JPH08304440A - Vehicle-speed detection apparatus - Google Patents

Abstract

PURPOSE: To provide an intelligent vehicle-speed detection apparatus which does not require a signal from the outside and in which the actual speed in the advance direction of a running body can be detected by an accelerometer. CONSTITUTION: A vehicle-speed detection apparatus is provided with a sensor part B which is arranged on the same axis as the advance direction of a running body and which comprises at least one accelerometer 1 and with a control part C which extracts a low-frequency component contained in an acceleration signal to be output from the accelerometer 1, which finds an acceleration in the advance direction on the basis of the posture angle, of the running body, computed from the extracted low-frequency component and on the basis of a running component extracted from a high-frequency component contained in the acceleration signal to be output from the accelerometer 1 and which computes the actual speed in the advance direction of the running body on the basis of the found acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the traveling acceleration of a traveling body as an acceleration signal with an accelerometer, calculates the posture angle of the traveling body from the detected acceleration signal, and accelerates in the traveling direction based on the calculated posture angle. And a vehicle speed detection device that measures the actual speed of the traveling body in the traveling direction from the calculated acceleration.

[0002]

2. Description of the Related Art Conventionally, by receiving radio waves from GPS satellites,
A car navigation system based on GPS navigation that recognizes the current position and traveling direction of the vehicle is well known.
Autonomous navigation is also used for proper navigation even in places where it is difficult to receive radio waves from GPS satellites, such as in tunnels, high-rise buildings, and underpasses. This autonomous navigation attaches a sensor to the vehicle, detects the traveling direction and speed of the vehicle,
The information obtained by this sensor is corrected by radio waves from GPS satellites. Therefore, as shown in FIG. 9, when the vehicle speed of the car navigation system 17 is taken in, the rotation sensor 16 takes in the rotation of the tire 15 as a pulse signal P. If the pulse interval is narrow (T1), the speed is high. If the interval is wide (T2), the vehicle speed is estimated to be slow, but this pulse signal P
Is not provided as a standard specification of the vehicle,
In order to obtain a pulse signal, it is necessary to attach a pulse signal output device such as a rotation sensor.

Therefore, when the car navigation system is introduced, the vehicle is remodeled, so that a vehicle-related sales company, a parts-related sales company, etc. are forced to sell exclusively, and cannot be handled by a general sales company. , It was not possible to make a dramatic expansion in the market.

Further, as described above, a general commercial vehicle does not provide the pulse signal P for car navigation. Therefore, in order to use the car navigation system, in addition to the system purchase cost, an extra remodeling cost is required. Had to pay.

[0005]

SUMMARY OF THE INVENTION The present invention has been made under the above background, and does not require a signal from the outside, and the actual speed in the traveling direction of the traveling body can be calculated from the acceleration signal detected by the accelerometer. It is an object of the present invention to provide an intelligent type vehicle speed detection device capable of detecting a vehicle speed.

[0006]

To achieve the above object, a vehicle speed detecting device of the present invention comprises a sensor section having at least one accelerometer arranged on the same axis as the traveling direction of a traveling body, and the acceleration described above. A low-frequency component included in the acceleration signal output by the meter is extracted, and the posture angle of the traveling body calculated from the extracted low-frequency component and a traveling component extracted from the high-frequency component included in the acceleration signal output by the accelerometer And a control unit that calculates the actual acceleration in the traveling direction of the traveling body from the obtained acceleration.

[0007]

According to the above construction, the sensor section detects the acceleration of the running body as an acceleration signal by the accelerometer and sends it to the control section. The control unit extracts the low frequency component and the high frequency component included in the acceleration signal, calculates the posture angle of the traveling object based on the extracted low frequency component, and calculates the traveling component based on the high frequency component. The acceleration in the traveling direction is calculated from the calculated posture angle and the traveling component, and the actual speed in the traveling direction of the traveling body is calculated from the calculated acceleration in the traveling direction.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, reference numeral A indicates a vehicle speed detecting device, and the vehicle speed detecting device A includes a sensor section B and a control section C.

The sensor section B is composed of the accelerometer 1, and the acceleration signal detected by the accelerometer 1 is provided so as to be sent to the control section C.

The accelerometer 1 is fixed on the same axis as the traveling direction d of the traveling body 3 on a substrate 2 horizontally arranged in the sensor section B, and the traveling direction (forward direction, backward direction) of the traveling body 3 is fixed. ) Is provided so as to detect the traveling acceleration and the posture angle (tilt angle) of the traveling body 3. The accelerometer 1 is a sensor developed for vehicle impact detection and is often used in vehicles (for example, an accelerometer SCA12 (trade name) manufactured by semiconductor technology manufactured by Baisara Co., Ltd.). Should be used.

The control unit C has an analog interface 5
An external interface 6, a CPU 7, and a memory 8
And a logic circuit 9 are provided so as to output the calculation result to a self-contained navigation unit (not shown) of the car navigation system, for example, via a signal cable 10.

The analog interface 5 is the accelerometer 1.
The high-speed analog data processing is performed, and includes an amplifier that amplifies the acceleration signal detected by the accelerometer 1 and an AD converter that digitizes the detection signal.

The CPU 7 processes the acceleration signal of the accelerometer 1 converted into a digital signal by the analog interface 5 according to a predetermined program stored in the memory 8. When the traveling body 3 is tilted, the accelerometer 1 also detects the gravitational acceleration at the same time, so it is necessary to subtract the gravity component from the output acceleration signal. The inclination of the traveling body 3 is calculated based on the low frequency component extracted from the acceleration signal. The angle is calculated, the acceleration in the traveling direction is calculated based on the calculated inclination angle, the calculated acceleration is subjected to rate integration calculation, and the calculated result is output as actual speed data.

The external interface 6 is the CPU 7 described above.
It is provided so that the actual speed (vehicle speed data) obtained by calculation in step 1 is converted and output according to the connected system. When connecting to a car navigation system, the external interface 6 may convert the vehicle speed data into a pulse signal P and output it.

FIG. 3 shows a hardware function diagram of the vehicle speed detecting device, and FIG. 4 shows a software configuration diagram.

A vehicle speed detecting device A constructed as described above.
Shows the frequency vs. posture angle / acceleration graph of FIG. 6 and the speed calculation algorithm of FIG. 7 regarding the measurement of the actual speed in the traveling direction when the vehicle is loaded on the traveling body 3 (automobile) as shown in FIG. It will be explained based on.

The accelerometer 1 detects the traveling state of the automobile 3 and inputs it to the control section as an acceleration signal γ. The control unit extracts the gravity component γ _L from the low frequency component included in the input acceleration signal γ, and calculates the attitude angle θ of the automobile 3 from the extracted gravity component γ _L. This low frequency component extracts the input acceleration signal γ through a low pass filter having a cutoff frequency F0.

Next, the traveling component γ _{H of the} automobile is extracted by utilizing the high frequency component contained in the acceleration signal γ, and the traveling acceleration β in the traveling direction is calculated based on the extracted traveling component γ _H and the posture angle θ. calculate. This high frequency component γ _H extracts the input acceleration signal γ through a high pass filter having a cutoff frequency F1.

The traveling acceleration β in the traveling direction is calculated by subjecting the traveling component γ _H of the acceleration signal γ to posture calculation processing (γ _H cos θ) to calculate the acceleration a in the traveling direction, and the calculated acceleration a is processed in the integrated acceleration velocity calculation processing. Calculate the actual speed in the direction.

In FIG. 8A, assuming that the vertical gravitational acceleration is g, the influence of the tilt of the automobile 1 on the accelerometer γ _L (gravitational component) is the calculation formula (1). Therefore, from the calculation formula (1), The attitude angle θ of the automobile 3 is obtained by the calculation formula (2).

Γ _L = g · sin θ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1) θ = sin ⁻¹ (γ _L / g) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・(2) In FIG. 8B, assuming that the traveling acceleration in the traveling direction is β, the traveling direction component β is obtained from the traveling component γ _H and the posture angle θ extracted from the high frequency components of the acceleration signal γ measured by the accelerometer. Is calculated by the formula (3).

Β = γ _H · cos θ (3) The above formulas (1), (2) and (3) are programmed in advance and stored in the memory 8. Therefore, the CPU 7 extracts the influence of gravity exerted by the inclination of the automobile 3 on the accelerometer 1 from the acceleration signal γ output from the accelerometer 1 through a low-pass filter, and based on the extracted influence of gravity (gravitational component) γ _L. The tilt angle θ of the automobile 1 is calculated (calculation formula (2)).
The acceleration β in the traveling direction is calculated from the traveling component γ _H and the posture angle θ extracted from the acceleration signal γ output from the accelerometer 1 through the high-pass filter (calculation formula (3)), and the calculated acceleration β in the traveling direction is accelerated. The actual speed V in the traveling direction of the automobile 1 can be obtained by performing the integral calculation in the integral speed calculation process.

Although the basic algorithm is as described above, the following measures are taken in order to correct the change in the measured value due to various noises generated by the actual vehicle.
The first is temperature countermeasures. In this temperature countermeasure, the operating temperature range of the vehicle speed detection device is set to -20 to +70 degrees Celsius. The accelerometer 1 used depends on the temperature and the data drifts. The temperature is corrected so that the calculation result is not affected even if the detection signal fluctuates. In this temperature correction, changes due to temperature are measured in advance, a correction table is created in a program, and a temperature detected by a temperature detecting means (not shown) and a temperature correction algorithm for correcting the acceleration signal by the correction table are added. . As the temperature detecting means, for example, a temperature sensor such as a thermistor or an integrated temperature sensor of a monolithic IC type may be incorporated in the control section C so that the temperature can be known by software.

Furthermore, since the automobile 3 is accompanied by vibration during traveling, noise due to vibration is mixed in the signal output from the sensor section B, and the calculation data becomes inaccurate. The accuracy of the actual speed V was increased by introducing it into the filtering process.

The actual speed V calculated by the CPU 7 is
As a signal form that the car navigation system 17 can process, it is converted into a pulse signal P by the external interface 6 and output.

As described above, when the traveling body 3 travels on the traveling road, the acceleration signal γ output from one accelerometer 1 is generated by traveling (starting, accelerating, decelerating, stopping, etc.) and is plus or minus at high speed. It utilizes that the acceleration component (traveling component γ _H ) that changes with the acceleration component and the acceleration component (gravitational component γ _L ) that occurs due to the posture angle (road inclination) of the traveling object and that changes at low speed are included. is there.

Since the acceleration signal γ obtained from the accelerometer 1 contains the gravity component γ _L due to the inclination of the automobile 3, the low frequency component extracted by the low-pass filter is converted into the gravity component γ _L and obtained. The attitude angle θ of the automobile is calculated from the gravity component γ _L, the acceleration β in the traveling direction is calculated based on the traveling component γ _H and the attitude angle θ extracted from the high frequency components of the acceleration signal γ, and the calculated traveling direction Since the actual velocity V in the traveling direction can be calculated by rate integration of the acceleration β of the above, it is not necessary to input an external signal such as a rotation sensor for detecting the rotation of the wheel, and the accelerometer 1 built in the device can be used. The actual speed V of the traveling body 3 in the traveling direction can be detected only by processing the obtained signal, and an intelligent type vehicle speed detection device A can be realized.

As a result, it is possible to construct a car navigation system that does not require the rotation sensor 16 for detecting the rotation of the wheels 15, so that the traveling body 3 does not need to be specially modified. Therefore, the sales company handling the car navigation system does not need to have any special conditions, it can be handled by a general electric appliance sales company, and the sales company is not limited, so that the system can be dramatically expanded.

Further, since the speed can be detected only by placing it in the vehicle, the labor and cost involved in the modification can be reduced, and the car navigation system can be easily remounted when it is moved to another traveling body.

Furthermore, since there are no subtle errors due to the number of passengers in the automobile 3, the gravity of the luggage, the wear of tires, etc., it is not necessary to automatically correct the actual speed on the car navigation system, and the load on the system is reduced. To be done.

Although the vehicle speed detecting device described above detects the posture angle and the acceleration in the traveling direction of the traveling body from one accelerometer, the acceleration sensor for detecting the posture angle and the acceleration for detecting the acceleration in the traveling direction are used. The accelerometer and the accelerometer are respectively placed on the board, and the attitude angle is calculated from the acceleration signal of one accelerometer from among the acceleration signals input from each accelerometer. The control unit may control the acceleration signal so as to calculate the acceleration in the traveling direction based on the posture angle obtained from the acceleration signal.

[0032]

According to the vehicle speed detection device of the present invention, the posture angle is calculated based on the low frequency component included in the acceleration signal output from the accelerometer, and the calculated posture angle and the traveling component obtained from the high frequency component are calculated. The acceleration in the traveling direction is calculated based on the obtained acceleration, and the actual speed in the traveling direction can be detected by rate integration of the obtained acceleration in the traveling direction. Therefore, an external signal such as a rotation sensor for detecting the rotation of the wheel is input. There is no need, and the actual speed of the traveling body in the traveling direction can be detected only by processing the signal obtained from the accelerometer built into the device, and an intelligent type vehicle speed detection device can be realized.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of a vehicle speed detection device of the present invention.

FIG. 2 is a perspective view showing an example of a configuration of the vehicle speed detection device.

FIG. 3 is a hardware functional diagram of the vehicle speed detection device.

FIG. 4 is a software configuration diagram of the vehicle speed detection device.

FIG. 5 is an explanatory diagram showing a traveling state of a traveling body equipped with a vehicle speed detection device.

FIG. 6 is a graph of frequency vs. attitude angle / acceleration showing a relationship between attitude angle and acceleration in a frequency band of an acceleration signal.

FIG. 7 is a block diagram showing a basic algorithm of software.

8A and 8B are vector diagrams showing the relationship between acceleration, gravitational acceleration and inclination angle.

FIG. 9 is an explanatory diagram showing a conventional speed detection method.

[Explanation of symbols]

 1 Accelerometer 3 Traveling object A Vehicle speed detection device B Sensor part C Control part

Claims (1)

[Claims] 1. A sensor unit having at least one accelerometer arranged on the same axis as a traveling direction of a traveling body, and a low frequency component included in an acceleration signal output from the accelerometer, and the extracted low frequency. The acceleration in the traveling direction is calculated based on the posture angle of the traveling body calculated from the components and the traveling component extracted from the high frequency components included in the acceleration signal output from the accelerometer, and the traveling direction of the traveling body is calculated from the obtained acceleration. A vehicle speed detection device comprising: a control unit that calculates an actual speed.