JPH02280077A - Vehicle attitude detecting device - Google Patents

Abstract

PURPOSE:To simplify the constitution of this device by using a sensor which can detect directly an inclined state against the road surface of a vehicle without allowing the car height to intervene. CONSTITUTION:A frequency fd of an irregular reflection wave received by a receiver 6 is shifted from a transmitting frequency fs by a Doppler effect caused by a car speed V, the shift quantity is varied together with a radiation angle theta, and when a distance h between a transmitter/a receiver and the road surface, and an interval 2S of the transmitter/the receiver are given, fd can be calculated and the radiation angle theta can be derived. Also, since a radiation angle theta0 in a state that a vehicle is not inclined in the beginning can also be known in advance, an inclination angle gamma=theta-theta0 of the vehicle can be derived. At the time of pitching centering around the transmitter and the receiver 4, 6, as well, although h is varied to some extent in the case of a loaded car, the influence exerted on fd is very small and h is decided to be invariable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle attitude detection device that detects changes in the attitude of a vehicle with respect to a road surface using the Doppler effect of ultrasonic waves.

(Prior Art) In recent years, automobiles detect changes in the attitude of the vehicle relative to the road surface, that is, changes in the tilt angle of the vehicle relative to the road surface due to roll, pitch, etc., and perform various controls based on the changes in the tilt angle.
For example, electronic suspension control is performed.

Conventionally, devices for detecting changes in the attitude of the vehicle (changes in inclination angle) include a reed switch type, Hall IC type, or photointerrupter type installed at multiple locations such as the front and rear of the vehicle, for example, at each location where the four wheels are located. etc., and the vehicle height value detected by each sensor, that is, 4
A device is used that is configured to detect the angle of inclination of the vehicle based on the vehicle height value at each location where the wheels are located.

However, these reed switch type, Hall IC
Both type and photo-interrupter type vehicle height sensors divide the vehicle height into several regions depending on the relative position between the elements that make up the sensor, for example, between the reed switch and the magnet in the case of a reed switch type. The detection is performed in a stepwise manner, and therefore it is not possible to continuously detect changes in vehicle height or even inclination angle of the vehicle.

On the other hand, for example, in Japanese Utility Model Application Publication No. 80-53077, the vehicle height is detected by transmitting ultrasonic waves towards the road surface, receiving reflected waves from the road surface, and measuring the propagation delay time between transmission and reception. An ultrasonic vehicle height sensor has been disclosed, and it is also possible to use this ultrasonic vehicle height sensor in place of the reed switch type vehicle height sensor or the like. When the ultrasonic vehicle height sensor is used in this manner, it becomes possible to continuously detect the vehicle height and, by extension, the change in the vehicle's inclination angle.

(Problem to be Solved by the Invention) However, all of the above-mentioned vehicle attitude detection devices are configured using a vehicle height sensor that measures the vehicle height rather than a sensor that directly measures the inclination angle of the vehicle. In order to determine the angle, as mentioned above, multiple vehicle height sensors must be used and they must be installed at separate locations on the vehicle, making the device configuration complicated and assembling the device difficult.
Various problems have arisen, such as an increase in the cost of the device and a decrease in reliability against device failure.

In view of the above circumstances, an object of the present invention is to provide a vehicle attitude detection device that uses a sensor that can directly detect the inclination of a vehicle with respect to a road surface rather than through the vehicle height, thereby simplifying the device configuration. It's about doing.

(Means for Solving the Problems) A vehicle attitude detection device according to the present invention includes a transmitter installed in a vehicle and transmitting ultrasonic waves at a predetermined radiation angle with respect to a road surface; a receiver 2 for receiving diffusely reflected waves from the road surface of the ultrasonic waves transmitted from the transmitter installed in the vehicle; and a frequency detecting means for detecting the frequency of the diffusely reflected waves received by the receiver; vehicle speed detection means for detecting; and inclination angle calculation means for calculating an inclination angle of the vehicle with respect to the road surface based on the frequency of the diffusely reflected wave detected by the frequency detection means and the vehicle speed detected by the vehicle speed detection means. It is characterized by comprising the following.

(Function) If a transmitter is provided in a vehicle to transmit ultrasonic waves at a predetermined radiation angle to the road surface as described above, the radiation angle changes depending on the inclination of the vehicle.

On the other hand, the frequency f is transmitted from the transmitter while the vehicle is running.

When an ultrasonic wave of There is a quantitative shift. The amount of frequency shift, that is, the amount of Doppler shift (f a f s
) of course depends on the speed of the vehicle, but
Furthermore, it changes depending on the change in the radiation angle with respect to the road surface.

Therefore, by detecting the change in the receiving frequency f, and subtracting the change in f6 due to the change in vehicle speed from the change, the change in f4 due to the change in the radiation angle with respect to the road surface can be obtained, and the change in f due to the change in the radiation angle can be calculated. Changes in angle, that is, changes in vehicle posture, can be determined.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the ifi dual attitude detection device according to the present invention. 2 is a rear side view of an automobile in which a transmitter and a receiver shown in FIG.

As shown in the figure, two similar types are arranged on the rear lower surface 2a of the vehicle 2 in the vehicle width direction and placed at a predetermined interval 2S = 10 mm.
Super wave transducer for 00KllZ (e.g. MA2
An ultrasonic transmitter 4 and a receiver 6 made of 0[]Al) are provided.

The transmitter 4 is connected to an oscillator 8 and has a predetermined frequency (
Transmission frequency) fs ultrasonic waves are transmitted to the road surface 10 at a predetermined radiation angle. More specifically, the transmitter 4 is installed at a height h-240 from the road surface IO,
The ultrasonic waves are transmitted toward the rear of the vehicle and to a point a distance S=35Mn away from the vehicle width direction receiver 6, and the radiation angle at that time is projected onto a plane perpendicular to the ground extending in the longitudinal direction of the vehicle. The angle is θ-45°. Note that the transmitter 4 adjusts the emission angle θ of the ultrasonic waves to the road surface from θ−0 to
It is configured so that it can be changed within a range of 90°.

The ultrasonic waves transmitted from the transmitter 4 are diffusely reflected by the road surface lO, and a part of the diffusely reflected waves are received by the receiver 6, and the amplifier circuit 12. The frequency (reception frequency) of the diffusely reflected wave inputted to the frequency counter 18 as a frequency detection means through the BPFI 4° amplification circuit 1B and received by the frequency counter 18 is detected, and the detected reception frequency f is The signal is input to an inclination angle detection means 24 consisting of a memory circuit 20 and an arithmetic circuit 22.

Further, the vehicle speed signal (vehicle speed V) detected by the vehicle speed detecting means 2G is input manually to the inclination angle detecting means 24. The vehicle speed detection means 26 includes a vehicle speed sensor 28 that generates pulses in response to the rotation of the vehicle engine, and a counter circuit 30 that counts the pulses output from the vehicle speed sensor 28.

The inclination angle detection means 24 detects the reception frequency f.

The tilt angle of the vehicle is detected based on the vehicle speed V and the vehicle speed V.

The detection principle is as follows.

That is, in the device configured as described above, the frequency f4 of the diffusely reflected wave received by the receiver 6 is lower than the transmission frequency fS by a predetermined amount (
Doppler shift amount), and the Doppler shift amount also depends on the radiation angle θ of the ultrasonic wave, and when the radiation angle θ changes, the Doppler shift amount also changes, and the reception frequency f4 of the diffusely reflected wave decreases. Formula (1)
is expressed by

c+Vcos α In addition, in the above formula, [, is the above transmission frequency.

C is the speed of sound, V is the vehicle speed, and α is the effective angle determined by the radiation angle θ, the distance between the transmitter/receiver and the road surface, and the distance M between the transmitter and receiver, cosa-018 □. θ)lh 2+ s 2+ (h
/la+, o> 2 r' (21).

Therefore, if the vehicle now tilts by an angle γ as shown by the broken line in Fig. 1 due to pitching, the emission angle θ of the ultrasonic wave will also change by γ (in this case, it will become smaller by γ), resulting in eO3α also changes, and the reception frequency f changes.

However, since the above fs, c, h, and s can be known in advance, if the vehicle speed V and reception frequency f are detected as above, the radiation angle can be determined based on them and the above equations (11 and (2)). Since θ can be determined and the radiation angle θ0 when the vehicle is not tilted can also be known in advance, the tilt angle γ−θ−〇 of the vehicle can be determined.

Incidentally, the inclination of the vehicle shown in FIG. 2 is due to pitching around the transceiver 4.degree. 6, and h does not change, but 11 changes somewhat in the actual inclination of the vehicle. However, the effect of this change in h on the reception frequency fd is very small, so there is almost no problem even if h is treated as not changing.

The inclination angle detection means 24 is based on the above-mentioned detection principle,
f3, which has been input in advance. c, h, s.

θ0, the frequency detection means 18 and the vehicle speed detection means 2G
The inclination angle γ of the vehicle is determined from the reception frequency f6 detected and input by the vehicle speed V, and any specific calculation method may be used. For example, the vehicle speed
A map showing the relationship between the radiation angle θ and the reception frequency fd may be created, and the tilt angle γ of the vehicle may be determined based on the map, or the reception frequency f may be calculated as in the illustrated embodiment. The previous received frequency f is inputted to the circuit 22 and the memory circuit 20, and the previous received frequency f is inputted from the memory circuit 20 to the arithmetic circuit 22, and the arithmetic circuit 22 constantly compares the previous received frequency f4 with the current received frequency f4. Check whether the frequency f6 has changed, and if it has changed, take into account the change in vehicle speed, subtract the change due to the change in vehicle speed from the change in f, and calculate the vehicle inclination angle from the remaining change. Changes may also be detected.

In the above embodiment, the case where the emission angle θ varies due to pitching has been explained, but even when the vehicle rolls, the ultrasonic emission angle θ changes due to a change in the vehicle's inclination angle, so the receiving frequency f , changes, and therefore, a change in the tilt angle of the vehicle can be detected from a change in the reception frequency f. Note that the magnitude of the change in reception frequency due to pitching and the magnitude of change in reception frequency due to rolling are different in order, with the former being larger, so it is possible to identify which change is due to the order.

The present inventor proposed that the embodiment shown in FIG. Tilting in the direction (pitching)
The vehicle is mounted on a vehicle that can be moved forward and backward, and the vehicle is driven at a constant speed of Go/Q++/hr on a flat road surface. The amount of change (f, -f,') in the received frequency was measured. The results are shown in FIG. Note that f6 above is the reception frequency when the vehicle is not tilted, and fd/ is the reception frequency when the vehicle is tilted by γ.
, -f,' are configured to be displayed by the display 32 connected to the arithmetic circuit 22 in the embodiment shown in FIG.

From FIG. 3, it can be seen that as the inclination angle of the vehicle changes, the amount of change in the reception frequency also changes, and a correlation equivalent to the theoretical value is obtained between the two.

The inventor also conducted a similar test in the speed range of 5 to 80)Q++/hr, and confirmed that a correlation equivalent to the theoretical value was obtained between the two.

The vehicle attitude detection device according to the present invention has the following features:
It is possible to detect changes in the tilt angle of the vehicle due to each of rolling and pitching with two transmitter/receiver units, but for example, as shown in FIG. One transmitter/receiver unit is provided symmetrically on the left and right as shown in FIG. The transmitters 4 may be arranged at intervals, and each transmitter 4 may be configured to transmit ultrasonic waves outward in the vehicle width direction and toward the rear. If configured in this way, the difference in reception frequency between the two transmitter/receiver units will be reduced. Therefore, it is possible to detect changes in the received frequency due to rolling, thereby making it possible to distinguish and accurately detect changes in the tilt angle of the vehicle due to both rolling and pitching.

(Effects of the Invention) As described above, the vehicle attitude detection device according to the present invention includes the inclination angle calculation means, and the calculation means determines that the frequency Doppler shift amount of the diffusely reflected wave reflected from the road surface depends on the vehicle speed and the radiation angle. Based on this, the radiation angle and the tilt angle of the vehicle are calculated from the reception frequency of the diffusely reflected wave and the vehicle speed, so it is possible to directly determine the tilt condition of the vehicle. This has the effect of simplifying the device configuration compared to the conventional detection via vehicle height.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a side view of the rear of a vehicle equipped with the transmitter and receiver of the embodiment shown in FIG. 1, and FIG. 3 is the same as shown in FIG. 1. FIG. 4 is a plan view showing the arrangement of transmitters and receivers in another example.

Claims (1)

[Scope of Claims] A transmitter installed in a vehicle that transmits ultrasonic waves at a predetermined radiation angle with respect to a road surface; and a transmitter installed in a vehicle that receives diffusely reflected waves from the road surface of the ultrasonic waves transmitted from the transmitter. a receiver for detecting the frequency of the diffusely reflected wave, a frequency detecting means for detecting the frequency of the diffusely reflected wave received by the receiver, a vehicle speed detecting means for detecting the vehicle speed, and a frequency of the diffusely reflected wave detected by the frequency detecting means and the vehicle speed detection. A vehicle attitude detection device comprising: inclination angle calculating means for calculating an inclination angle of the vehicle with respect to the road surface based on the vehicle speed detected by the means.