JPH0610617B2 - 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 As a conventional azimuth detecting device, for example, the actual kai 61-72
618.

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. It has the advantage that it is less susceptible to external influences, but has the drawback that the traveling direction of the moving body gradually shifts due to the drift 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 when the difference between the two becomes larger than a certain value, the output of the absolute azimuth sensor is regarded as an abnormal value. Judgment is made by adding the output of the relative azimuth sensor to the traveling azimuth of the moving body calculated immediately before to make a new traveling azimuth. I was guessing.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, when a vehicle is assumed as a moving body, a relatively expensive sensor cannot be used as a direction sensor in many cases, so that the accuracy of the relative direction sensor cannot be sufficiently ensured in many cases. Also, although there are two types of drift of the relative direction sensor, one that changes depending on the time and one that changes depending on the moving distance of the moving body, only the sensor having one of the characteristics is used. Since it was not available, it could not be said to be sufficient for supplementing the absolute 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 is directed to an azimuth storage unit that stores a traveling azimuth of a moving body, an absolute azimuth sensor that detects an absolute azimuth of a traveling direction,
A first relative direction sensor that detects the relative azimuth of the traveling direction and has the characteristic that the drift depends on the moving distance of the moving body, and a second relative sensor that detects the relative azimuth of the traveling direction and that has the characteristic that the drift depends on the time. Azimuth sensor, first azimuth adding means for adding the outputs of the first relative azimuth sensor and the azimuth storage means, and second azimuth for adding the outputs of the second relative azimuth sensor and the azimuth storage means. Adder means, a distance sensor for detecting a moving distance of the moving body, a first relative azimuth error calculating means for estimating an error range of the first relative azimuth sensor from an output of the distance sensor, and an elapsed time for obtaining an elapsed time. Detecting means, second relative azimuth error calculating means for estimating the error range of the second relative azimuth sensor from the output of the elapsed time detecting means, the absolute azimuth sensor and the first azimuth adding means, and the second Azimuth Azimuth calculating means for estimating a new moving azimuth of the moving body from the outputs of the calculating means, the first relative azimuth error calculating means, and the second relative azimuth error calculating means, and outputting it to the azimuth storing means, and the azimuth storing means. And an output unit that outputs the value of the traveling direction of the moving body stored in the azimuth detecting apparatus.

Operation The present invention has a total of 3 types of the relative azimuth sensor and the absolute azimuth sensor having the characteristics that the drift depends on the moving distance of the moving body and the characteristics that depend on the time due to the above-described configuration.
There will be different types of orientation sensors. 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. .

EXAMPLES Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an azimuth detecting apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an absolute azimuth sensor such as a geomagnetic sensor that detects the absolute azimuth of a moving body such as a car, and 2 is a relative azimuth of the moving azimuth of the moving body. A first relative azimuth sensor such as a wheel sensor having a dependent characteristic is a second relative azimuth sensor such as an angular velocity sensor having a characteristic that the relative azimuth in the traveling direction of the moving body is detected and the drift depends on the elapsed time. is there. Is a first azimuth addition means for adding the azimuth change amount calculated by the first relative azimuth sensor and the traveling azimuth immediately before the moving body, and 5 is the azimuth change amount calculated by the second relative azimuth sensor. And a second azimuth adding means for adding the moving azimuth of the moving body immediately before that. Reference numeral 6 is a distance sensor for detecting the moving distance of the moving body, and 7 is a first relative bearing error calculating means for calculating a bearing error of the first relative bearing sensor from the moving distance of the moving body detected by the distance sensor. is there. Reference numeral 8 is an elapsed time detecting means for detecting an elapsed time, and 9 is a second relative bearing error calculating means for calculating a bearing error of the second relative bearing sensor from the elapsed time detected by the elapsed time detecting means. Reference numeral 10 is an azimuth for calculating the traveling azimuth of the moving body from the outputs of the absolute azimuth sensor, the first azimuth adding means, the second azimuth adding means, the first relative azimuth error calculating means, and the second relative azimuth error calculating means. Computing means, 1
Reference numeral 1 is an azimuth storing means such as a memory for storing the traveling azimuth calculated by the azimuth calculating means, and 12 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. Note that the azimuth calculating means, the first relative azimuth error calculating means, the second relative azimuth error calculating means, the first azimuth adding means, and the second azimuth adding means can be configured by hardware, but a microprocessor is used here. I will describe the case that it is realized by software. FIG. 4 is a flowchart showing the processing procedure. First, in step 401, an initial value 0 is substituted for a constant T indicating the elapsed time after the drift correction of the second relative azimuth sensor. Next, at step 402, the direction change amount Δθ ₁ of the moving body detected by the relative direction sensor ₁
And the moving amount Δθ ₂ of the moving body detected by the second relative direction sensor 2 and the moving direction θ ′ of the moving body immediately before stored in the direction storage means, the moving body moves as determined by the relative direction sensor. The azimuths θ ₁ and θ ₂ are calculated. In step 403,
The constant time T is added with the elapsed time Δt since the traveling direction immediately before the moving body detected by the elapsed time detecting means is calculated, and the elapsed time T after the second relative direction sensor performs the drift correction. To calculate. In step 404, the error range of the azimuth error due to the drift of each relative azimuth sensor is obtained. Since the azimuth error due to the drift of the first relative azimuth sensor depends only on the distance traveled by the moving body, if the error is proportional to the travel distance Δ1, the azimuth error Δθ _E1 is expressed as Δθ _E1 = a × Δ1. Here, a is a proportional constant. On the other hand, the azimuth error due to the drift of the second relative azimuth sensor depends only on time. If the drift is proportional to the elapsed time T after correcting the drift of the sensor and the proportional constant is b,
The drift ω _{E2 at a} certain time t is ω _E2 = b × t. Therefore, the azimuth error Δθ _E2 is Δθ _E2 = ∫ω _E2 dt = b × Δt × (T + Δt / 2) by integrating the drift ω _E2 from T to T + Δt. To derive the error range of each relative direction sensor,
These relational expressions are used. This is shown in FIG.
Corresponds to the relative azimuth error calculating means and the second relative error calculating means. In step 405, using the traveling directions θ ₁ and θ _{2 of} the moving body calculated up to step 404 and the error ranges Δθ _E1 and Δθ _E2 expected from the drift, the traveling direction of the moving body estimated from the two relative direction sensors is used. Direction estimation range θ ₁
Find the common range of ± Δθ _E1 , θ ₂ ± Δθ _E2 . Second (a),
Figure (b) shows an example. In this case, since the presumed range of heading of the moving body to be inferred from the second relative direction sensor are included in the presumed range of heading of the moving body is estimated from the first relative direction sensor, the common area theta ₂ It becomes ± Δθ _E2 . If there is a common area, let the maximum value be θ _R-MAX and the minimum value be θ _R-MIN . In this example, θ _R-MAX = θ ₂ + Δθ _E2 θ _R-MIN = θ ₂ −Δθ _E2 . The opposite of this example, such as when they both share only a part, or when there is no shared area, etc., but especially when there is no shared area, θ _R-MAX , θ
_A value that cannot be taken normally is assigned to _{R-MIN so} that the presence or absence of the shared area can be determined by θ _R-MAX and θ _R-MIN . In step 406, the presence or absence of the common area is determined from the values of θ _R-MAX and θ _R-MIN . If the common area exists, the process proceeds to step 407, and if not, the process proceeds to step 411. In step 407, the traveling azimuths θ _a of the moving body, which are obtained from the absolute azimuth sensor, and θ _R-MAX and θ _R-MIN are compared. θ _a is θ _R-MIN ≤ θ _a ≤
If the condition of θ _R-MAX is satisfied, the process proceeds to step 411, and if not satisfied, the process proceeds to step 408. Step 408
Then, it is determined whether or not θ _a > θ _R-MAX is satisfied. If θ _a > θ _R-MAX , the process proceeds to step 410, and if θ _a <θ _R-MIN , the process proceeds to step 409. In steps 409, 410, and 411, 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 such as a memory (θ ').
← θ). Then, in step 413, the new heading θ is sent as an output. The relationship between the new traveling direction θ and θ _R-MIN , θ _R-MAX , θ _a is as shown in FIGS. 3 (a), (b), (c) and (d). In step 414, it is determined whether the drift of the relative azimuth sensor 2 has been corrected. If the drift is corrected, the process proceeds to step 401 and the azimuth is calculated from the beginning by the same procedure. However, if it is not corrected, the process proceeds to step 402 and the value of the elapsed time T is saved to calculate a new azimuth. To do.

As described above, according to the present embodiment, one kind of relative azimuth sensor is obtained by using two kinds of relative azimuth sensors having a distance-dependent drift characteristic and time-dependent drift characteristics with the same weight. The error range of the relative azimuth sensor is narrower than that when it is used. Therefore, it is possible to improve the accuracy of the traveling azimuth of the moving body obtained in combination with the absolute azimuth sensor as compared with the case of combining one absolute azimuth sensor and one relative azimuth sensor.

In this embodiment, two types of relative azimuth sensors having a distance-dependent drift characteristic and a time-dependent drift characteristic are used with the same weight, but one of them is weighted to determine the relative azimuth. It 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. Further, in the present embodiment, the software is realized by using the microprocessor, but this may be realized by the hardware. Further, the expected error range of the relative azimuth obtained from the first relative azimuth sensor is said to be proportional to the moving distance of the moving body. However, even if this is not proportional, the error characteristic depends on the moving distance. Good. Further, the expected error range of the relative azimuth obtained from the second relative azimuth sensor is said to be proportional to the elapsed time after the drift sensitivity of the sensor corrects the drift. Need only depend on the elapsed time.

EFFECTS OF THE INVENTION As described above, the present invention has two types of the first relative azimuth sensor having the drift characteristic depending on the moving distance of the moving body and the second relative azimuth sensor having the drift characteristic depending on the elapsed time. Since it has a relative azimuth sensor, the elapsed time is long but the moving distance of the moving body is short.It is used independently when traveling slowly in a traffic jam in an urban area or at high speed running where the elapsed time is relatively short but the moving distance is long. It is possible to calculate the relative azimuth with less error than when using the 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 explanatory views of azimuth determination in the present embodiment, and FIG. 4 is a flowchart of the azimuth detecting apparatus in the present embodiment. is there. 1 ... Absolute direction sensor, 2 ... First relative direction sensor
(1), 3 ... second relative direction sensor (2), 4 ... first direction adding means (1), 5 ... second direction adding means (2), 6 ...
Distance sensor, 7 ... First relative bearing error calculating means (1),
8 ... Elapsed time detecting means, 9 ... Second relative heading error calculating means (2), 10 ... Heading calculating means, 11 ... Heading storing means, 12 ... Outputting 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 direction sensor that detects the relative azimuth of the traveling direction and has the characteristic that the drift depends on the moving distance of the moving body, and a second relative sensor that detects the relative azimuth of the traveling direction and that has the characteristic that the drift depends on the time. Azimuth sensor, first azimuth adding means for adding the outputs of the first relative azimuth sensor and the azimuth storage means, and second azimuth for adding the outputs of the second relative azimuth sensor and the azimuth storage means. Adder means, a distance sensor for detecting a moving distance of the moving body, a first relative azimuth error calculating means for estimating an error range of the first relative azimuth sensor from an output of the distance sensor, and an elapsed time for obtaining an elapsed time. Detecting means, second relative azimuth error calculating means for estimating the error range of the second relative azimuth sensor from the output of the elapsed time detecting means, the absolute azimuth sensor and the first azimuth adding means, and the second Who An azimuth calculating means for estimating a new traveling azimuth of the moving body from the outputs of the adding means, the first relative azimuth error calculating means, and the second relative azimuth error calculating means, and outputting it to the azimuth storing means, and the azimuth storing means. And a means for outputting the value of the traveling direction of the moving body stored in the azimuth detecting apparatus. 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 direction sensor is a steering angle sensor for detecting a steering angle of a steering wheel of a moving body. 4. The azimuth detecting device according to claim 1, wherein the second relative azimuth sensor 2 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 an acceleration of a moving body and an acceleration in a direction perpendicular to the traveling direction.