JPH11304529A - Method of calculating travel distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of calculating the travel distance whereby whether a slope is uphill or downhill can be determined. SOLUTION: Based on the output al of a first acceleration sensor 1 with its sensing direction aligned with the moving direction of a moving body and the output a2 of a second acceleration sensor 2 with its sensing direction aligned with a direction 90 deg. to the moving direction of the moving body, the absolute value of the tilt angle α of a road surface 3 is obtd. from a2 and whether a1 increases or decreases is judged from a sampling time to judge whether a road which the vehicle is running slopes upward or downward. The true acceleration A of the vehicle is calculated from the output a1 of the first acceleration sensor 1, tilt angle α and its positive/negative sign to calculate the travel distance of the vehicle from the true acceleration A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a traveling distance in a position detecting device incorporated in a navigation system of an automobile or the like, and more particularly to a method for calculating a traveling distance using an acceleration sensor.

[0002]

2. Description of the Related Art In a car navigation system, a GPS system for receiving a radio wave from a GPS satellite to detect a current position and a moving distance from a departure position of a vehicle are integrated to estimate a current position on a map. There is a self-contained navigation system. In this self-contained navigation system, a travel distance of a vehicle is calculated using a vehicle speed pulse generally generated according to rotation of a wheel.

[0003] In the navigation system, the map displayed on the television screen is viewed from directly above, but the roads displayed on the screen include not only flat roads but also inclined roads. Such a ramp is displayed on the screen in the same way as a flat road, and the distance on the screen ignores the actual inclination, and the actual distance of the ramp is longer than the distance on the screen. is there.

[0004] Therefore, if the distance traveled when the vehicle is traveling on an incline is calculated using the vehicle speed pulse as described above and is used as it is for calculating the current position of the vehicle, the vehicle distance on the television screen is calculated. There is a problem that a difference occurs between the position and the actual position of the vehicle. Therefore, conventionally, a position detecting device equipped with a vehicle tilt angle sensor has been proposed (for example, Japanese Patent Application Laid-Open No. 5-1920). In this conventional technique, the acceleration in the horizontal direction of the vehicle is calculated from the outputs of both the acceleration sensor and the inclination angle sensor, and the horizontal acceleration is double integrated to calculate the horizontal movement distance. The tilt angle sensor includes, for example, a sensor using a gyro and a sensor detecting optically. However, an inclination angle sensor using a gyro cannot detect unless the vehicle is moving. Further, even when the vehicle is stopped on a slope, if the inclination angle is θ and the gravity is g, the acceleration sensor is affected by the gravity, and gsi
When an output of nθ is generated and this is double integrated, (g sin
θ) to generate a t ^2/2 becomes error. On the other hand, optically detecting the inclination angle θ is mechanically expensive, and it is not practical to mount it on an automobile or the like.

Therefore, the present inventors have already proposed a method of calculating an inclination angle by using an acceleration sensor and capable of detecting the inclination angle even when the moving body is stopped (Japanese Patent Application No. Hei 10-26139). No. 7-193530). This inclination angle calculation method is based on a first mounting method which is mounted parallel to the traveling direction of the moving body.
And a first acceleration sensor attached at a predetermined angle to the traveling direction of the moving body,
The first and second accelerations are detected, respectively, and based on the first and second accelerations, a slope angle of the slope when the moving body advances on the slope is calculated, and a gravity component in the slope direction is calculated based on the slope angle. The gravity component in the slope direction is removed from the first acceleration to calculate the acceleration in the slope direction.

[0006]

However, in the above-described method of calculating the inclination angle, the absolute value of the inclination angle of the traveling road can be obtained, but the sign of the sign cannot be obtained. That is, the inclination angle θ is obtained by two acceleration sensors.
Is obtained by the following equation.

[0007]

[Number 1] _{^{θ = cos -1 {(α B}} -α A cosθ 2) / (gsinθ 2)} α A: not tilt mounting sensor output alpha _B: inclined mounting sensor output theta _2: inclination sensor Angle (Mounting Angle) As shown in Expression 1, since the inclination angle θ is represented by cos, even if θ is positive or negative, (α _B −α _A co
The value of (sθ ₂ ) / (g sin θ ₂ ) becomes the same, and the sign of θ cannot be determined.

For this reason, in the conventional method, it cannot be determined whether the running slope is an uphill or a downhill, and the influence of the gravity component due to the inclination angle cannot be removed. There are difficulties. For this reason, the acceleration of the moving object cannot be detected accurately, and the distance cannot be obtained accurately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a traveling distance calculation method capable of determining whether the vehicle is traveling uphill or downhill.

[0010]

A travel distance calculating method according to the present invention is characterized in that an output a1 of a first acceleration sensor whose detection direction coincides with a traveling direction of a moving object and a detection direction coincides with the traveling direction of the moving object. On the basis of the output a2 of the second acceleration sensor in the direction of an angle of 90 °, the absolute value of the road surface inclination angle α is calculated from a2, and the increase or decrease of a1 within a predetermined time is determined. It is characterized in that it is determined whether the road on which the mobile body is traveling is uphill or downhill.

In this running distance calculating method, the first
The true acceleration of the moving object can be calculated from the output a1 of the acceleration sensor, and the inclination angle α and the sign thereof. Then, the traveling distance of the moving body can be calculated from the true acceleration. When the output of the second acceleration sensor is equal to the gravitational acceleration g, it can be determined that the road is a flat road. Furthermore, when the output a1 of the first acceleration sensor matches gsinα, it can be determined that the vehicle has stopped uphill, and when it matches −gsinα, it can be determined that the vehicle has stopped downhill. . Furthermore, when the output a1 of the first acceleration sensor is 0, it can be determined that the vehicle has stopped on a flat road.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. First, the principle of determining whether the vehicle is going uphill or downhill on a ramp and the method of measuring the distance in the case of a ramp using the method of the present invention will be described. As shown in FIG. 1, it is assumed that an automobile equipped with a position detection device including a first acceleration sensor 1 and a second acceleration sensor 2 is climbing a slope 3. The inclination angle of the slope 3 is α, the acceleration detection direction of the first acceleration sensor 1 is the traveling direction of the vehicle, and the acceleration detection direction of the second acceleration sensor 2 is the inclination angle β with respect to the traveling direction of the vehicle. Shall be inclined. A is the true acceleration of the automobile, a1 is the first acceleration obtained as the sensor output of the first acceleration sensor 1, and a2 is the second acceleration obtained as the sensor output of the second acceleration sensor 2.

As a result, if the gravitational acceleration is g, the second
The second acceleration a2 detected by the acceleration sensor is expressed by the following equation (2).

[0014]

A2 = A cos β + g sin (α + β) In this equation 2, when β = 90 °, the following equation 3
Becomes

[0015]

A2 = Acos90 + gsin (α + 90) = gcosα This is a case where the detection direction of the second acceleration sensor 2 is upward and perpendicular to the detection direction of the first acceleration sensor 1, that is, the moving direction of the vehicle. It is. In this case, the inclination angle α of the slope is expressed by the following equation (4).

[0016]

Since α = cos ⁻¹ (a2 / g) −90 ° ≦ α ≦ 90 °, as is clear from Equation 4, α is α> 0, and the absolute value of the inclination angle is obtained. The sign, i.e., uphill or downhill, is not known.

On the other hand, when β = 0 °, the output of the second acceleration sensor 2 matches the output of the first acceleration sensor 1 and is expressed by the following equation (5).

[0018]

(A2 =) a1 = Acos0 + gsin (α + 0) =
A + g sin α In the present embodiment, the angle β between the detection direction of the second acceleration sensor 2 and the traveling direction of the vehicle is set to 90 °.
And the output α1 of the first acceleration sensor 1 at β = 0 °
The true acceleration A is obtained from (Equation 5) and the output α2 (Equation 3) of the second acceleration sensor 2 at β = 90 °.

First, in the case of a flat road, since α = 0 °, a1 = A is obtained from the above equation (5). Therefore, the acceleration on a flat road is obtained as the output a1 of the first acceleration sensor 1. By the way, the output a2 of the second acceleration sensor 2
Is a2 = g from Equation 3.

Next, a description will be given of a method of determining when the vehicle moves uphill from a flat road. As shown in FIG. 2, it is assumed that when the vehicle traveling on the flat road at time t1 moves uphill at an inclination angle α at time t2, t2-t1 is sufficiently short. This means that the sampling time of the calculation is, for example, 50 m.
s It may be sufficiently short as follows.

Thus, if t2−t1 is sufficiently short,
True acceleration A of the vehicle at time t1 (t = t1);
It can be assumed that the true acceleration A (t = t2) of the vehicle at time t2 is equal. Then, the acceleration a1 of the first acceleration sensor 1 is a1 = A on a flat road, whereas a1 = A + gsinα is obtained from Equation 5 on an inclined road, and sinα> 0 on an uphill road. The acceleration a1 (t = t2) of the first acceleration sensor 1 is larger than the acceleration a1 (t = t1) of the first acceleration sensor 1 at time t1. That is, a (t = t2)> a (t = t
Since this condition is obtained, it can be determined that the vehicle is traveling uphill.

Conversely, when the vehicle moves from a flat road to a downhill, since sinα <0, the output a1 of the first acceleration sensor 1 becomes smaller at time t2 than at time t1. That is, a1 (t = t2) <a1 (t = t1)
It is. Therefore, when this condition is obtained, it can be determined that the vehicle is going downhill.

In this manner, the vehicle can determine whether the current traveling road surface is an uphill or a downhill, and can calculate the absolute value of the inclination angle from Equation (4). Thus, the true acceleration A of the vehicle can be calculated from Expression 5.

Although the sampling time needs to be sufficiently short as described above, it is sufficient if the sampling time is about 50 ms or less. As shown in FIG. 3, consider a case where the road surface moves from an uphill slope with an inclination angle α to a downhill slope with an inclination angle α via a flat road of length L. When traveling at a speed of 100 km / h (approximately 28 m / s), the sample time is set to L in order to detect that the vehicle has moved from an uphill to a downhill.
/ 28 or less, and the sample time is 3 even if this L is extremely short, for example, 3 m when viewed from a normal road surface.
(M) / 28 (m / s) = approximately 100 ms or less. Therefore, the calculation load is not large.

The sign of the road surface inclination angle α is:
Since it is based only on the output of the first acceleration sensor 1,
Since a plurality of sensors are not used, the influence of temperature drift variation is small, and the calculation error does not increase.

Next, an embodiment of the present invention will be described with reference to FIGS. 4 to 6 are flow charts showing the method of this embodiment. Starting from a state in which the car is stopped (regardless of a flat road or a sloping road), the traveling distance is calculated every sampling time t. Note that Cα, C
A, Ca1, and S0 are respectively α,
This is a buffer area for temporarily storing A, a1, and S.
S indicates the traveling distance. First, set these initial values to 0
To clear. Then, the output a of the second acceleration sensor 2
It is determined whether 2 does not match g (step S1),
If they do not match (YES), the absolute value of the road surface inclination angle α is obtained from Expression 4 (step S2). If a2 matches g (NO), it is determined that the road is a flat road, and step S
Move to 3. In the case of this flat road, the first acceleration sensor 1
If the acceleration a1 is zero (YES), it is determined that the vehicle is stopped on a flat road, and if a1 is not zero (N
In O), this a1 becomes the true acceleration A of the vehicle (step S3).

On the other hand, when the road surface is inclined, a1 = g
If it is sinα, it is determined that the vehicle has stopped on an uphill (step S4). When a1 = −g sin α, it is determined that the vehicle is stopped on the downhill (step S5). Note that S transfer means transmitting the calculation result of S to navigation or the like.

When a1 is not ± gsinα,
The vehicle is traveling on a ramp. Therefore, FIG.
According to the flowchart shown in FIG.
If | does not change from the previous time (YES), step S7
When it is determined that there is no change in the sign (YE
S) means an uphill if the previous time was an uphill, and a downhill if the last time was a downhill, and the true acceleration A is obtained by equation P1. Also,
If there is a change in sign (NO), it means a downhill if the previous time was an uphill, and an uphill if the previous time was a downhill.
Is obtained by Expression P2. On the other hand, in step S6, if | α | has changed from the previous value (NO), it is determined whether or not the previous time is a flat road (step S8), and if it is a flat road (Y).
ES) determines whether or not the output a1 of the first acceleration sensor 1 has increased from the value at the previous sampling time (step S9). If a1 has increased (NO), It is determined that the vehicle has moved uphill from a flat road, and a
If 1 has decreased (YES), it is determined that the vehicle has shifted from a flat road to a downhill. In that case, the true acceleration A is obtained by equations P3 and P4, respectively.

If it is determined in step S8 that the previous time is not a flat road (NO), it means that the vehicle has changed from a sloping road to a sloping road, and whether the previous α is positive or negative is determined. A determination is made (step S10). If the previous α is positive, the previous time is up, and if negative, the previous time is down. If the previous time was an uphill, a1 was Ca1 +
It is determined whether or not gsin (α−Cα) (step S11). In the case of YES, the change is from up to up, and the true acceleration A is given by equation P5. On the other hand, in the case of NO, it is a change from ascending to descending, and the true acceleration A is obtained by equation P6. If it is determined in step S10 that the last time was a descent, a
It is determined whether or not 1 is Ca1 + gsin (α-Cα) (step S12), and if YES, it has changed from descent to descent, and the true acceleration A is given by equation P7. On the other hand, in the case of NO, the vehicle has changed from descending to ascending, and the true acceleration A is obtained by equation P8.

Next, in the flowchart of FIG.
It is determined whether or not the true acceleration A is 0 (step S13),
If it is not 0, it is determined whether or not the previous true acceleration CA and the current true acceleration A match (step S1).
4). Originally, this should match, but for example, if there is a slight error in relation to the sampling time,
If it is within 5%, for example, it is determined to be the same (ignored) and the value calculated as described above is set as a true value (step S1).
4). If the error is large, the true acceleration A1 is recalculated using the previous inclination angle Cα (step S15). Then, since the true acceleration of the previous time and the true acceleration of the present time are basically the same, the one with the smaller absolute value difference is selected as the true acceleration (step S16). That is, if A obtained as described above is closer to the previous value, this A is set to the true acceleration, and if A1 recalculated is closer to the previous value, this A1 is set to the true acceleration A (step S17). ). Thereafter, the distance is calculated using the true acceleration A (step S18),
The calculated distance S and the true acceleration A are stored in a buffer of the computer. Further, the distance S is transferred to a navigator or the like.

[0031]

As described above, according to the present invention,
A first acceleration sensor having a traveling direction as a detection direction and a second acceleration sensor having a detection direction perpendicular to the traveling direction are used. It is determined whether the vehicle has moved uphill or downhill, and the absolute value of the inclination angle of the road surface is obtained from the output of the second acceleration sensor. Therefore, the acceleration of the moving object is measured with high accuracy regardless of the road surface can do. Further, according to the present invention, it is possible to detect an uphill or downhill and an inclination angle even when the moving body is stopped. Since the acceleration is detected by the acceleration sensor as described above, the vehicle speed pulse is unnecessary, and the position detecting device can be easily mounted on the vehicle body.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a traveling distance calculation method according to the present invention.

FIG. 2 is a diagram illustrating the principle of a traveling distance calculation method according to the present invention.

FIG. 3 is a diagram illustrating sample timing.

FIG. 4 is a flowchart illustrating a method according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method according to an embodiment of the present invention.

FIG. 6 is a flowchart illustrating a method according to an embodiment of the present invention.

[Explanation of symbols]

 1: first acceleration sensor 2: second acceleration sensor 3: road surface

Claims (7)

[Claims] 1. An output a1 of a first acceleration sensor whose detection direction matches the traveling direction of a moving body, and a second acceleration whose detection direction is at an angle of 90 ° with respect to the traveling direction of the moving body. Based on the output a2 of the sensor, the absolute value of the road surface inclination angle α is calculated from a2, and the increase or decrease of a1 within a predetermined time is determined to determine whether the road on which the moving body is traveling is uphill or downhill. A traveling distance calculation method characterized by determining whether the vehicle is on a slope. 2. An output a1 of the first acceleration sensor,
The travel distance calculation method according to claim 1, wherein a true acceleration of the moving body is calculated from the inclination angle α and the sign thereof. 3. The travel distance calculation method according to claim 1, wherein the travel distance of the moving body is calculated from the true acceleration. 4. The method according to claim 1, wherein when the output of the second acceleration sensor is located at a gravitational acceleration g, the road is determined to be a flat road. Driving distance calculation method. 5. An output a1 of the first acceleration sensor is gsin
The travel distance calculation method according to any one of claims 1 to 4, wherein it is determined that the vehicle has stopped on an uphill when the vehicle speed is equal to α. 6. The output a1 of the first acceleration sensor is -gsi
The travel distance calculation method according to any one of claims 1 to 4, wherein it is determined that the vehicle is stopped on a downhill when the vehicle speed is equal to nα. 7. The traveling distance according to claim 1, wherein when the output a1 of the first acceleration sensor is 0, it is determined that the vehicle is stopped on a flat road. Calculation method.