuth of the moving object based on changes in the frequency of received radio waves caused by the Doppler effect as the moving object moves, and the accuracy determining means detects the azimuth of the moving object based on changes in the frequency of received radio waves caused by the Doppler effect as the moving object moves. Claim 3 characterized in that the accuracy of direction detection is determined based on the radio wave reception status and whether the speed of the moving object is equal to or higher than a predetermined value.
The orientation detection device described. 5. 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.