JPH11211745A - Speed distance meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a speed distance meter inexpensively which can measure highly accurately without being influenced by a tire pressure and slips. SOLUTION: An accelerometer 12 of an input shaft parallel to a back-forth direction of a moving body is set to the moving body. An angle θ of a road face at the present position to a horizontal face is taken from a database 21 based on present position data. A gravitational acceleration component ag= Gsinθ is obtained at gravitational acceleration processing unit 23, and subtracted from an output (a) of the accelerometer 12. The function (a-ag) is integrated twice, so that a running distance L is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed and distance meter for measuring the speed or moving distance of a moving body such as an automobile or a railway train using an accelerometer.

[0002]

2. Description of the Related Art Conventional speed / distance meters measure speed or distance by measuring the number of revolutions of wheels, as found in speedometers of automobiles. On the other hand, there are radio wave Doppler speed and inertial navigation system.

[0003]

The conventional speed / distance meter based on the rotational speed of the wheel has a disadvantage that the diameter of the wheel changes due to a change in the tire air pressure, resulting in an error. There is also a disadvantage that the wheels cannot slip at the time of acceleration or braking, and the correct speed cannot be obtained. On the other hand, the Doppler type and the inertial navigation system have a disadvantage that they are expensive.

An object of the present invention is to provide a low-cost and high-accuracy speed / distance meter that eliminates the conventional disadvantages.

[0005]

According to the present invention, there is provided a database in which a front-back inclination angle of a road surface with respect to a traveling position is stored,
The inclination angle of the traveling position is read from the inclination angle data based on the traveling position detected by the traveling position detection means, and the magnitude of the gravitational acceleration input to the longitudinal axis of the moving body is determined from the inclination angle in the longitudinal direction of the moving body. The acceleration is detected by an accelerometer which is calculated by a calculating means and the longitudinal axis of the moving body is used as an input axis, and the gravitational acceleration in the longitudinal direction of the moving body is corrected by the correcting means, and the corrected acceleration data is corrected. Is integrated by the integrating means to calculate the traveling speed of the moving body, and the traveling speed is further integrated to calculate the traveling distance (that is, the traveling position) of the moving body.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1A, an accelerometer 12 whose input axis is parallel to the front and rear of the moving body is attached to the moving body 11. The moving body 11 travels along the road surface 14 from the starting point 13 and is currently traveling on an inclined road surface inclined at an angle θ with respect to the horizontal plane.

FIG. 2 shows a functional configuration of an embodiment of the present invention. The accelerometer 12 detects the acceleration of the moving body 11 in the front-rear direction, and at the same time, this detection output includes the component of the earth's gravitational acceleration along the road surface 14. This is shown in FIG. 1B. Although the moving body 11 is in a stopped state, that is, the acceleration of the moving body itself is zero, the earth gravity acceleration G
A component ag = Gsin θ along the road surface 14 (the direction of the vector is upward) is generated at the output a of the accelerometer 12.

Therefore, the road surface inclination angle θ at each position of the road surface 14
Is provided, and the mobile unit 11 is stored.
Is read out from the database 21 based on the current position data. The road surface inclination angle θ and the output a of the accelerometer 12 are input to the speed / distance calculation unit 22, and the gravitational acceleration component ag = Gsin θ due to the inclination is calculated by the earth gravity acceleration component calculation unit 23. On the other hand, ag is subtracted from the input accelerometer output a by the subtraction unit 24, and the true acceleration magnitude ao of the moving body 11 is obtained. The moving body acceleration ao is integrated by the integration unit 25 to determine the speed v, and the speed v is integrated again by the integration unit 26 to obtain the travel distance L.

In order to determine the current position, the position detecting section 27 integrates the obtained instantaneous value of the speed v for each short time (appropriately determined according to the speed) to obtain a short running distance Δ
L is obtained, and this ΔL is multiplied by cos θ to obtain this ΔLcos θ
Is added and the starting point position L input initially at the start of traveling is calculated.
Add to o. Thus, the moving distance is obtained, that is, the current position on the map is obtained, and the database 21 may be read based on the current position. The current position may be detected by other means such as GPS.

When the moving body 11 is supported by a wheel suspension or the like, the input shaft of the accelerometer 12 is
May not be parallel to the front-back direction. This parallelism error becomes a speed error. Therefore, distance sensors 31 and 32 such as optical sensors are provided before and after the moving body to measure the distance between the road surface and the vehicle body.
1 calculates the angle Δθ with respect to the road surface 14 in the front-rear direction by the parallelism calculation unit 33, and corrects the θ by adding and subtracting the θ in the correction unit 34 according to the angle Δθ. You can get it right.

[0011]

As described above, according to the present invention,
The measurement can be performed with high accuracy irrespective of changes in tire pressure, wheel slip, and the like, and the configuration can be made at low cost.

[Brief description of the drawings]

FIG. 1A is a diagram illustrating a state in which a moving body is traveling on an inclined road surface, and FIG. 1B is a diagram illustrating the influence of the output of the accelerometer 12 on the earth's gravitational acceleration.

FIG. 2 is a block diagram showing a functional configuration of the embodiment of the present invention.

Claims (3)

[Claims] 1. A speed odometer mounted on a moving body traveling along a road surface and measuring a speed distance of the moving body, wherein a database storing a forward-backward inclination angle of the road surface with respect to a running position is provided; Means for detecting the traveling position of the vehicle, means for reading the inclination angle of the traveling position from the database, and calculating the magnitude of the gravitational acceleration input to the longitudinal axis of the moving body from the inclination angle; An accelerometer having an input axis of: a means for correcting the calculated gravitational acceleration in the longitudinal direction of the moving object from an output of the accelerometer; and a means for calculating the traveling speed of the moving object by integrating the corrected acceleration data. Means for calculating the traveling distance of the moving body by integrating the traveling speed. 2. The speed range finder according to claim 1, further comprising means for correcting a parallelism error of an input shaft of the accelerometer on the moving body with respect to the road surface. 3. The parallelism error correcting means according to claim 1, wherein the parallelism error is corrected by measuring a parallelism by measuring a distance between the moving body and a road surface. 2. The speed rangefinder according to 2.