JPH09218264A - Object detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detecting apparatus which never fails to detect an object even when a level of a receiving signal becomes small, by changing a threshold level to be smaller as an angle defined between an advancing direction and a front/rear direction of one's vehicle is increased, and projecting transmission signals slantwise to an object on a line of one's vehicle. SOLUTION: In an object detecting apparatus M2, a signal is transmitted in an advancing direction of one's vehicle detected by an advancing direction detecting means M1, and a signal reflected by a front object on a line of one's vehicle is received. When the receiving signal exceeds a threshold level, the object is detected. The apparatus M2 has a threshold level changing means M3 for changing the threshold value to be smaller as an angle of the detected advancing direction of one's vehicle to a front/rear direction of the vehicle is increased. Therefore, when the angle between the advancing direction of the vehicle which is the transmitting direction of the signal and the front/rear direction of the vehicle becomes large to decrease the level of the receiving signal, the threshold value is changed and reduced. The apparatus is accordingly prevented from failing to detect the object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detecting device, and more particularly to an object detecting device mounted on a vehicle for detecting a target object on a vehicle lane.

[0002]

2. Description of the Related Art Conventionally, various devices have been developed and mounted on a vehicle for the purpose of improving a driver's low operation range and improving safety. Development of a radar device for detecting the is also active. As a radar device, a device using radio waves such as millimeter waves or a device using laser light has been proposed.
Japanese Unexamined Patent Publication No. 7-49380 discloses a radar device that detects a target object in the traveling direction of the host vehicle, a steer device that changes the deflection angle of the beam irradiation direction of the radar device, and a curvature of a curve of a running road. An object detecting device is described which has a curvature calculating means for calculating and a deflection control means for controlling a deflection angle of a steer device on the basis of a time change amount of a curvature of a road.

[0003]

In the conventional device, the threshold level of the radar device is kept constant regardless of the angle of deflection of the beam irradiation direction. The radar device detects an object when the reception level exceeds the threshold level.

However, in the curve, even if the beam irradiation direction of the radar device is deflected, the radar beam is obliquely incident on the preceding vehicle, and therefore the reception level of the radar beam reflected by the preceding vehicle and received by the radar device. Becomes smaller. This reception level is greatly reduced as the curvature of the curve increases. Therefore, there is a problem that it is difficult to accurately detect the preceding vehicle in the curve.

The present invention has been made in view of the above points, and the threshold level is changed to be smaller as the angle formed by the traveling direction of the vehicle and the front-rear direction is increased.
An object of the present invention is to provide an object detection device that does not fail to detect an object even when an object on its own lane is obliquely irradiated with a transmission signal and the level of a reception signal becomes small.

[0006]

According to a first aspect of the present invention, as shown in FIG. 1, a signal is transmitted in the traveling direction of the vehicle detected by the traveling direction detecting means M1, and an object in front of the vehicle lane is transmitted. In the object detection device M2 which receives the reflected signal and detects the object when the received signal level exceeds the threshold level, the detected traveling direction of the own vehicle,
There is provided a threshold level changing means M3 for decreasing the threshold level as the angle formed by the front-rear direction of the vehicle increases.

For this reason, the angle formed by the traveling direction of the vehicle, which is the signal transmission direction, and the front-back direction of the vehicle becomes large, the inclination of the transmission signal with respect to the object on the vehicle lane becomes large, and the reception signal level becomes small. When the level becomes low, the threshold level is changed so that the threshold level is reduced, and therefore even if the received signal level is low, the object can be detected and the omission of detection can be prevented.

[0008]

FIG. 2 is a block diagram showing an embodiment of the apparatus according to the present invention. In the figure, 10 is a steering signal generator, which generates a steering neutral position detection signal and a steering detection signal indicating a steering direction and a steering amount, and supplies the steering control signal to an electronic control unit (ECU) 11.

The ECU 11 is supplied with the vehicle speed of the host vehicle from the speed sensor 13, and obtains the current steering angle and the curvature of the curve from the vehicle speed and the neutral position detection signal and the steering detection signal. The estimated curvature is obtained, and the deflection angle of the radar device is calculated from the estimated curvature of this future curve. The ECU 11 supplies the deflection angle to the steering device 12. The steering device 12 deflects the beam deflection angle of the radar device 14 so as to be the deflection angle. The radar device 14 emits (transmits) a beam,
The beam reflected by the target object is received, frequency analysis is performed, and the analysis result is supplied to the ECU 11.

The ECU 11 obtains the relative distance and the relative speed with respect to the target object from this analysis result, and the ECU 11 determines from the relative distance and the relative speed with respect to the target object whether or not the target object is dangerous to the own vehicle, and thus it is dangerous. In some cases, an alarm signal is generated to activate the alarm device 15.

FIG. 3 is a block diagram of the radar device 14. In the figure, the transmission side circuit includes a carrier wave generator 20, a frequency modulator 22, a modulation voltage generator 24, a directional coupler 26,
And a transmitting antenna 28. Carrier wave generator 2
A carrier wave is output from 0 and supplied to the frequency modulator 22. On the other hand, the modulation voltage generator 24 outputs a triangular wave having a repeating frequency fm whose amplitude changes in a triangular shape, and is supplied to the frequency modulator 22 as a modulating wave. As a result, the carrier wave from the carrier wave generator 20 is frequency-modulated,
A transmission signal whose frequency changes triangularly with time is output. This transmission signal is supplied to the transmission antenna 28 via the directional coupler 26 and is radiated toward the object to be detected. On the other hand, a part of the transmission signal is supplied to the mixer 32 of the receiving side circuit described later via the directional coupler 26.

The receiving side circuit comprises a receiving antenna 30, a mixer 32, an amplifier 34, a filter 36, and a fast Fourier transform processor (FFT signal processor) 38. The reflected wave from the object to be detected is received by the receiving antenna 30 and supplied to the mixer 32. In the mixer 32, a reception signal and a part of the transmission signal from the directional coupler 26 are combined by a difference calculation to generate a beat signal. The beat signal from the mixer 32 is amplified by the amplifier 34, and is supplied to the FFT signal processor 38 and the target recognizer 40 via the anti-aliasing filter 36. The FFT signal processor 38 obtains a power spectrum in each of the frequency rising section and the frequency falling section, and supplies the power spectrum to the ECU 11 shown in FIG.

The ECU 11 detects the peaks of the power spectrum in each of the frequency rising section and the frequency falling section and performs pairing to form a peak pair corresponding to each target object.
The relative velocity frequency fd and the relative distance frequency fr fd = (fdown-fup) / 2 (1) fr = (fdown + fup) obtained from the peak frequency fup in the frequency rising section and the peak frequency fdown in the frequency falling section of this peak pair. / 2 (2) and fd = 2 · V · f0 / C (3) fr = 4 · fm · Δf / C · R (4) where V: relative speed, C: speed of light, f0: center frequency , F
m: modulation frequency, Δf: frequency shift width of, for example, 75 MH
z, R: Relative distance R and relative velocity V are simultaneously obtained from the relative distance.

FIG. 4 shows a flowchart of the processing executed by the ECU 11. This process is repeatedly executed at predetermined time intervals. In the figure, in step S10, the neutral position detection signal and the steering detection signal from the steering signal generator 10 are fetched, and the current steering angle θ is calculated from these detection signals.

Next, in step S20, the speed sensor 13
The vehicle speed SPD of the own vehicle is taken in from and the curvature P _i of the curve currently traveling is calculated from the equation (5). Ρ _i = (1 + A × SPD ² ) × L × Kg / θ (5) where A is a stability factor (constant), Kg is a steering gear ratio (constant), and L is a wheel base (constant).

Next, in step S30, the deflection angle θ _S is calculated by the equation (6), and the steering device 12 deflects (steers) the radar beam. θ _S = sin ⁻¹ [R / (2 · Ρ _i )] (6) Here, R is the relative distance of the preceding vehicle obtained by the previous process of FIG. 4. The above steps S10 to S30 correspond to the traveling direction detecting means M1 and detect the deflection angle θ _S as the traveling direction of the vehicle.

Next, the threshold level changing means M2
In step S40, the threshold level is obtained by referring to the map shown in FIG. 5 using the above deflection angle θ _S. In the map of FIG. 5, as the deflection angle θ _S becomes larger, the radar beam is obliquely irradiated to the preceding vehicle and the reception level of the reflected beam becomes smaller, so the threshold level is set smaller. Then, in step S50, the relative distance R and the relative speed V of the target object such as the preceding vehicle are calculated using equations (1) to (4) for the reception level exceeding the threshold level.

In the next step S60, it is determined whether or not a target object is detected. If there is a target object, step S7
In step 0, it is determined whether the target object is dangerous to the vehicle based on the relative distance and relative speed of the target object, and if the target object is dangerous, a determination / warning process for activating the alarm device 15 is executed and the process ends. . If there is no target object, the process ends.

As described above, the angle formed between the traveling direction of the vehicle, which is the signal transmission direction, and the front-back direction of the vehicle becomes large, the inclination of the transmission signal with respect to the object on the vehicle lane becomes large, and the reception signal level increases. When it becomes smaller, the threshold level is changed so as to become smaller. Therefore, even if the received signal level is small, it is possible to detect an object and prevent detection failure.

The horizontal axis of the map shown in FIG. 5 may use the curvature P _{i of the} curve instead of the deflection angle θ _S , and the map may use a quadratic curve or the like. Further, although the above-described embodiment uses the steer-type radar device, even when the deflection angle of the scan center is changed according to the curvature of the curve in the scan-type radar device that scans the radar beam left and right, The deflection angle is plotted on the horizontal axis, as shown in FIG.
The threshold level can be varied by referring to the map of.

The curvature P _{i of the} curve may be obtained from the yaw rate, may be obtained by recognizing a white line on the road, and may be obtained from the map information of the navigation system. Further, the radar device 14 is not limited to the FMCW radar and may be a Doppler radar, and is not limited to the above embodiment.

[0022]

As described above, the invention according to claim 1 is
A signal is transmitted in the traveling direction of the vehicle detected by the traveling direction detecting means, a signal reflected by an object in front of the vehicle lane is received, and the object is detected when the received signal level exceeds the threshold level. In the object detecting device, the threshold level changing means for decreasing the threshold level as the angle between the detected traveling direction of the vehicle and the front-rear direction of the vehicle increases.

Therefore, the angle formed between the traveling direction of the vehicle, which is the signal transmission direction, and the front-back direction of the vehicle becomes large, the inclination of the transmission signal with respect to the object on the vehicle lane becomes large, and the reception signal level becomes small. When the level becomes low, the threshold level is changed so that the threshold level is reduced, and therefore even if the received signal level is low, the object can be detected and the omission of detection can be prevented.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a block diagram of the device of the present invention.

FIG. 3 is a block diagram of a radar device.

FIG. 4 is a flowchart of a deflection process.

FIG. 5 is a diagram showing a map.

[Explanation of symbols]

 10 Steering signal generator 11 ECU 12 Steer device 13 Speed sensor 14 Radar device 15 Alarm device 20 Carrier wave generator 22 Frequency modulator 24 Modulation voltage generator 26 Directional coupler 28 Transmit antenna 30 Receive antenna 32 Mixer 34 Amplifier 36 Filter 38 FFT signal processor M1 traveling direction detecting means M2 threshold level changing means

Claims (1)

[Claims] 1. A signal is transmitted in the traveling direction of the vehicle detected by the traveling direction detecting means, a signal reflected by an object in front of the vehicle lane is received, and a received signal level exceeds a threshold level. At this time, the object detection device for detecting the object has threshold level changing means for decreasing the threshold level as the angle between the detected traveling direction of the vehicle and the front-back direction of the vehicle increases. An object detection device characterized by: