JP2003232853A - Physical object detecting device for vehicle, safety controlling method, and automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for accurately forecasting the progressing direction and moving speed of a physical object itself by detecting distance to the object and its relative velocity finely with high accuracy when the object is detected by a sensor used for detecting collision. <P>SOLUTION: This physical object detecting device for a vehicle has a course forecasting part for forecasting a course of the detected object from an object movement forecasting part which recognizes positional information on a plurality of points of the detected object based on electromagnetic waves from a plurality of points on the object detected by an object detecting part and computes velocity vectors from change of the positional information with time and velocity information on the plurality of points. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detecting the position and relative speed of an object existing around a vehicle and predicting the course of the object as seen from the vehicle. It also relates to safety control for preventing collision between the object and the vehicle.

[0002]

2. Description of the Related Art Conventionally, as a vehicle-to-vehicle distance measuring device, a radio wave is radiated to receive a reflected wave from an object such as a vehicle or an obstacle, and the propagation time of the radio wave, the intensity of the reflected wave, a frequency Doppler shift, etc. A radar device has been developed which detects a wave and measures the distance to an object from the result.

For example, in the description of Japanese Patent Application Laid-Open No. 8-124080, a plurality of electromagnetic wave beams are transmitted and reflected waves are received to detect a vehicle or an obstacle. According to this technique, distance information between the host vehicle and a plurality of detection points (a plurality of distance information) is used as an output of the radar device, and a plurality of detection point data (distance information) is grasped as one group (grouping), It detects the group as vehicles and obstacles. Further, the speed of the detected object is calculated by taking the time-series change of the distance information, that is, the time differential to predict the course.

[0004]

In order to prevent a vehicle collision, a radar device or the like mounted on the vehicle is used to detect a preceding vehicle or an obstacle to perform driving control, or to detect a collision in advance. Then, a method of controlling an occupant protection means such as an airbag or a seat belt is conceivable, but in any case,
It is desirable to detect the position of an object such as a preceding vehicle or an obstacle with high accuracy and to clearly determine whether or not it will be an obstacle to the own vehicle.

However, in the above-mentioned conventional technique, the radar device outputs the distance information of the vehicle or the obstacle (that is, the object to be inspected), and it is difficult to accurately predict the movement or moving speed of the object to be inspected.

For example, when positional information of a plurality of points of an object to be inspected is detected, even if relative velocities of the respective points with respect to the own vehicle are calculated by taking time differentiation, firstly, the first of the grouped ranges is first calculated. At the point and the last point, the plurality of detection point data are not information at the same time, and secondly, if two data at the same point are not collected, the relative speed of each point with respect to the own vehicle can be calculated. Since it is not possible to do so, at least the calculation time for the sampling cycle will be required, and the behavior of the actual inspected object and the predicted behavior of the inspected object cannot theoretically match, and the point closest to the host vehicle cannot be found. It was difficult to calculate and predict the time of collision with the host vehicle and the collision location.

It is an object of the present invention to solve the above problems and provide an object path predicting apparatus capable of predicting the behavior and moving speed of an object to be inspected more accurately and in a shorter time than ever before. And

Another object of the present invention is to provide a safety control method for a vehicle collision.

Another object of the present invention is to provide a vehicle that executes collision avoidance control or safety device operation control.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an object detecting section 1 which radiates a radio wave, receives a reflected wave from an object, and simultaneously measures the relative velocity, distance and angle of a plurality of points of the object, Based on the electromagnetic waves from the plurality of points of the object detected by the object detection unit 1, the position information of the plurality of points of the object to be inspected is recognized from the distance and the angle, and the temporal displacement of the position information and the speed of the plurality of points are detected. This is achieved by providing an object detection device for a vehicle that includes an object motion prediction unit 4 that calculates a velocity vector from information.

Another object of the present invention is to calculate a velocity vector from the temporal displacement of the position information and velocity information of a plurality of points, predict the course of the object to be inspected, and change the velocity vector of the plurality of points. From the object movement predicting unit 4 for calculating the relative attitude change of the object to be inspected.

Another object of the present invention is to predict a temporal change in the relative positional relationship between the object to be inspected and itself based on the position information of the representative point of the object to be inspected and the position information of the object itself. And a safety control method for a vehicle collision, which includes a step of selectively executing at least one of collision avoidance control of the object to be inspected or its own and operation control of a safety device based on the prediction result. be able to.

Another object of the present invention is to provide an object detecting section 1 for radiating a radio wave and receiving a reflected wave from an object to simultaneously measure the relative velocity, distance and angle of a plurality of points of the object. Based on the electromagnetic waves from a plurality of points of the object detected by 1, the position information of the plurality of points of the object to be inspected is recognized from the distance and angle, and the velocity vector is calculated from the temporal displacement of the position information and the velocity information of the plurality of points. Of the collision avoidance control of the object to be inspected or itself and the operation control of the safety device from the object motion prediction unit 4 for calculating This is achieved by providing a vehicle including a control unit that selectively executes at least one of them.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments, the detection of a vehicle collision will be described as an example with reference to FIGS.

FIG. 1 shows the configuration of an embodiment of the present invention. This embodiment relates to a radar device for short distance, for example, a detection distance of 5 m, and describes a system for detecting a collision.

For example, the speed difference between the vehicle and the object to be inspected is 6
In case of 0km / h, 5m (detection distance) is 300ms
Is converted to. Therefore, when the collision is detected in advance and the result is used to avoid the collision or to control the collision so that the damage is small, the behavior of the own vehicle appears / completes by obtaining information from the object to be inspected. Time to do
It is required to be performed within 300 ms. If the speed of the preceding vehicle is low or the speed of the oncoming vehicle is high and the speed difference between the host vehicle and the object to be inspected is large, the detection time, control time, etc. are further shortened to shorten the overall time. Is required.

The object detecting section 1 is required to detect a plurality of points in the shortest possible time. Further, by recognizing the detected attitude change including the speed and rotation of the vehicle, it is possible to calculate how fast and from which direction the vehicle will collide. In FIG. 1, the object detection unit 1 uses a radar device (hereinafter, referred to as a radar device) capable of calculating relative speeds and positions of a plurality of points of the object.

The vehicle speed sensor 14 in FIG. 2 corresponds to the own vehicle speed detecting section 2 in FIG. 1, and the gyro 15 in FIG. 2 corresponds to the yaw rate detecting section 3 in FIG. 1, the object motion prediction unit 4, the vehicle motion prediction unit 5, and the collision time estimation unit 6 are the microcomputer 25 in FIG.
Will be realized in.

First, an example in which the position information of the object to be inspected is calculated based on the electromagnetic waves from each point of the object detected by the radar device and the course is predicted will be described.

The output of the radar device is distance information, relative velocity information, and angle information (information on the direction of collision).
Regarding the method of measuring relative speed and distance with a radar device,
This will be described with reference to FIG. The antenna part is the transmission antenna 16
And a receiving antenna 17, and a millimeter-wave band high frequency signal (30 GHz to 300 GHz) transmitted from an oscillator 18 at a transmission frequency based on a modulation signal from a modulator 19.
Is radiated from the transmitting antenna 16. A radio signal reflected by a reflector such as a car or an object along the road and returned is received by the reception antenna 17 and frequency-converted by the mixer circuit 20. A signal from the oscillator 18 is also supplied to the mixer circuit 20, and a low frequency signal generated by mixing the two signals is output to the analog circuit 21.

The signal amplified and output by the analog circuit 21 is converted into a digital signal by the A / D converter 22 and supplied to the FFT processing section 23. In the FFT processing unit 23, the fast Fourier transform (Fast Fourier Trans
form) to measure the frequency spectrum of the signal as amplitude and phase information and send it to the signal processing unit. FFT processing unit 2
The distance and relative speed are calculated by the signal processing unit 24 from the data in the frequency domain obtained in 3, and are output as the distance measurement value and the relative speed measurement value.

In this example, the relative speed of the front vehicle is measured by using the Doppler shift, and two frequencies are switched to measure the distance to the front vehicle from the phase information of the received signal at each frequency. (Contin
An example of using a continuous wave (millimeter wave) radar will be described with reference to FIGS.

In the case of the two-frequency CW type millimeter-wave radar, a modulation signal is input to the oscillator 18 and, as shown in FIG. 3A, the two frequencies f ₁ and f ₂ are transmitted while being temporally switched. The electric wave transmitted from the transmitting antenna 16 is reflected by the vehicle ahead and the reflected signal is received by the receiving antenna 17 (a) and the receiving antenna 17 (b). Received signal and oscillator 1
The signals of 8 are multiplied by the mixer circuit 20 to obtain their beat signals. In the case of the homodyne method of directly converting to the base band, the beat signal output from the mixer circuit 20 becomes the Doppler frequency f _d , which is calculated by the following equation.

[0024]

[Equation 1]

On the receiving side, the reception signals at the respective transmission frequencies are separated and demodulated by the analog circuit 21, and the reception signals for the respective transmission frequencies are A / D converter 2
A / D conversion in 2. The FFT processing unit 23 performs a fast Fourier transform process on the digital sample data obtained by the A / D conversion to obtain a frequency spectrum in the entire frequency band of the received beat signal. With respect to the peak signal obtained as a result of the FFT processing, the transmission frequency f ₁ and the transmission frequency f ₂ as shown in FIG.
The power spectrum of the peak signal for each is measured, and the distance (ran
ge) is calculated by the following formula.

[0026]

[Equation 2]

Next, the measurement of the direction will be described with reference to FIG. FIG. 8 shows a received power pattern of each receiving antenna with respect to an angle. As shown in FIG. 8, the reception antenna 17 (a) and the reception antenna 17 (b) each have a maximum received power when θ is 0. Sum signal (Ps) of the signals input to the receiving antennas 17 (a) and 17 (b)
um) and the difference signal (Pdiff) are calculated. Reception antenna 17
Since the antenna patterns of (a) and 17 (b) are constant, the azimuth angle θ can be specified from the power ratio of the received signal. For example, when FFT is applied to 2048 points of data at the sampling frequency F _s = 50 [Hz], the relative velocity and position information of the detected object are measured at intervals of about 44 ms. Therefore, in the conventional method, at least two points are required to calculate the relative speed, which requires 44 ms or more, but according to the present embodiment, the relative speed can be calculated at the same time (only the calculation time).

FIG. 4 shows a processing flow for an example of performing signal processing on the peak signal obtained as a result of the FFT processing and predicting the position of the object after Δt [s].

In the example in which the own vehicle 35 in which the radar device 34 is attached to the front of the vehicle body detects the vehicle 33 as shown in FIG. 5A, the power spectrum 37 of the peak signal with respect to the transmission frequency f ₁ is shown in FIG. 5B. Shown in. This is the result of performing the FFT processing on the detected reflected wave of the vehicle, and the power spectrum 36 of the peak signal with respect to the transmission frequency f ₂ is also obtained. These peak signals are detected, and the relative speed and distance of the vehicle can be calculated from the frequencies by using Expressions 1 and 2. That is, the radar device outputs at least distance information and relative velocity information. When the speed of each detected vehicle (relative speed to the own vehicle) is different with respect to the radar of the own vehicle, the speed distribution appears as shown in FIG. 5B on the frequency axis. Therefore, first, at step 26, a peak value at which the signal strength is equal to or higher than a predetermined value is calculated. In the conventional method, when grouping data of a plurality of points, for example, in order to scan radio waves for a vehicle width, T
If it takes [s], a vehicle running at a speed of 100 [km] travels 100 T [m] in the meantime, so the detected distance at each point includes an error of at least (100 T-100) m. However, since the measurement can be performed at a plurality of points at the same time by the above method, the accuracy is improved.

In step 27, relative velocity, distance and angle are calculated for each detected peak value. here,
In the coordinate system where the radar is the origin and the traveling direction of the vehicle is the y-axis, the coordinates of each position detected at time t are (x
_i (t), y _i (t)). The detected position coordinates can be expressed by the following equation, where the distance r _i (t) and the angle θ _i (t) to each point of the detected object are given.

[0031]

## EQU00003 ## x _i (t) = r _i (t) sin θ _i (t) y _i (t) = r _i (t) cos θ _i (t) Further, the position information of k [pieces] detected here The values obtained by averaging the x-coordinates and the y-coordinates are defined as representative points (X (t), Y (t)) representing the position of the vehicle. X (t) and Y (t) can be calculated by the following equations.

[0032]

[Equation 4]

Next, in step 28, the detected vehicle speed is calculated. The vehicle speed V is the vehicle position (X (t-Δt), Y (t-Δt)) calculated at the time (t-Δt).
And the vehicle position (X (t), Y (t)) calculated at time (t) is calculated by the following equation.

[0034]

[Equation 5]

Next, in step 29, the position of each detected vehicle point after Δt [s] is calculated. The position (x _i (t + Δt), y _i (t + Δ) of each point of the vehicle after Δt [s]
t)) can be calculated by the following equations with the own vehicle as the origin.

[0036]

X _i (t + Δt) = (r _i (t) −VΔt) sin θ _i (t) y _i (t + Δt) = (r _i (t) −VΔt) cos θ _i (t) Detected by the above steps By calculating the position information of not only one point of the car, but also a plurality of points, the position change of the car can be predicted in detail.

Next, it is determined whether or not there is a collision between the predicted vehicle path and the own vehicle path, and in accordance with the result, collision avoidance control and safety device operation control are performed. An example will be described with reference to FIGS. The device for performing the collision avoidance control and the safety device will be described later.

Predict the position of the vehicle after Δt [s],
FIG. 6 shows a processing flow of an example of executing the collision avoidance control and the safety device operation control according to the result.

In step 30, the vehicle position after Δt [s] is calculated. When the vehicle speed information detected by the vehicle speed detection unit 2 is V _h [m / s] and the yaw rate information detected by the yaw rate detection unit 3 is ω [rad / s],
The curve radius R, which is the course of the vehicle, is calculated by the following equation.

[0040]

Equation 7] R = V _h / ω Therefore, the lateral distance H _c and longitudinal distance H _d of the vehicle and the vehicle as shown in FIG. 7 is calculated by the following equation.

[0041]

[Equation 8]

Therefore, assuming the center of the radar at time t as the origin, the vehicle position after Δt [s] is Is expressed as

In the same manner, the front left and right positions of the vehicle are also obtained using the equations 7 and 8. Position coordinates (X _left (t + Δt), Y in front of the left side of the vehicle after Δt [s]
_left (t + Δt)) is expressed by the following equation.

[0044]

[Equation 9]

Similarly, the position coordinates (X _right (t + Δt), Y _right (t + Δ) of the front right of the own vehicle after Δt [sec].
t)) is expressed by the following equation.

[0046]

[Equation 10]

In step 31, the distance at each point of the vehicle detected as the own vehicle after Δt [s] is calculated. Vehicle position calculated by Equation 7, Equation 8, Equation 9, and Equation 10 , Front left of the vehicle (X _left (t + Δt), Y _left (t + Δt)),
Front right of the vehicle (X _right (t + Δt), Y _right (t + Δt))
And each point of the detected object ((r _i (t) −VΔt) sin θ _i
The distances to (t) and (r _i (t) −VΔt) cos θ _i (t)) are calculated, and the respective distances of these j [pieces] are defined as D _j .

Further, in step 32, the distance D = 0 at the place where the distance between the vehicle and the object is the shortest.
Then, the time t is calculated. For example, in the example of FIG.
The left front of the own vehicle and the representative point of the detected vehicle ((r ₁ (t) −VΔ
When it is determined that the distance of t) sin θ ₁ (t) and (r ₁ (t) −VΔt) cos θ ₁ (t) is the shortest, t that satisfies the following formula is obtained.

[0049]

(11) ((r ₁ −VΔt) sin θ ₁ −X _left (t + Δt)) ²
+ ((R ₁ −VΔt) cos θ ₁ −Y _left (t + Δt)) ² = 0 Next, after the time t until the collision of the vehicle with the object is obtained, it is calculated by Equation 11 in step 38. It is determined whether the time t is smaller than the predetermined value _Tc .
When t is large, it means that it takes a long time for the detected vehicle and the detected object to approach each other, and the process proceeds to step 41, and it is determined that the possibility of collision is low, and the control unit 7 does nothing. To

If the time t is shorter than the predetermined value T _c , it is determined that the possibility of collision is high, and the process proceeds to step 39. It is particularly dangerous if the vehicle speed V _h and the object speed V are higher than a predetermined value V _c when there is a possibility of collision. Therefore,
When the following equation is established, the routine proceeds to step 40, where control is performed to activate both the collision avoidance device and the safety device.

[0051]

[Formula 12] V _h + V ≧ V _{c In} step 39, when the formula 12 is not satisfied, the control for operating only the collision avoidance device is performed.

Here, the collision avoidance device means, for example, an alarm device, a brake, a throttle, a transmission, and the like. Therefore, if a collision is detected in advance, sound an alarm,
In order to reduce the speed of collision, the four wheels are automatically braked independently and the steering operation is automatically controlled. The automatic brake can also control how to apply the four-wheel brake so that the vehicle will collide with a place where the safety of the occupant is secured as much as possible, depending on the direction in which the vehicle collides. For example, when the driver alone is driving a right-hand drive vehicle, the right and left front wheel brakes are applied more strongly than on the left side so that the object to be inspected approaches the front passenger seat side without the driver. It is conceivable to turn the car to the right. The automatic steering can perform control such that the own vehicle moves in the direction without the obstacle by calculating the detected direction in which the vehicle collides. In addition, the automatic steering can control the collision of the detected vehicle and the position of the own vehicle where the vehicle collides with the vehicle so that the vehicle can collide with a location where the safety of the occupant is secured as much as possible. it can.

The safety device is, for example, an airbag or a seat belt, and controls them. The airbag can be controlled to be deployed as early as possible by calculating the time of collision. Further, control is performed so that an airbag to be deployed (for example, a side airbag) can be selected depending on the detected direction in which the vehicle collides. The seatbelt calculates the timing to operate by predicting the collision time, and controls based on the calculation result.

In the embodiment, the object detecting device is a dual frequency C
Although the W type millimeter wave radar has been described as an example, the present invention can be applied to other types of millimeter wave radars and optical radars. The use of other types of millimeter-wave radar has the advantage of high range resolution. On the other hand, the use of the optical radar has the advantages of high spatial resolution and good distance accuracy. Further, in this embodiment, the system for detecting a collision is described with respect to a short-distance radar device. However, not only the short-distance radar device but also a radar device capable of detecting up to 120 m, for example, can be applied to an inter-vehicle distance control system. Applicable. In that case, there is an advantage that one sensor can detect both long distance and short distance with high resolution. In addition, by also being used as a radar device capable of detecting a distance of up to 30 m, for example, it becomes possible to detect a vehicle ahead when the vehicle distance is relatively narrow, and a vehicle-to-vehicle distance control system (stop & go) with automatic starting and stopping functions is provided.
It can also be applied to an ACC system that can
In that case, there is an advantage that it also has an ACC function for general roads.

[0055]

According to the present invention, when detecting an object, the path of the object can be accurately predicted based on the electromagnetic waves from each point of the object, and the moving speed and relative posture change of the object can be predicted. Made possible In addition, safety can be improved by executing collision avoidance control and operation control of the safety device based on this prediction result.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example including an object path prediction device and a control device for collision avoidance.

FIG. 2 is a diagram showing an example of a configuration of an object path prediction device.

FIG. 3 is a diagram showing a principle of a radar device.

FIG. 4 is an example of a flowchart showing a process of predicting the path of an object.

FIG. 5 is a diagram showing an example of the principle of predicting the path of an object.

FIG. 6 is an example of a flowchart showing a process of controlling operations of a collision avoidance device and a safety device.

FIG. 7 is a diagram showing an example of predicting the course of the own vehicle and the vehicle.

FIG. 8 is a diagram showing a received power pattern of each receiving antenna with respect to an angle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Object detection unit, 2 ... Vehicle speed detection unit, 3 ... Yaw rate detection unit, 4 ... Object motion prediction unit, 5 ... Own vehicle motion prediction unit, 6
... collision time estimation unit, 7 ... control unit, 8 ... alarm device control unit,
9 ... Airbag control unit, 10 ... Seatbelt control unit, 1
1 ... Brake control unit, 12 ... Throttle control unit, 13 ...
Transmission control unit, 14 ... Vehicle speed sensor, 15 ... Gyro, 1
6 ... Transmission antenna, 17 ... Reception antenna, 18 ... Oscillator, 19 ... Modulator, 20 ... Mixer circuit, 21 ... Analog circuit, 22 ... A / D converter, 23 ... FFT processing section,
24 ... Signal processing unit, 25 ... Microcomputer, 33 ... Car, 34 ...
Radar device, 35 ... Own vehicle, 36 ... Power spectrum for transmission frequency f ₂ , 37 ... Power spectrum for transmission frequency f ₁ .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B60R 21/32 B60R 21/32 5J070 22/46 22/46 B60T 7/12 B60T 7/12 C F02D 29 / 02 301 F02D 29/02 301D G08G 1/16 G08G 1/16 C (72) Inventor Satoshi Kuragaki 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Mitsuo Kayano Hitachi 1-1, Omika-cho, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Tokuji Yoshikawa 7-1-1, Omika-cho Hitachi City Ibaraki Hitachi F-term inside Hitachi Laboratory, Hitachi Ltd. Reference) 3D018 MA00 3D046 BB18 HH00 HH20 HH22 3D054 AA02 AA06 EE09 EE17 EE18 EE19 EE20 EE22 EE27 EE34 EE35 EE36 3G093 BA23 BA24 DB00 DB05 DB16 5H180 AA01 BB15 CC12 CC14 LL01 LL02 LL04 LL06 LL09 5J070 AB15 AB17 AB21 AB24 AC02 AC06 AE01 AF03 AH35 BA01 BF02 BF03 BF11

Claims (4)

[Claims] 1. A radio wave is emitted to receive a reflected wave from an object,
An object detection unit that simultaneously measures the relative velocity, distance, and angle of a plurality of points of the object is provided, and based on electromagnetic waves from a plurality of points of the object detected by the object detection unit, position information of the plurality of points of the object to be inspected is obtained. An object detection device for a vehicle, comprising: an object motion prediction unit that calculates from a distance and an angle, and calculates a velocity vector from temporal displacement of the position information and velocity information of a plurality of points. 2. A radio wave is emitted to receive a reflected wave from an object,
An object detection unit that simultaneously measures the relative velocity, distance, and angle of a plurality of points of the object is provided, and based on electromagnetic waves from a plurality of points of the object detected by the object detection unit, position information of the plurality of points of the object to be inspected is obtained. In addition to calculating from the distance and angle, the velocity vector is calculated from the temporal displacement of the position information and the velocity information of a plurality of points, the course of the object to be inspected is predicted, and the velocity vector of the plurality of points is used to detect the object. An object detection device for a vehicle, comprising: an object motion prediction unit that calculates a relative attitude change of an object. 3. The method according to claim 1 or 2, based on the position information of the representative point of the object to be inspected and the position information of itself.
Predicting a temporal change in the relative positional relationship between the object to be inspected and itself, and selecting at least one of collision avoidance control of the object to be inspected or itself and operation control of the safety device based on the prediction result. Safety control method for a vehicle collision. 4. A radio wave is emitted to receive a reflected wave from an object,
An object detection unit that simultaneously measures the relative velocity, distance, and angle of a plurality of points of the object is provided, and based on electromagnetic waves from a plurality of points of the object detected by the object detection unit, position information of the plurality of points of the object to be inspected is obtained. While recognizing from the distance and the angle, an object motion prediction unit that calculates a velocity vector from the temporal displacement of the position information and velocity information of a plurality of points, the path of the object to be examined obtained by the object motion prediction unit, and its own An automobile provided with a control unit that selectively executes at least one of collision avoidance control of the object to be inspected or itself and operation control of a safety device based on position information.