JPH06186335A - Distance measuring equipment - Google Patents

Abstract

PURPOSE:To measure the distance between vehicles correctly while eliminating erroneous detection or measurement by means of software by sorting a plurality of values calculated by a distance calculating means into weighted groups and then deciding presence/absence of an object and calculating the distance upto the object. CONSTITUTION:A distance measuring section 3 comprises a distance calculating circuit 9 for calculating the distance R upto an object based on the light projection timing of a light projecting section 1 and the light reception timing of a light receiving section 2, and a control section 10 for performing predetermined processing using values calculated at the circuit 9 and finally calculating the distance R. The control section 10 sorts the distance R into a plurality of weighted groups and every time when the circuit 9 calculates a distance R, weight of the group to which the distance R belongs is decremented and every time when scanning finishes for each of a plurality of angular ranges, a group having smallest weight smaller than a threshold is extracted. When the distance R is calculated 9 for the group thus extracted, erroneous detection can be eliminated without requiring any modification of hardware.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle device mounted on a vehicle such as an automobile, and more particularly, the invention relates to a distance between a moving vehicle and an object such as a roadside reflector. The present invention relates to a distance measuring device used for measuring.

[0002]

2. Description of the Related Art Conventionally, for example, as a device for realizing safe running of a vehicle, a vehicle-to-vehicle distance (hereinafter referred to as "own vehicle") and a preceding vehicle is measured to prevent a collision with the preceding vehicle. Or a device that maintains a constant vehicle-to-vehicle distance between the vehicle and the preceding vehicle, or a device that measures the distance between the vehicle and the roadside to determine the traveling direction of the road or the state of the curve. .

Generally, as a distance measuring device for measuring a distance to an object, an electromagnetic wave such as a laser beam is swept and projected in a traveling direction of the vehicle, and the laser beam is reflected on a rear surface of a preceding vehicle or a roadside. Is used to calculate the distance to the preceding vehicle or the roadside based on the propagation delay time from the projection of the laser light to the reception of the reflected light .

[0004]

However, in the conventional distance measuring device, the distance measurement is performed on the assumption that the object exists even though the object does not exist due to the influence of noise caused by the hardware configuration. In some cases, the measurement operation is performed assuming that the target object exists in a place different from the place where the target object exists, and even if the target object is correctly detected, the measured distance value may not be accurate. It is good if the distance to the object is measured as being closer than the actual distance, but if the distance to the object is measured as being farther than the actual distance, it may lead to a collision accident and cause a fatal defect. Becomes

Further, when this type of distance measuring device is applied to a fixed vehicle distance traveling device or the like, it is necessary to improve performances such as detection accuracy of an object and measurement accuracy of distance. There is a problem in that there is a limit to the measure and the cost increases.

The present invention has been made in view of the above problems. Even if there is an erroneous detection of an object or an erroneous measurement of a distance due to the influence of noise, an appropriate distance measurement is performed by distinguishing them. It is an object of the present invention to provide an inexpensive distance measuring device which can be improved in performance by software, regardless of the improvement in performance in hardware configuration.

[0007]

According to the present invention, a projection unit for sweeping an electromagnetic wave over a predetermined angle range and projecting it at regular intervals, and a reflected wave from a target object of the projection wave by the projection unit are received. A distance measuring device including a wave receiving unit and a distance measuring unit that measures a distance to an object, wherein the distance measuring unit is configured by a projection timing of the projection unit and a reception timing of the wave receiving unit. The distance calculation means for calculating the distance to the object for each projection of electromagnetic waves, the weight setting means for dividing the distance to the object into groups and setting a predetermined weight for each group, and the distance calculation means One of the weight changing means for changing the weight set in the weight setting means of the group to which the calculated value belongs every time the distance is calculated, and the weight of each group at the time when the sweep of the angular range is completed. A group extraction means for extracting a loop, in which a distance calculating means to calculate the distance to the object using the calculated value by the distance calculation means belonging to the group extracted by the group extraction unit.

Further, in the invention according to claim 2, the projection unit, the wave receiving unit, and the measuring unit are mounted on the vehicle in order to measure the distance to the preceding vehicle or the roadside.

Further, in the invention according to claim 3, in order to further improve the accuracy of distance measurement, the weight setting means divides the distances to the objects into groups with overlapping, and sets a predetermined weight for each group. Has been done.

[0010]

The distance to the object is not immediately determined from the value calculated by the distance calculating means, but the plurality of calculated values by the distance calculating means are classified into weighted groups to detect the presence or absence of the object. Since the distance to the target is calculated, even if affected by noise, it is possible to detect incorrect detection of the target or erroneous measurement of the distance and perform proper detection of the target and measurement of the distance. Is. In addition, since each configuration can be realized by software, the performance is not influenced by the hardware configuration, and the hardware configuration does not need to be changed to improve the performance, so that the cost is not likely to increase.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of a distance measuring device according to an embodiment of the present invention. Although the illustrated example shows a distance measuring device as an in-vehicle device mounted in a vehicle such as an automobile, the distance measuring device of the present invention is not limited to the in-vehicle device, and can be applied to, for example, the visual sense of a monitoring robot or the like. Is.

The distance measuring device in the illustrated example comprises a light projecting section 1, a light receiving section 2 and a distance measuring section 3. The light projecting section 1 includes a light projector 4, a scanning mechanism 5 and a drive circuit 6, and a light receiving section. 2 is provided with a light receiver 7 and a light receiving circuit 8.

The projector 4 of the projector 1 is, for example, a laser diode, and the laser beam 1 output by the projector 4
1 is projected by the scanning mechanism 5 in a traveling direction of the host vehicle while being scanned at a constant speed over a predetermined scan angle θ. The scanning mechanism 5 is composed of a reflecting mirror for reflecting the laser 11 from the projector 4, a rotating mechanism for swinging the reflecting mirror, and the like. However, the scanning mechanism 5 is not limited to this, and the rotating mechanism is directly connected to the projector 4. It may be configured such that the swinging motion is performed.

The drive circuit 6 outputs a trigger pulse signal p1 for pulse-driving the light projector 4 at regular intervals. In this embodiment, the period T of the trigger pulse signal p1 is 1
The scanning angle θ of the scanning mechanism 5 is set to 00 microseconds (μs), and the scanning angle θ of the scanning mechanism 5 is set to 100 milliradians (mrad). The speed is set.

FIG. 2 shows the relationship between the cycle T of the trigger pulse signal p1, the scan angle θ of the scan mechanism 5 and the scan speed. In FIG. 2, 11 is output from the light projecting section 1 at a constant cycle. Represents the laser light emitted. According to the figure, 1 time is required during 1 scan (100 ms).
Since the laser beam is output every 00 μs, the laser beam 11
The number of outputs in one scan is 1000 times.

Returning to FIG. 1, the light receiver 7 of the light receiving unit 2 is, for example, a photodiode, and the reflected light 12 from the object received by the light receiver 7 is converted into an electric signal to receive the light. Then, the signal processing such as amplification and waveform shaping is performed. Trigger pulse signal p1 for pulse-driving the projector 4 and amplified signal p output from the light receiving circuit 8
2. The scan angle signal of the scan mechanism 5 is given to the distance measuring unit 8 to measure the distance and direction of the object.

The distance measuring unit 8 calculates a distance R to the object from the light projecting timing of the light projecting unit 1 and the light receiving timing of the light receiving unit 2 for each projection of the laser light. And a control circuit 10 for finally calculating the distance to the object by performing a predetermined process described later using each calculated value by the distance calculating circuit 9.

As shown in FIG. 3, the distance calculating circuit 9 calculates the distance R by the pulse echo method from the time from the rising of the trigger pulse signal p1 to the rising of the amplified signal p2, that is, the propagation delay time Δt. The calculation formula is as shown in the following formula (1).
In the formula, c is the speed of light (c = 3 × 10 ⁸ m / sec).

[0019]

[Equation 1]

The calculation of the distance R is not limited to this pulse echo method, and other methods may be used.

The control circuit 10 has a plurality of groups G0 to G0 as shown in FIGS.
A weight setting means for grouping into G14 and setting a predetermined weight for each group, and a weight for decrementing the weight of the group to which the calculated value belongs every time the distance calculating circuit 9 calculates the distance R Changing means, a weight having a weight smaller than a predetermined threshold value TH and a minimum weight each time a scan of each of the angular ranges θ0 to θ49 divided into a plurality (50 in the illustrated example) is completed as illustrated in FIG. A group extracting means for extracting any one of the groups, and a distance R to the object using the calculated value by the distance calculating circuit 9 belonging to the group extracted by the group extracting means.
_It constitutes a distance calculation means for calculating _T. This control circuit 1
0 and the distance calculation circuit 9 are, specifically, a microcomputer and ROM or RAM as a hardware configuration.
And a program stored in the ROM (a control procedure is shown in FIG. 8) as a software configuration.

FIG. 4 shows an angular range in which an object can be detected, that is, a scan angle θ of the laser beam 11 by the light projecting unit 1. In this embodiment, the scanning angle θ of the laser light 11 is 100 mrad, and the laser light 11 is
The projection interval of 100 μs is 100 μs.
The number of outputs in scanning is 1000, and therefore, the detection capability (resolution) in 1000 directions is obtained.

In this embodiment, the angular range in which the object can be detected is divided into 50 angular regions θ0 to θ49, and each time the scanning of the laser light is completed, that is, the laser light is scanned. Each time the number of outputs of 11 reaches 20, the above-described group extraction processing and distance calculation processing are performed. The division of the angle range does not necessarily have to be even, and may be appropriately set depending on the reality performance of the scan and the application.

FIG. 5 shows a specific example in which the distance to the object is divided into 15 groups G0 to G14 evenly. In this embodiment, the distance at which the object can be detected is 0 to 150 m, and 0 m to 10 m is the 0th.
Groups G0, 10m to 20m are the first group G1, and similarly, 140m to 150m are the 14th group G1.
They are divided into four groups.

FIG. 6 specifically shows an example of setting weights for the groups G0 to G14. According to the figure, the weight is large for groups with a short distance,
The far group is set small. The difference in the size of the weight depending on the distance is that even if the objects have the same size, the number of samples is large when the distance is short,
This is because when the distance is long, the number of samples is small.

For example, when an object having a lateral length of 4 cm (for example, a reflector of a preceding vehicle) is observed under the above-described measurement conditions (scan angle θ, scan speed, laser light output period T), the object is If it exists at a distance of 10 m, the number of samples is 40, while the distance is 1
If it exists at the point of 00m, the number of samples will be four. The weight is set to a large or small value in order to reduce the deviation of the number of samples due to this distance.

The magnitude of this weight may be determined empirically in accordance with the distance, or may be determined in consideration of the place where noise is generated, the frequency of noise generation, and the like. For example, the weight is increased for a group of distances in which noise frequently appears. As a result, a group for which a large weight is set cannot be extracted as a distance calculation target unless the number of samples corresponding to the weight is obtained.

FIG. 7 shows a histogram of the weight setting example of FIG. 6, in which groups G0 to G14 are plotted on the horizontal axis.
The vertical axis represents the weight. In the figure, the dotted line indicates the initial setting value of the weight, and the distance calculating circuit 9 indicates the distance R
Each time the is calculated, the weight of the group to which the calculated value belongs is decremented. Of course, the weight set for each group and the distance R calculated by the distance calculation circuit 9 are stored in a predetermined storage area such as a RAM.

The solid line in FIG. 7 shows the weight distribution state at the time when the scanning of one angle range (for example, the angle range θ0) is completed. At this point, a group having a weight smaller than a predetermined threshold value TH and a group having a minimum weight among them is extracted. In the example shown,
Groups with weights smaller than the threshold TH are G1, G
There are five groups of 4, G5, G7 and G11. Since there are two groups G5 and G11 having the smallest weight, in this case, the group G5 having the smaller distance is extracted.

When this group extraction is performed, the value calculated by the distance calculation circuit 9 belonging to the next extracted group is read from the storage area and the average value thereof is calculated, and this average value is calculated as the distance to the object. Let it be the calculated value R _T. Such processing is sequentially executed for each of the angular regions θ0 to θ49.

FIG. 8 shows a control procedure by the control circuit 10 for carrying out the distance measuring method described above in step 1.
(Indicated by "ST1" in the figure) to step 14. First, in step 1 of the figure, the number of measurements k, each group Gi (i = 0, 1, ..., 1 in the example of FIGS.
4) After the number of samples N (i) for each calculated distance and the total sum S (i) of the calculated distances for each group Gi are zero-cleared, the weight W of each group Gi is calculated in the next step 2.
Set (i) to the initial value. Of course, zero-clearing and setting of each of these values are performed in a predetermined storage area such as a RAM.

Next, the light projecting unit 1 is operated to scan the laser beam and project the laser beam at regular intervals. The timer is started in the next step 3, and the next steps 4, 5 are performed.
Then, it is determined whether or not the reflected light from the object is received by the light receiving unit 2 within the fixed time set by the timer. If the light receiving unit 2 receives the reflected light within a certain period of time, Step 4 becomes "YES" and the process proceeds to Step 6, and the control circuit 10 of the distance measuring unit 8 causes the projection timing of the projection light (the rise of the trigger pulse signal P1). ) To the reception timing of the reflected light (the rising edge of the amplified signal P2), the distance R from the propagation delay time Δt to the object is calculated by the equation (1).

Next, at step 7, the control circuit 10 causes the calculated distance R to be any of the groups G0 to G14 described above.
Whether or not it belongs to the group, the number of samples N (i) is incremented for the groups searched in the following steps 8 and 9, and the distance R is added to the sum S (i) of the calculated distance values and stored. Weight W given to this group
Decrement (i) by 1.

If the light receiving section 2 does not receive the reflected light within a certain period of time, the determination in step 4 is "NO", step 5
The determination is “YES” and the process proceeds to step 10.

Next, in step 10, the number of measurements k is incremented, and in the following step 11, the number of measurements k is 20.
It is determined whether the number of times has been reached. If the determination is “NO”, the process returns to step 3, and the determination in step 11 is “Y
The same procedure is repeatedly executed until it becomes “ES”. In this repeating procedure, when the reflected light from the actual object is received, the reflected light is continuously received and the calculated value of the distance does not vary greatly, but the influence of noise due to the hardware configuration etc. When the amplified signal P2 rises in response to this, the same phenomenon does not continue, and the calculated value of the distance also greatly varies.

Thus, the determination in step 11 is "YES".
If so, the process proceeds to the next step 12, and the control circuit 10 next determines whether or not there is a group having a weight smaller than a predetermined threshold value TH among the groups G0 to G14. If the determination is “YES”, then in step 13, the group having the smallest weight is searched and extracted, and the sum S (i) of the distance calculation values is calculated as the sample number N.
Divide by (i) to obtain the average value of the distances, and use this average value as the calculated value R _T of the distance to the object.

If the judgment in step 12 is "NO", it is judged that there is no object in this angular region. When the processing in step 14 is completed or when the determination in step 12 is "NO", the procedure proceeds to the measurement procedure for the next angular region.

9 and 10 concretely show another grouping method and a weight setting method for each group. In the grouping method of the illustrated example, assuming that the calculated value by the distance calculating circuit 9 may vary near the boundary between the adjacent groups and the measurement accuracy may deteriorate, the distances to the objects are overlapped. Two group groups AG and BG are set and divided into groups.

For example, in the first group AG, 0 m to 1
0m is the first group AG1 and 10m to 20m is the second group AG2, while the first group AG of the second group BG is
The group AG1 is divided into groups such that the boundary value 10m between the first group AG1 and the second group AG2 in the first group group AG is an intermediate value.

When the grouping shown in FIGS. 9 and 10 is performed, the procedure from step 7 to step 9 in FIG. 8 is executed for the two group groups AG and BG. When the determination is “YES”, for each group group AG and BG, the group having a weight smaller than the threshold and having the minimum weight is extracted, and the average distance for the extracted group is obtained.

[0041]

As described above, according to the present invention, the distances to the object are divided into groups, a predetermined weight is set for each group, and each time the distance calculation means calculates the distance, the calculated value belongs to the group. The weight is changed, and when the sweep of a predetermined angle range is completed, one of the groups is extracted based on the weight of each group, and the distance to the object is calculated using the calculated value of the distance belonging to that group. Therefore, even if affected by noise, it is possible to properly detect the target and measure the distance by determining the erroneous detection of the target or the erroneous measurement of the distance. Moreover, since each configuration can be realized by software, the performance is not affected by the hardware configuration, and the hardware configuration does not need to be changed to improve the performance, which may lead to high cost. Absent.

Further, in the invention according to claim 2, since the projecting portion, the wave receiving portion and the measuring portion are mounted on the vehicle, it is possible to measure the distance to the preceding vehicle or the roadside, and the collision preventing device. It can also be applied to fixed distance driving devices.

Further, in the invention according to claim 3, the weight setting means divides the distances to the object into groups with overlapping, and sets a predetermined weight for each group. The effect is that it can be further increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship among a cycle of a trigger pulse signal, a scan angle, and a scan speed.

FIG. 3 is an explanatory diagram showing a distance calculation method.

FIG. 4 is an explanatory diagram showing an example in which an angular range in which an object can be detected is divided into a plurality of parts.

FIG. 5 is an explanatory diagram showing a specific example of grouping.

FIG. 6 is an explanatory diagram specifically showing a weight setting method for each group.

7 is an explanatory diagram showing a histogram of an example of setting weights in FIG.

FIG. 8 is a flowchart showing a control procedure of distance measurement by a control circuit.

FIG. 9 is an explanatory diagram showing another grouping method.

FIG. 10 is an explanatory diagram specifically showing a weight setting method for each group.

[Explanation of symbols]

 1 Light emitting unit 2 Light receiving unit 3 Distance measuring unit 9 Distance calculating circuit 10 Control circuit

Claims (3)

[Claims] 1. A projection unit that sweeps an electromagnetic wave over a predetermined angle range and projects the electromagnetic wave at regular intervals; a wave reception unit that receives a reflected wave of a projection wave of the projection unit from an object; and an object. And a distance measurement unit that measures the distance, the distance measurement unit calculates the distance from the projection timing of the projection unit and the reception timing of the wave reception unit to the object for each projection of the electromagnetic wave. Means, a weight setting means for dividing the distance to the object into groups and setting a predetermined weight for each group, and each time the distance calculating means calculates the distance, the weight of the group to which the calculated value belongs A weight changing means for changing the weight set in the setting means; a group extracting means for extracting one of the groups based on the weight of each group at the time when the sweep of the angular range is completed; Distance measuring apparatus comprising a distance calculating means to calculate the distance to the object using the calculated value by the distance calculation means belonging to the group extracted by the-loop extraction means. 2. The projection unit, the wave receiving unit, and the measuring unit,
The distance measuring device according to claim 1, which is mounted on a vehicle. 3. The distance according to claim 1 or 2, wherein the weight setting means divides the distances to the object into groups with overlapping and sets a predetermined weight for each group. Measuring device.