JP2580032B2 - Running direction detector for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a traveling azimuth detecting device for a vehicle that accurately detects the traveling azimuth of a vehicle.

(Prior Art) In recent years, various types of so-called navigation systems have been developed in which a destination point, a departure point, a running locus from the departure point, and a current position of a vehicle are displayed on a map.

In such a navigation system, a vehicle traveling direction detection device for detecting the traveling direction of the vehicle is incorporated.

Conventionally, as such a vehicle traveling direction detection device,
By using a combination of a geomagnetic sensor capable of detecting the absolute azimuth of the vehicle and a gyro sensor capable of detecting a relative azimuth change of the vehicle, the traveling azimuth of the vehicle can be accurately detected. (Japanese Patent Laid-Open No. 58-34)
No. 483).

Japanese Patent Application Laid-Open No. 58-151512 discloses a vehicle traveling position display device which accurately displays the position of the vehicle even at the start of driving. In this conventional example, when the vehicle is stopped and the power switch is turned off, a non-volatile memory is used as a storage device so that information related to the map number, the position of the vehicle, the traveling direction, and the traveling locus before the stop is not lost. The above-mentioned information is stored therein, and at the start of operation, the information is read out and displayed on the display device.

(Problems to be Solved by the Invention) However, in the case of such a conventional device, the absolute azimuth of the vehicle is determined as a reference of the azimuth of the vehicle, and the azimuth of the vehicle is determined with reference to a change in the relative azimuth of the vehicle. Therefore, when the error of the obtained absolute azimuth of the vehicle is large, there is a problem that the detection accuracy of the actual azimuth of the actual vehicle is significantly deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle azimuth detecting device that can accurately detect the actual azimuth of a vehicle.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides an absolute azimuth detecting means 101 for detecting an absolute azimuth of a vehicle, as shown in FIG. A relative azimuth detecting means 102 for detecting a relative azimuth of the vehicle, and a vehicle azimuth detecting device for calculating the azimuth of the vehicle based on the detected absolute azimuth and relative azimuth; A switch 103 for switching between operation and non-operation of the traveling azimuth detecting device, storage means 104 for storing the traveling azimuth of the vehicle, and when the switch 103 is switched from non-operation to operation, the information is stored in the storage means 104. The running azimuth of the vehicle is read as an initial value, and the relative azimuth detecting means 102 is used as a reference based on the running azimuth of the vehicle.
First traveling direction calculating means 105 for calculating the first traveling direction of the current vehicle based on the relative direction of the vehicle detected in step 105
When the switch 103 is switched from non-operation to operation, the absolute azimuth of the vehicle detected by the absolute azimuth detecting means 101 is input, and the relative azimuth detecting means 102 is input with reference to the absolute azimuth. Calculating a second running direction of the vehicle this time based on the relative direction of the vehicle detected in the second step.
When the switch 103 is switched from inactive to active, the first and second travel azimuth calculation means 105 and 106 calculate the first and second travel azimuth calculation means 105 and 106 respectively.
Are compared, and when the collation results match, the first traveling direction of the vehicle calculated by the first traveling direction calculating means 105 is compared.
Is determined as the actual azimuth of the vehicle, and if the collation results do not match, the second azimuth calculation means
Driving direction determining means 107 for determining the second driving direction of the vehicle calculated in 106 as the actual driving direction of the vehicle.

(Operation) According to the traveling azimuth detecting device for a vehicle according to the present invention, the first
As shown in the figure, when the switch 103 is switched from non-operation to operation, the first traveling direction calculating means 105 reads the traveling direction of the vehicle stored in the storage means 104 as an initial value, and reads the traveling direction. The first traveling direction of the current vehicle is calculated based on the relative direction of the vehicle detected by the relative direction detecting means 102 based on the traveling direction of the vehicle, while the second direction is calculated.
The traveling azimuth calculating means 106 inputs the absolute azimuth of the vehicle detected by the absolute azimuth detecting means 101, and calculates the relative azimuth of the vehicle detected by the relative azimuth detecting means 102 based on the absolute azimuth. Based on this, the second traveling direction of the vehicle is calculated. Then, when the switch 103 is switched from non-operation to operation, the traveling direction determination means 107
Calculated by both of the traveling azimuth calculating means 105 and 106
And the second traveling direction is collated, and when the collation results match, the first traveling direction of the vehicle calculated by the first traveling direction calculation means 105 is determined as the actual traveling direction of the vehicle, If the collation results do not match, the second traveling direction of the vehicle calculated by the second traveling direction calculating means 106 is determined as the actual traveling direction of the vehicle. Here, the case where the first running direction matches the second running direction means that the running direction of the vehicle does not fluctuate while the device is not operating, and in such a case, It is considered that the first running direction has a smaller error than the second running direction, while the first running direction and the second running direction do not match when the vehicle is not operating. Means the direction of travel has changed,
In such a case, it is considered that the second traveling direction has a smaller error than the first traveling direction. As described above, when the switch is switched from inactive to active, the first running direction and the second running direction are collated, and the running direction of the vehicle fluctuates during non-operation of the device based on the presence / absence of the same. It is determined whether or not the driving direction is determined to be small according to the determination result, and the selected direction is adopted as the driving direction of the actual vehicle. The detection accuracy of the traveling azimuth of the vehicle can be significantly improved.

Embodiment An embodiment according to the present invention will be described below in detail with reference to the drawings.

First, with reference to FIG. 2, the configuration of the vehicle traveling direction detecting device according to the present invention will be described.

The distance sensor 1 is, for example, a photoelectric sensor, an electromagnetic sensor, a mechanical contact sensor, or the like, and generates a pulse signal every time the vehicle travels a predetermined distance. The geomagnetic sensor 2 is an absolute azimuth detecting means shown in FIG. 1 for detecting an absolute running azimuth of the vehicle. The gyro sensor 3 is a relative azimuth detecting means shown in FIG. 1 for detecting a relative running azimuth of the vehicle, and outputs a signal proportional to the azimuth or the amount of change in the azimuth according to the running azimuth of the vehicle. It is a rate type gyro sensor.

The controller 5 is connected to each of the distance sensor 1, the geomagnetic sensor 2, the gyro sensor 3, and the display device 7. The controller 5 has arithmetic processing means such as a microcomputer, for example, and receives a pulse signal from the distance sensor 1 and counts the number of pulses of the input pulse signal to calculate the travel distance of the vehicle. Further, the controller 5 sequentially calculates the current position of the vehicle on the two-dimensional coordinates for each predetermined traveling distance based on the distance information and the direction information from the distance sensor 1, the geomagnetic sensor 2, and the gyro sensor 3.

The display device 7 includes, for example, a CRT display device, a liquid crystal display device, or the like, and displays information on a target point, a departure point, and the above-described current position of the vehicle, which are input by input means (not shown), along with a road map of the surrounding area. .

Further, the storage unit 9 and the buffers 11 and 13 are connected to the controller 5.

In the storage unit 9 as the storage means in FIG. 1, distance information, azimuth information, information on the current position of the vehicle, and the like are sequentially stored at predetermined time intervals or at predetermined traveling distances.
The storage unit 9 has a nonvolatile RAM (RANDOM ACCESS R).
EAD WRITE MEMORY), so that even after the ignition key is turned off, various kinds of information immediately before the ignition key is turned off are reliably stored.

The buffer 11 is a first running direction storage means for storing the first running direction, and calculates the information stored in the storage unit 9 as an initial value when the system is turned on, that is, when the ignition key is turned on. The running directions are sequentially stored.

The buffer 13 is a second running direction storage means for storing the second running direction. When the system is turned on, that is, when the ignition key is turned on, the running direction calculated by initial resetting the initial value is sequentially stored. It is memorized.

The controller 5 has counters 15a, 15b, 15c and 1
Each of 5d is connected.

Next, the overall control processing will be described with reference to the main flow of FIG.

First, at step 300, when the ignition switch is turned on, the system ON flag is set to 1. That is, the ignition switch corresponds to the switch in FIG. Next, in step 302, the vehicle azimuth θ stored in the storage unit 9, which is a nonvolatile memory, that is, the value of the previously calculated traveling azimuth θ is set as the traveling azimuth θ. Then set the absolute azimuth That geomagnetic direction theta _M read from the geomagnetic sensor 2 in step 304 as the running direction theta _S. Next, in step 306, the nonvolatile RAM, that is, the storage unit 9
The previous vehicle position (X, Y) stored in the vehicle is stored in the vehicle position (X, Y)
Set as

In step 308, the counts S, SS, SSS and SSSS of the counters 15a, 15b, 15c and 15d are initialized. When the initial process is performed in step 308, the process proceeds to step 310, where the current location is set by key operation of input means (not shown). As a result, the input current position and the map information of the surrounding area and the like are displayed on the display screen of the display device 7.

Next, in step 312, the interruption in steps 320 and 322 is permitted, whereby the following main loop is entered.

At step 314, it is determined whether or not the system is off. If the system is on, the control process of the main loop from step 316 is executed. When the current position of the vehicle has moved in response to the interrupt processing in step 320 and the interrupt processing in step 322, the main loop proceeds from step 316 to step 318, and the current position of the vehicle on the display screen of the display device 7 Is changed, and the map information of the surrounding area is updated.

If the system is in the off state in step 314, the process proceeds to step 324, and the traveling direction θ and the vehicle position (X, Y) at this time are stored in the storage unit 9.

Next, the interrupt processing in step 320 will be described in detail with reference to the flowchart of FIG.

The interrupt processing shown in FIG.
This is executed in correspondence with the pulse signal generated by the distance sensor 1 every time the vehicle travels on D. For example, the distance sensor 1 is a wheel 1
When 24 pulse signals are generated per rotation, the predetermined distance ΔD is set to be 6 to 7 cm.

In the interrupt processing shown in FIG. 4, four types of counters are used.
15a, 15b, 15c and 15d are used.

First, the counter 15c is a counter used for determining whether or not the vehicle is stopped. The count number SSS of the counter 15c is incremented by one every time an interrupt process is performed as shown in step 400.
It is incremented by one.

Further, the counter 15b and the counter 15a are counters used when calculating the traveling azimuth of the vehicle, and the count number SS of the counter 15b is set every time the interrupt processing is performed 12 times as shown in steps 404 and 406, that is, It is incremented each time the wheel makes a half turn. Also counter
The counter number S of 15a is incremented each time interrupt processing is performed once as shown in step 402. That is, the counter 15a is a counter for counting digits below the counter 15b. When the count number S of the counter 15a is incremented 12 times, that is, when the counter 15a counts 12 pulse signals, the count number SS of the counter 15b is increased. The value is incremented by +1.

The counter 15d is a counter for calculating the moving amount of the vehicle when calculating the current position of the vehicle. The count number SSSS of the counter 15d is incremented by +1 every time the interrupt processing is performed once as shown in step 410. Incremented.

The counter 15a is cleared to 0 in step 408, and the other counters are cleared to 0 after the count is read in the main routine.

Next, the interrupt processing in step 322 in FIG. 3 will be described in detail with reference to FIG.

The interrupt processing shown in FIG. 5 is executed every unit time ΔT, for example, every 100 ms.

First, in step 500, it is determined whether or not the vehicle is stopped based on the value of the count number SSS of the counter 15c.
When the count number SSS is 0, that is, when the vehicle is stopped, the traveling direction of the vehicle does not change. Therefore, the process proceeds to step 504 without performing the direction calculation process, and only the drift correction of the gyro sensor 3 is performed. Done. In consideration of the fact that the amount of angular velocity during stoppage is 0, the output value of the gyro sensor 3 at that time is used as the drift amount.

If the count number SSS is not 0 in step 500, that is, if the vehicle is moving, step 502
Then, the count SSS of the counter 15c is cleared to 0.

From step 506 to step 508, the azimuth information from the geomagnetic sensor 2 is processed. First, in step 506 reads the absolute running direction theta _M of the vehicle detected by the geomagnetic sensor 2. Then determine the difference △ theta _M with step 508 traveling azimuth theta _M and the previous traveling direction ShitaMOLD. The running direction θMOLD
Is the traveling direction calculated at the time of the previous interruption processing in step 534 as described later, and is sequentially stored in the storage unit 9.

Next, in steps 510 to 516, the direction information from the gyro sensor 3 is processed.

First, at step 510, each speed Ω _G from the gyro sensor 3 is read. Subsequently, at step 512, the azimuth change amount △ θ by the gyro sensor 3 since the previous interrupt processing is performed.
_G (△ θ _G = Ω _G × ΩT) is calculated.

The next step 514 and step 516 are to cut the azimuth change amount Δθ _G in a certain area. That is, the gyro sensor 3 has an error due to drift,
Even if the amount of drift for each time is small, errors increase due to repeated integration. Therefore, the azimuth change amount △
When the absolute value of θ _G is equal to or less than a predetermined value, for example, a value near 0,
Specifically, if the value is smaller than 0.3 (deg / sec) × △ T, by setting △ θ _G = 0 at step 516, the integration of the drift can be suppressed within a range that does not adversely affect the azimuth calculation. I have to.

Next, in step 517, it is determined whether or not the system-on flag is 1. If the system-on flag is 1, the process proceeds from step 517 to step 519, and a series of processes after the system is started is executed.

Next, a series of processes in step 519 shown in FIG. 5 will be described with reference to FIG.

In the process shown in FIG. 6, a first traveling azimuth θ calculated by using information stored in the storage unit 9 as an initial value when the system is turned on, and a first running direction θ calculated by initial resetting the initial value when the system is turned on. successively calculating a second travel direction theta _S, by matching the travel direction of these both if the result both traveling azimuth of the collation does not match, the second traveling direction or initial value initial reset This is to correct the traveling direction of the vehicle according to the calculated traveling direction value.

More specifically, in step 600, the previously calculated running direction θ is set as the running direction θ ₁ , and the absolute direction θ _S from the geomagnetic sensor 2 obtained after initial reset of the initial value is calculated as the running direction θ _1S Set as Subsequently, at step 602, the direction change Δθ _G by the gyro sensor 3 is added to the direction of travel θ ₁ , and this value is set as the direction of travel θ ₂ (processing of the first direction of travel calculation means in FIG. 1). And sets a value obtained by adding the azimuth variation △ theta _G by a gyro sensor 3 with respect to step 602 in the travel direction theta _1S as the running direction theta _2S (the second traveling azimuth calculation means of FIG. 1 processing).

Next, at step 604, a magnetic field environment index β which is an index indicating the degree of magnetic disturbance is calculated. The magnetic field environment index β is calculated by the following equation (1), and is obtained by calculating a difference between the output from the geomagnetic sensor 2 and the output from the gyro sensor 3 in a short distance or a short time, for example, It is an index indicating the disturbance of the magnetic field at a short distance of m.

β = | △ θ _G − △ θ _M | (1) The above-mentioned magnetic field environment index β has the following meaning.

That is, when the vehicle is traveling on an elevated road, for example, the output of the geomagnetic sensor 2 increases by a variation that changes every several meters. This is considered to be the effect of the metallic structural members of the elevated road.

Similarly, even when the vehicle is running under such an elevated road, the output of the geomagnetic sensor 2 has a variation that changes every several meters as the vehicle travels due to the influence of the elevated support member for supporting the elevated road. To increase. The magnetic field environment index β is intended to be captured as a numerical value indicating the disturbance of the magnetic field for each short traveling distance, and the output of the gyro sensor 3 and the output of the geomagnetic sensor 2 which are expected to be accurate at short distances Are compared and quantified.

Subsequently, at step 606, a magnetic field environment index γ is calculated as shown in the following equation (2).

γ = | θ ₂ −θ _M | (2) The magnetic field environment index γ is a disturbance of the magnetic field at a longer distance than the case of the above-mentioned magnetic field environment index β, for example, several tens to several hundreds of meters, that is, the geomagnetic sensor 2 This is an index that quantifies the degree of output disturbance. Such a disturbance in the output of the geomagnetic sensor 2 in a unit of several tens to several hundreds of meters is caused, for example, when the vehicle is running on a road parallel to a railway line or on a road where a subway is buried. It is thought to occur in the case.

Next, at step 608, a coefficient K is calculated as shown in the following equation (3).

The coefficient K is a coefficient for defining the speed at which brought closer to the traveling direction theta _M based traveling azimuth theta ₂ of the vehicle in the geomagnetic sensor 2.

Subsequently, at step 610, a coefficient K _S is calculated as shown in the following equation (4).

As is apparent from the equation (4), the coefficient K _S does not include the magnetic field environment index γ. This means that when the system is turned on, the initial value is initially reset and the second running direction θ _2S
This is for calculating.

Next, in step 612, the following steps 614 and 616 are repeated the number of times corresponding to the value of the count number SS.

In step 614 calculates a first travel direction theta ₂ as shown in the following first equation (5), calculating a second travel direction theta _2S as shown in equation (6).

_{θ 2 = K × (θ M} -θ 2) + θ 2 ... (5) θ 2S = K S × (θ M -θ 2S) + θ 2S ... (6) In step 616 the first traveling direction theta ₂ buffers 11 And the second traveling direction θ _2S is stored in the buffer 13.

In step 617, it is determined whether or not the processing in steps 614 and 615 has been repeated the same number of times as the value of the count number SS. Clear the value to 0.

Next, in step 620 in preparation for the next processing stores the other magnetic azimuth theta _M as ShitaMOLD.

Similarly traveling azimuth theta ₂ calculated in step 614 as described above in step 622 stores as theta, and stores the travel azimuth theta _2S as theta _S.

Next, at step 624, it is determined whether or not a predetermined amount of data has been stored in the buffers 11 and 13, that is, whether or not the vehicle has traveled a specified distance after the system is turned on. If the data is stored, the process proceeds to step 626.

In step 626, a set of running directions θ and θ _S are sequentially read from the buffers 11 and 13, and a difference between the set of running directions θ and θ _S is calculated. The calculation of the difference between such a set of data is performed for all the data numbers N stored in the buffers 11 and 13, and the average value W of these differences is calculated. The average value W of the difference as shown in (7) of the next step 626 it is determined whether or larger than a predetermined reference value W _S.

In step 626, if the value of the average difference W is larger than the reference value W _S , that is, if there is no match between the vehicle orientations θ ₂ and θ _2S , while the system is off, that is, the vehicle stops. It is determined that the azimuth of the vehicle has changed due to the rotation of the vehicle or the like, and the process proceeds to step 628.

In step 628 the initial value sets the value of the second traveling direction theta _S which is calculated by initial reset as the running direction theta of the vehicle.

In step 626, the value of the average value W of the difference is equal to the reference value W.
If the value is less than the value of _S , that is, if there is a match between the traveling azimuths θ ₂ and θ _2S , the process proceeds to step 630, and the system on flag is set to 0. That is, in steps 626 to 630, the processing of the traveling direction determining means 107 in FIG. 1 is executed.

Note The value of the reference value W _S in step 626 is set to, for example, 20 degrees.

Also, when a predetermined number of data is stored in the buffers 11 and 13 as described above, the vehicle orientations θ ₂ and θ _2S are collated, but this is an instantaneous value immediately after the system is turned on, for example, noise. This is to prevent an erroneous determination due to the above.

Referring again to FIG. 5, steps 518 to 5
Steps 18 to 532 are processes for normal traveling, that is, a process for calculating the traveling direction of the vehicle based on both direction information from the geomagnetic sensor 2 and the gyro sensor 3.

First, the traveling azimuth theta is the vehicle azimuth is obtained by the calculation up to the previous step 518 is set as theta _1. Note that the traveling azimuth θ is stored in the storage unit 9 for the next arithmetic processing in step 536 described later.

Next, at step 520, the azimuth change Δθ _G detected by the gyro sensor 3 is added to the running azimuth θ ₁ described above. This traveling azimuth theta ₂ obtained thereby is a value of the traveling direction of the vehicle that reflects the absolute direction detected by the gyro sensor 3.

Next, at step 522, the magnetic field environment index β is calculated based on the above-mentioned equation (1).

Similarly, in step 524, the magnetic field environment index γ is calculated by the above-described equation (2).

Next, at step 526, the coefficient K is calculated by the same formula as the above-mentioned formula (3).

In the equation (4), the magnetic field environment indices β and γ are the values obtained in steps 522 and 524 in FIG. 5 as described above, and α1, α2, α3, α4, n1, and n2 are constants. is there. The values of these constants are set, for example, as follows.

α1 = 0.58 α2 = 0.02 α3 = 2 α4 = 0.1 n1 = 6 n2 = 1 Substituting the values of these constants into the above-mentioned equation (3) gives the following equation (8).

The above equation (8) is expressed as the following equation (9).

And coefficient K is a coefficient K ₁ As is clear from the above as the (9), can be divided into a coefficient K _2, the value of the coefficient K ₁ is determined by the magnetic environment index beta, coefficient K ₂ Is determined by the magnetic field environment index γ. That is, when the magnetic field environment indexes β and γ increase, both the coefficients K ₁ and K ₂ decrease.

 The meaning of each constant described above is as follows.

When the disturbance of the geomagnetism is the least, that is, when the values of the magnetic field environment indices β and γ are both 0, the value of the coefficient K becomes maximum, but the constant α1 is used to define the upper limit value at this time. It is a constant, and the speed of approaching the azimuth based on the geomagnetic sensor 2, that is, the terrestrial magnetic azimuth increases as the value of the constant α1 increases.

Next, when the geomagnetism is disturbed by several meters, but when the geomagnetism is small over a long distance, that is, when the magnetic field environment index β is a large value and the magnetic field environment index γ is 0, the value of the constant α2 Defines the speed of approaching the geomagnetic azimuth according to. Therefore, the smaller the value of the constant α2, the lower the speed of approaching the geomagnetic azimuth, and the higher the dependence on the gyro sensor 3 becomes.

The constant α3 is a constant for defining how much the magnetic field environment index γ is reflected in the speed of approaching the geomagnetic direction. The larger the value of the constant α3, the smaller the magnetic field environment index γ is, which is reflected in the speed of approaching the value magnetic azimuth.
That is, the degree of dependence on the gyro sensor 3 is increased even when the value of the magnetic field environment index γ is small.

The constant α4 is a constant for adjusting the speed of approaching the geomagnetic azimuth as a whole.

Constant n1 is a constant for defining the characteristics of varying the coefficient K ₁ by the magnetic field environment index beta.

Constant n2 is a constant for defining the characteristics of the coefficient K ₂ is changed by a magnetic field environment index gamma.

Whether these constants n1 and n2 should change the value of the coefficient K gradually as the magnetic field environment index β or γ changes, or whether it is better to change rapidly around a predetermined value. Is determined by

Next, in step 528, and 530, is brought close to the geomagnetic direction theta _M to the traveling direction theta ₂ obtained was detected this time in step 520. The shift ratio at this time, that is, the ratio approaching each time the interruption process is performed every ΔT, is the coefficient K. Value is greater the closer to the geomagnetic direction theta _M speed of the coefficient K, i.e. the ratio increases closer.

For example, if K = 1 in step 530, then θ ₂ = 1 × (θ _M −θ ₂ ) + θ ₂ = θ _{M. After} passing through this routine once, the running direction θ ₂ is equal to the geomagnetic direction θ _M turn into. On the other hand, when K = 0, that is, when the value of the coefficient K is the minimum value, the geomagnetic azimuth is not reflected at all.

Therefore, the traveling azimuth of the vehicle approaches the geomagnetic azimuth when the value of the coefficient K is large, that is, when the value of the coefficient K is closer to one. Conversely, when the value of the coefficient K is small, that is, as the value of the coefficient K is closer to 0, the speed of approaching the geomagnetic azimuth decreases.

The traveling direction θ ₂ of the vehicle in step 530 as described above.
Is repeated by the count number SS of the counter 15b, that is, the number of times corresponding to the moving distance of the vehicle (step 528). When the value of the count number SS of the counter 15b is 0, that is, when the vehicle is stopped, the process proceeds from step 528 to step 532 without performing the process in step 530.

The reason why step 530 is repeated as many times as the number of times corresponding to the moving distance of the vehicle is that, in practice, the calculation is performed for each unit distance ΔT, but equivalently for each unit distance.
Ideally, the interrupt processing should be performed for each predetermined traveling distance. However, in practice, a method of obtaining the same effect as the calculation for each predetermined traveling distance by performing the interrupt processing for each unit time is practical. is there.

The above-described coefficient K is determined by the magnetic field environment indices β and γ as follows.

For example, if there is no terrestrial magnetic disturbance and the terrestrial azimuth is exactly the same as the movement of the gyro sensor 3, β = γ = 0, so that K ₁ = 0.6, K2 = 1.0, and thus K = 0.6. On the other hand, geomagnetic disturbance is large, for example, β = + 大 き く, γ =
In the case of + ＝, K = 0. If the state of K = 0 continues for a long time, the traveling azimuth is calculated only by the output from the gyro sensor 3, but in this case, the errors due to the draft of the gyro sensor 3 are integrated. However, since the value of the coefficient K actually takes a value between the maximum value 0.6 and the minimum value 0, it is almost impossible that the traveling azimuth is calculated only by the output from the gyro sensor 3. Hence the running direction theta of the vehicle in the long run approaches the geomagnetic direction theta _M errors due to drift of the gyro sensor 3 is canceled.

Referring to FIG. 5 again, in step 532, the value of the count number SS is reset to 0 to prepare for the next processing.
In step 534, the geomagnetic azimuth θ is prepared for the next process.
_M is stored as θMOLD.

Then register the theta ₂ calculated in step 530 as described above in step 536 as the running direction theta vehicle, the current position of the vehicle using the running direction theta of the vehicle at step 538 (X, Y) the rewriting . In step 540, the count number SSSS of the counter 15d for rewriting the current position of the vehicle is reset to zero.

Note the counter 15a with the travel azimuth theta is the heading of θMOLD and vehicle in the initial processing of the time of system startup Power is initialized by the geomagnetic direction θ _M, 15b, 15c and 15d each count number S of, SS , SSS, S
SSS is reset to 0.

Next, the effects of the embodiment according to the present invention will be described with reference to FIG.

FIGS. 7 (A), 7 (B), and 7 (C) show the case where the vehicle is rotated by a turntable or the like and the ignition key is turned off when parking in the parking lot at the point PA. This shows a case in which the vehicle direction and the vehicle direction when the ignition key was subsequently turned on significantly changed, and then the case where the ignition key was turned on from the point PA, that is, the system was turned on, and the vehicle was driven on a straight road. ing.

FIG. 7 (A) shows a case where there is no disturbance of the magnetic field, and the second value calculated by initial resetting the initial value even when the direction of the vehicle changes significantly at the point PA.
The running direction theta _S of indicate the same direction as the direction in which the traveling vehicle actually. On the other hand, the first running azimuth θ calculated using the information of the storage means storing the data immediately before the ignition key is turned off as an initial value is approaching the direction of the absolute azimuth which is the actual running azimuth.

As described above, when there is no coincidence between the running direction θ _S and θ after turning on the ignition key, the running direction of the vehicle is determined based on the running direction θ _S calculated by initial resetting the initial value. Since the correction is performed, the traveling direction of the vehicle can be accurately detected even when the vehicle rotates while the vehicle is stopped.

FIG. 7 (B) shows that the disturbance of the geomagnetism is a predetermined distance La, for example, several meters.
Are present in each of the periods. When the system is turned on at the point PA, the running azimuth θ _S is initialized by the absolute azimuth from the geomagnetic sensor 2,
Traveling azimuth theta _S occurs some deviation in accordance with the geomagnetic disturbances at this time. However the calculation of the running direction theta _S indicates the actual direction and substantially the same value which the vehicle is traveling after a lapse of some time because it is the consideration of only magnetic environment index beta.

Figure 7 (C) shows a case where the calculated also using a magnetic field environment index not magnetic environment index β only when calculating the traveling azimuth theta _S gamma.

That is, this is a case where the calculation is performed using the coefficient K calculated in step 608 instead of the coefficient K _S in the calculation formula of the traveling azimuth θ _2S shown in Expression (6).
_{If the} magnetic field environment index γ is also taken into account when calculating _S , the speed at which the vehicle approaches the actual traveling direction will decrease.

7 (D), 7 (E) and 7 (F) show that the ignition key is turned off at point PA, and then the ignition key is turned on without turning the vehicle. This shows a case where the vehicle has run.

FIG. 7D shows a case where the magnetic field is hardly disturbed. FIG. 7E shows a case where the magnetic field is disturbed by a predetermined distance La, for example, several m.
Are present in each of the periods. As is clear from FIGS. 7 (D) and 7 (E), when the vehicle is not rotated between the time when the ignition key is turned off and the time when the ignition key is next turned on. Is that the traveling azimuths θ _S and θ are almost the same value.

FIG. 7 (F) shows a case where the disturbance of the magnetic field exists in the vicinity of the point PA at a predetermined distance Lb, for example, at a period of several tens of meters to several hundreds of meters, and the traveling azimuth θ _S according to the disturbance of the magnetic field. Is not affected by the magnetic field disturbance.

Thus if the first and the traveling direction theta and second traveling azimuth theta _S coincide, that is, when such rotation of the vehicle is not made until then turns on the ignition key to the ignition key from the OFF operation The running azimuth θ calculated using the information stored in the storage unit 9, which is the information immediately before the ignition key is turned off, as an initial value.
Therefore, the actual azimuth of the vehicle can be detected more accurately.

Note sets a predetermined interval Lv for performing a seventh diagram (F) are shown as average, when configured to calculate the average value of the difference between the travel azimuth theta and theta _S in the interval Lv that this set And the reliability can be further improved.

In the embodiment shown in FIG. 2, a gyro sensor 3 is used as relative azimuth detecting means for detecting a relative azimuth.
However, the present invention is not limited to this, and can be configured using other sensors such as a two-wheel vehicle speed difference sensor or an appropriate relative azimuth detecting means such as a steering angle sensor. .

[Effect of the Invention] As described above, according to the traveling azimuth detecting device for a vehicle according to the present invention, when the switch is switched from non-operation to activation, the first traveling azimuth and the second traveling azimuth are changed. It is determined whether or not the traveling direction of the vehicle has changed during the non-operation of the apparatus from the presence or absence of the identity, and a traveling direction that is considered to have a small error is selected according to the determination result. Since the azimuth is adopted as the actual azimuth of the vehicle, there is an extremely excellent effect that detection accuracy of the azimuth of the vehicle immediately after the start of the device can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram, FIG. 2 is a block diagram of one embodiment according to the present invention, FIG. 3 is a flowchart showing overall control processing, and FIG. 4 is an interrupt processing for each unit drive. Flowchart, FIG. 5 is a flowchart showing an interruption process per unit time, FIG. 6 is a flowchart showing a series of processes when the system is started next after the vehicle stops, and FIG. 7 is a first traveling. It is explanatory drawing which showed and compared the direction and the 2nd running direction. 101 Absolute azimuth detecting means 102 Relative azimuth detecting means 103 Switch 104 Memory means 105 First azimuth calculating means 106 Second azimuth calculating means 107 Decision means

Claims (2)

(57) [Claims] An absolute azimuth detecting means for detecting an absolute azimuth of a vehicle, and a relative azimuth detecting means for detecting a relative azimuth of the vehicle, wherein the vehicle is provided based on the detected absolute azimuth and relative azimuth. A vehicle azimuth detecting device for calculating the running azimuth of the vehicle, a switch for switching operation / non-operation of the vehicle azimuth detecting device, storage means for storing a running azimuth of the vehicle, and When the mode is switched to the operation, the running azimuth of the vehicle stored in the storage means is read as an initial value, and the relative azimuth of the vehicle detected by the relative azimuth detecting means based on the read running azimuth of the vehicle is used as a reference. First running direction calculating means for calculating a first running direction of the current vehicle based on the vehicle, and a vehicle detected by the absolute direction detecting means when the switch is switched from non-operation to operation. A second traveling azimuth for calculating the second traveling azimuth of the current vehicle based on the relative azimuth of the vehicle detected by the relative azimuth detecting means based on the absolute azimuth. Calculating means, when the switch is switched from non-operation to operation, collating the first and second traveling azimuths calculated by both the first and second traveling azimuth computing means, and the collation result Are determined as the actual running azimuth of the vehicle calculated by the first running azimuth calculating means, and when the collation results are not identical, the second running azimuth calculation is performed. And a traveling direction determining means for determining the second traveling direction of the vehicle calculated by the means as an actual traveling direction of the vehicle. 2. The traveling direction determining means calculates a difference between the first and second traveling directions a plurality of times after traveling a predetermined distance when the switch is switched from non-operation to operation.
The running azimuth detecting device for a vehicle according to claim 1, wherein an average value of the calculated differences is obtained, and a running azimuth is determined based on a magnitude of the obtained average value.