JPH036473B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a device that transmits electromagnetic waves in the direction of travel of a vehicle, receives reflected waves from a reflector, and detects the distance and direction to the reflector. The present invention relates to a vehicle radar device that can accurately determine whether a preceding vehicle is on the same lane as the host vehicle on a curved road or the like.

[Technical Background and Problems of the Invention] With the development of electronics technology in recent years, by attaching a radar device to a vehicle, it is possible to detect preceding vehicles and obstacles in the direction of travel of the vehicle, thereby ensuring driving safety. In addition, systems are being considered that control the speed of the vehicle so that the vehicle can follow the vehicle in front while maintaining a safe distance between the vehicle and the vehicle in front.

Such a vehicle radar device uses, for example, an optical radar device to send out a light beam in front of the vehicle.
The reflected light of this light beam by the reflector is received, and the distance to the reflector is detected based on the light propagation delay time from the sending of the light beam to the reception of the reflected light (for example, 58−203524). By the way, such conventional optical radar devices are fixedly attached to the front of a vehicle, for example, and the light beam sent out is a single beam, and the direction in which it is sent out is often fixed. . For this reason, when driving on a curved road, for example, depending on the size of the radius of curvature, the light beam may hit vehicles in other lanes, such as adjacent lanes other than the one in which the own vehicle is traveling, and reflect light from vehicles in other lanes. In such cases, it is difficult to determine whether the reflected light received is from the vehicle in front traveling in the own lane or from a vehicle traveling in the other lane. There is a problem in that it is not possible to accurately judge whether a vehicle traveling in another lane is a preceding vehicle traveling in the own lane. Such erroneous judgments may occur not only due to vehicles traveling in the other lane, but also due to things such as roadside strips that exist on one side of the other lane. and,
In systems that use such conventional optical radar devices to perform automatic tracking control or collision prevention control for vehicles in front as described above, due to the above-mentioned erroneous judgment, vehicles in other lanes or on the side of the road may Problems arise in which malfunctions occur, reducing operability and safety.

In addition, when driving ahead on a curved road, the radius of curvature of the curved road is detected from the steering angle, and from this radius of curvature, it can be determined whether the reflector is on the own lane or on the other lane. However, the steering angle is not completely proportional to the radius of curvature of the curved road you are driving on, and it depends on the size, weight, speed, tire characteristics, steering wheel play, road surface conditions, etc. As a result, the radius of curvature of a curved road cannot be accurately determined from the steering angle. Therefore, with this method, it is not possible to accurately determine whether the reflector is on the own lane or on the other lane, and as in the case above, problems occur.

[Object of the Invention] This invention has been made in view of the above, and its purpose is to accurately determine whether or not a reflector is on the same lane as the own vehicle even on curved roads. An object of the present invention is to provide a vehicle radar device that can be used in a vehicle.

[Summary of the Invention] In order to achieve the above object, the present invention, as shown in FIG. a distance calculation means 3 for calculating the distance to the reflector based on the propagation delay time from the transmission of the electromagnetic wave in the radar means 1 to the reception of the reflected wave; angle detection means 5 for detecting an angle with respect to a predetermined direction of the vehicle in which the reflector is present from the sweep angle of electromagnetic wave transmission when receiving a reflected wave from a body; and angle change detection means for detecting a change in the angle with respect to distance. 7, and determining means 9 for determining the position of the reflector with respect to the driving lane of the vehicle based on changes in the distance to the reflector and the angle.

[Embodiments of the Invention] Examples of the invention will be described below with reference to the drawings.

FIG. 2 shows a vehicle radar device according to an embodiment of the present invention, and FIG. 3 shows signal waveforms of essential parts of the vehicle radar device of FIG. In both figures, the pulse modulation circuit 11 generates a pulse current ip with a pulse width Tw, a peak value + ampere, and a repetition period Tp, and pulse modulates the laser diode 13 with this pulse to obtain a pulse width Tw and a peak value number Watt. emits pulsed laser light. This laser beam has a vertically elongated elliptical cross section due to the cylindrical lens 15, and the beam spread angle α in the horizontal direction is several degrees.
mrad, the beam spread angle β in the vertical direction is shaped into a light beam of several + mrad, and the light beam is input to the optical deflection device 17. The optical deflection device 17 is composed of, for example, a movable mirror type, electro-optic, or acousto-optic deflector, and is provided at, for example, the front part of the vehicle, and sweeps the light beam left and right with respect to the traveling direction of the vehicle. It is something. The sweeping operation of the optical deflection device 17 is controlled by a deflection control circuit 27, which is supplied from the pulse modulation circuit 11 in synchronization with the pulse current ip from the pulse modulation circuit 11 that drives the laser diode 13. A deflection control signal Sd is supplied to the optical deflection device 17 under the control of a synchronization signal St. As a result, the optical deflection device 17
Lt is sent in the direction of travel of the vehicle while being deflected to the left and right around the center axis g of the vehicle in the travel direction within a range of a maximum sweep angle φ = 200 m rad. And the light beam
If the deflection angle θ when Lt coincides with the central axis g of the vehicle is Orad, then the deflection angle θ of the transmitted light beam Ltr with respect to the central axis g of the vehicle when the transmitted light beam Lt is deflected to the right as much as possible is +φ /2m rad,
Also, the transmitted light beam when deflected to the left as much as possible
The deflection angle θ of Ltl is −φ/2m rad. In this way, the maximum +φ/
The operation of sweeping the deflection angle φ to a maximum of −φ/2m rad in the left direction by 2 m rad is repeated at a period 400 times the repetition period Tp of the pulse current as shown in Fig. 4. . Note that the synchronization signal St from the pulse modulation circuit 11 is also supplied to the distance detection circuit 25, so that the distance detection circuit 25 can also know the point in time when the transmitted light beam Lt is sent out.

The traveling beam Lt thus sent out while being swept left and right from the optical deflection device 17 hits, for example, a preceding vehicle, and a portion of the reflected light is reflected after a propagation delay time τ as shown in FIG. The light Lr is focused by a Fresnel lens 19, received by a light receiving element 21 including a pin photodiode, an avalanche photodiode, etc., and converted into an electrical signal. Since the output signal of the light receiving element 21 is a minute pulse signal, it is amplified by the broadband amplifier 23 and supplied to the distance detection circuit 25 as an echo signal S ₀ . The distance detection circuit 25 calculates the optical propagation delay time τ from sending out the light beam Lt to receiving the reflected light Lr based on the synchronization signal St and the echo signal _S0 supplied from the pulse modulation circuit 11,
Furthermore, this propagation delay time τ and the speed of light c=3×
Calculate the distance L to the reflector based on 10 ⁸ m/s,
This distance information L is supplied to an information processing circuit 29 comprising, for example, a 16-bit microcomputer. Further, deflection angle information θ of the transmitted light beam Lt by the optical deflection device 17 when this reflector is detected is also supplied from the deflection control circuit 27 to the information processing circuit 29. Furthermore, a vehicle speed detection device 20 is provided, and the own vehicle speed Va is detected from this vehicle speed detection device 20.
is supplied to the information processing circuit 29. and,
The information processing circuit 29 determines whether or not the reflector is on the same lane as the own lane based on the distance information L, deflection angle information θ, and own vehicle speed Va thus supplied. It's getting old.

FIG. 5 shows a light beam Lt sent out from the radar device shown in FIG. 2 installed at the front of the vehicle A, which is shown in FIG. This is an explanatory diagram of the case where the reflector Or is located at a position separated by a deflection angle θ with respect to the central axis g of the own vehicle A. Further, the own vehicle A is traveling at the own vehicle speed Va.

Next, before explaining the operation of the above embodiment, when the own vehicle A is traveling on a curved road and there is a preceding vehicle, it is necessary to check whether the preceding vehicle is traveling in the same lane as the own vehicle A. The concept or principle for determining whether or not the data is present will be explained with reference to FIGS. 6 to 9.

First, with reference to FIG. 6, a case where the preceding vehicle B is traveling on the same lane as the own vehicle A on a curved road will be described.

As shown in Fig. 6, on a curved road with a radius R, it is assumed that the host vehicle A and the preceding vehicle B are traveling on the center line m of a partially circular arc in the same lane with an inter-vehicle distance L apart. The angle of the preceding vehicle B with respect to the central axis g is assumed to be θ. Also, let O be the center line m of a partial circular arc shape with radius R, that is, the center point of circle m. central axis g
is a tangent to circle m at point A, so if we connect this tangent to points O and B in the figure and extend it to P, then the angle ∠PAO=90°. If we draw a perpendicular from the apex O to the base AB in the isosceles triangle △AOB and let the intersection be H, the angle ∠OHA = 90°, so the angle ∠AOH = θ. because,
This is because θ+∠OAH=90°=∠AOH+∠OAH. Therefore, since the distance AH=R·sinθ, the distance L between the own vehicle A and the preceding vehicle B is expressed as follows.

L=2・AH=2R×sinθ Therefore, the relationship between the angle θ and the inter-vehicle distance L is as follows.

L/2R=sinθ≒θ (1) This is because the angle θ≪1 in general.

Next, referring to FIG. 7, a case will be described in which the preceding vehicle B is traveling on a curved road on a lane adjacent to the lane in which the own vehicle A is traveling.

On a curved road with radius R, vehicle A is traveling on the center line m of its own lane, and vehicle B in front is traveling on the center line n of the adjacent lane, and the distance between both vehicles is L,
Let θ' be the angle at which the preceding vehicle B exists with respect to the central axis g of the own vehicle A, and let d be the lane width. central axis g
is the tangent to circle m at point A, so the angle ∠
OAB=90°−θ. Applying the cosine law to triangle ΔAOB, we get the following equation.

R ² +L ² −2RLcos(90°−θ′) =(R+d) ² …(2) Also, since cos(90°−θ′)=sinθ, transforming equation (2) yields the following equation. It becomes like this.

L ² - d (2R + d) = 2RLsinθ' Normally, the lane width d is about 3.5 m (d3.5 m), and the radius R of a curved road is about 300 m or less (R300 m), so it can be approximated as 2R + d≒2R. The above equation becomes the following equation.

L/2R-d/L≒sinθ′……(3) Also, the normal distance L between vehicles is approximately 100m or less and 30m or more (100mL30m), and the radius R is 1000m or less.
Assuming that it is over 300m (1000mR300m) and the lane width d is approximately 3.5m (d3.5m), |
Since it can be approximated as sin θ'≈θ' within the range of sin θ'|

θ'=L/2R-d/L...(4) From the relationships shown in equations (1) and (4) above, if vehicle A and preceding vehicle B are traveling on the same lane, and if preceding vehicle B is A graph of the relationship between angles θ, θ' and inter-vehicle distance L when vehicle A is traveling in a lane adjacent to the lane in which it is traveling is shown in FIG. In Fig. 8, the line Lθ indicates the relationship when vehicle A and the preceding vehicle B are traveling on the same lane, and the curve Lθ' indicates the relationship between the vehicle A and the preceding vehicle B.
indicates the relationship when vehicle A is traveling in the lane adjacent to the lane in which it is traveling, and curve Ld is -d/
This is a plot of L.

Further, when the rate of change of the angles θ and θ' with respect to the inter-vehicle distance L, that is, the differential value, is calculated, the following equations are obtained.

For the change in angle θ with respect to distance L in the case of the same lane, differentiate equation (1) with respect to L: dθ/dL = 1/2R ...(5) For the change in angle θ' with respect to distance L in case of adjacent lanes, use the formula Differentiating (4) with respect to L gives dθ′/dL=1/2R+d/L ² ……(6).

From the relationships shown in equations (5) and (6) above, if vehicle A and preceding vehicle B are traveling on the same lane, and if preceding vehicle B is traveling in a lane adjacent to the lane in which vehicle A is traveling, When the relationship between the change in angles θ and θ' with respect to the inter-vehicle distance L and the inter-vehicle distance L is plotted as a graph, it is as shown in FIG. In this figure 9, the straight line
What is indicated by Dθ indicates the relationship when own vehicle A and preceding vehicle B are traveling on the same lane, and the curve
What is indicated by Dθ' shows the relationship when the preceding vehicle B is traveling in the lane adjacent to the lane in which the host vehicle A is traveling.

Observing FIG. 9, it can be seen that either the preceding vehicle B is traveling on the same lane as the own vehicle A, or the preceding vehicle B is traveling in another lane such as an adjacent lane different from the lane in which the own vehicle A is traveling. The following conclusions can be drawn as criteria for determining whether

(1) If the angle changes dθ/dL and dθ'/dL are calculated and their values are examined, even if the radius R of the curved road is unknown,
In the range of a radius R of 300 m and an inter-vehicle distance L of 40 m, it is possible to identify whether the preceding vehicle B is on the same lane or on the other lane. Furthermore, when driving on a steeply curved road with R<300m, even the human eye is obstructed by roadside objects and cannot see the road in front of the road.In such situations, radar detection is difficult. Since the ability cannot be expected in practical terms, it is excluded from consideration.

(2) Even when the inter-vehicle distance L is 40 m, it is possible to approximately determine the lane in which the preceding vehicle B exists depending on whether dθ/dL is approximately constant.

(3) In the case of a beam-sweeping optical radar, the beam-sweeping resolution is required to be approximately 1 mrad to several mrad.

That is, by checking the change dθ/dL of the angle θ of the preceding vehicle B with respect to the distance L or the change of the change dθ/dL with respect to the distance L, it is possible to determine whether the preceding vehicle B is on the same lane as the host vehicle A or It is possible to accurately identify whether the vehicle is on another lane.

Next, the lane and reflector identification operation of the above embodiment will be explained with reference to the flowchart of FIG.

First, the information processing circuit 29 calculates the distance L to the reflector detected by the distance detection circuit 25 and the deflection control circuit 27.
The angle θ from the reflector to the vehicle speed
Va is taken in (step 110), and from the distance L, the relative speed of the reflector with respect to the own vehicle is dL/dt,
That is, the time differential dL/dt of the distance L is calculated (step 120). Further, from the angle θ and the distance L, a change in the angle θ with respect to the distance L, that is, a differential dθ/dL of the angle θ with respect to the distance L is calculated (step 130). Next, it is checked whether the distance L is 40 m or more (step 140). As can be seen from Figure 9, if the distance L is 40m or less, the value of the distance differential dθ/dL of the angle θ indicates that the reflector is on the same lane as the own vehicle or that the reflector is behind the own vehicle. This step is used to check whether the distance L is 40 m or more because it is possible to directly and clearly identify whether the vehicle is on a lane other than the lane.

If distance L is less than 40m, step 15
Proceed to 0 and the distance differential of the angle dθ/dL is 2m rad/m
Check whether it is or not. In other words, as can be seen from Figure 9, if the distance L is less than 40 m and dθ/dL is less than 2 m rad/m, this means that the reflector is on the same lane as the own vehicle. , and if dθ/dL is 2m rad/m or more, this is because a reflector exists on a lane other than the own lane, and this is checked in this step. Therefore, as a result of this check, if dθ/dL is smaller than 2m rad/m, it can be determined that the reflector is at least a preceding vehicle or an obstacle that is on the same lane as the host vehicle. If so, the process then proceeds to step 160 to identify whether the reflector is a preceding vehicle or an obstacle. That is, step 16
At 0, the relative speed of the reflector to the own vehicle
Check whether dL/dt is equal to own vehicle speed Va. If the relative speed dL/dt is equal to the own vehicle speed Va, it can be determined that the detected reflector is a non-moving obstacle (step 180). However, if the relative speed dL/dt is not equal to the host vehicle speed Va, it can be determined that the detected reflector is a preceding vehicle traveling at a certain speed (step 170).

Further, as a result of the check in step 140, if the distance L is 40 m or more, as can be seen from FIG. For the distance L when the vehicle is on another lane other than
dθ/dL may be approximately the same value, but if the reflector is traveling on the same lane as the own vehicle,
Since dθ/dL is a nearly constant straight line, in the next step 190, this relationship, ie, dθ/
Check whether dL is constant. If this is constant, this means that the reflector is on the same lane as the host vehicle, so the process proceeds to step 160 and performs the same process as described above. However, if dθ/dL is not constant, it can be determined that the reflector is present on a lane other than the own lane, and the process proceeds to the next step 200.
Furthermore, as a result of the check in step 150, if dθ/dL is 2m rad/m or more, as can be seen from FIG. Therefore, the process similarly proceeds to step 200. In step 200, in order to identify whether a reflector existing on a lane other than the own vehicle is a preceding vehicle or a reflector, the reflector is detected relative to the own vehicle in the same way as in step 160. Relative speed dL/dt is own vehicle speed
Checks whether it is equal to Va. relative speed
If dL/dt is equal to the own vehicle speed Va, it can be determined that the reflector is a stationary object existing on the roadside, that is, a roadside object such as a signboard, sign, guardrail, or tree (step 220). Also, the relative speed
If dL/dt is not equal to the own vehicle speed Va, it can be determined that the reflector is a preceding vehicle traveling at a certain speed (step 210).

As described above, in this embodiment, it is possible to determine whether the reflector is on the same lane as the own vehicle or on another lane other than the own vehicle, and whether the reflector is in front of the vehicle. It is possible to accurately identify whether it is a car, an obstacle, or a roadside object. By applying the device of this embodiment, it is also possible to have the vehicle accurately and automatically follow the preceding vehicle traveling on the own lane, and also as a collision warning system, it is possible to automatically follow the preceding vehicle traveling on the own lane. It is also possible to reliably detect this and issue a warning to avoid a collision, and in realizing this, it is possible to prevent malfunctions caused by roadside objects or vehicles in other lanes.

[Effects of the Invention] As explained above, according to the present invention, the distance to the reflector and the angle at which the reflector exists with respect to a predetermined direction of the own vehicle are detected while sweeping the light beam from the radar means, and the distance to the reflector is detected. Since the position of the reflector, that is, the position relative to the own lane, is identified based on the change in angle with respect to distance, it is possible to navigate curved roads without being affected by various influences, such as in the conventional case of identifying based on the steering angle. Even when driving, it is possible to accurately identify whether a reflector is present on the own lane or on another lane. Further, when the present invention is applied to, for example, an automatic tracking device, a collision prevention device, etc., it is possible to realize a highly reliable device that does not malfunction and improves driving safety.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a configuration diagram of a vehicle radar device showing an embodiment of the present invention, FIG. 3 is a signal waveform diagram of the main part of the device in FIG. 2, and FIG. The figure is a diagram showing changes in the deflection angle θ of the light beam transmitted by the device shown in FIG. 2, FIG. Fig. 7 and Fig. 7 are explanatory diagrams when the host vehicle and the preceding vehicle drive in the same lane and an adjacent lane, respectively. Fig. 8 is a graph showing the deflection angle θ versus distance L, and Fig. 9 is a graph showing the deflection angle θ versus distance L. FIG. 10 is a flowchart showing the operation of the apparatus shown in FIG. 2. DESCRIPTION OF SYMBOLS 11... Pulse modulation circuit, 13... Laser diode, 17... Light deflection device, 21... Light receiving element, 25... Distance detection circuit, 27... Deflection control circuit, 29... Information processing circuit.

Claims (1)

[Claims] 1 Radar means that sends out electromagnetic waves while sweeping left and right with respect to the direction of vehicle travel and receives reflected waves of the sent electromagnetic waves by a reflector, and propagation from sending out the electromagnetic waves to receiving the reflected waves in the radar means distance calculation means for calculating the distance to the reflector based on the delay time; and a predetermined direction of the vehicle where the reflector is present based on the sweep angle of electromagnetic wave transmission when the radar means receives the reflected wave from the reflector. angle detection means for detecting an angle relative to the vehicle; angle change detection means for detecting a change in the angle with respect to the distance; and angle change detection means for detecting a change in the angle with respect to the distance; 1. A vehicle radar device comprising: determining means for determining a position.