JP2000074931A - Car-speed detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make obtainable an accurate car speed value even when no output of a sensor for the ground speed of car can be utilized by setting the ground speed of a car as output car speed when both of rotary speed and the ground speed of a car can be detected, calculating and holding the correction coefficient of the rotary speed, and multiplying the rotary car speed by a held correction coefficient when the ground speed of a car cannot be measured. SOLUTION: An operation circuit 3 takes in a rotary car speed and a ground speed of a car from a rotary car speed sensor 1 and a sensor 2 for the ground speed of a car to judge whether the ground speed of a car is within a set error range with respect to the rotary car speed. When both are within the set error range, it is judged that the ground speed of the car is a normal value, thus calculating the correction coefficient of the rotary car speed for the ground speed of the car, holding it in a memory 5, and at the same time, outputting the ground speed of the car as car speed information. When the ground speed of the car is not within a set error range for the rotary car speed, it is judged that the car speed cannot be detected accurately due to the change in road surface condition, correction coefficients of on times in the past are subjected to running averaging, the rotary car speed is multiplied by the obtained result, and the value is outputted as the current vehicle speed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed detecting device for a vehicle including both a rotary vehicle speed sensor for detecting a vehicle speed corresponding to a wheel rotational speed and a ground vehicle speed sensor for directly detecting a ground vehicle speed such as a Doppler system. About. The present invention relates to an automatic cruise device, a speed limit device, and other devices that perform automatic control in accordance with a detected vehicle speed, and other devices suitable for use as a measured value input of the device.

[0002]

2. Description of the Related Art A rotating vehicle speed sensor is a device that measures a rotating speed from an output of a wheel rotation sensor or a rotation sensor of a propeller shaft and outputs a vehicle speed value. On the other hand, various types of ground vehicle speed sensors are known that detect reflected ground waves using sound waves (including ultrasonic waves) or electromagnetic waves and directly detect ground speed using the Doppler effect. In general, the output value of the rotating vehicle speed sensor does not become unmeasurable, but the error included in the output value is large because the effective diameter of the tire fluctuates due to the tire pressure and the load of the vehicle, and the output of the ground vehicle speed sensor is The value may be unmeasurable depending on road conditions, while the measured value is accurate.
For example, on a smooth road surface having almost no physical unevenness, an output value may fluctuate greatly and an incorrect value may be displayed.

For this reason, conventionally, the ground vehicle speed sensor cannot be used alone, and is used in combination with the rotating vehicle speed sensor. Then, when a value significantly different from the value of the rotating vehicle speed sensor is detected by the ground vehicle speed sensor, a technique is known in which two detection outputs are switched and used so as not to use the output value of the ground vehicle speed sensor ( JP-A-4-
212086).

[0004]

In the above prior art, when the output of the ground vehicle speed sensor cannot be used, the vehicle speed value can be obtained from the rotating vehicle speed sensor. It is a value that fluctuates depending on the tire pressure and the vehicle load, and is not necessarily an appropriate value for use as a measured value input for control.

[0005] The present invention has been made in such a background, and even when the output from the ground vehicle speed sensor cannot be used temporarily, an accurate vehicle speed value can be used. It is intended to provide a device. SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle speed detecting device that can always detect a vehicle speed value having an accuracy almost equal to the accuracy of a ground vehicle speed sensor.

[0006]

SUMMARY OF THE INVENTION The present invention corrects the detected value of a rotary vehicle speed sensor when the detected value of a ground vehicle speed sensor outputs an incorrect value due to the condition of a road surface and corrects the vehicle speed. The information is output as information.

That is, the present invention relates to a vehicle speed detecting device provided with a rotating vehicle speed sensor for measuring a rotating vehicle speed (Vc) corresponding to a wheel rotating speed and a ground vehicle speed sensor for directly measuring a ground vehicle speed (Vt). When both the rotating vehicle speed (Vc) and the ground vehicle speed (Vt) are detected, the ground vehicle speed (Vt) is set as the output vehicle speed, and a correction coefficient (α) of the rotating vehicle speed with respect to the ground vehicle speed is calculated. α), and means for outputting a value obtained by multiplying the rotation vehicle speed (Vc) by the correction coefficient held by the holding means when the ground vehicle speed cannot be measured as an output vehicle speed. .

The holding means includes a means for holding, as a correction coefficient, a moving average value of the past n correction coefficients calculated by the calculating means, and stores the measured n past ground vehicle speed (Vt). Simultaneously measured rotating speed (V
When a value exceeding the error range set for c) is included, it is desirable to include means for removing the value from the original data for calculating the moving average value.

The output of the rotating vehicle speed sensor and the output of the ground vehicle speed sensor are taken, and the rotating vehicle speed (Vc) corresponding to the wheel rotating speed is obtained.
And the ground vehicle speed (Vt) is directly measured and detected. When the difference between the detected output values of the rotating vehicle speed sensor and the ground vehicle speed sensor (difference or ratio of deviation) is within a set error range, the detected rotating vehicle speed (Vc) and ground vehicle speed (Vt) are Assuming that the vehicle has substantially the same accuracy, a ground vehicle speed (Vt) that is more accurate than the rotational vehicle speed (Vc) is output as vehicle speed information, and at the same time, a correction coefficient (α) of the rotational vehicle speed (Vc) with respect to the ground vehicle speed (Vt) is obtained. = Vt / Vc) and stores it in the memory.

The state of the road surface changes and the ground vehicle speed (Vt) indicated by the ground vehicle speed sensor and the rotating vehicle speed (V) indicated by the rotating vehicle speed sensor are detected.
If c) exceeds the set error range, it is determined that accurate ground vehicle speed (Vt) cannot be measured, and the rotational vehicle speed (Vc) detected by the rotational vehicle speed sensor is determined.
Is multiplied by the correction coefficient (α) stored in the memory and output as accurate vehicle speed information.

The memory holds the moving average value of the correction coefficient calculated over the past n times. However, if the measured and detected past ground vehicle speed (Vt) includes a value exceeding an error range set for the simultaneously measured and detected rotating vehicle speed (Vc), the value is calculated as a moving average. The value is removed from the original data to be calculated, and the correction coefficient (α) by which the rotating vehicle speed (Vc) is multiplied is made more accurate.

It is considered that the error of the rotating vehicle speed (Vc) is caused by the change of the effective diameter due to the tire pressure and the load, and this error hardly changes suddenly, but changes gradually with the passage of time. I do. Therefore, when the measurement and detection of the ground vehicle speed (Vt) becomes impossible, the correction is performed by assuming that the tire pressure or the cargo amount immediately before that is maintained as it is, and the rotation vehicle speed (Vt) is corrected.
The vehicle speed calculated from c) becomes accurate.

Thus, when the detection output from the ground vehicle speed sensor cannot be used temporarily, it is possible to output, as vehicle speed information, a vehicle speed value having an accuracy almost equal to the accuracy of the ground vehicle speed sensor in a normal state. it can.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of an embodiment of the present invention.

The embodiment of the present invention includes a rotating vehicle speed sensor 1 for measuring a rotating vehicle speed (Vc) corresponding to a wheel rotating speed, a ground vehicle speed sensor 2 for directly measuring a ground vehicle speed (Vt), and the rotating vehicle speed sensor 1. And an arithmetic circuit 3 which takes in the output of the ground vehicle speed sensor 2 and sets and outputs the vehicle speed in accordance with the situation at that time. Further, as a feature of the present invention, the arithmetic circuit 3 includes a rotating vehicle speed (Vc) and a ground vehicle speed. When both (Vt) are detected, the calculation means 4 calculates the correction coefficient (α) of the rotation vehicle speed (Vc) with respect to the ground vehicle speed (Vt) while using the ground vehicle speed (Vt) as the output vehicle speed, and the correction coefficient (α). α) and an output means 6 for outputting a value obtained by multiplying the rotation vehicle speed (Vc) by the correction coefficient (α) stored in the memory 5 as an output vehicle speed when the ground vehicle speed cannot be measured. Erareru.

The memory 5 has a means for holding a moving average value of the past n correction coefficients α calculated by the calculation means 4 as a correction coefficient, and a memory for the past n measured ground vehicle speeds (V
When t) includes a value exceeding an error range set for the simultaneously measured rotational speed (Vc), means for removing the value from the original data for calculating the moving average value is included. .

Next, a control operation by the arithmetic circuit of the embodiment of the present invention thus configured will be described. FIG. 2 is a flowchart showing the flow of the control operation by the arithmetic circuit according to the embodiment of the present invention.

The arithmetic circuit 3 fetches the vehicle speed (Vc) and the vehicle speed (Vt) from the vehicle speed sensor 1 and the vehicle speed sensor 2, and calculates the vehicle speed (Vt) based on the vehicle speed (Vt).
It is determined whether or not it is within an error range set in advance for c).

If the ground vehicle speed (Vt) and the rotation vehicle speed (Vc) are within the set error range, the ground vehicle speed (Vc) is assumed to indicate a normal value, and the ground vehicle speed (Vt) is assumed to be normal.
Correction coefficient (α = Vt / V)
c) is calculated. Next, the calculated correction coefficient (α)
Is stored in the memory 5 and the ground vehicle speed (Vt) is output as vehicle speed information.

If the ground vehicle speed (Vt) is not within the error range with respect to the rotating vehicle speed (Vc), it is assumed that accurate vehicle speed detection has not been performed due to a change in road surface conditions, and the past n correction coefficients (α ) Is calculated. This moving average value is multiplied by the rotation speed (Vc) and the value is output as the current true vehicle speed value.

[0022]

[Outside 1] The correction coefficient (α) is calculated based on the rotational speed (Vc) and the ground speed (Vc) taken from the rotational speed sensor 1 and the ground speed sensor 2.
t) is calculated at a predetermined time interval,
Each time the map in the memory 5 is updated with the latest n times (for example, 50
Times). However, among the rotational speed (Vc) and the ground speed (Vt) measured at the same time,
If there is a value in which the ground vehicle speed (Vt) exceeds an error range set with respect to the rotating vehicle speed (Vc), this value is removed, and a moving average value [outside 1] based on the latest n data within the error range is calculated. Is the correction coefficient (α) at that time.

As described above, the latest n including no abnormal value
The correction value (α) is calculated based on the data of each time, and the ground speed (Vt) is estimated and calculated using the correction value (α) each time. Therefore, the vehicle speed value close to the true value is always output as control information. Can be.

[0024]

As described above, according to the present invention, when the output from the ground vehicle speed sensor cannot be used temporarily, the output of the rotating vehicle speed sensor is corrected and calculated, so that the ground speed is always calculated. A vehicle speed with an accuracy almost equal to the accuracy of the vehicle speed sensor can be detected, and an accurate vehicle speed value can be output as control information.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of a control operation by an arithmetic circuit according to the embodiment of the present invention.

[Description of Signs] 1 Rotating vehicle speed sensor 2 Ground speed sensor 3 Operation circuit 4 Operation means 5 Memory 6 Output means

Claims (3)

[Claims] 1. A rotating vehicle speed (V) corresponding to a wheel rotating speed.
c) In a vehicle speed detection device provided with a rotating vehicle speed sensor for measuring c) and a ground vehicle speed sensor for directly measuring ground vehicle speed (Vt), when both the rotating vehicle speed (Vc) and the ground vehicle speed (Vt) are detected Means for setting the ground vehicle speed (Vt) to the output vehicle speed and calculating a correction coefficient (α) of the rotation vehicle speed with respect to the ground vehicle speed; and means for holding the correction coefficient (α)
Means for outputting a value obtained by multiplying the rotation vehicle speed (Vc) by the correction coefficient held by the holding means when the ground vehicle speed cannot be measured, as an output vehicle speed. 2. The vehicle speed detecting apparatus according to claim 1, wherein said holding means includes means for holding, as a correction coefficient, a moving average value of the past n correction coefficients calculated by said calculating means. 3. The measured ground vehicle speed (Vt) for the past n times
3. A method according to claim 2, further comprising the step of, when a value exceeding an error range set for the simultaneously measured rotating vehicle speed (Vc) is included, removing the value from the original data for calculating the moving average value. Vehicle speed detection device.