JPH0324967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a front road surface condition detection device that detects the unevenness of a front road surface in the direction of movement of an automobile.

Prior Art Recently, a system has been developed that adjusts the suspension strength of an automobile according to the unevenness of the road surface. Feedback control is performed by detecting the unevenness of the road surface, and there is an unavoidable control delay when adjusting the strength of the suspension according to the unevenness of the road surface.

Purpose The present invention was made in consideration of the above points, and
The front road condition detection device is capable of accurately predicting the unevenness of the road surface in front of the vehicle in the direction of travel of the vehicle, and is able to perform optimal control of the vehicle's general suspension system, such as suspension without delay due to feed forward. This is what we provide.

In particular, in the present invention, a directional beam is emitted from the vehicle body onto the road surface at a certain distance in front of the vehicle, and the distance is measured by receiving the reflected wave, and the unevenness of the road surface is determined from changes in the beam length. The present invention provides a front road surface condition detection device which detects the condition and takes a correction means according to the change in beam length due to pitching of the vehicle body.

Configuration An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the principle of detecting the front road surface condition by the front road surface condition detection device of the present invention.
An optical system that uses triangulation to measure distances, with a light-emitting section at the front that emits a directional laser beam onto the road at a certain distance ahead, and a light-receiving section that receives the reflected waves from the road surface. A distance sensor 2 is provided, and when the distance measured by the distance sensor 2 is constant, the road ahead is flat (a), and when the measured distance is longer than the constant, the road ahead is concave (b). If it is short, it is detected that the road surface in front is a convex part (c).

FIG. 2 shows an example of the configuration of a basic front road surface condition detection device according to the present invention, in which a directional laser beam is emitted in a fixed direction and reflected from an object (in this case, the road surface) 3. It is comprised of an optical distance sensor 2 that receives waves and measures the distance therebetween, and a road surface condition determination circuit 4 that determines the unevenness of the road ahead based on the measurement results.

In addition, the optical distance sensor 2 uses a modulator 22 to modulate a laser drive signal from a power source 20 with a pulse signal having a constant period from a pulse generator 21, and the modulation signal to generate a laser emitter (semiconductor laser). 23, and the laser emitter 23 emits the laser beam with directionality through the collimating lens 24,
An optical position sensor 27 in which photoelectric conversion elements such as photodiodes and CCDs are arranged in an array so that the modulated beam reflected by the beam enters through a light receiving lens 25 and an optical filter 26.
and an amplification and demodulator 28 that amplifies and demodulates the signal outputted in time series from the sensor 27;
The encoder 29 decodes which element of the optical position sensor 27 outputs the demodulated signal and outputs data corresponding to the distance to the object 3. In addition, in the optical position sensor 27, a large number of photoelectric conversion elements P1 to Pn are arranged perpendicular to the optical axis, and as the distance to the object 3 changes, the photoelectric conversion elements P1 to Pn change. The position of the photoelectric conversion element that receives reflected waves is changed. However, in the optical distance sensor 2 configured in this way,
In particular, since a modulated laser beam is emitted from the light emitting part and the reflected light from the object 3 is demodulated by the light receiving part to measure the distance, it is possible to measure the distance without being affected by external light. Since the optical position sensor 27 uses photoelectric conversion elements arranged in a line, the distance to the object 3 can be measured with high accuracy even with a relatively low power beam output. Become something.

However, in the forward road surface condition detection device according to the present invention configured as described above, the optical distance sensor 2 is attached to the front of the automobile 1, for example, and the road surface at a certain distance in front of the sensor is irradiated with a modulated laser beam. If the reflected waves are received and subjected to amplification, demodulation, and encoding processing to measure the length of the distance according to the change in beam length, the road surface condition determination circuit 4 can detect the vehicle based on the measured data. It becomes possible to detect the uneven state of the road surface in front of the vehicle in the direction of travel.

In particular, the present invention is characterized in that such a forward road surface condition detection device takes into account pitching of the vehicle body and takes measures to correct an error in the measured distance due to pitching. In other words, when the device is fixedly attached to the vehicle body, the change in beam length due to pitching of the vehicle body accounts for a larger proportion than the change in beam length due to unevenness of the road surface in front of the vehicle, which is the object to be detected. The measurement result by the sensor 2 will include an error, and therefore it is necessary to take some kind of correction means to eliminate the effect of pitching of the vehicle body.

Therefore, in particular, in the present invention, as shown in FIG. 3, a pitching rate sensor 5 detects the pitching rate as the vehicle 1 travels, and a vertical displacement speed sensor detects the vertical displacement velocity at the virtual pitching center of the vehicle body. 6 and a vehicle speed sensor 7 that generates a sampling pulse signal corresponding to the running speed of the vehicle 1, and the outputs of these sensors are given to a road surface condition determination circuit 4' to perform arithmetic processing at a predetermined sampling period. The error due to pitching is corrected.

That is, when the car 1 pitches as shown in Fig. 4, the measurement beam length L is a function of h and θ under the relationship shown in Fig. 4, so dL/dt=∂L/∂θ・dθ/dt+∂ L/∂h ・dh/dt …(1) is given. Here, since L=1/cos θ, h=H−x, and H≈Ho+∫dθ/dt·dt, equation (1) is transformed into the following equation. Note that l is the distance from the virtual pitching center O of the vehicle body to the optical distance sensor 2.

cosθdL/dt=Lsinθdθ/dt+dH ₀ /dt +dθ/dt−dx/dt (2) Here, the output signal Vs of the optical distance sensor 2 and the output signal Vp of the pitting rate sensor 5 are respectively Vs=a(L −Lo) and Vp=bdθ/dt, equation (2) is transformed into the following equation. Note that Lo is the reference beam length when the vehicle 1 is stopped on a flat road and the flat road ahead is irradiated, and a and b are each constant coefficients.

dx/dt=(Vs/a+Lo)sinθ・Vp/b+dHo/dt+/Vp−cosθ/a・dVs/dt…(3) Also, θ changes depending on the pitching of the vehicle body, but here sinθ=α, cosθ=β(α,
β is a constant), equation (3) can be approximated as follows. In addition, the output signal of the vertical displacement speed sensor 31
Vh is given by Vh=cdHo/dt. c is a constant coefficient.

dx/dt≒{(Vs/a+Lo)α+}Vp/b-β/a ・dVs/dt+Vh/c...(4) Therefore, the time rate of change dx/dt of the unevenness information x on the front road surface is (4) Given by the equation, the unevenness ratio of the front road surface per unit detection interval τ as the vehicle 1 travels is τdx/dt.

In the road surface condition determination circuit 4', the output signal Vs of the optical distance sensor 2, the output signal Vp of the pitting rate sensor 5, and the output signal Vh of the vertical displacement speed sensor 6 are read, respectively.
For example, by calculating τ・dx/dt for each period τ of the sampling pulse sent from the vehicle speed sensor 7 according to the traveling speed of the automobile 1 by a predetermined calculation and making it continuous data, As shown, as the vehicle 1 travels, the unevenness of the road surface ahead is detected sequentially, with the error caused by pitching of the vehicle body being compensated for. In addition, the vehicle speed sensor 7
The period τ of the sampling pulse sent from
is given by τ=D/v, where v is the traveling speed of the automobile 1 and D (for example, 1 cm) is the traveling distance resolution. Further, the function of the road surface condition determining circuit 4' can be performed by a microcomputer.

Normally, the rate of displacement in the vertical direction of the virtual pitching center O of the vehicle body is sufficiently small compared to the rate of change in unevenness of the road surface, so there is no practical problem even if the term Vh/c in equation (4) is ignored. Therefore, the vertical displacement speed sensor 6 can be omitted.

In addition, in the forward road surface condition detection device according to the present invention, instead of the optical distance sensor 2 that uses a laser beam as a distance measuring medium, a general distance sensor that uses a beam such as an ultrasonic wave or a radio wave is used. Needless to say, this is a good thing.

Effects As described above, the forward road surface condition detection device according to the present invention can detect changes in beam length by irradiating a directional beam onto the road surface at a certain distance in front of the vehicle body and receiving the reflected waves. When measuring the length of the distance and determining the unevenness of the road surface in front of the vehicle based on the measurement results, a correction method is used to compensate for changes in beam length caused by pitching of the vehicle body. It has the excellent advantage of being able to accurately detect the unevenness of the road surface in front of the vehicle in the direction of travel without being affected by the noise, and allowing optimal control of the suspension and other systems without delay due to feed forward. have.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of detecting the unevenness of the front road surface in the front road surface condition detection device of the present invention, and FIG.
The figure is a block diagram showing an example of the basic configuration of the front road condition detection device according to the present invention, Figure 3 is a block diagram showing an example of the present invention, and Figure 4 is a diagram showing how the beam length changes due to pitching of the vehicle body. FIG. 5 is a characteristic diagram showing an example of the uneven state of the road surface ahead detected by the same embodiment. DESCRIPTION OF SYMBOLS 1...Car, 2...Optical distance sensor, 3...Object, 4, 4'...Road surface condition determination circuit, 5...Pitching rate sensor, 6...Vertical displacement speed sensor, 7...
Vehicle speed sensor.

Claims (1)

[Claims] 1. A distance measuring means that measures the length of the distance from changes in beam length by emitting a directional beam onto the road surface at a certain distance in front of the vehicle body and receiving the reflected waves; and A forward road surface condition detection device comprising means for determining a change in length, and means for correcting a measurement result by a distance measuring means according to the determined change and determining an uneven state of the road surface ahead. .