JPH0421145B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention detects road surface roughness or ground speed using an FM-CW radar, and detects the road surface roughness or ground speed necessary for automobile suspension control and anti-skid brakes. The present invention relates to a device that outputs information, and also outputs distance and relative speed to a preceding vehicle, especially forward information necessary for slow driving.

(Prior Art) Conventionally, devices of this type include long-range collision prevention radars, close-range radars, and ground radars, which use ultrasonic waves, microwaves, millimeter waves, light, or the like as transmission sources. Among these, the close-range radar related to the present invention was mainly developed as a predictive sensor for air (gas) packs, and is intended to protect human life in the event of a vehicle collision.

In addition, in recent years, anti-slip measures have become an issue in vehicle comfort, and electronically controlled suspensions have been commercialized for the former, and anti-skid brakes or anti-lock brakes have been commercialized for the latter.

(Problems to be Solved by the Invention) In terms of performance, the above-mentioned close-range radar only needs to be able to detect relative distances of 2 m or more and relative speeds of 30 km/h or more, and there is a limit to its widespread use as a close-range radar. .

In addition, electronically controlled suspensions use passive elements such as G sensors (acceleration sensors) to detect the roughness of the road surface, and are activated after an impact to electronically control the damping force of the suspension. , there are limits to riding comfort. Anti-skid brakes have independent rotary speed sensors on two or four wheels, and detect the difference in the rotational speed of each wheel and control the braking of each wheel to compensate for it. Unlike controlling the wheels by detecting the discrepancy between the speed and the number of rotations of the wheels, this is not a measure to prevent the vehicle from slipping in the strict sense.

Furthermore, as an improvement to the electronically controlled suspension mentioned above, the applicant has filed Japanese Patent Application No. 61-162598 (Japanese Patent Application Laid-open No.
018211) disclosed a technology to perform suspension control by actively detecting road surface roughness, but did not mention anti-skid brake control.

(Means for Solving the Problems) In order to solve these drawbacks, the present invention provides means for obtaining the roughness of the road surface, the ground speed, the distance from the preceding vehicle, and the relative speed. Therefore, the sweep signal generated by the sweep voltage generation circuit causes the FM
a microwave transmitting/receiving unit that transmits and receives modulated microwaves, extracts a beat signal between the transmitted signal and the received signal, and identifies only the beat signal from the target; and a microwave transmitting/receiving unit that receives the beat signal from the microwave transmitting/receiving unit. In a road information detection device comprising a signal processing unit that obtains target object information by processing, an FM-CW modulation signal in which the microwave is FM modulated in a part of the modulation period and the other part is CW. means for generating, a means for switching the transmission and reception direction of the microwave of the FM-CW method between an angle suitable for detecting the road surface and an angle suitable for detecting a preceding vehicle; means for separating the signals, switching the switching means to road surface detection to obtain the ground speed, switching to detecting the preceding vehicle to obtain the relative speed with the preceding vehicle, and FM modulation from the beat signal by the transmitted and received signal The switching means is switched to road surface detection to obtain the road surface roughness from the amplitude information of the beat signal, and the switching means is switched to detection of the preceding vehicle to obtain the distance to the preceding vehicle from the frequency information of the beat signal. It is equipped with means. Hereinafter, examples will be described in detail with reference to the drawings.

(Embodiment) FIG. 1 is a basic configuration diagram of an embodiment of the present invention, which consists of a microwave transmitting/receiving section 1 and a signal processing section 2. The microwave transmitting/receiving section 1 is composed of a microwave circuit 11, an antenna circuit 12, and a receiving circuit 13, and the microwave FM modulated by the microwave circuit 11 is radiated by the antenna circuit 12.
The microwaves returned from the reflecting object are received, the microwave circuit 11 extracts the beat signal, the receiving circuit 13 amplifies the beat signal, and supplies the amplified beat signal to the signal processing section 2. In the signal processing section 2, this beat signal is divided into a distance detection circuit 23 and a speed detection circuit 24, subjected to analog processing, digitized, and sent to an arithmetic circuit 22. The distance detection circuit 23 extracts distance information and deflection information, and the calculation circuit 22 performs distance calculation or roughness calculation. The speed detection circuit 24 extracts speed information, and the calculation circuit 22 performs speed calculation. The signal processing section 2 also includes a sweep voltage generation circuit 21 that generates a reference clock signal to the arithmetic circuit 22 and a sweep signal for FM-CW modulating the microwave in the microwave transmitter/receiver section 1.

By the way, the operation and signal components of the FM-CW system used in the present invention will be explained based on FIG. 6. A in Figure 6 shows the modulation method of the transmitted wave,
A solid line indicates a waveform representing a method of modulating radio waves emitted from the microwave transmitter/receiver 1 in FIG. For example, the dotted line is the modulated waveform of the received wave reflected from the preceding vehicle at a distance R, indicating that it returns with a time delay of τ (=2R/C, C: free space velocity of the radio wave) than the transmission time. ing. B shows the frequency component of the difference in the signal obtained by mixing the transmitted wave and the received wave, and C shows the beat signal with frequency components of the FM part and the CW part by removing unnecessary signals by gating. It represents. The CW portion generates a Doppler frequency fd that indicates the relative speed between the preceding vehicle and the host vehicle, and the FM portion generates a frequency fb that is reduced by fd from the frequency f _R corresponding to the time delay τ. f _R depends on the slope coefficient of the modulating waveform, e.g. fd
It can be set so that ≧10fd. It is assumed that the receiving circuit 13 in FIG. 1 outputs a signal containing these beat frequencies.

Next, the operation will be explained with reference to the detailed block diagram shown in FIG. The microwave transmitter/receiver 1 receives FM-CW from an oscillator 101 in the microwave circuit 11.
The modulated microwave is output, and the coupler 102
The transmitting antenna 10 of the antenna circuit 12 through
Sent to 03. The antenna circuit 12 consists of a transmitting antenna 103 and a receiving antenna 14.
As shown in Figure B, one partition plate is placed on one plate.
It is a batch type printed antenna divided by 08. The mounting position of the antenna circuit 12 is the third
As shown in Figure A, it is installed on the front bumper of the car, and the height is approximately 45 cm above the road surface. A mechanical or electronic switching means is used to switch the incident angle to the road surface to about 75 degrees when obtaining road surface information, and to make it parallel to the road surface when obtaining forward information (Figure 3). c a, b). The mounting position of the antenna circuit 12 when obtaining road surface information is an optimal position and angle that allows discrimination between the road surface and other targets, reduces vehicle-specific vibrations, and allows identification of road surface roughness. .

Microwaves reflected from the road surface or the preceding vehicle are received by a receiving antenna 104, sent to a mixer circuit 105, mixed with a transmission signal obtained from a coupler 102, and converted into a beat signal. The beat signal passes through a low pass filter (LPF) 106 and is amplified by a low noise amplification circuit 107. As shown in FIG. 3, the microwave transmitting/receiving section 1 has a structure in which a microwave circuit 11 and a receiving circuit 13 are built into the back side of the antenna circuit 12 described above, and the microwave circuit 11 is a microwave IC. Receiving circuit 1
3 consists of a hybrid IC.

Functionally, the signal processing section 2 can be roughly divided into a sweep voltage generation circuit 21, an arithmetic circuit 22, a distance detection circuit 23, and a speed detection circuit 24.

As shown in FIG. 4, the sweep voltage generation circuit 21 determines the sweep period based on a signal (FIG. 4A) obtained by dividing the clock signal generated by the reference clock generation circuit 201 by a frequency dividing circuit I202. This frequency-divided signal is sent to a sweep trigger circuit 203, a frequency divider circuit 205, a monomulti circuit 206, and a step sweep generation circuit 207.The sweep trigger circuit 203 generates a sweep trigger, and the sweep generation circuit 204 generates a sweep voltage. (FIG. 4B). This sweep voltage changes the capacitance of the varactor diode of the oscillator 101, and modulates the oscillation frequency of the oscillator 101 in FM-CW mode. Outputs a signal that determines the sweep period of the signal (Fig. 4 E) (Fig. 4)
Figure c). The period of this step is determined by the frequency dividing circuit 202.
determined by the signal. The monomulti circuit 206 generates a sample signal of the Doppler signal of the speed detection circuit 24 (FIG. 4D).

On the other hand, the beat signal (FIG. 4) containing the Doppler signal amplified by the low-noise amplifier circuit 107 of the microwave transmitter/receiver 1 is passed through a high-pass filter (HPF).
208 and a low pass filter (LPF) 218, the distance detection circuit 23 and speed detection circuit 24 are separated, respectively. The cutoff frequency is set to the beat frequency (fb min) corresponding to the shortest detection distance.
A beat signal having a frequency component fb (FIG. 4) that has passed through the HPF 208 is amplified by a low noise amplifier circuit 209 and sent to a mixer circuit 210. In the local oscillator 211, the oscillation frequency fl is subjected to FM modulation in which the frequency changes every step by the output voltage of the step sweep generating circuit 207. This output signal sends the beat signal fb to the mixer circuit 210.
The signal is up-converted and supplied to a bandpass filter (BPF) 212. The center frequency of the BPF 212 is the maximum frequency of the local oscillator 211 (fl
max) and fb min (fl max + fb
min), and the bandwidth is set to a beat frequency width corresponding to the required distance accuracy. Here, when fb is the minimum (shortest detection distance), the output of the BPF 212 is maximum at the step where fl is maximum (last step), and when fb is maximum (longest detection distance), the output is maximum at the step where fl is minimum. (first step) is the maximum. Therefore, if fb is intermediate, it will be maximum at an intermediate step. That is, BPF2
The position of the step with the maximum output of step 12 has frequency information of the beat signal, and distance information can be obtained by detecting this position (time information). The signal obtained from the BPF 212 is amplified by the amplifier circuit 213, and the peak value detection circuit 214
, the peak voltage (P-P voltage value) is held for each step (FIG. 4, h). This holding voltage (DC voltage) is reset by the monomulti circuit 206.
The output signal is used for each step. This holding voltage is then applied to the A/D converter 215 at each step.
is converted into digital data and passed through the latch circuit 216.
It is input to the CPU 217.

On the other hand, the cutoff frequency of the LPF 218 of the speed detection circuit 24 is set so as to extract the beat frequency (Doppler frequency) fd due to the Doppler effect. The beat signal extracted by this LPF 218 is amplified by an amplifier circuit 219, and sampled and held by a sample and hold circuit 220 using the output signal of the mono multi circuit 206 that is synchronized with the output signal of the frequency divider circuit 202 (Fig. 4 N). , passes through a waveform shaping circuit 221, and is converted into a pulse having a period corresponding to the Doppler frequency in a pulse shaping circuit 222 (see FIG. 4). The obtained pulse signal is supplied to a counter circuit 223, and the period is measured using the output signal of the frequency dividing circuit 202 as a lock. The binary signal corresponding to the Doppler frequency obtained by the counter circuit 223 is passed through the latch circuit 216 as speed information (ground speed or relative speed to the preceding vehicle).
It is input to the CPU 217.

The arithmetic circuit 22 includes a latch circuit 216 and a CPU 2.
It consists of 17. The CPU 217 uses the clock signal from the reference clock generation circuit 201 as a system clock.

When the information is switched to forward information (Fig. 3 C-b),
As described above, the output of the peak detection circuit 214 (FIG. 4 H) is digitized by the A/D converter 215 and then held in the latch circuit 216. The peak value of each retained step is
The CPU 217 compares the levels, and in order to find the step position at the maximum level, a counter in the CPU 217 counts from the start of the step sweep. Distance is calculated from this count value,
The CPU 217 outputs it as an inter-vehicle distance signal.
Also, the relative speed with respect to the preceding vehicle is determined by the speed detection circuit 24.
Based on the binary signal obtained by the counter circuit 223, the CPU 217 calculates the speed and outputs it as a relative speed signal.

Next, when switching to road surface information (a in Figure 3), the beat frequency from the road surface (corresponding to 1 m to 2 m) is fixed, so the sweep period of the step sweep generating circuit 207 is shortened. Also, the step sweep voltage is changed to a local oscillation frequency such that an output can be obtained from the BPF 212 depending on the beat frequency from the road surface (FIG. 5B). In this case, the output of the peak detection circuit 214 has a waveform as shown in the fourth diagram. Microwaves reflected from a road surface are diffused more when the road surface is smooth, and the strength of the signal that can be received is weaker.The rougher the road surface is, the less diffusion there is and the stronger the received signal is. Therefore, the strength of the received beat signal indicates the roughness of the road surface. The detected peak value of each step is supplied to an A/D converter 215 and digitized, and then held in a latch circuit 216.
The peak value of each retained step is
The levels are compared at 217, the maximum level is stored, and the levels are averaged every step sweep period. This averaging is performed between the average value performed so far and the level detected this time. Next, the magnitude of this averaged level is converted to road surface roughness, and the roughness signal is sent to the CPU 217.
is output from. In addition, the signal input from the speed detection circuit 24 to the CPU 217 as speed information is
A speed calculation is performed in the same manner as the calculation of the relative speed with respect to the preceding vehicle, and the result is output from the CPU 217 as a ground speed signal.

The signals of the road surface roughness, ground speed, inter-vehicle distance to the preceding vehicle, and relative speed obtained in this manner are respectively supplied to the controlled circuit.

(Effects of the Invention) As explained above, by using the device of the present invention as a vehicle sensor, it is possible to actively detect road surface conditions, and ground speed can also be measured in anti-skid brakes. This allows for more practical brake control. In addition, by switching to forward information detection, the inter-vehicle distance and relative speed to the preceding vehicle can be measured in real time, making inter-vehicle control possible in combination with auto transmission, resulting in greater fuel efficiency.

In particular, it can reduce the burden on humans during traffic jams, and the aim is to achieve fully automated driving when combined with cruise control at high speeds.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of an embodiment of the present invention, Fig. 2 is a detailed block diagram of the embodiment, Fig. 3 is an explanatory diagram of the installation and structural operation of the microwave transmitting/receiving section, and Fig. 4 is an output of each circuit. Waveform diagram. Figure 5 is a comparison diagram of step sweep voltage forward information and road surface information, Figure 6 is FM
- It is a figure which shows the modulation waveform of the transmission wave of a CW system, and a reception waveform. DESCRIPTION OF SYMBOLS 1...Microwave transmission/reception unit, 2...Signal processing unit, 11...Microwave circuit, 12...Antenna circuit, 13...Reception circuit, 21...Sweep voltage generation circuit, 22...Arithmetic circuit, 23... ...Distance detection circuit, 24...Speed detection circuit.

Claims (1)

[Claims] 1 A microwave transmitting/receiving unit that transmits and receives microwaves modulated by FM using a sweep signal generated by a sweep voltage generation circuit, extracts a beat signal from the transmitted signal and a received signal, and identifies only the beat signal from the target object. , and a signal processing unit that receives and processes the beat signal from the microwave transmitting/receiving unit to obtain target object information. means for generating an FM-CW modulated signal whose portion is CW, and means for switching the transmission and reception direction of the FM-CW microwave between an angle suitable for detecting a road surface and an angle suitable for detecting a preceding vehicle; Means for separating a signal corresponding to a Doppler frequency from the beat signals of the transmitted and received signals, switching the switching means to road surface detection to obtain ground speed, and switching to detecting a preceding vehicle to obtain relative speed with the preceding vehicle; , separating the beat signal resulting from the FM modulation from among the beat signals resulting from the transmitted and received signals, switching the switching means to road surface detection to obtain road surface roughness from amplitude information of the beat signal, and switching to detecting a preceding vehicle. 1. A road information detection device comprising: means for obtaining a distance to a preceding vehicle from frequency information of a beat signal.