JP2708092B2 - Azimuth angle acquisition device for automobile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for acquiring an azimuth in a traveling direction of a vehicle used for controlling a beam direction when a directional antenna for communication is mounted on a car navigation or a vehicle. Speaking of this, a reliable azimuth in the traveling direction is obtained from the absolute azimuth and rotation angular velocity obtained from the magnetic azimuth meter and rotational angular velocity sensor installed on the car and the traveling speed obtained from the car without being affected by the driving environment of the car The present invention relates to an azimuth acquisition device for an automobile.

[0002]

2. Description of the Related Art Conventionally, automobiles are different from airplanes and ships,
Information such as the azimuth in the traveling direction (information taking a value of 0 ° to 359 ° clockwise with reference to the north) was not required to operate it. 2. Description of the Related Art In recent years, demand for car navigation, mobile communication, and the like has rapidly increased, so that information about a running state, such as an azimuth angle, has been required for an automobile.

[0003] Currently, car navigation mainly uses GPS.
Is used to acquire the current position and the azimuth information of the traveling direction of the vehicle, and to display the current position and the traveling locus of the vehicle in the map information. Here, the position and the azimuth angle are calculated by a method called map matching. The measurement error of is accepted.

In recent years, with the spread of satellite broadcasting, systems for receiving satellite broadcasting (BS) on trains and buses have been developed. Since a directional antenna is used as the antenna of these satellite broadcast receiving apparatuses, it is necessary to control the beam direction of the antenna in the direction of the satellite according to the movement of a moving object such as a train or a bus.

A method of controlling the beam direction of a directional antenna mounted on a moving body uses a method in which the beam direction of the antenna is programmed according to the place where the train travels, since the track on which the train travels is predetermined. It is not necessary to acquire the azimuth angle while driving. In addition, the bus uses a step track method that uses signal strength information obtained when a signal transmitted from a target satellite is received, and a phase information obtained when the same satellite signal is received by a plurality of antennas, and determines a beam direction of an antenna. For example, a monopulse method for controlling is used. However, when satellite signals are blocked or attenuated by buildings or trees, such information cannot be obtained, and the beam direction of the antenna is determined based on the azimuth information obtained from the azimuth measurement sensor such as a magnetic compass or gyro. Is performed.

[0006]

The GPS is a global positioning system (satellite navigation system) that can easily measure the position and the azimuth of the traveling direction, but the satellite is managed and operated by the United States. Currently, it only releases some of its functions to the private sector, and does not guarantee stable use in the future.

In the GPS, the azimuth in the traveling direction of the vehicle is obtained from a change in position due to the movement of the moving body. Therefore, the azimuth reliability is determined by the position determination accuracy and the determined 2
The position determination accuracy of a general GPS receiver used for car navigation is about 30 to 100 m with respect to the true value, and depends on the distance between the two points. Reliability is not so high. However, in car navigation, a technique called map matching is used in combination, so that highly accurate azimuth information is not required. In addition, GPs are used for tunnels and building shielding, etc.
If the S satellite cannot be received, the position cannot be determined. Therefore, recent systems use a self-contained navigation sensor such as a gyro.

[0008] The car is agile, the road on which it travels is not predetermined, and the azimuth in the traveling direction changes frequently, so it is necessary to always acquire and grasp the azimuth. . In satellite broadcasting and satellite communication, there is a method of receiving a signal wave transmitted from a satellite and using information such as the received signal strength to determine the satellite direction. Trees often block signals from the satellite, and it is not always possible to determine the direction of the satellite.

As can be seen from the current state of car navigation systems, it is expected that car navigation will become more widespread in the future, and that satellite communication systems will be mounted on automobiles and used by ordinary users. Therefore, there is a need for a device that can easily and stably acquire a reliable azimuth angle and control the direction of an on-vehicle antenna, not only in a conventional train or bus, but also in a small passenger car. Also,
It is important for the device to be small and light, low in power consumption and low in cost in order to promote its spread in such a way that it does not significantly reduce the running and carrying functions of small passenger cars and the like.

Therefore, the present invention can realize an azimuth angle acquisition device suitable for a car navigation system or a satellite communication system mounted on an automobile at a small size, light weight, and low cost, and has a high reliability without being affected by the driving environment of the automobile. It is an object of the present invention to provide an azimuth angle acquisition device capable of acquiring azimuth angle information having a high azimuth angle.

[0011]

In order to solve the above-mentioned problems, a vehicle azimuth obtaining apparatus according to the present invention comprises:
A small, lightweight, low-cost magnetic azimuth sensor, rotational angular velocity sensor, and arithmetic device are installed in the car, and the relative rotational angle obtained by integrating the absolute azimuth angle obtained from the magnetic azimuth angle and the rotational angular velocity obtained from the rotational angular velocity sensor is used. For the change of the azimuth angle in the traveling direction of the car, use the relative rotation angle obtained from the rotation angular velocity sensor which is not affected by the driving environment of the car, and add this to the reference azimuth angle to obtain the basic azimuth angle Means, furthermore, from the angle difference between the basic azimuth angle and the absolute azimuth angle obtained from the magnetic compass, when an error included in the reference azimuth angle, a measurement error of the relative rotation angle and a disturbance of the geomagnetism are generated, Error angle obtaining means for obtaining an error of the absolute azimuth angle due to this effect, and correction for obtaining a correction angle for correcting the basic azimuth angle from the error angle obtained by the error angle obtaining means Acquisition means, azimuth angle acquisition means for correcting the basic azimuth angle acquired by the basic azimuth angle acquisition means to obtain an azimuth angle using the correction angle acquired by the correction angle acquisition means, and calculating the corrected azimuth angle. By using the reference azimuth storage means as a new reference azimuth, a highly reliable azimuth can be obtained without being affected by the driving environment of the automobile.

[0012]

According to the azimuth angle acquiring apparatus for a vehicle according to the present invention, the magnetic azimuth meter, the rotational angular velocity sensor and the arithmetic unit are installed in the automobile, and the absolute azimuth in the traveling direction of the automobile and the rotational angular velocity are integrated. The relative rotation angle and the traveling speed of the vehicle are acquired, and based on the information, a highly reliable azimuth in the traveling direction is acquired by the following means.

[0013] The absolute azimuth obtained in an environment in which an automobile generally travels is calculated in a place where geomagnetism is locally disturbed by a magnetic field generated by an artificial structure such as a building around a road, an elevated road, or a buried object on a road. Since an error is included, an accurate azimuth cannot always be obtained. Therefore, by using a rotational angular velocity sensor that is not affected by geomagnetic disturbance and adding the relative rotational angle obtained from the rotational angular velocity sensor to the reference azimuth angle, reliability can be maintained even when geomagnetic disturbance occurs. Is effective. Note that an absolute azimuth obtained from a magnetic compass is used as the initial reference azimuth.

However, since the relative rotation angle also includes a small measurement error, the measurement error is also accumulated only by the above basic azimuth angle acquisition means, so that the azimuth angle obtained over time can be obtained. Since the error increases and the reliability decreases, the measurement error included in the basic azimuth is corrected by using an error angle acquisition unit and an azimuth angle acquisition unit that acquire and correct the measurement error described below, and a highly reliable azimuth is obtained. Get the corner. When the absolute azimuth used for the initial reference azimuth includes a measurement error, the measurement error becomes a quantitative error and remains in the reference azimuth, but this error is also corrected.

Considering the case where no terrestrial magnetism is disturbed, the absolute azimuth angle is accurate within the measurement accuracy of the magnetic compass (approximately ± 1 ° using a commonly available magnetic compass), so that the measurement error is large. Can be obtained from the angle difference between the basic azimuth obtained by adding the relative rotation angle to the reference azimuth and the absolute azimuth obtained by the magnetic compass at that time. Since the measurement error itself is given, the measurement error included in the basic azimuth can be corrected by adding this angle difference to the basic azimuth. However, depending on the driving environment, geomagnetic disturbance may occur,
The absolute azimuth measured at that time includes an error with respect to the true value due to its influence, and the magnitude is much larger than the measurement error of the relative rotation angle. Cannot be corrected.

For this reason, this angle difference is compressed to reduce an error with respect to the true value of the absolute azimuth angle due to the disturbance of the geomagnetism, and is used for correction. Further, when compressing the angle difference, the azimuth fluctuation after the correction should be approximately within ± 1 °, and in consideration of the magnitude of the error contained in the absolute azimuth, the magnetic compass should Since it is desirable to change the compression ratio depending on the degree of turbulence,
It is assumed that the compression ratio is changed in accordance with the influence of terrestrial magnetism acting on the magnetic compass.

That is, the disturbance of the geomagnetism is mainly caused by artificial structures such as buildings, but the range of the influence is local, and the time affected by the vehicle passing through the range is as follows. Assuming that the range of the geomagnetic disturbance generated by each artificial structure does not change, it depends on the relative speed between the vehicle and the artificial structure. In addition,
Since it is almost a structure that causes geomagnetic disturbance, the relative speed of the artificial structure and the vehicle can be regarded as the running speed of the vehicle. Is affected by the running speed of the vehicle. Therefore, when the running speed is slow, the compression ratio is increased because the influence of terrestrial magnetism is long.On the contrary, when the running speed is high, the compression ratio is reduced because it is short. It can be made substantially constant irrespective of the speed, and the error of the initial reference azimuth included in the angle difference and the measurement error of the relative rotation angle can also be obtained according to the compression ratio.

As described above, when geomagnetic disturbance occurs, the angle difference includes an error due to this effect. However, when geomagnetic disturbance occurs sporadically,
Since the difference in absolute azimuth angle due to this effect is reduced in angle difference, even if it is added to the basic azimuth angle, the variation in azimuth angle obtained is small regardless of the degree of the influence of geomagnetism. Is corrected according to the compression ratio, so that the measurement error included in the acquired azimuth angle is reduced.

Next, considering the case where the disturbance of the geomagnetism is continuously generated, such a running environment has a large influence on the magnetic compass provided with the artificial azimuth meter in which the artificial structure exists continuously. For this purpose, it is necessary to be near an automobile, so that the vehicle travels on an elevated road or an iron bridge in a general traveling environment in most cases. In such an artificial structure, it can be considered that substantially the same structure is continuously present, and it is considered that the same tendency is substantially periodically repeated with respect to a change in the position of the geomagnetic disturbance. Therefore,
The variation of the absolute azimuth angle due to the influence is considered to be caused by the superposition of the horizontal component of the magnetic field locally closed by the artificial structure on the horizontal component of the terrestrial magnetism. Therefore, the absolute azimuth angle given only by the horizontal component of the terrestrial magnetism Is likely to be oscillating around the true value of the error, and even if the above-described error angle correction means is repeatedly performed, the error unilaterally increases in the azimuth obtained by the error due to the influence of the terrestrial disturbance. In addition, the fluctuation of the obtained azimuth angle is constant and small irrespective of the degree of the influence of the geomagnetism. As a result, the measurement error can be corrected according to the compression ratio of the angle difference.

The compression of the angle difference is necessary only when the terrestrial magnetism is disturbed. However, since the terrestrial magnetism suddenly occurs and its occurrence is difficult to predict, it is always compressed. To do. By adding the angle difference obtained in this way to the basic azimuth, it is possible to obtain an azimuth in which the quantitative error included in the initial reference azimuth and the measurement error of the relative rotation angle are corrected. Since the difference is compressed, the measurement error can be corrected only slightly according to the compression ratio.Therefore, the corrected azimuth is set as a new reference azimuth, and the addition of the relative rotation angle and the correction of the error are repeatedly performed. Try to converge to the true value.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an azimuth acquisition device for a vehicle according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a functional block diagram showing a schematic configuration of an azimuth angle acquiring device 1 according to the present invention. The magnetic compass 2, the rotational angular velocity sensor 3, and the arithmetic unit 4 are installed in a vehicle.
When the magnetic compass 2 is installed in an automobile, since the vehicle body is magnetized (this is called magnetization), it is necessary to perform magnetization correction in advance to correct the influence of the vehicle body. In addition, the rotational angular velocity sensor 3 is installed so that the measurement axis of the sensor and the axis to be measured (vertical axis) coincide with each other in order to reduce the measurement error. The traveling speed is acquired by installing a speedometer or a vehicle speed sensor 5 of the vehicle. Since the present apparatus 1 is an experimental apparatus for confirming functions, a personal computer was used as the arithmetic unit 4. However, by specializing functions for obtaining azimuth angles, it is possible to reduce the size, weight, and cost. .

When the apparatus 1 is started and reset,
Alternatively, when the reference azimuth is not stored, the absolute azimuth measured by the magnetic azimuth meter 2 is stored by the reference azimuth storage means 6 as the initial reference azimuth. Next, a basic azimuth angle is obtained by the basic azimuth angle acquisition means 7 from the relative rotation angle measured by the rotational angular velocity sensor 3 and the reference azimuth angle.
Further, from the absolute azimuth and the basic azimuth, an error angle for correcting the basic azimuth is obtained by the error angle obtaining means 8, and the obtained error angle is obtained by the error angle compressing means 9 a of the correction angle obtaining means 9. To obtain a correction angle. The obtained correction angle is added to the basic azimuth by the azimuth obtaining means 10 to obtain the azimuth. The acquired azimuth is stored by the reference azimuth storage means 6 as a new reference azimuth.

The compression ratio (to be described in detail later) used by the error angle compression unit 9a is obtained by the compression ratio determination unit 9b from the vehicle speed information obtained by the vehicle speed acquisition unit 11. In addition, by using the compression ratio setting means 12, the ratio of the compression ratio obtained according to the vehicle speed can be finely adjusted. Depending on the use of the obtained azimuth angle, when it is desired to further reduce the fluctuation included in the obtained azimuth angle, or Can be dealt with even if the correction of the error is to be prioritized even if is tolerated to some extent.

Further, in the azimuth angle obtaining apparatus according to the present embodiment, the correction angle obtaining means 9 is provided with an error angle evaluating means 9c. The error angle evaluation means 9c includes:
A general range of the variation of the absolute azimuth angle due to terrestrial magnetism disturbance which may occur in a general driving environment (described later in detail) is stored as allowable variation range information, and the error angle obtained by the error angle obtaining means is used as the allowable variation range. If the error angle exceeds the permissible variation range as compared with the range information, the error angle is determined to be defective. When the error angle evaluation means 9c makes a failure determination, a command signal for setting the error angle to zero is sent to the error angle compression means 9a and output from the error angle compression means 9a. The correction angle is forcibly set to zero. By doing so, the correction angle output from the correction angle obtaining means 9 becomes 0 only when the error angle obtained by the error angle obtaining means 8 is extremely unreliable. On the other hand, it is possible to effectively prevent erroneous correction from being performed (performing a correction operation that widens the error). The rate at which the error angle obtaining means 8 obtains an error angle determined to be a clear defect by the error angle evaluating means 9c is rare in a general driving environment in which an automobile runs (the occurrence rate is also low). In addition, the error angle is added to the basic azimuth angle as a correction angle obtained by compressing based on a compression ratio corresponding to the traveling speed. Even if the discrimination is not performed, the azimuth angle acquisition device according to the present invention can acquire the azimuth angle with necessary and sufficient accuracy.

FIG. 2 shows a basic azimuth angle obtaining algorithm of the present apparatus, which will be described in the order of steps. Step S1:
Start or reset the device. Step S2: Obtain an absolute azimuth from the magnetic azimuth meter and set this as the reference azimuth. Step S3: Obtain absolute azimuth angle, relative rotation angle, and vehicle speed information from the magnetic azimuth meter, the rotational angular velocity sensor, and the vehicle speed sensor. Step S4: A basic azimuth angle and an error angle are obtained from the azimuth information, and a compression ratio of the error angle is obtained from the vehicle speed information. Step S5: Determine whether the error angle is good or bad. Step S6: If it is determined that the error angle is obviously bad, the correction angle is set to 0. Step S7: The error angle is compressed by the compression ratio to obtain a correction angle. Step S
8: The basic azimuth is corrected by adding the correction angle to the basic azimuth, and the azimuth is acquired. The acquired azimuth is set as a new reference azimuth. After the azimuth is obtained in step S8, the process returns to step S3, and a series of processes in steps S3 to S8 is repeated. In the arithmetic unit 4 used as the present embodiment, a series of these processes is performed at a cycle of about 110 msec. However, the cycle of the azimuth angle acquisition process is not particularly limited, and the capacity of the arithmetic unit to be used is limited. It is desirable that the processing be performed at a cycle as fast as possible.

FIG. 3 is a conceptual diagram of an azimuth angle obtaining method. Now, when S ₀ is given as the reference azimuth and then the relative rotation angle ΔF ₁ and the absolute azimuth M ₁ are given as the azimuth information, it is considered to obtain a highly reliable azimuth. In the driving environment of an automobile, the disturbance of the geomagnetism occurs suddenly and cannot be predicted in advance, so that the value of the absolute azimuth cannot be directly believed. Therefore, it is considered that the azimuth obtained by adding the relative rotation angle for measuring the change in azimuth with high accuracy without being affected by the disturbance of the geomagnetism to the reference azimuth is the most reliable. This is called a basic azimuth.

[0027]

(Equation 1)

In the above equation 1, S ₁ is a basic azimuth, S ₀ is a reference azimuth, and ΔF ₁ is a relative rotation angle. However, this ΔF
_{Since a} slight measurement error is included in ₁ as well, if the process of adding the relative rotation angle to the reference azimuth is repeated, this measurement error is also added, and the error gradually becomes unacceptable. If S ₀ is the initial reference azimuth, if the absolute azimuth used for S ₀ includes a measurement error, it will remain at the basic azimuth as a quantitative initial error.

Therefore, the absolute azimuth M measured at this time is
_If the angle difference between ₁ and S ₁ is taken, M ₁ is accurate within the measurement accuracy of the magnetic compass when there is no terrestrial disturbance, so this angle difference is the measurement error of ΔF ₁ and the initial _value of S ₀ . represents the error, the angular difference can be obtained an accurate azimuth by adding to S _1. However, if terrestrial magnetism is disturbed, this angle difference is ΔF ₁ measurement error,
It represents the initial error of S ₀ and the measurement error of the magnetic compass due to terrestrial turbulence. At this time, since the measurement error of the magnetic compass is larger than the other errors, it cannot be added to S ₁ as it is, so that the data compressed as in the following equation 2 is used as S
Add to ₁ to get the azimuth.

[0030]

(Equation 2)

In the above equation 2, M ₁ is the absolute azimuth, and 1 / Q is the compression ratio. Since the disturbance of the geomagnetism occurs suddenly and cannot be predicted in advance, the expression for obtaining the azimuth angle regardless of the presence or absence of the disturbance of the geomagnetism is defined as Expression 3 below using Expression 2.

[0032]

(Equation 3)

In the above equation (3), S _i is the i-th acquired azimuth, Δ
F _i is the absolute azimuth obtained (i-1) relative rotation angle has changed to i-th from th, M _i is the i-th. In the above equation 3, (S _i-1 + ΔF _i ) is the basic azimuth, 1 / Q ·
(M _i- (S _i-1 + ΔF _i )) represents an error correction angle. Also,
By expanding Expression 3, the following Expression 4 is obtained.

[0034]

(Equation 4)

When the azimuths are sequentially obtained by using Equation 4, the acquired azimuth is replaced with a new reference azimuth, and the correction angle of Equation 3 is accumulated in the reference azimuth. Therefore, the behavior of the obtained azimuth angle S _i at this time is represented by the following Expression 5.

[0036]

(Equation 5)

In equation (5), S _i ⁰ is the true azimuth, R ₀ is a quantitative error such as an error in the initial reference azimuth, and δm _j is an error due to the influence of the disturbance of the terrestrial magnetism. Although the value takes a large value, when the disturbance of the geomagnetism continuously occurs and fluctuates in the vicinity of the true value and fluctuates in the vicinity, the amount becomes smaller on average, and δd is a measurement error of the rotational angular velocity sensor, and one value is small. Is an amount that accumulates and increases.

As can be seen from Equation 5, a quantitative error such as an error in the initial reference azimuth angle becomes significantly smaller when error angle correction processing is repeated. The error due to the influence of geomagnetic disturbance is
When the disturbance of the geomagnetism is continuously generated and fluctuates in the vicinity of the true value, the average value is reduced, and the influence of one time is compressed to 1 / Q. Does not significantly affect accuracy. The error in which the measurement error of the rotational angular velocity sensor is accumulated is suppressed to within Qδd by the error angle correction processing, and since δd itself is a very small amount, it does not affect the accuracy of the azimuth angle. Therefore, in the obtained azimuth angle, the absolute azimuth error due to the influence of terrestrial magnetism is compressed and accumulated, and the corrected azimuth angle error remains so that the measurement error of the rotational angular velocity sensor does not unilaterally increase. Become. However, these values are also small amounts and fluctuate around the true value, so that the acquired azimuth tends to converge to the true value, and the reliability is high.

Next, Q for determining the compression ratio used in Expressions 3 to 5 will be described. The angle difference used for error correction is 1 /
The purpose of compression to Q is that when terrestrial magnetism is generated, a large error is included in the absolute azimuth measured by the magnetic azimuth meter due to the influence. This is because the difference cannot be used as it is as the correction angle.

In order to obtain the value of Q, it is necessary to consider the driving environment most affected by the disturbance of the geomagnetism. Therefore, here, the case where the disturbance of the geomagnetism continuously occurs will be considered. FIG. 4 is an enlarged view of the measurement results of the magnetic compass when the geomagnetic disturbance is continuously occurring. The traveling place is a metropolitan expressway where most traveling environments are elevated roads, and the traveling speed is about 75 km / h. From the figure, it can be seen that the measured absolute azimuth fluctuates periodically and oscillatingly. The cause of the geomagnetic disturbance in this driving environment is the elevated road, and when the elevated road is viewed as a single structure between the bridge girder and the bridge girder, it is composed Is likely to fluctuate periodically. Therefore, it is considered that the period of the fluctuation is determined by the length of one structure and the traveling speed. Furthermore, the length of one structure does not seem to differ significantly considering the total weight of the vehicle running on it and the load capacity of the structure. It is thought that it is possible.

In the apparatus used in the embodiment, the measured values of the magnetic compass and the rotational angular velocity sensor are obtained by isochronous sampling (about 110 msec / dat at the marker position in FIG. 4).
a). Assuming that the average value of the fluctuations is substantially the true value of the azimuth, when performing error correction using an absolute azimuth obtained in a plus range with respect to the true value, if there is no error in the reference azimuth, the obtained azimuth is obtained. Means that the error increases in the positive direction with respect to the true value, and vice versa in the negative range. The total amount of correction in each range is the sum of the angle difference (error angle) between the azimuth and the absolute azimuth obtained in each range. If the running speed is constant, the variation in the absolute azimuth can be approximated by a sine wave as shown in the figure. Therefore, the maximum value of the approximate total correction amount in each range can be obtained by the following equation.

[0042]

(Equation 6)

In the above equation 6, G is the total amount of correction, E
_max is the maximum value of the absolute azimuth error, f is the frequency of the absolute azimuth fluctuation (0.76 Hz at a running speed of 75 km / h), Speed is the running speed, x is the number of data acquired in each range,
0.11 (second) is a data sampling period. Also,
If the length of one of the artificial structures is substantially constant, the frequency of the variation of the absolute azimuth angle can be obtained in direct proportion to the traveling speed. Therefore, based on the case of 75 km / h shown in FIG. F is obtained from the running speed at the time. In addition, the maximum value of the absolute azimuth error is obtained by considering 30 ° from the example of the cumulative probability distribution of the magnitude of the variation with respect to the average value of the absolute azimuth shown in FIG. It can be seen that over 90% of the data can be considered.

FIG. 5 can be viewed as showing the frequency of occurrence of an angle (error angle) that fluctuates with respect to the average value of the absolute azimuth. For example, the ratio of the error angle exceeding 20 ° is about 10% of all data. In the figure, the curve gradually falls from 0 ° to around 30 °, but becomes horizontal at around 33 ° and falls again. The part where the curve is horizontal indicates that there is very little data. In other words, up to around 30 ° can be considered as a series of fluctuations, and it is considered that an error angle larger than 30 ° may have increased due to some cause. Therefore, the permissible fluctuation range information (the general range of the fluctuation of the absolute azimuth angle due to the disturbance of the geomagnetism that can occur in a general driving environment) of the error angle evaluation means 9c of the correction angle obtaining means 9 is regarded as a series of fluctuation ranges. 3
By setting the angle to 0 °, an error angle exceeding this range is determined to be defective, and is not used in the processing related to azimuth angle correction, so that the probability of erroneous correction can be reduced. The lower limit of this range is desirably set so as to include as much data as possible in consideration of the fact that the error angle is used for correcting the basic azimuth angle.

Considering that the practical measurement accuracy of a generally available magnetic compass is ± 1 ° to 2 °, the absolute azimuth angle can be obtained by compressing G obtained by Equation 6 into this range. If the average value of is substantially a true value, the fluctuation of the obtained azimuth angle can be made within a practical measurement accuracy range. For example, when Q is obtained for a traveling speed of 80 km / h, G at that time becomes approximately 105 ° from Expression 6, and G / Q
If <1 °, and Q is about 100, the variation of the acquired azimuth can be made up to about 1 °. As described above, the compression ratio is determined based on the running speed of the automobile at that time, the sampling period of data, and the allowable range of fluctuation of the acquired azimuth. In the present azimuth angle acquiring apparatus, the actual processing is simplified by using the following equation.

[0046]

(Equation 7)

Next, the case where the period of the fluctuation of the absolute azimuth angle due to the influence of the terrestrial magnetism is different will be considered. As shown in Equation 6, the period of the fluctuation is related to the total amount G of the correction amount. If the obtained cycle of the change in the absolute azimuth is faster than the cycle used as the reference in Equation 6, the actual G becomes smaller than that obtained in Equation 6, and therefore the Q obtained from the result of Equation 6 is used. If the angle difference is compressed by using, the same correction effect can be obtained because the compression ratio does not change if the running speed is the same for the measurement error, but the change in the absolute azimuth angle due to the disturbance of the geomagnetic field is obtained. Since the influence on the azimuth is reduced, the fluctuation of the obtained azimuth is reduced. Conversely, if the obtained period of the fluctuation of the absolute azimuth is slower than the period that is the reference of Expression 6, the actual G becomes larger than that obtained by Expression 6, so that the result of Expression 6 When the angle difference is compressed by using the obtained Q, the same correction effect can be obtained because the compression ratio does not change if the traveling speed is the same for the measurement error, but the absolute azimuth angle due to the disturbance of the geomagnetism can be obtained. Since the influence of the fluctuation on the acquisition azimuth becomes large, the fluctuation of the acquisition azimuth becomes large.

Therefore, when the period of the change becomes faster, there is no problem with the obtained azimuth, but when the period of the change becomes slower, the change of the obtained azimuth becomes larger, and the ratio of the change to the reference period is larger. It is almost directly proportional. However, if the period of the fluctuation largely depends on the length of the artificial structure, it is rare that the length is significantly different, and the period of the fluctuation is, for example, 2 to 3 times the reference period. Even if it is doubled, the fluctuation of the acquired azimuth is about ± 2 to 3 °, and the reliability does not decrease rapidly.

Next, the influence of terrestrial turbulence which is a problem when measuring the absolute azimuth will be described with reference to FIG.
It is considered that the disturbance of the geomagnetism is mainly caused by the magnetic field generated by the artificial structure around the road, and the situation related to the disturbance of the geomagnetism in the general running environment can be roughly classified into three. The first situation is when there is no geomagnetic disturbance (environment with few artificial structures such as suburbs), the second situation is
The third situation is when geomagnetic disturbance occurs locally (small city area, etc.), or when geomagnetic disturbance occurs frequently or continuously (continuous elevated roads such as large cities and the Tokyo Metropolitan Expressway). It is. Among them, the most problematic in obtaining the absolute azimuth is an environment where it is difficult to obtain a highly reliable azimuth when turbulence in the geomagnetism frequently or continuously occurs.

The characteristic of the absolute azimuth measured by the magnetic compass when the geomagnetic disturbance occurs will be described with reference to FIG. The driving environment is the Tokyo Metropolitan Expressway where geomagnetic disturbances are continuously generated. The absolute azimuth and relative rotation angle of OFG-3 manufactured by Hitachi Cable Co., Ltd. are installed in the car, and an arithmetic unit is used for the isochronous sampling ( About 9 data / sec)
Acquired in. OFG-3 is an azimuth measuring sensor in which a magnetic compass and a rotational angular velocity sensor (optical fiber gyro) are integrated, and selects either the rotational angular velocity or the relative rotational angle obtained by integrating the rotational angular velocity from the rotational angular velocity sensor. Can be output. Here, the relative rotation angle is output. Further, when the magnetic compass is mounted on an automobile, if the vehicle body is magnetized, the measured values include an error. Therefore, the influence is corrected in advance. The running speed during the measurement is about 80 km / h.

From the figure, it can be seen that the absolute azimuth obtained from the magnetic compass changes vibratingly due to the disturbance of the geomagnetism. However, the azimuth obtained from the rotational angular velocity sensor is not affected by the disturbance of geomagnetism, and the accumulated error in the measured value is very small within a short time. It is considered that is accurately detected. What is particularly important in the drawing is that the average value of the absolute azimuth that is vibrating is well matched to the change of the azimuth obtained by accumulating the relative rotation angle to the reference azimuth. This indicates that the measured absolute azimuth is substantially and oscillatingly changed from the true value. The azimuth of the optical fiber gyro shown in the figure is the one that gives the correct initial reference azimuth before traveling and accumulates the relative rotation angle measured with respect to the reference azimuth, but the measurement error also Due to the accumulation, an angular difference is generated between the absolute azimuth and the average value over time as shown in the figure. Therefore, it can be seen from the figure that a reliable azimuth cannot be obtained only by accumulating the relative rotation angle to the reference azimuth.

Next, FIG. 8 shows the result of obtaining the azimuth angle using the azimuth angle obtaining algorithm of the azimuth angle obtaining apparatus for an automobile according to the present invention and the absolute azimuth angle and the relative rotation angle shown in FIG. Will be explained. First, when there is no error in the initial reference azimuth, the obtained azimuth indicates the average value of the absolute azimuth. The change in the azimuth shows almost the same tendency as the change in the relative rotation angle which is not affected by the disturbance of the geomagnetic field. Next, when there is an error in the initial reference azimuth, the value approaches the value in the case where there is no error in the initial reference azimuth in a relatively short time, and thereafter, the same value and change are shown. Therefore, it is understood that the quantitative error included in the initial reference azimuth is corrected in a short time. Note that the compression ratio of the angle difference used for the correction is Q = 100 since the traveling speed is generally constant at 80 km / h within the time shown in the figure.
And In obtaining the actual azimuth angle, the determination of the quality of the error angle was not performed, and all data were used.

FIG. 9 shows the result of obtaining the azimuth angle when there is no disturbance of geomagnetism and when it occurs sporadically.
Shown in The absolute azimuth angle and the relative rotation angle can be obtained by installing OFG-3 manufactured by Hitachi Cable Co., Ltd. in the interior of the car as in FIG.
ec). From the figure, it can be seen that when no geomagnetic disturbance occurs, the fluctuation of the absolute azimuth is extremely small, and the obtained azimuth has almost the same azimuth and change as the absolute azimuth. It is considered that it has the same accuracy as. In the first half of the figure, geomagnetic disturbance occurs, and the absolute azimuth angle fluctuates by about ± 40 ° with respect to the average value due to the influence. However, the obtained azimuth angle is suppressed to a fluctuation of about ± 2 °, and the obtained azimuth angle shows the change of the absolute azimuth angle and the relative rotation angle before and after the occurrence of geomagnetic disturbance. Considering this, it is considered that it is required with high accuracy. In obtaining the actual azimuth angle, the quality of the error angle is not determined.
All data were used.

Next, an experimental result of evaluating the reliability of the azimuth angle obtained by the present apparatus will be described with reference to FIG. The experimental method uses the azimuth obtained by this device to control the directional antenna attached to the roof of the running car in the direction of a geostationary satellite (technical test satellite 5 / ETS-V), This is to receive the transmitted 1.5-GHz unmodulated wave and record the received power level. The driving environment of a car is a continuous elevated road and an environment in which geomagnetic disturbance is continuously occurring. The directional antenna used in the experiment was a four-element spiral antenna having a beam half-width in the horizontal plane of about ± 15 °, which only tracks in the azimuth direction and the elevation direction is fixed. The value of Q was determined from the running speed every time the absolute azimuth and relative rotation angle were obtained.

The vertical axis in the figure is the azimuth angle and the relative received power when the received power when the satellite is in line of sight is 0 dB,
The horizontal axis indicates the running time. From the figure, it can be seen that the absolute azimuth is continuously affected by terrestrial magnetism and is oscillatingly changed by the influence. The obtained azimuth indicates the average value of the absolute azimuth, and the change is almost the same as the change of the azimuth obtained by accumulating the relative rotation angle to the initial reference azimuth. I have. As a result of the experiment, the received signal level from the satellite is almost the same as the line-of-sight reception level except when the signal is blocked or attenuated by a building or the like, and the antenna is accurately pointed toward the satellite. It indicates that.
Note that if the antenna direction deviates from the satellite direction by an angle indicated by the beam half width, the reception power decreases by 3 dB.

Further, there may be a maximum angle difference of about 20 ° between the azimuth obtained by accumulating the relative rotation angle to the initial reference azimuth and the azimuth obtained by the present apparatus. . This is mainly because measurement errors of the relative rotation angle have accumulated. Therefore, when the same antenna direction control is performed by using the azimuth angle obtained by accumulating the relative rotation angle to the initial reference azimuth angle, the influence of the geomagnetic disturbance is not affected, but the accumulation of the measurement error causes 3 dB or more. It is considered that the reception level has decreased. In obtaining the azimuth angle in this experiment, the quality of the error angle was determined.
When the error angle exceeds 30 °, the correction angle is set to 0, and the correction of the basic azimuth is not performed. The rate at which the error angle exceeds 30 ° is about 9% of all data.

[0056]

As described in detail above, according to the azimuth angle acquiring apparatus for an automobile according to the present invention, the magnetic azimuth meter and the rotational angular velocity sensor are installed in the automobile, and the rotational angular velocity obtained from the rotational angular velocity sensor is integrated. A basic azimuth angle obtaining means for obtaining a basic azimuth angle by adding the obtained relative rotation angle to a reference azimuth angle, and a difference between the basic azimuth angle obtained by the basic azimuth angle obtaining means and the absolute azimuth angle obtained from the magnetic compass. Using an error angle obtaining unit for obtaining a barrel error angle, a correction angle obtaining unit for obtaining a correction angle for correcting a basic azimuth angle from the error angle obtained by the error angle obtaining unit, and a correction angle obtained by the correction angle obtaining unit. Azimuth angle obtaining means for correcting the basic azimuth angle obtained by the basic azimuth angle obtaining means to obtain an azimuth angle, and reference azimuth storage means for using the corrected azimuth angle as a new reference azimuth angle. In a general driving environment, a highly reliable azimuth angle can be obtained by a small and light-weight and inexpensive magnetic azimuth meter, a device constituted by a rotational angular velocity sensor and an arithmetic unit, and a simple azimuth angle acquisition algorithm. An azimuth acquisition device for a vehicle suitable for a system or a satellite communication system can be realized at a small size, a light weight, and a low price.

[Brief description of the drawings]

FIG. 1 is a diagram showing a functional configuration of an azimuth acquisition device for a vehicle.

FIG. 2 is a diagram showing a basic azimuth angle acquisition algorithm of the azimuth angle acquisition device for a vehicle.

FIG. 3 is a conceptual diagram of an azimuth angle obtaining method.

FIG. 4 is a diagram showing a state of a change in an absolute azimuth angle in a traveling environment in which geomagnetic disturbance is continuously occurring and that the change can be approximated by a sine wave.

FIG. 5 is an example of the cumulative probability distribution of the absolute value of the error of the absolute azimuth caused by the disturbance of the geomagnetism with respect to the average value of the absolute azimuth.

FIG. 6 is a diagram showing a state of occurrence of terrestrial magnetism for each occurrence frequency;

FIG. 7 is a diagram showing characteristics of absolute azimuth angle data when disturbance of geomagnetism continuously occurs.

FIG. 8 is a diagram showing an azimuth angle acquisition result in a driving environment in which geomagnetic disturbances continuously occur.

FIG. 9 is a diagram showing an azimuth angle acquisition result in a traveling environment where there is no disturbance of geomagnetism and in a traveling environment where disturbance of geomagnetism occurs sporadically.

FIG. 10 is a diagram illustrating a result of an evaluation experiment of the reliability of the azimuth angle acquired by using the acquisition apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Azimuth angle acquisition device 2 Magnetic compass 3 Rotation angular velocity sensor 6 Reference azimuth angle acquisition means 7 Basic azimuth angle acquisition means 8 Error angle acquisition means 9 Correction angle acquisition means 10 Azimuth angle acquisition means

Claims (1)

(57) [Claims] A basic azimuth is obtained by integrating a magnetic azimuth meter installed in an automobile, a rotational angular velocity sensor installed in the automobile, and a rotational angular velocity obtained from the rotational angular velocity sensor and adding the result to a reference azimuth. Azimuth angle obtaining means, error angle obtaining means for obtaining an error angle between the basic azimuth angle obtained by the basic azimuth angle obtaining means and the absolute azimuth angle obtained from the magnetic compass, and error angle obtained by the error angle obtaining means orientation to obtain basic and correction angle obtaining means for obtaining the correction angle azimuth correcting, and the azimuth angle by correcting the basic azimuth obtained by the basic azimuth acquisition unit using the correction angle thus obtained in the correction angle acquisition means from the Angle acquisition means, and reference azimuth storage means for setting the corrected azimuth angle as a new reference azimuth angle, wherein the correction angle acquisition means is adapted to a predetermined traveling environment.
From the geomagnetic effect and the speed of the vehicle
The error angle is compressed based on the compression ratio
Automotive azimuth acquisition apparatus according to claim to Rukoto correction angle difference angle.