JPH01172757A - Correlation type speedometer also used in measurement of friction coefficient - Google Patents

Abstract

PURPOSE:To use a sensor and an operational processing system in the detection of a speed and that of a friction coefficient in common, by calculating a speed from a shift time when the correlation function of the detection outputs of two sensors arranged in a moving direction becomes max. CONSTITUTION:The signals detected by sensors 1, 3 and the signal detected by a blind sensor 5 are respectively amplified by noise compensation amplifiers 7, 9. The effect of an electromagnetic wave is removed from the sensor 5 by subtraction processing. The signals compensated in noise are applied to high-pass filters 11, 13 to extract high frequency components. The outputs of the BPFs 11, 13 are inputted to automatic gain controllers (AGC) 17, 19 and the output of the AGC 17 is rectified in a waveform through a limiter 21. Further, the output of the AGC 19 is inputted to an analogue multiplexer 21 and, further, the output of the multiplexer 21 is inputted to a limiter 25 and the outputs of the respective limiters are converted by A/D converters 31, 33 to be red by a digital signal processor (DSP) 35. By this method, the sensors and the operational processing apparatus can be used in the detection of a speed and that of a friction coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a correlation type speedometer, and particularly to a correlation type speedometer that can also measure the friction coefficient of a road surface at the same time.

[Conventional technology]

Correlation type speedometers are generally used to detect speeds such as flow speeds and vehicle speeds.

The principle of a conventionally used correlation type speedometer will be explained with reference to FIGS. 4 and 5.

For example, suppose that the previous generation sensor A and sensor B are mounted on a car with an interval l as shown in Fig. 5, and are detecting reflected light from the road, as shown in Fig. 4 (a) and (b), respectively. Suppose that a sensor output like this is obtained.

Then, the detection output of sensor A is set to M at sampling period Δt.
The detection output of sensor B is
(N>M) samples. The sum of products P for these sampling periods ta is determined as follows.

(However, iS j is an integer.) From this, the correlation function 5(j) is obtained as follows. For this 5(j), by increasing the time by Δt (N
-M) Calculate the correlation function, and from the deviation time nΔt (n is the number of deviations) that gives the largest correlation function, the speed ■ is determined as V = R/ nΔt.

In addition, switching between 2 wheels and 74 wheels, controlling the center differential lock, controlling the braking force, etc. are performed by comparing and determining the engine driving force and the force acting on the wheels. When calculating the coefficient of friction, the road surface condition is determined by the light reflected from the road surface.

[Problem that the invention seeks to solve]

By the way, by measuring the actual vehicle speed and the friction coefficient of the road surface at the same time,
When performing drive control or braking control of a vehicle, it is necessary to install similar optical sensors separately for speed detection and friction coefficient measurement, which requires a processing system for each detection signal, which is wasteful and There were problems in terms of sensor installation space and cost.

The present invention is intended to solve the above-mentioned problems.By combining speed detection, a sensor for determining the friction coefficient, and a signal processing system, the device can be made more compact and the cost can be reduced. The purpose is to provide a type speedometer.

[Means for solving problems]

To this end, the present invention provides a calculation processing means into which the detection output of two sensors arranged in the movement direction is input, a light source for illuminating the road surface, and a means for turning on and off the light source controlled by the calculation processing means. The calculation means calculates a correlation function between the detection outputs of the two sensors, determines the speed from the time lag at which the correlation function value becomes maximum, and calculates the difference between the sensor detection outputs when the light source is turned on and off. It is characterized by calculating the road surface friction coefficient from

[Action and effect of the invention]

The present invention calculates the speed from the time difference when the correlation function between the detection outputs of two sensors arranged in the moving direction becomes maximum, and also calculates the reflectance of the road surface from the difference in sensor output when the light source is turned on and off. By detecting and determining the friction coefficient, the sensor and processing system can be shared for speed detection and friction coefficient detection, making the device more compact and
Cost reduction can be achieved.

〔Example〕

Examples will be described below based on the drawings.

Fig. 1 is a block diagram showing the configuration of the correlation type speedometer for measuring the friction coefficient of the present invention, Fig. 2 is a waveform diagram, and Fig. 3 is a diagram showing a time chart. 1.3 is a sensor, and 5 is a blind sensor. , 7.9 is a noise compensation amplifier, 11.13 is a high-pass filter, 15 is a buffer, 17.19 is an auto gain controller (AGC), 21 is an analog multiplexer, 23.25 is a limiter, 27 is a light source/switch controller, 29 is a light source, 31.33 is an A/D converter, 35 is D S P (D 1g1tal S ig
nal Processer), 37.39 is an internal RAM, and 41 is a Schalbot memory sled.

In FIG. 1, the signal detected by the sensor 1.3 and the signal detected by the blind sensor 5 are each subtracted and amplified by a noise compensation amplifier 7.9. The blind sensor is in a light-shielded state, and the effects of electromagnetic waves and the like are removed by subtraction processing.

High-frequency components of the noise-compensated signal are extracted by high-pass filters 11.13. When calculating the correlation function, this is the offset correction calculation (-A, -B) due to the DC component.
This is because it is possible to omit the sampling time and to shorten the sampling time. High pass filter 11.13
The output of AGCl 7 is input to AGC 17, 19, and the output of AGCl 7 is waveform-shaped via limiter 23. Also ACC
The output of 19 is input to analog multiplexer 21 . The analog multiplexer 21 is also supplied with the output of the buffer amplifier 15 to which the output of the noise compensation amplifier is input, and when it is sent to the terminal ■, the ACC1
The output of buffer 15 is transmitted when the output of buffer 9 is sent to terminal ■. The output of the analog multiplexer is input to the limiter 25, and the output of each limiter is input to the A/D
The signals are A/D converted by converters 31 and 33 and read into the DSP 35. The true port memory 41 receives the output of the A/D converter 33 manually, and takes in vehicle speed data and road surface friction coefficient (road surface μ) data. In this example, the number of data for sensor 1 is 500, the number of data for sensor 3 is 2000, and the DS
Since the internal RAM capacity of P35 is only for 500 pieces of data, we will use the true port memory 41 here.
1500 pieces of vehicle speed data and 500 pieces of friction coefficient data are imported. true port memory 41
can be accessed from the A/D converter and DSP 35, and when the sampling of vehicle speed data is completed, it outputs an address count signal to drive the light source/switch controller 27, switch the analog multiplexer 21, and output the light [29]. Turns ON and OFF. Also DSP
35 calculates the correlation function from the imported vehicle speed data and calculates the deviation time at which the correlation value becomes maximum to calculate the actual vehicle speed, and also calculates the reflectance from the road surface friction coefficient data, and calculates the reflectance and friction created in advance. The road surface friction coefficient is read out from a conversion table with the coefficient, and this output is used to perform four-wheel drive control, braking control, etc.

Next, the operation will be explained in detail with reference to FIGS. 2 and 3.

Initially, the analog multiplexer 21 is sent to the ■ side, and the light 6jA 29 is turned on. In this state, sensor 1.3
The outputs of are each noise-compensated by taking the difference with the output of the blind sensor, and are passed through high-pass filters 11, 13, and A.
GC1? , 19, Analog multiplexer 21 contact ■
, limiter 23.25, A/D converter 31.33 to D
The data is taken into the internal RAM 37 and 39 of the SP 35 and the true port memory 41. The internal RAM capacity is only for 500 pieces of data, so when 500 pieces of data are imported, D
A clear signal is output from the SP 35 to clear the real port memory 41, and thereafter, data from the sensor 3 is taken in by the real port memory 41. And the data import of the real port memory 41 is 1
When the number reaches 500, an address count signal is output, and the light source/switch controller 27 is driven to switch the contact of the analog multiplexer 21 to ■. Thereafter, the output of the buffer 15 will be input to the true port memory 41. And 25 with true port memory
When 0 pieces of data are taken in, an address count signal is output, the light source 29 is turned off, and 250 pieces of data are taken in. During this time, the DSP 35 calculates the correlation function in parallel, calculates the actual vehicle speed, and
After that calculation, the friction coefficient of the road surface is calculated. The friction coefficient is determined by calculating the difference in signal levels when the light source is turned on and off, as shown in FIG. 2, and the reflectance is measured with the influence of external light eliminated. Then, the friction coefficient corresponding to the reflectance is read out from the table and output. When measuring the reflectance, it is best to measure it several times and discard abnormal values, or use the average value of several measurements, to avoid accidentally detecting a white line on the road and misjudging it as a snowy road. .

In addition, when actually using the friction coefficient for automobile control, it is detected in high friction and low friction categories, and the control is made to judge snowy roads, puddles, asphalt, the ground, etc.
41U may be performed.

Note that in the above embodiment, a real port memory is used in addition to the DSP, but it goes without saying that if the internal memory of the DSP has a large capacity, there is no need to use a real port memory.

As described above, according to the present invention, a sensor and an arithmetic processing device can be used in common for speed detection and friction coefficient detection, so it is possible to downsize the device and reduce costs.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the correlation type speedometer that also measures the friction coefficient of the present invention, the second area is a waveform diagram, Figure 3 is a time chart, and Figures 4 and 5 are correlation type speedometers. It is a figure for explaining the principle of a needle. 1.3...Sensor, 5...Blind sensor, 7.
9... Noise compensation amplifier, 11.13... High pass filter, 15... Buffer, 21... Analog multiplexer, 27... Light source/switch controller, 29... Light source, 3L33... A /D converter, 35
...DSP, 37.39...Internal RAM, 41...
・Sualport memory. Applicant Aisin Warner Co., Ltd. (1 other person) Agent Patent attorney Masanobu Hirukawa (3 others) Figure 2 Figure 3

Claims (3)

[Claims] (1) comprising an arithmetic processing means into which the detection outputs of two sensors arranged in the moving direction are input, a light source that illuminates the road surface, and a means that is controlled by the arithmetic processing means and turns on and off the light source; The calculation means calculates a correlation function between the detection outputs of the two sensors, determines the speed from the time difference at which the correlation function value becomes maximum, and calculates the road surface friction coefficient from the difference between the sensor detection outputs when the light source is turned on and off. A correlation type speedometer that can also be used to measure the coefficient of friction. (2) The correlation type speedometer for measuring the friction coefficient according to claim 1, wherein the signal for calculating the correlation function is a signal obtained by passing the sensor detection output through a high-pass filter. (3) A correlation-type speedometer for both friction coefficient measurement and friction coefficient measurement according to claim 1, wherein the correlation function value and the friction coefficient are measured in a time-sharing manner.