JPH0690036B2 - Azimuth detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention is required when displaying a map on a moving body such as a car to indicate the current position of the moving body or when searching for or guiding a route to a destination. The present invention relates to an azimuth detecting device that obtains the traveling azimuth of a moving body.

2. Description of the Related Art A conventional azimuth detecting device is disclosed, for example, in Japanese Utility Model Laid-Open No. 61-72618.

As shown in this example, in an azimuth detecting device used in a moving body such as a car, it is general to combine an absolute azimuth sensor and a relative azimuth sensor in order to correct an error that occurs when the sensor is used alone. There is. In this case, the absolute direction sensor may be a geomagnetic sensor, and the relative direction sensor may be an angular velocity sensor, an acceleration sensor, a wheel sensor that uses the rotation speed of wheels on both sides of the moving body, or the like. The geomagnetic sensor, which is an absolute azimuth sensor, has the advantage of being able to detect the absolute azimuth of the moving body, but at the same time has the drawback of being easily affected by external magnetic anomalies. Although it has the advantage of being less susceptible to external influences, it has the drawback that the moving direction of the moving body gradually shifts due to the zero drift and sensitivity error of the sensor itself. In order to take advantage of such characteristics of each sensor, in the conventional example, the outputs of the absolute azimuth sensor and the relative azimuth sensor are compared, and if the difference between the two becomes larger than a certain value, the output of the absolute azimuth sensor is judged to be an abnormal value. Then, the output of the relative azimuth sensor is added to the traveling azimuth of the moving body calculated immediately before to make a new traveling azimuth. Was.

[Problems to be Solved by the Invention]

However, when a vehicle is assumed as the moving body, a relatively expensive sensor cannot be used as the azimuth sensor, and therefore the accuracy of the relative azimuth sensor cannot be often ensured in many cases. Moreover, the error characteristic peculiar to the relative direction sensor is 1
It could not be said to be sufficient as a supplement for the absolute direction sensor, because it was not possible to correct it with only one type of relative direction sensor.

In view of such a point, the present invention has an object to provide an azimuth detecting device that calculates a more accurate traveling azimuth of a moving body.

[Means for Solving the Problems]

The present invention, an azimuth storage means for storing the traveling azimuth of a moving body, an absolute azimuth sensor for detecting the absolute azimuth of the traveling direction,
A first relative azimuth sensor having a characteristic that a relative azimuth in a traveling direction is detected and a zero-point drift depends on a moving distance of a moving body;
A first relative direction sensor that detects the relative direction of the traveling direction and has a characteristic that the zero-point drift depends on time, a first relative direction sensor, and a first addition for adding the outputs of the direction storage means.
Azimuth adding means, second azimuth adding means for adding the outputs of the second relative azimuth sensor and the azimuth storage means, a distance sensor for detecting a moving distance of a moving body, and an elapsed time detection for obtaining an elapsed time. A first relative azimuth error calculating means for estimating a sensitivity error range from the output of the first relative azimuth sensor; and a first relative azimuth error calculating means for estimating a zero point drift error range of the first relative azimuth sensor from the output of the distance sensor. 2 relative azimuth error calculating means, 3rd relative azimuth error calculating means for estimating the sensitivity error range from the output of the 2nd relative azimuth sensor, and 2nd relative azimuth sensor from the output of the elapsed time detecting means. Fourth relative azimuth error calculating means for estimating a zero point drift error range, and a first error range for calculating an error range of the first relative azimuth sensor from outputs of the first and second relative azimuth error calculating means. Calculating means, second error range calculating means for calculating an error range of the second relative direction sensor from outputs of the third and fourth relative direction error calculating means, the absolute direction sensor and the first The second azimuth adding means, the azimuth calculating means for estimating a new traveling azimuth of the moving body from the outputs of the first and second error range calculating means, and outputting it to the azimuth storing means, and the azimuth storing means. An azimuth detecting apparatus comprising: an output unit that outputs a value of a traveling azimuth of a moving body.

Operation The present invention has a total of three types of azimuth sensors having two types of relative azimuth sensors and absolute azimuth sensors having different error characteristics due to the configuration described above. As a result, it is possible to improve the accuracy of the calculation of the relative azimuth, which is relatively difficult to increase, and it is also possible to further improve the accuracy of the traveling azimuth of the moving body calculated by the combination of the absolute azimuth sensor and the relative azimuth sensor. .

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows a block diagram of an azimuth detecting apparatus in an embodiment of the present invention. In FIG. 1, 1 is an absolute azimuth sensor such as a geomagnetic sensor that detects an absolute azimuth of a moving body such as a car, and 2 is a zero-point drift in a moving distance of the moving body that detects a relative azimuth of the moving body. Is a first relative direction sensor such as a two-wheel sensor having a characteristic that depends on, and a second relative direction sensor such as an angular velocity sensor having a characteristic that the zero point drift depends on the elapsed time by detecting the relative direction of the moving body in the traveling direction. A direction sensor. 4 is a distance sensor for detecting the moving distance of the moving body, 5 is elapsed time detecting means for detecting the elapsed time, and 6 is the amount of change in direction calculated by the first relative direction sensor 2 and the advance of the moving body immediately before that. The first azimuth adding means for adding the azimuths, and the second azimuth adding means for adding the azimuth change amount calculated by the second relative azimuth sensor 3 and the traveling azimuth of the moving body immediately before the azimuth change amount. 8 is a first relative azimuth error calculating means for calculating a sensitivity error range of the azimuth expected from the output of the first relative azimuth sensor 2, and 9 is the first relative azimuth error from the moving distance of the moving body detected by the distance sensor. The second relative azimuth error calculating means calculates the zero-point drift error range of the first relative azimuth sensor. Reference numeral 10 is a third relative azimuth error calculation means for calculating a sensitivity error range of the azimuth expected from the output of the second relative azimuth sensor 3, and 11 is the second relative azimuth from the elapsed time detected by the elapsed time detecting means. It is a fourth relative azimuth error calculation means for calculating the zero point drift error range of the relative azimuth sensor 3. Reference numeral 12 is a first error range calculating means for comparing the outputs of the first and second relative azimuth error calculating means 8 and 9 and selecting one having a larger error range, and 13 is a third and fourth relative azimuth error. This is a second error range calculation means for comparing the outputs of the calculation means 10 and 11 and selecting one having a larger error range. Reference numeral 14 is an azimuth calculation means for calculating the traveling azimuth of the moving body from the outputs of the absolute azimuth sensor 1, the first and second azimuth addition means 6, 7, and the first and second error range calculation means 12, 13. Is an azimuth storage means such as a memory for storing the traveling azimuth calculated by the azimuth computing means 14, and 16 is an output means for outputting the traveling azimuth of the moving body.

The operation of the azimuth detecting apparatus of the present embodiment configured as described above will be described below. The azimuth calculation means 14,
1st, 2nd, 3rd, 4th relative azimuth error calculation means 8, 9, 10, 11,
The first and second error range calculating means 12 and 13, and the first and second azimuth adding means 6 and 7 can be configured by hardware, but here, a case where they are realized by software using a microprocessor will be described. To do. FIG. 4 is a flowchart showing the processing procedure. First, at step 401, an initial value 0 is substituted for a constant T indicating the elapsed time after the zero point drift correction of the second relative azimuth sensor 3 is performed.
Then the moving body orientation change amount [Delta] [theta] ₁ and orientation change amount [Delta] [theta] ₂ of the detected moving object from the second relative direction sensor 2 detected from the first relative direction sensor 2 in step _402, the azimuth storage means 15 The moving direction θ of the moving body obtained from the relative direction sensor from the stored moving direction θ ¹ of the moving body immediately before
Calculate ₁ and θ ₂ . In step 403, the second relative azimuth sensor 3 performs zero point drift correction by adding to the constant T the elapsed time Δt since the traveling direction immediately before the moving body detected by the elapsed time detecting means 5 was calculated. The elapsed time T since then is calculated. In step 404, the error range of the azimuth error of each relative azimuth sensor is obtained. Since the azimuth error due to the zero point drift of the first relative azimuth sensor 2 depends only on the distance traveled by the moving body, if the error is proportional to the traveling distance Δ1, the azimuth error Δθ _E1 due to the zero point drift Δθ _E1 = a × Δ1 Is expressed as Here, a is a proportional constant. If the sensitivity error is proportional to the detected azimuth change amount, Δθ _E2 = b × | Δθ ₁ can be expressed with the proportionality constant b. On the other hand, the orientation error due to the zero-point drift of the second relative orientation sensor 3 depends only on time. If the zero point drift is proportional to the elapsed time T after the zero point drift of the sensor is corrected, and the constant of proportionality is c, the zero point drift ω _{E3 at} a certain time t is ω _E3 = c × t. Therefore, the azimuth error Δθ _E3 is the zero point drift ω _E3
To T + Δt, the integral is Δθ _E3 = ∫ω _E3 dt = c × Δt × (T × Δt / 2). If the sensitivity error is proportional to the detected azimuth change amount, Δθ _E4 = d × | Δθ ₂ | These relational expressions are used to derive the error range of each relative direction sensor. This is shown in FIG.
It corresponds to the first, second, third, and fourth relative azimuth error calculating means 8, 9, 10, 11. Step 405 compares each of the zero-point drift error and sensitivity error in the relative direction sensor in, the values each [Delta] [theta] by selecting the larger of the error range _ER1, is substituted for [Delta] [theta] _ER2. In step 406, the moving directions θ ₁ and θ _{2 of} the moving body calculated up to step 405 and the error ranges Δθ _ER1 and Δθ _ER2 expected from the zero point drift are used to estimate the moving body of the moving body from the two relative direction sensors. Estimated range of traveling direction θ _1
Find the common range of ± Δθ _ER1 and θ ₂ ± Δθ _ER2 . FIG. 2 shows an example thereof. In this case, the estimated range of the traveling azimuth of the moving body estimated by the second relative azimuth sensor is included in the estimated range of the traveling azimuth of the moving body estimated by the first relative azimuth sensor 2, so that the common range is θ. ₂ ± Δθ _ER2 . When there is a common range, _let the maximum value be θ _R-MMAX and the minimum value be θ _R-MIN .
In this example, θ _R-MAX = θ ₂ + Δθ _ER2 θ _R-MIN = θ ₂ -Δθ _ER2 . It is conceivable that the case is the opposite of this example, that they both share a part, or that there is no common range, but if there is no common range in particular, then θ _R-MAX , θ
_A value that cannot be taken normally is assigned to _{R-MIN so} that the presence or absence of the common range can be determined by θ _R-MAX and θ _R-MIN . In step 407, the presence or absence of the common range is determined from the values of θ _R-MAX and θ _R-MIN . If the common range exists, the process proceeds to step 408, and if not, the process proceeds to step 412. In step 408, the traveling directions θ _a and θ of the moving body obtained from the absolute direction sensor 1 are calculated.
Compare _R-MAX and θ _R-MIN . θ _a is θ _R-MIN ≦ θ _a ≧
If the condition of θ _R-MAX is satisfied, the process proceeds to step 412, and if not satisfied, the process proceeds to step 409. In step 409, θ _a >
It is determined whether θ _R-MAX is satisfied, and θ _a >
If θ _R-MAX, the process proceeds to step 411, and if θ _a <θ _R-MIN , the process proceeds to step 410. In steps 410, 411, and 412, θ _R-MIN , θ _R-MAX , and θ _a are respectively substituted into the traveling direction θ of the new moving body. In this way, a new heading is calculated, and in step 412 the new heading is stored in the heading storage means 15 such as a memory (θ ¹ ← θ). Then, in step 414, the new traveling direction θ is output and transmitted. The relationship between the new heading θ and θ _R-MIN , θ _R-MAX , θ _a is as shown in FIG. (a) shows the case where the condition of θ _R-MIN ≤ θa ≤ θ _R-MAX is satisfied, (b) shows the case of θ _a > θ _R-MAX , and (c) shows θ _a <
The case of θ _R-MIN shows the case where (d) has no common range. In step 415, it is determined whether the zero point drift of the second relative azimuth sensor 3 has been corrected. For example, when a moving body such as a car stops for a certain period of time, the output of the second relative azimuth sensor 3 such as an angular velocity sensor should be zero.
However, in reality, the sensor output does not become zero due to the zero drift of the output. Therefore, for example, if the value of the sensor output while the vehicle is stopped is regarded as the zero point drift amount and this amount is subtracted from the subsequent sensor output as the correction amount, the effect of the zero point drift can be eliminated at this point. I.e. step 41
In 5, we are looking at whether the amount of zero drift has been calculated. After the zero point drift amount is calculated, when the second relative direction sensor 3 is used to calculate the direction change amount Δθ ₂ , the value obtained by subtracting the zero point drift amount from the sensor output is used as the true sensor output. Calculate the amount.
If the zero point drift is corrected, the process proceeds to step 401 and the azimuth is calculated in the same procedure from the beginning, but if not corrected, the process proceeds to step 402 and the value of the elapsed time T is saved to calculate a new azimuth. I do.

As described above, according to the present embodiment, by using the two relative relative azimuth sensors having different zero-point drift characteristics, the expected error range can be limited as compared with using only one type of relative azimuth sensor. In particular, considering both the coldness error and the zero point drift error expected in each relative azimuth sensor and considering the wider error range as the calculated error range of the relative azimuth, Is large, the sensitivity error is adopted as the error range, and when the moving body keeps going straight for a long time, it is adopted as the zero point drift error range, so that an appropriate error range can be set. Since this error range is used, the accuracy of the traveling azimuth of the moving body obtained in combination with the absolute azimuth sensor can be improved as compared with the case of combining one absolute azimuth sensor and one relative azimuth sensor.

In the present embodiment, two types of relative azimuth sensors having a distance-dependent zero-point drift characteristic and a time-dependent zero-point drift characteristic are used with the same weight. The azimuth may be calculated. Further, in this embodiment, the output of the absolute azimuth sensor is output as a new traveling azimuth within the error range expected from the relative azimuth sensor, but the output of the absolute azimuth sensor does not exceed the error range expected from the output of the relative azimuth sensor. If it exceeds, the output of the absolute direction sensor may be ignored and the output of the relative direction sensor may be output as a new traveling direction. In addition, in the present embodiment, although realized by software using a microprocessor,
This may be realized by hardware. Further, the range of the expected zero-point drift error of the relative azimuth obtained from the first relative azimuth sensor is said to be proportional to the moving distance of the moving body, but even if it is not proportional, the error characteristic depends on the moving distance. All you have to do is Further, the range of the expected zero-point drift error of the relative azimuth obtained from the second relative azimuth sensor is said to be proportional to the elapsed time after the sensor corrects the zero-point drift. It is sufficient that the characteristics depend on the elapsed time. Further, the sensitivity error of the relative azimuth sensor is said to be proportional to the calculated azimuth change amount, but it does not have to be proportional as long as it depends on the azimuth change amount. Further, in the present embodiment, the sensitivity error and the zero point drift error are compared and the larger error range is calculated as the error range by the error range calculation means.
The error range may be calculated by taking the value obtained by adding the maximum values of both errors as the maximum value of the error, or the maximum value of both errors may be squared and added, and the square root thereof may be taken to determine the error as the maximum error. The range may be calculated.

EFFECTS OF THE INVENTION As described above, since the present invention includes two types of relative direction sensors, the elapsed time is long but the moving distance of a moving body is short. In the case of high-speed traveling that is relatively short but has a long moving distance, it is possible to calculate the relative azimuth with less error than using a single relative azimuth sensor. As a result, it is possible to further improve the accuracy of the traveling direction of the moving body that is obtained in combination with the absolute direction sensor, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an azimuth detecting apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are vector diagrams of azimuth determination in the present embodiment, and FIG. 4 is a flowchart of the azimuth detecting apparatus in the present embodiment. . 1 ... Absolute direction sensor, 2 ... First relative direction sensor (1), 3 ... Second relative direction sensor (2), 4 ... Distance sensor, 5 ... Elapsed time detecting means, 6 ... First azimuth adding means (1), 7 ... Second azimuth adding means (2), 8
...... First relative azimuth error calculating means (1), 9 ...... Second relative azimuth error calculating means (2), 10 ...... Third relative azimuth error calculating means (3), 11 ...... Fourth Relative azimuth error calculating means (4), 12 ... First error range calculating means (1), 13 ...
Second error range calculation means (2), 14 ... azimuth calculation means,
15 ... Direction storage means, 16 ... Output means.

Claims (5)

[Claims] 1. An azimuth storing means for storing a moving azimuth of a moving body, an absolute azimuth sensor for detecting an absolute azimuth of a moving direction,
A first relative azimuth sensor having a characteristic that a relative azimuth in a traveling direction is detected and a zero-point drift depends on a moving distance of a moving body;
A first relative direction sensor that detects the relative direction of the traveling direction and has a characteristic that the zero-point drift depends on time, a first relative direction sensor, and a first addition for adding the outputs of the direction storage means.
Azimuth adding means, second azimuth adding means for adding the outputs of the second relative azimuth sensor and the azimuth storage means, a distance sensor for detecting a moving distance of a moving body, and an elapsed time detection for obtaining an elapsed time. A first relative azimuth error calculating means for estimating a sensitivity error range from the output of the first relative azimuth sensor; and a first relative azimuth error calculating means for estimating a zero point drift error range of the first relative azimuth sensor from the output of the distance sensor. 2 relative azimuth error calculating means, 3rd relative azimuth error calculating means for estimating the sensitivity error range from the output of the 2nd relative azimuth sensor, and 2nd relative azimuth sensor from the output of the elapsed time detecting means. Fourth relative azimuth error calculating means for estimating a zero point drift error range, and a first error range for calculating an error range of the first relative azimuth sensor from outputs of the first and second relative azimuth error calculating means. Calculating means, second error range calculating means for calculating an error range of the second relative direction sensor from outputs of the third and fourth relative direction error calculating means, the absolute direction sensor and the first The second azimuth adding means, the azimuth calculating means for estimating a new traveling azimuth of the moving body from the outputs of the first and second error range calculating means, and outputting it to the azimuth storing means, and the azimuth storing means. An azimuth detecting device comprising: an output unit that outputs a value of a traveling azimuth of a moving body. 2. The azimuth detecting device according to claim 1, wherein the first relative azimuth sensor is a wheel sensor that calculates a relative azimuth from the rotational speeds of the wheels on both sides of the moving body. 3. The azimuth detecting device according to claim 1, wherein the first relative azimuth sensor is a steering angle sensor for detecting a steering angle of a steering wheel of the moving body. 4. The azimuth detecting device according to claim 1, wherein the second relative azimuth sensor is an angular velocity sensor. 5. The azimuth detecting device according to claim 1, wherein the second relative azimuth sensor is an acceleration sensor that detects acceleration in the traveling direction of the moving body and in a direction perpendicular to the traveling direction.