JP2001021644A - Obstacle detecting system, on-vehicle radar apparatus, and portable radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make discriminable a specific object in an obstacle detecting system which uses an on-vehicle radar apparatus. SOLUTION: In this on-vehicle radar apparatus starting waves Wk which are frequency-modulated by a modulating signal which expresses a starting command are transmitted, and, after that, probing waves Wt which are frequency-modulated to triangular waves which are used in an FMCW radar are transmitted. When a wireless card which is carried by a pedestrian or the like receives the starting waves Wk, the on-vehicle radar apparatus is operated for a set time, and it returns response waves Wr which are formed by modulating the received probing waves Wt by using a modulating signal which expresses a response command. Consequently, in the on-vehicle radar apparatus, when the response command is superposed on the response waves Wr with reference to the probing waves Wt, a detected obstacle is recognized as an object which carries the wireless card, i.e., the pedestrian, and, when the response command is not superposed, the detected object can be recognized as an object other than the pedestrian.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detection system for transmitting and receiving radio waves in a specific frequency band to detect various obstacles existing around a vehicle, an on-vehicle radar device used in the obstacle detection system, and a radio system. Related to portable devices.

[0002]

2. Description of the Related Art Conventionally, auto cruise control for automatically traveling while maintaining a constant inter-vehicle distance with a preceding vehicle, and collision alarm control for generating an alarm when an object approaching another object located in front of the vehicle, etc., are required more than necessary. 2. Description of the Related Art There is known an on-vehicle radar device that collects data for recognizing a situation around a vehicle (a distance to an object in front of the vehicle, a relative speed, and the like) for use in various vehicle controls.

The on-vehicle radar devices include a laser radar device using a laser beam and a radio wave radar device using a radio wave such as a millimeter wave or a microwave. Of these, the radio wave radar device is more preferable. Attention has been paid to the fact that the antenna can be downsized if the millimeter wave of a short wavelength is used as a radar wave because it has excellent resistance to bad environments such as rain, snow and fog. I have.

Further, in a radio wave type radar apparatus, a radar wave modulated so that the frequency continuously changes is transmitted, a reflected wave reflected by an object and returned is received, and these transmission signals and FMC that calculates the distance and relative speed to the object reflecting the radar wave based on the frequency difference from the received signal
After transmitting the W system or pulsed radar wave,
2. Description of the Related Art A pulse method for measuring a time until a reflected wave reflected on an object is received is known.

That is, in the FMCW type radar apparatus, as shown by a solid line in FIG. 11A, a transmission signal Ss which is frequency-modulated by a triangular modulation signal and whose frequency gradually increases and decreases linearly with time. Transmit as a radar wave and receive the radar wave reflected by the target object. At this time, the reception signal Sr is delayed by a time Td corresponding to the time required for the radar wave to reciprocate with the target object, that is, the time Td according to the distance to the target object, as indicated by the dotted line in FIG. , A Doppler shift by a frequency Fd corresponding to the relative speed between the radar and the target object.

By mixing the received signal Sr and the transmitted signal Ss with a mixer, a mixer shown in FIG.
As shown in FIG. 7, a beat signal B which is a frequency component of the difference between these signals Sr and Ss is generated, and the frequency of the beat signal B when the frequency of the transmission signal Ss increases (hereinafter, referred to as the beat frequency during uplink modulation). ) Is fu, and the beat frequency when the frequency of the transmission signal Ss decreases (hereinafter referred to as the beat frequency during downlink modulation) is fd, and the distance R to the target object is represented by fd.
f and the relative speed Vf are calculated using the following equations (1) and (2).

[0007]

(Equation 1)

[0008]

(Equation 2)

Note that C is the radio wave propagation velocity, T is the period of the triangular wave that modulates the transmission signal, ΔF is the frequency fluctuation width of the transmission signal, and Fo is the center frequency of the transmission signal. The resolution ΔRf of the detection distance is given by the following equation (3). As is clear from this equation, the larger the ΔF, the higher the resolution. However, in an on-vehicle radar device, usually ΔF = about 100 MHz (accordingly, ΔRf = about 50 cm).

[0010]

(Equation 3)

On the other hand, a pulse type radar apparatus transmits a pulse-like radar wave and measures a time td until the radar wave is reflected by a reflecting object and returns. Then, the distance Rp to the reflecting object is calculated using the equation (4).

[0012]

(Equation 4)

[0013]

By the way, millimeter waves are
Reflection and reflection by objects of various materials, not only glossy objects
Due to scattering, a radar device using millimeter waves can detect pedestrians, falling objects on various roads, and the like, in addition to vehicles, guardrails, and signs. However, since the characteristics of the radio wave do not change due to the material of the object that reflects or scatters the radio wave, it is impossible to identify the type of the object from the received radio wave.

For this reason, in an auto cruise control or the like in which a preceding vehicle is a control target, only an automobile (including a motorcycle) moves forward at several tens to hundreds of kilometers per hour while traveling on a road. The control is performed by determining that such an object is the preceding vehicle.

However, when the detection result of the on-vehicle radar device is used for various danger prevention control, a roadside object installed on the side of the road, a falling object on the road, a vehicle stopped or traveling at a low speed, etc. And cyclists (hereinafter simply referred to as pedestrians, etc.) can be distinguished from each other so that more effective control can be performed by estimating the risk of jumping out. It is hoped that it will be possible.

Accordingly, an object of the present invention is to make it possible to identify a specific object in an obstacle detection system using an on-vehicle radar device.

[0017]

An obstacle detection system according to a first aspect of the present invention is an in-vehicle radar for detecting an object existing around a vehicle by transmitting and receiving radio waves in a specific frequency band. The radio wave transmitted by the on-vehicle radar device is composed of a device and a wireless portable device carried by a specific object. And a starting wave used for starting.

When the radio portable device receives a radio wave of a specific frequency band for a certain period of time after receiving the start-up wave, the radio portable device modulates a response signal obtained by modulating a predetermined specific signal with a response modulation signal. Operate to return. For this reason, the on-vehicle radar device can identify, as the specific object, the object whose response wave is returned among the detected objects.

Therefore, according to the obstacle detection system of the present invention, if a person is specified as a specific object and each person carries a wireless portable device, the on-vehicle radar device can detect a pedestrian or the like from among the detected objects. Can be reliably recognized in distinction from other objects. Note that the specific frequency band is 76 to 7 that is recognized in Japan as a frequency for millimeter wave radar.
The 7 GHz band or the 60 to 61 GHz band is desirable, and in particular, the 76 to 77 GHz band which is recognized in Europe and the like and is a global common band is more desirable.

The millimeter wave, unlike laser light, penetrates clothes and leather goods, so that even if the wireless portable device is stored in a pocket or a power van, it can be detected by the on-vehicle radar device. Next, in the wireless portable device according to the second aspect, the receiving means receives a radio wave of a specific frequency band, and when the received radio wave is a starting wave, the starting means starts the responding means, and thereafter, only for a predetermined time. Activate the response means. When the receiving means receives the radio wave, the response means returns a response wave obtained by modulating a predetermined specific signal with a modulation signal for response.

That is, the wireless portable device of the present invention has the following features.
When configuring the described obstacle detection system, it can be suitably used. In addition, since the response wave can be returned only for a certain period of time after receiving the starting wave, it is possible to reliably prevent the power from being wasted when not in use.

[0022] When the radio portable device is carried by a person, for example, when the vehicle-mounted radar device first detects the radio portable device, the vehicle equipped with the vehicle-mounted radar device is referred to as a radio portable device. The time may be sufficiently longer than the time required to pass a pedestrian or the like carrying a container.

The response means may use a signal received from the receiving means as a specific signal, as described in claim 3, or generate a high-frequency signal in a specific frequency band as described in claim 4. An oscillator may be provided, and a signal generated by the oscillator may be used as the specific signal. Further, as described in claim 5, an amplifier for amplifying the specific signal may be provided.

That is, in the wireless portable device of the third aspect, the device configuration can be simplified, and in the wireless portable devices of the fourth and fifth aspects, the power of the response wave to be returned is increased. Therefore, the specific object that carries the wireless portable device can be detected by the on-vehicle radar device from a greater distance.

However, the modulation of the specific signal by the modulation signal is as follows.
Any modulation method such as amplitude modulation, frequency modulation, and phase modulation may be used. According to a sixth aspect of the present invention, transmission and reception of radio waves by the receiving means and the response means are performed by a single antenna element, or a power supply to each unit by a solar cell is provided as described in the seventh aspect. If the configuration is such that external charging is not required by supplying power, the size of the wireless portable device can be reduced.

When the specific object is a person (pedestrian or the like), it is necessary to carry the wireless portable device of the present invention with each person at all times. For this purpose, for example, the wireless portable device may be built in or external to a portable wireless telephone, attached to a name tag, or the like, or may be about the size of a telephone card. And may be configured to be stored in a purse, a pocket of clothes, or the like.

[0027] Next, in the vehicle-mounted radar device according to the ninth aspect, the transmitting means is used for an exploration wave used to detect at least a distance from an object irradiated with radio waves, and for activating the wireless portable device. A radio wave in a specific frequency band including the starting wave is transmitted, and the receiving unit receives a radio wave from an object located in a radio wave transmission direction of the transmitting unit. Then, the signal processing means obtains at least the distance to the object based on the transmission signal and the reception signal for the search wave. Along with this, the determining means determines whether or not the radio wave received by the receiving means is modulated by a predetermined modulation signal after transmitting the starting wave by the transmitting means, and when the determination is affirmative. The specific object identifying means identifies an object located in the radio wave transmission direction of the transmitting means as a specific object.

Therefore, according to the on-vehicle radar device of the present invention, it can be suitably used for the configuration of the obstacle detection system according to the first aspect. Various methods can be used to detect an object by transmitting and receiving radio waves.
For example, as set forth in claim 10, the transmitting means uses, as the exploration wave, a signal modulated so that the frequency continuously changes in a triangular wave shape, and the signal processing means uses the transmission signal and the reception signal for the exploration wave. A so-called FMCW method can be used in which a beat signal composed of a frequency component of a difference from a signal is generated, and a distance and a relative speed with respect to an object located in a radio wave transmission direction of the transmission means are determined based on the beat signal.

Further, the transmitting means uses a pulse-like search wave, and the signal processing means detects a time difference between a transmission signal and a reception signal of the search wave, and detects the time difference. , A so-called pulse method may be used to determine the distance to an object located in the radio wave transmission direction of the transmission means based on.

In particular, when the distance to the object is determined by the pulse method, the twelfth aspect of the present invention is described.
As described above, it is preferable that the transmitting unit transmits an unmodulated wave having a pulse width larger than that of the search wave, following the transmission of the starting wave. That is, the pulse-like search wave need only be able to detect the leading edge of the signal, and therefore the pulse width may be small. However, if the pulse width is too small, even if the response wave modulated by the response means of the wireless portable device is received, it is difficult for the on-vehicle radar device to determine whether the response wave is modulated. There may be. For this reason, by transmitting an unmodulated wave having a sufficient pulse width and receiving a modulated response wave, it is possible to reliably determine whether or not the specific object carries a wireless portable device. It is.

By the way, when the radio portable device receives a radio wave, a specific signal (a received signal or a signal generated by an oscillator)
Is modulated and output as a response wave, the response is delayed as compared with a case where the radio wave is simply reflected on the surface of the object.
The delay of the response time becomes an error of a detection value based on the transmission signal and the reception signal (that is, the frequency of the beat signal in the case of the FMCW system, and the time difference between the transmission signal and the reception signal in the case of the pulse system), In any case, the detection accuracy of the distance to the object or the like is deteriorated.

According to a thirteenth aspect of the present invention, the signal processing means, when the determination result is affirmative, determines the detection value based on the transmission signal and the reception signal of the search wave by a response time delay in the wireless portable device. It is desirable to correct according to minutes. Further, in the on-vehicle radar device, in addition to the distance to the object, it is also important to detect so-called azimuth information in which direction the object exists. For this purpose, it is necessary to provide a beam displacing unit so as to change the beam direction of the radio wave transmitted and received by the transmitting unit and the receiving unit. In this case, if the transmitting means transmits the starting wave every time the beam displacing means changes the beam direction, it can reliably detect whether or not the specific object exists in each beam.

The beam displacement means may change the beam direction by mechanically changing the direction of the antenna, or prepare a plurality of antennas arranged in different directions and use an electric switch. The beam direction may be changed by sequentially switching the antennas used. Further, a plurality of beams may be simultaneously formed by using digital beam forming.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing a schematic configuration of each component (an in-vehicle radar device and a wireless portable device) of an obstacle detection system according to a first embodiment, and FIG. 2 is a usage state of each component. FIG.

As shown in FIG. 2, the obstacle detection system according to the present embodiment has a millimeter wave band (76 GHz to 7 GHz in this embodiment).
7 GHz) by transmitting and receiving an electric wave of 7 GHz) to detect the distance and relative speed to the obstacle and the direction in which the obstacle is present. And a wireless card 30 as a wireless portable device which responds to the radio wave of FIG.

It should be noted that communication between the on-vehicle radar device 10 and the wireless card 30 is performed according to a predetermined communication protocol. That is, the on-vehicle radar device 10 includes the starting wave Wk frequency-modulated by the modulation signal representing the starting command, and subsequently, the exploration wave Wt frequency-modulated so that the frequency continuously increases and decreases like a triangular wave. On the other hand, while the wireless card 30
Upon receiving the start-up wave Wk, when a search wave Wt is received for a certain period of time thereafter, a response wave Wr obtained by frequency-modulating the search wave Wt with a modulation signal representing a response command is returned.

Hereinafter, details of the on-vehicle radar device 10 and the wireless card 30 will be described individually. First, as shown in FIG. 1 (b), the wireless card 30 responds to an antenna 32 for transmitting and receiving radio waves in the millimeter wave band, an amplification circuit 34a for amplifying a signal received from the antenna 32, and an output of the amplification circuit 34a. A response unit 34 that comprises a modulation circuit 34b that modulates with a modulation signal representing a command, and supplies an output (return signal) of the modulation circuit 34b to the antenna 32.
And a switch 38 for interrupting a power supply line from the power supply circuit 36 to the response unit 34, a demodulation circuit 40a for demodulating a signal received from the antenna 32, and a demodulation signal from the demodulation circuit 40a represent a start command. In this case, the switch 38 is turned on for a certain period of time (30 seconds in this embodiment) to supply power to the response unit 34.
b.

The antenna 32 and the response unit 34,
The starting unit 40 is connected via a directional coupler 42, and a reception signal from the antenna 32 is supplied to an amplification circuit 34a and a modulation circuit 34b, and the modulation circuit 34b
Is supplied to the antenna 32. In addition, unlike the response unit 34, the activation unit 40 always operates and consumes power, but is configured to operate with low current and consume low power.

Further, the starting unit 4 is connected via a power supply line.
0 and a power supply circuit 36 for supplying power to the response unit 34
Has a chargeable and dischargeable battery and a solar cell,
The battery is charged by the solar cell. In the wireless card 30 configured as described above,
When the switch 38 is open, the response unit 34
Stops, and only the activation unit 40 operates, and the activation wave W
The state is a start command waiting state for monitoring whether or not k (that is, the start command) has been received.

In this state, when a millimeter wave is received, demodulation is performed by the demodulation circuit 40a of the activation unit 40. Then, as a result of demodulation, when the received millimeter wave is a starting wave Wk modulated by a modulation signal Mk representing a starting command,
The judgment circuit 40b operates the switch 38 only during the predetermined time.
Is closed, and power is supplied to the response unit 34.

The response unit 34, which has been supplied with power, amplifies the reception signal supplied from the antenna 32 via the directional coupler 42, that is, the reception signal of the search wave Wt received subsequently to the starting wave Wk. , And the response wave Wr is transmitted as a return signal to the antenna 32 via the directional coupler 42.

The response wave Wr is obtained by converting the received signal of the search wave Wt into a directional coupler 42, an amplifier circuit 34a, and a modulation circuit 34.
b, the time tr required to pass through b (in this embodiment, 0.2
μs) is delayed from the case where the search wave Wt is simply reflected on the surface of the wireless card 30.

When the above-mentioned fixed time has elapsed since the start of the power supply to the response unit 34, the determination circuit 40b opens the switch 38, whereby the power supply to the response unit 34 is stopped. A start command standby state in which only the start unit 40 operates is set.

In the wireless card 30, the antenna 32 is a receiving unit and a response unit 3 according to claim 2.
4 and the antenna 32 correspond to a response unit, and the activation unit 40 and the switch 38 correspond to an activation unit. Next, as shown in FIG. 1A, the on-vehicle radar device 10 includes a millimeter-wave transmission circuit including a voltage-controlled oscillator that generates a high-frequency signal in a millimeter-wave band (in this embodiment, a center frequency of 76.5 GHz). 12
And a start-up modulation circuit 14 for generating a modulation signal Mk for frequency-modulating a high-frequency signal generated by the voltage-controlled oscillator.
And a search modulation circuit 16 for generating a modulation signal Mt for frequency-modulating a high-frequency signal. The modulation signal Mk generated by the start-up modulation circuit 14 has a predetermined pattern so as to represent a start-up command.
t has a triangular waveform pattern so that the frequency of the signal modulated by the modulation signal Mt linearly increases and decreases with time.

The on-vehicle radar device 10 transmits a millimeter wave in accordance with a transmission signal Ss (a high-frequency signal frequency-modulated by the modulation signal Mk or Mt) from the millimeter-wave transmission circuit 12, and transmits a millimeter wave coming from the radio wave transmission direction. A beam forming circuit 18 configured to receive a wave and displace a beam direction of a millimeter wave to be transmitted and received;
A lens 26 for narrowing the beam width of the millimeter wave transmitted and received by 8;
The transmission signal Ss is added to the reception signal Sr from the beam forming circuit 18.
And a millimeter-wave receiving circuit 20 for generating a beat signal B composed of a frequency component of a difference between the two signals, based on the beat signal B from the millimeter-wave receiving circuit 20. An arithmetic circuit 22 that is located in the millimeter wave transmission direction and obtains the distance and relative speed to an object that reflects, scatters, or returns the millimeter wave, and a control circuit 28 that controls the operation timing and the like of each unit of the device 10 is provided. This is configured as a so-called FMCW type radar device.

The millimeter wave transmitting circuit 12, the beam forming circuit 18, and the millimeter wave receiving circuit 20 are connected via a directional coupler 24, and the transmission signal Ss from the millimeter wave transmitting circuit 12 is used as a beam forming circuit. 18, and the received signal Sr from the beam forming circuit 18 is supplied only to the millimeter wave receiving circuit 20.

The beam forming circuit 18 includes a single transmitting / receiving antenna having directivity and a mechanical displacement mechanism for changing the direction of the transmitting / receiving antenna in a stepwise manner, as shown in FIG. , 10 (in this embodiment, ten) beam directions BM1 to BM10 can be set.

Next, the arithmetic circuit 22 includes a CPU, a ROM,
It is mainly composed of a well-known microcomputer composed of a RAM, and converts the beat signal B into a digital signal to
An A / D converter for taking in the data, a digital signal processor (DSP) for performing fast Fourier transform, and the like are provided.

The control circuit 28 controls each part of the device 10 at the following timing. However, the control circuit 2
It is assumed that the beam forming circuit 18 has been initialized to transmit and receive millimeter waves in the beam direction BM1 before the control starts. That is, when the control circuit 28 starts the control, first, the activation modulation circuit 14 is activated, and the modulation signal Mk representing the activation command is supplied for a predetermined time (1 m in this embodiment).
s), and repeatedly output during the exploration modulation circuit 1
6 is started, and a triangular wave having a cycle of 1 ms is repeatedly output three times. The high frequency signal modulated by the modulation signal Mt has a center frequency of 76.5 GHz and a frequency modulation width of 1
It is set to be 0 MHz.

Thereafter, the beam direction is set by the beam forming circuit 18 from BMi (i = 1, 2,..., 9) to BMi +
After waiting for the time required for this displacement operation (6 ms in this embodiment), the same procedure as above is repeated again. Thereby, as shown in FIG. 3, the modulation signal Mk
The starting wave Wk frequency-modulated by the above and the exploration wave Wt frequency-modulated by the modulation signal Mt are transmitted in each beam direction BM1.
To BM10.

Further, the control circuit 28 controls each beam direction BM
The arithmetic circuit 22 is started every time the transmission of the millimeter wave (starting wave Wk + searching wave Wt) is completed by the 1 to BM 10, and the distance and relative speed to the obstacle are determined based on the beat signal B from the millimeter wave receiving circuit 20. At the same time, and an arithmetic identification process for identifying whether the detected object is a pedestrian or the like is executed.

That is, in this embodiment, since processing for one beam direction requires 10 ms including the displacement operation to the next beam direction, all beam directions BM1 to BM
The detection result for 10 is obtained every 100 ms. Here, FIG. 4 shows the same speed (relative speed Vf = vehicle M1) as the vehicle M1 equipped with the on-vehicle radar device 10 in the beam direction BM1.
0), there is a vehicle M2 traveling, and the beam direction BM10
When a pedestrian M3 carrying the wireless card 30 is present (see FIG. 2), a response wave Wr (received signal S
6 is a graph showing a change in frequency of r). Note that the dotted lines in the figure represent changes in the frequencies of the starting wave Wk and the exploration wave Wt (transmission signal Ss).

First, as shown in FIG. 4A, during the search period in the beam direction BM1 in which the vehicle M2 exists in the beam, the vehicle M2 does not respond to the starting wave Wk from the on-vehicle radar device 10 (wireless). Since the card 30 is not mounted), the starting wave Wk and the exploration wave Wt are reflected and scattered on the surface of the vehicle M2. Therefore, the on-vehicle radar device 1
0 receives the search wave Wt reflected and scattered on the surface of the vehicle M2 as the response wave Wr.

The response wave Wr (received signal Sr) at this time is
Compared to the search wave Wt (transmission signal Ss), the millimeter wave is delayed by a time required for the millimeter wave to reciprocate between the vehicles M1 and M2. Here, the case where the relative speed between the two vehicles M1 and M2 is zero is shown, and the beat frequency is equal (fu = fd) between the time of up-modulation and the time of down-modulation.

However, if the relative speed between the vehicles M1 and M2 is non-zero, the frequency of the response wave Wr is Doppler-shifted accordingly, and the graph is shifted vertically along the frequency axis. The beat frequency also differs between the up-modulation and the down-modulation (fu も fd). In addition,
Here, illustration of the reflected wave with respect to the starting wave Wk is omitted to make the drawing easy to see.

Next, as shown in FIG. 4B, the beam direction BM2 in which no object reflecting the millimeter wave exists in the beam.
In each of the search periods 〜 to BM9, the response wave Wr is not received by the on-vehicle radar device 10, and therefore, the beat signal B is not obtained. Next, as shown in FIG. 4C, during a search period in the beam direction BM10 in which the pedestrian M3 carrying the wireless card 30 is present in the beam, the wireless card 30 responds in response to the starting wave Wk. The unit 34 is activated, and returns a response wave Wr obtained by frequency-modulating the search wave Wt with a modulation signal Mr representing a response command.
r is received by the on-vehicle radar device 10.

That is, the response wave Wr is double-modulated with the modulation signal Mt and the modulation signal Mr, and the frequency of the beat signal B generated based on this is also superimposed with the response command (modulation signal Mr). If the response command has not been performed, it will vary by the influence of the response command around the normal beat frequency to be detected.

Hereinafter, the calculation / identification processing executed by the arithmetic circuit 22 will be described with reference to the flowchart shown in FIG. As described above, this process is started by the control circuit 28 activating the arithmetic circuit 22 every time the transmission of the search wave Wt is completed. When this processing is started, FIG.
First, in S110, the millimeter wave receiving circuit 2
At 0, it is determined whether or not the beat signal B has been generated. If the determination is negative, that is, if the response wave Wr has not been received and the beat signal B has not been generated (see FIG. 4B), , S120, the recognition result that there is no obstacle in the beam direction where the search has been performed previously is obtained, and this processing ends.

On the other hand, if a positive determination is made in S110,
That is, when the response wave Wr is received and the beat signal B is generated, the process proceeds to S130, and the FFT processing is performed on the sampling value of the beat signal B at each of the up / down modulation using the DSP. To perform frequency analysis.

At S140, whether or not the response command is superimposed on the received response wave Wr, that is, the frequency analysis result at S130 has a frequency distribution peculiar to the response wave Wr modulated by the modulation signal Mr. It is determined whether or not the processing has been performed. If a negative determination is made, the process proceeds to S150.

In S150, a recognition result is obtained that the obstacle existing in the beam direction that has been searched earlier is an object not carrying the wireless card 30, that is, an object other than a pedestrian or the like. Then, in S160, from the frequency analysis result in S130, a peak frequency is extracted for each of the up / down modulation, and set as beat frequencies fu and fd, and the process proceeds to S210.

If a positive determination is made in S140,
That is, when it is determined that the response command is superimposed on the received response wave Wr, the process proceeds to S170, and the obstacle existing in the beam direction searched earlier is the object carrying the wireless card 30, That is, a recognition result of a pedestrian or the like is obtained, and the process proceeds to S180.

In S180, for each up / down modulation,
The upper end frequency (fhu, fhd) and the lower end frequency (flu, fld) in the frequency distribution are extracted (see FIG. 6), and then S19 is performed.
At 0, the center frequency (fcu = {fhu + flu} / 2, fcd = {fhd +
fld｝ / 2). FIG. 6 is an enlarged graph of the beat frequency shown in FIG. 4C.

In subsequent S200, the center frequencies fcu and fcd for each modulation are corrected by a frequency error δf based on the response delay tr of the wireless card 30, and are set as beat frequencies fu and fd. And S
Proceed to 210. That is, S190 and S200 correspond to executing the operations represented by the following equations (5) and (6).

[0065]

(Equation 5)

[0066]

(Equation 6)

However, assuming that the period in which the frequency of the search wave Wt changes in a triangular waveform is T and the modulation width is ΔF, the frequency error δf based on the response delay tr can be expressed by equation (7).

[0068]

(Equation 7)

Specifically, in this embodiment, ΔF = 100
MHz, T = 1 ms, and tr = 0.2 μs.
f = 40 kHz. Then, in S210, S16
Based on the beat frequencies fu and fd for each of the up / down modulations set in 0 or S200, the distance Rf to the detected object and the relative speed Vf are calculated according to the above equations (1) and (2).
And terminates the present processing.

In the on-vehicle radar device 10, the millimeter wave transmitting circuit 12, the starting modulation circuit 14, the search modulation circuit 16, and the beam forming circuit 18 are transmitting means, the beam forming circuit 18 is receiving means, and the millimeter wave receiving circuit 20 And S130, S
160, S180 to S210 are signal processing means, S140
Corresponds to the determination means, and S170 corresponds to the specific object identification means.

As described above, in the obstacle detection system 2 of the present embodiment, the wireless card 30 receives the start wave Wk on which the start command is superimposed (modulated by the modulation signal Mk) from the on-vehicle radar device 10. In such a case, the response wave Wr is formed by superimposing (modulating with the modulation signal Mr) a response command on the subsequently received search wave Wt, and the on-vehicle radar device 10 is configured to return the start wave W
k is transmitted, and it is checked whether a response command is superimposed on a response wave Wr for the search wave Wt transmitted subsequently.
It is configured to identify whether the data is returned from the computer 30 or reflected or scattered on the surface of another object.

Therefore, the obstacle detection system 2 of the present embodiment
According to this, a pedestrian or the like possessing the wireless power cord 30 can be distinguished and recognized from other objects. In other words, in a vehicle equipped with the on-vehicle radar device 10, by using this recognition result, when a pedestrian or the like exists in the traveling direction, the driver is notified by various warnings when the pedestrian is present, or the vehicle is approached at a more dangerous distance. In such a case, various controls for preventing a personal accident, such as automatically applying braking, can be realized.

In the present embodiment, the wireless card 30 operates only for a certain period of time when receiving the starting wave Wk from the on-vehicle radar device 10, so that power is not wasted. Moreover, since the battery is configured to be charged by the solar cell, it can be used continuously for a long time.

By the way, in this embodiment, the wireless card 30 has a telephone card size. However, it is shown below that communication with the on-vehicle radar device 10 can be sufficiently performed even with this size. That is, the received power Pr when the radio wave radiated from the transmitting antenna is received by the receiving antenna separated by the transmission distance d is generally obtained by the Fries transmission formula expressed by the following equation (8). Can be.

[0075]

(Equation 8)

Here, At is the area of the transmitting antenna, Ar is the area of the receiving antenna, Pt is the transmission power, and λ is the wavelength. The wavelength of a millimeter wave having a frequency of 76.5 GHz is λ = 4 mm.
It is. The beam forming circuit 1 of the on-vehicle radar device 10
When a 10 cm square planar antenna is used as the antenna constituting 8, the area becomes At = 100 cm ² ,
On the other hand, when the wireless force 30 is the telephone force size (8.6 cm × 5.4 cm) and a planar antenna formed on the entire surface is used as the antenna 32, the area becomes Ar = 46.4 cm ² . Further, it is assumed that the transmission power is the upper limit value Pt = 10 mW in the millimeter wave radar standard.

When the antennas of the on-vehicle radar device 10 and the wireless card 30 face each other, the received power Pr on the wireless card 30 that has received the radio wave radiated from the on-vehicle radar device 10 is equal to the transmission distance d = 30m
Pr = 32 μW in case of d, Pr = 8 in case of d = 60 m
μW.

Then, it is assumed that a gain of 10 dB can be obtained in the response unit 34 including the amplifier circuit 34a. In this case, the received power Pr in the on-vehicle radar device 10 that has received the radio wave radiated from the wireless card 30 is d = 30
m, Pr = 1 μW (= −30 dBm), d = 60
In the case of m, Pr = 0.06 μW (= −42 dBm).

In other words, considering that the received power is -84 dBm when a satellite broadcast (12 GHz band) is received using a parabolic antenna having a diameter of 30 cm, even a wireless card 30 of a telephone card size can be used sufficiently. It can be seen that a level at which communication is possible is obtained. [Second Embodiment] Next, a second embodiment will be described.

In the first embodiment, a so-called FMCW type millimeter wave radar using a millimeter wave frequency-modulated in a triangular wave as the search wave Wt is basically configured.
In this embodiment, a so-called pulse-type millimeter-wave radar using a pulse-like millimeter wave as the search wave Wt is basically configured. In the following, components that are the same as those of the first embodiment are given the same reference numerals, description thereof is omitted, and the description will focus on portions having different configurations.

As in the first embodiment, the obstacle detection system of this embodiment includes an on-vehicle radar device 10A and a wireless card 30A as a portable radio device. And the wireless card 30A in the present embodiment is shown in FIG.
As shown in the figure, the wireless card 30 of the first embodiment is configured in exactly the same manner except that the amplifier circuit of the response unit 35 is omitted, and that the activation unit 41 processes the millimeter wave that has been analog-modulated. I have.

That is, in this embodiment, the response unit 3
The modulation circuit 35b of No. 5 modulates the received signal supplied from the antenna 32 via the directional coupler 42 with a modulation signal representing a response command, and uses the output as a return signal via the directional coupler 42. It operates to supply the signal to the antenna 32. The start unit 41 includes a demodulation circuit 41a.
Performs demodulation of the analog-modulated received signal, and when the demodulated signal indicates a start command, the determination circuit 41b operates to close the switch 38 for a predetermined time.

On the other hand, the on-vehicle radar device 10A is
As shown in (a), the millimeter wave band (76.5 in this embodiment).
Millimeter-wave transmission circuit 13 having a high-frequency oscillator capable of generating a high-frequency signal (GHz) and changing the amplitude in accordance with the modulation signal, and for amplitude-modulating the high-frequency signal generated by the millimeter-wave transmission circuit 13. The modulation signal Ma and the unmodulated pulse generation signal M having a predetermined pulse width (1 ms in this embodiment)
A start modulation circuit 15 for generating g and a search pulse generation circuit 17 for generating a search pulse generation signal Mp having a predetermined pulse width (about several μs in this embodiment) are provided.

The modulation signal Ma generated by the start-up modulation circuit 15 has a predetermined pattern so as to represent a start-up command. Also, the on-vehicle radar device 10A
The millimeter wave receiving circuit 21 performs amplification, waveform shaping, and the like on the received signal from the beam forming circuit 18 and the search pulse generating circuit 17 outputs the search pulse generation signal Mp. Time difference td before output
Time difference detecting circuit 19 for measuring the
Demodulation circuit 25 which demodulates the received signal from the demodulator and determines whether or not the demodulated signal represents a response command.
And an arithmetic circuit for calculating a distance between the object located in the transmitting direction of the millimeter wave and reflecting, scattering or returning the millimeter wave based on the time difference td detected by the time difference detecting circuit 19 and the determination result of the demodulation circuit. 23 and a control circuit 29 for controlling the operation timing and the like of each unit of the device 10A. Note that the beam forming circuit 18, the directional coupler 24, and the lens 26 are configured exactly the same as in the first embodiment.

The control circuit 29 controls each part of the device 10 at the following timing. However, the control circuit 2
It is assumed that the beam forming circuit 18 has been initialized to transmit and receive millimeter waves in the beam direction BM1 before the control starts. That is, when the control circuit 29 starts the control, first, the activation modulation circuit 15 is activated, and the modulation signal Ma representing the activation command is supplied for a predetermined period (1 m in this embodiment).
The output is repeated during s), and subsequently, an unmodulated pulse generation signal Mg having a pulse width of 1 ms is output. Further, subsequently, the search pulse generation circuit 17 is activated to output a search pulse generation signal Mp.

Then, after waiting for a few ms for receiving the response wave Wr, the beam forming circuit 18 sets the beam direction to B.
From Mi (i = 1, 2,..., 9) to BMi + 1,
After further waiting for the time required for this displacement operation, again
Repeat the same procedure as above. Thus, as shown by the dotted line in FIG. 8, the starting wave Wa amplitude-modulated by the modulation signal Ma, the unmodulated pulse wave Wg based on the unmodulated pulse generation signal Mg, and the search pulse wave Wp based on the search pulse generation signal Mp Are sequentially transmitted in each of the beam directions BM1 to BM10.

The control circuit 28 controls each beam direction BM
Whenever the transmission of the millimeter wave (starting wave Wa + unmodulated pulse wave Wg + exploration pulse wave Wp) in 1 to BM10 is completed, the arithmetic circuit 23 is started to obtain the distance to the obstacle and to walk the detected object. An operation identification process for identifying whether or not the user is a user is executed.

The graph shown by the solid line in FIG.
As in the case of, the on-vehicle radar device 1 is moved in the beam direction BM1.
0A is present in the vehicle M2 and the beam direction BM10
7 is a graph showing a change in reception intensity of a response wave Wr (received signal Sr) obtained when a pedestrian M3 carrying the wireless card 30A is present (see FIG. 2).

First, during the search period in the beam direction BM1 in which the vehicle M2 exists in the beam, the vehicle M2 does not respond to the starting wave Wa from the on-vehicle radar device 10A (because the wireless card 30 is not mounted). The starting wave Wa, the unmodulated pulse wave Wg, and the search pulse wave Wp are reflected and scattered on the surface of the vehicle M2.

When the on-vehicle radar device 10A receives the response wave Wrg for the unmodulated pulse wave Wg, the response wave Wrg remains unmodulated, and the demodulation circuit 25 superimposes the response command on the response wave Wrg. It outputs a judgment value indicating that it has not been performed. Subsequently, when the response wave Wrp for the search pulse wave Wp is received, the time difference detection circuit 19 causes the delay time td of the response wave Wrp (received signal Srp) for the search pulse wave Wp (search pulse generation signal Mp), that is, The time required for the millimeter wave to reciprocate between the vehicles M1 and M2 is measured.

Next, in the respective search periods in the beam directions BM2 to BM9 in which no object reflecting the millimeter wave exists in the beam, the response waves Wrg and Wrp are not received by the on-vehicle radar device 10A. Cannot be performed, and the time difference detection circuit 19 cannot perform measurement.

Next, the wireless card 3 is inserted in the beam.
During the exploration period in the beam direction BM10 in which a pedestrian carrying 0A is present, the wireless card 30A activates the activation wave Wk.
, The response unit 35 is started, and response waves Wrg and Wrp obtained by amplitude-modulating the unmodulated pulse wave Wg and the search pulse wave Wp with a modulation signal Mr representing a response command are returned. , Wrp are received by the on-vehicle radar device 10A.

When the on-vehicle radar device 10A receives the response wave Wrg for the unmodulated pulse wave Wg, the response wave
Since rg is amplitude-modulated by the modulation signal Mr, the demodulation circuit 25 outputs a determination value indicating that the response command is superimposed on the response wave Wrg. Following this, the exploration pulse wave W
When the response wave Wrp for p is received, the time difference detection circuit 1
9 measures the delay time td of the response wave Wrp (received signal Srp) to the search pulse wave Wp (search pulse generation signal Mp).

The operation / identification processing executed by the operation circuit 23 will be described below with reference to the flowchart shown in FIG. This process is started when the arithmetic circuit 23 is started by the control circuit 29 after the transmission of the search pulse wave Wp is completed. Then, when this processing is started, as shown in FIG. 9, first, in S310, the measurement time td is read from the time difference detection circuit 19, and the judgment value of the demodulation result is read from the demodulation circuit 25.

At S320, it is determined whether or not the measured time td indicates a valid value (a value equal to or less than the time corresponding to the maximum detection distance). If a negative determination is made, that is, the response wave If Wrp has not been received and measurement is not possible, the process moves to S330, and a recognition result indicating that there is no obstacle in the beam direction where the search was performed earlier is obtained, and this processing ends.

On the other hand, if a positive determination is made in S320,
That is, if the response wave Wrp has been received, S340
Then, it is determined whether or not a response command is superimposed on the response wave Wrg based on the determination value of the demodulation result read in S310, and if a negative determination is made, S350
Then, a recognition result is obtained that the obstacle existing in the beam direction that has been searched earlier is an object not carrying the wireless card 30A, that is, an object other than a pedestrian or the like, and the process proceeds to S380. move on.

If the result of the above S340 is affirmative, that is, if it is determined that the response command is superimposed on the response wave Wrg, the flow shifts to S360 to change the beam direction to the previously searched beam direction. A recognition result is obtained that an existing obstacle is an object carrying the wireless card 30A, that is, a pedestrian or the like.

In S370, the measurement time td read in S310 is corrected by the response delay tr in the wireless card as shown in equation (9).
Proceed to. td ← td−tr (9) Then, in S380, based on the measurement time td obtained in S310 or corrected in S370, the distance to the obstacle detected using the above equation (4) is calculated. After the calculation, the process ends.

In the on-vehicle radar device 10A, the millimeter wave transmitting circuit 13, the starting modulation circuit 15, the search pulse generating circuit 17, and the beam forming circuit 18 are transmitting means, the beam forming circuit 18 is receiving means, and the millimeter wave receiving circuit 21 is provided. , The time difference detection circuit 19, and S310, S370, and S380 are signal processing means, the demodulation circuit 25 is determination means, and S340 and S36.
0 corresponds to the specific object identification means.

As described above, in the obstacle detection system 2 according to the present embodiment, when the wireless card 30A receives the activation wave Wa on which the activation command is superimposed from the on-vehicle radar device 10A, the wireless card 30A is continuously received. Response waves Wrg and Wrp formed by superimposing a response command on the unmodulated pulse wave Wg and the search pulse wave Wp.
On the other hand, the on-vehicle radar device 10A transmits the starting wave Wa,
By checking whether or not a response command is superimposed on the response wave Wrg for the unmodulated pulse wave Wg transmitted subsequently, the response wave Wrg is determined by the wireless card 3.
It is determined whether the data is returned from 0A or reflected or scattered on the surface of another object. The wireless card 30A operates only for a certain period of time when receiving the start-up wave Wa from the on-vehicle radar device 10A.

Therefore, the obstacle detection system 2 of the present embodiment
According to this, the same effect as that of the first embodiment can be obtained. Moreover, in the present embodiment, since the wireless card 30A has a configuration in which the amplifier circuit is omitted, further downsizing can be achieved.

In this case, the return power of the response waves Wrg and Wrp decreases, but it is sufficient to make up for it by increasing the antenna 32 or to limit the detection distance to a short distance. Further, in the present embodiment, the wireless card 30A
Uses the received signals of the unmodulated pulse wave Wg and the search pulse wave Wp from the on-vehicle radar device 10A to generate the response wave Wrg,
Although Wrp is generated, when the amplitude modulation is performed as in the present embodiment, unlike the case of the FMCW method, the frequency does not always exactly match between the search pulse wave Wp and the response wave Wrp. You don't need to be. Therefore, an oscillator 3 oscillating at substantially the same frequency as the millimeter wave received from the on-vehicle radar device 10A, such as a wireless card 30B shown in FIG.
7c and a modulation circuit 37b for amplitude-modulating the output of the oscillator 37c constitute a response unit 37, and generate response waves Wrg and Wrp without using the received signals of the unmodulated pulse wave Wg and the search pulse wave Wp. You may do so. In this case, since the signal strength of the response waves Wrg and Wrp can be increased, the wireless card 30B can be detected from a long distance by the on-vehicle radar device 10A.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented in various modes. For example, in the above-described embodiment, a method of mechanically displacing the antenna is used as a method of switching the beam directions BM1 to BM10 of the on-vehicle radar devices 10 and 10A, but a plurality of antennas arranged so as to have mutually different beam directions are used. , And the antenna to be used may be switched using an electric switch.

In the above-described embodiment, the wireless card 30, 30A, 3 is formed as a portable wireless device in the form of a card to be carried in a pocket, a purse or a bag.
Although the example of 0B is shown, the outer shape may be any shape as long as it has a similar function.

For example, it may be built in or externally attached to a portable device such as a mobile phone when going out.
In particular, when the wireless portable device is built in a mobile phone, if power is supplied from the mobile phone, there is no need to provide a power supply circuit in the wireless portable device itself, and the wireless portable device can be made smaller.

Further, in the above embodiment, frequency modulation is used in the first embodiment and amplitude modulation is used in the second embodiment as a modulation method of the starting wave and the response wave. In the second embodiment, frequency modulation may be used.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an internal configuration of a vehicle-mounted radar device and a wireless card according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating an outline of an obstacle detection system.

FIG. 3 is an explanatory diagram showing a transmission pattern of a starting wave and a search wave transmitted from a vehicle-mounted radar device.

FIG. 4 is an explanatory diagram showing the entire operation.

FIG. 5 is a flowchart showing the contents of a calculation / identification process.

FIG. 6 is an enlarged view of a graph showing a frequency of a beat signal obtained when a response wave is received from a wireless card.

FIG. 7 is a block diagram illustrating an internal configuration of a vehicle-mounted radar device and a wireless card according to a second embodiment.

FIG. 8 is a flowchart showing the contents of a calculation / identification process in the second embodiment.

FIG. 9 is an explanatory diagram showing an overall operation in the second embodiment.

FIG. 10 is a block diagram illustrating a modification of the wireless card.

FIG. 11 is an explanatory diagram showing the principle of the FMCW method.

[Explanation of symbols]

2: Obstacle detection system 10, 10A: In-vehicle radar device 12, 13: Millimeter wave transmission circuit 14, 15: Modulation circuit for start-up 16: Modulation circuit for search 17: Search pulse generation circuit 18: Beam forming circuit 19: Time difference detection Circuits 20, 21 ... Millimeter wave receiving circuit 22, 23 ... Arithmetic circuit 24, 42 ... Directional coupler 25 ... Demodulation circuit 26
... Lens 28,29 ... Control circuit 30,30A, 30B ... Wireless card 32 ... Antenna 34,35,37 ... Response unit
34a: amplifying circuit 34b, 35b, 37b: modulating circuit 36: power supply circuit 37c: oscillator 38: switch 40, 41 ... starting unit 40
a, 41a ... demodulation circuit 40b, 41b ... judgment circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G08G 1/16 G01S 13/93 Z F-term (Reference) 2G005 DA04 5H180 AA01 BB09 BB12 CC12 CC14 LL01 LL04 LL06 LL09 5J070 AA14 AB01 AB19 AB24 AC02 AC06 AC13 AD01 AD20 AE01 AE09 AF03 AH25 AH31 AH35 AJ13 AK04 AK14 AK40 BA01 BC13 BC15 BC16 BC22 BC29 BD03 BF02 BF03 BF04 BF10 BF12 BF16

Claims (14)

[Claims] 1. An obstacle detection system comprising: an on-vehicle radar device for detecting an object present around a vehicle by transmitting and receiving radio waves in a specific frequency band; and a wireless portable device carried by the specific object. The radio waves transmitted by the device include an exploration wave used to detect at least the distance to the object irradiated with the radio waves, and a start-up wave used to start the wireless portable device, wherein the wireless portable device is For a certain time after receiving the starting wave,
When receiving the radio wave of the specific frequency band, returns a response wave obtained by modulating a predetermined specific signal with a modulation signal for response, the on-vehicle radar device, of the detected object, of the response wave An obstacle detection system, wherein a returned object is identified as the specific object. 2. A wireless portable device used in the obstacle detection system according to claim 1, wherein: a receiving means for receiving a radio wave in a specific frequency band; and a predetermined specific signal when the receiving means receives the radio wave. Response means for returning a response wave obtained by modulating the response signal with a modulation signal for response; and activation means for operating the response means for a fixed time thereafter when the radio wave received by the reception means is the activation wave. A wireless portable device comprising: 3. The wireless portable device according to claim 2, wherein the response unit uses a signal received from the receiving unit as the specific signal. 4. The wireless portable device according to claim 2, wherein the response unit includes an oscillator that generates a high-frequency signal in the specific frequency band, and uses a signal generated by the oscillator as the specific signal. Wireless portable device. 5. The wireless portable device according to claim 2, wherein the response unit includes an amplifier that amplifies the specific signal. 6. The wireless portable device according to claim 2, wherein transmission and reception of radio waves by said receiving means and said response means are performed by:
A wireless portable device characterized in that the operation is performed with a single antenna element. 7. The wireless portable device according to claim 2, wherein a power supply circuit for supplying power to each unit of the device includes a solar cell. 8. The wireless portable device according to claim 2, wherein the portable wireless device is built in or externally attached to a portable wireless telephone. 9. An on-vehicle radar device constituting an obstacle detection system together with the wireless portable device according to claim 2, wherein a search wave used for at least detecting a distance from an object irradiated with radio waves; A transmitting unit for transmitting a radio wave in a specific frequency band including a starting wave used for starting the wireless portable device; a receiving unit for receiving a radio wave from an object positioned in a radio wave transmitting direction of the transmitting unit; A signal processing unit for determining at least a distance to the object based on the transmission signal and the reception signal of the starting signal; and, after transmitting the starting wave by the transmission unit, a radio wave received by the reception unit for a predetermined response. Determining means for determining whether or not the signal is modulated by the modulated signal of the above; if the determination means makes an affirmative determination, the object located in the radio wave transmission direction of the transmitting means is the specific object. Vehicle radar device characterized by and a specific object identifying means for identifying a. 10. The on-vehicle radar device according to claim 9, wherein the transmitting means uses, as the exploration wave, a signal modulated so that a frequency continuously changes in a triangular wave shape. A beat signal including a frequency component of a difference between a transmission signal and a reception signal of the search wave is generated, and based on the beat signal, a distance and a relative speed of an object positioned in a radio wave transmission direction of the transmission unit are obtained. An on-vehicle radar device, comprising: 11. The on-vehicle radar device according to claim 9, wherein the transmitting unit uses a pulse-like one as the search wave, and the signal processing unit determines a transmission signal and a reception signal of the search wave. An on-vehicle radar device, wherein a time difference is detected, and a distance to an object located in a radio wave transmission direction of the transmission means is obtained based on the time difference. 12. The on-vehicle radar device according to claim 11, wherein the transmitting unit transmits an unmodulated wave having a pulse width larger than that of the search wave, following transmission of the starting wave. . 13. The radar apparatus according to claim 9, wherein said signal processing means detects said search wave based on a transmission signal and a reception signal when said determination means makes a positive determination. An on-vehicle radar device, wherein the value is corrected according to a response time delay in the wireless portable device. 14. The radar device according to claim 9, further comprising: a beam displacement unit that changes a beam direction of a radio wave transmitted and received by the transmission unit and the reception unit; The on-vehicle radar device transmits the starting wave each time the displacement unit changes the beam direction.