DE102019209846A1 - Method of operating a 3D distance sensor device - Google Patents

Abstract

A method for operating a 3D distance sensor device, comprising the steps: - providing a defined number of detected measuring points; - evaluating the detected measuring points with the aid of at least one defined criterion; and estimating a visual range of the 3D distance sensor device from the evaluated measurement points.

Description

The invention relates to a method for operating a 3D distance sensor device. The invention also relates to a 3D distance sensor device. The invention also relates to a computer program. The invention also relates to a machine-readable storage medium.

Highly and fully automated vehicles (level 3-5) will be found more and more often on our roads in the next few years. There are various concepts of how such an automated vehicle can be implemented. All of these approaches require a wide variety of sensors (e.g. video cameras, LiDAR, radar, ultrasonic sensors, etc.). For safe driving in all weather conditions, it is necessary that all sensors independently provide an estimate of their current range of vision.

DE 199 31 825 A1 discloses a device for visibility measurement, in particular for motor vehicles, which has at least one optical transmission element, at least one optical reception element and a measurement signal evaluation unit which determines a current visibility from the light reflected at one or more different spatial zones.

DE 10 2016 014 549 A1 discloses an autonomous vehicle that includes both a LiDAR sensor and a camera. The LiDAR sensor can work in the range of visible light, in the IR range or another wavelength range. If signs have an IR-reflective print, the IR range can be used.

DE 10 2016 014 549 A1 discloses a method for determining the visual range from a vehicle by means of a LiDAR sensor.

EP 2 101 193 A1 discloses a safety sensor and a method for contactless measurement of positions, distances and / or speeds.

U.S. 6,362,773 B1 discloses a combination of several sensors or an adapted, complex evaluation of raw sensor data. However, these raw data are not available in many sensor architectures of the central sensor fusion and evaluation unit.

Disclosure of the invention

It is an object of the present invention to provide an improved method for operating a 3D distance sensor device.

• - Bereitstellen einer definierten Anzahl von detektieren Messpunkten;
• - Auswerten der detektierten Messpunkte mit Hilfe von wenigstens einem definierten Kriterium; und
• - Schätzen einer Sichtweite der 3D-Distanzsensorvorrichtung aus den ausgewerteten Messpunkten.

According to a first aspect, the invention creates a method for operating a 3D distance sensor device, comprising the steps:

• - Provision of a defined number of detected measuring points;
• - Evaluation of the detected measuring points with the aid of at least one defined criterion; and
• - Estimating a visual range of the 3D distance sensor device from the evaluated measuring points.

In this way it can advantageously be recognized whether there is an impairment of the visual range for the 3D distance sensor device. This advantageously makes it possible to quantify how much the visibility is reduced, it being possible to distinguish a reduced visibility from a blockage. The proposed method advantageously represents a method at the system level, i.e. that an already evaluated 3D point cloud of measuring points is used and raw sensor data is therefore not required.

According to a second aspect, the object is achieved with a 3D distance sensor device which is designed to carry out the proposed method.

According to a third aspect, the object is achieved with a computer program.

According to a fourth aspect, the object is achieved with a machine-readable storage medium.

Preferred embodiments of the proposed method are the subject of the respective dependent claims.

An advantageous further development of the method is characterized in that measuring points of a geometrically lowest level of the 3D distance sensor device are analyzed, the number of detected measuring points being compared with a defined first threshold value. It is expected that all scan or measurement points of the geometrically lowest level are always available, because a road is arranged in this level, on which the vehicle with the 3D distance sensor device is located, whereby the road is usually only approx. 10m far from the 3D distance sensor device. If this is not the case, appropriate conclusions can be drawn from it.

A further advantageous development of the method is characterized in that in the event that the proportion of the detected measurement points is defined below the first threshold value, one Occlusion of a cover glass of the 3D distance sensor device is determined. In this case, a cleaning process of the 3D distance sensor device can be triggered, for example, to produce the full range of vision.

A further advantageous development of the method provides that in the event that the proportion of detected measuring points is defined above the first threshold value, an evaluation of a defined, calibrated distance histogram of the measuring points is carried out, a decay rate of the frequency of the measuring points being determined over the distance. The distance histogram is evaluated in this way in order to be able to make more precise statements about the visual range. For example, reduced visibility due to fog or rain can be determined in the distance histogram.

A further advantageous development of the method provides that in the event that the proportion of the detected measuring points is defined below a second threshold value of the decay rate, a defined high visual range of the 3D distance sensor device is determined. This is determined by the fact that the distance histogram slowly declines at a high visibility range.

Another advantageous development of the method is characterized in that, in the event that the proportion of the detected measuring points is defined below a second threshold value of the decay rate, an evaluation of a total number of the measuring points is carried out. Here, in particular, the influence of fog on the visibility is determined, which is particularly irrelevant for short distances, in which case the total number of measurement points is evaluated.

A further advantageous embodiment of the method is characterized in that when the total number of measurement points falls below a third threshold value, a defined low visual range of the 3D distance sensor device is determined and, when the third threshold value of the total number of measurement points is exceeded, a blockage of the 3D distance sensor device is determined . In this way, suitable knowledge can be obtained depending on the number of measuring points. The distance histogram drops rapidly, but there are a large number of measurement points in the 3D point cloud, which can be an indication of a blockage in the view of the 3D sensor device.

Another advantageous embodiment of the method is characterized in that a driving function of a vehicle is adapted from the estimated visual range and / or cleaning of the 3D distance sensor device is initiated. As a result, suitable measures can be taken to adapt to the reduced visibility of the 3D distance sensor device.

Another advantageous embodiment of the method is characterized in that the method is carried out in normal operation of the 3D distance sensor device. As a result, the visual range of the 3D distance sensor device can advantageously be determined in real time.

Another advantageous embodiment of the method is characterized in that the method is carried out within the 3D distance sensor device or on an external computer device. In this way, an “intelligent 3D distance sensor” can be implemented or the computing power required for this can be suitably outsourced.

The invention is described in detail below with further features and advantages using two figures. The figures are intended in particular to clarify the principles essential to the invention and are not necessarily drawn to scale.

• 1 ein prinzipielles Ablaufdiagramm eines vorgeschlagenen Verfahrens zum Betreiben einer 3D-Distanzsensorvorrichtung; und
• 2 ein beispielhaftes Distanzhistogramm, welches im Rahmen des vorgeschlagenen Verfahrens analysiert werden kann.

In the figures shows:

• 1 a basic flowchart of a proposed method for operating a 3D distance sensor device; and
• 2 an exemplary distance histogram that can be analyzed within the framework of the proposed method.

Description of embodiments

A core idea of the present invention is in particular to provide an improved method for operating or analyzing a 3D distance sensor device.

One advantage of the proposed method is that, for example, a central evaluation unit of a 3D distance sensor can determine or estimate the visual range, with additional sensors advantageously not being required for this.

Estimating the range of vision of a sensor in all weather conditions is necessary to enable safe driving of a partially or fully autonomous vehicle.

For example, it is necessary to adjust the speed to the current visibility of the sensors. However, the range of vision of a sensor can under certain circumstances be great due to various atmospheric weather influences such as rain, fog, snowfall, etc. be affected. A distinction must be made as to whether the performance of the sensor is impaired due to such atmospheric influences or due to statistically distributed blockages on the sensor cover, such as raindrops, dirt, etc. The proposed method also makes it possible to recognize situations in which the view of the 3D distance sensor is blocked by one or more objects (e.g. a vehicle parked in a garage) and therefore no statement is made about the current view of the 3D distance sensor can.

The proposed method for operating a 3D distance sensor device based on a 3D point cloud is based on a combination of several usable parameters. In the following, a 3D point cloud is understood to be a three-dimensional accumulation of measuring points that are recorded by means of a three-dimensional distance sensor (e.g. LiDAR, radar sensor, etc.). The number of points in the environment detected by the 3D distance sensor is primarily used. The method is described below by way of example for a 3D LiDAR distance sensor arranged on a vehicle, but is advantageously also suitable for improved operation of a radar sensor.

1 shows a basic sequence of a proposed method. In one step 100 the 3D distance sensor device provides a 3D point cloud with a defined number of measurement points in the environment.

In one step 101 an analysis of the number of points of the measurement points of a geometrically lowest level of the 3D distance sensor device is carried out. The geometrically lowest level of a 3D distance sensor device typically covers a road at a short distance from the vehicle, measurement data provided in this way therefore often also being used to identify open spaces. The short distance means that all measuring points of this plane should be present in the 3D point cloud even if the visibility is limited.

This parameter therefore does not represent a measure for a visual range of the 3D distance sensor device, but it does allow, for example, a blockage of vision on the cover of the 3D distance sensor device to be recognized. The test is carried out in one step 102 a total number of measurement points of the geometrically lowest level, wherein in the event that the total number of measurement points falls below a defined first threshold value SW1 in a defined manner, it is determined that a cover of the 3D distance sensor device is blocked. For example, this can be caused by a deposit (eg dirt, snow, ice, etc.) on the sensor cover, which is why a cleaning process for the 3D distance sensor device is initiated in this case.

If the total number of measuring points of the geometrically lowest level of the 3D point cloud exceeds the first threshold value SW1 in a defined manner, in one step 110 an analysis of a decay rate of a related 2 detailed distance histogram of the entire 3D point cloud carried out.

To analyze the distance histogram of the entire 3D point cloud, all points of the 3D point cloud are shown in the distance histogram, which represents a graph that shows the frequency of the measurement points of the 3D point cloud as a function of distance. A suitable mathematical function can be provided for this data, in which case an exponentially decreasing function is selected which is characterized by the two parameters amplitude and decay rate.

These two parameters are influenced by different processes. The amplitude is influenced by blockages on the sensor cover of the 3D distance sensor device. The decay rate is influenced by the atmospheric visibility, since a short visibility only affects the detection of objects that are far away, but not the detection of objects arranged close to the 3D distance sensor device. Furthermore, the decay rate is influenced by the landscape structure or by a blockage of the 3D distance sensor device's view by other objects (e.g. a garage, location behind a truck, etc.). As a result, the distance histogram allows a value for the visual range of the 3D distance sensor device to be specified based on the decay rate.

In one step 111 it is checked whether the decay rate of the measurement points of the distance histogram has a certain second threshold value SW2, in the case that this is smaller than the defined second threshold value SW2, in one step 112 a defined high visual range for the 3D distance sensor device is determined.

If, on the other hand, the rate of decay of the distance histogram is greater than the second threshold value SW2, this means that, for example, the 3D distance sensor device may have a low visual range or an object blockage, which is subsequently done in one step 120 is examined more closely. This is done in step 121 an analysis of the total number of points of the measuring points of the 3D point cloud is carried out.

In one step 122 it is determined that the stated total number of points of the measuring points the 3D point cloud is smaller than a defined third threshold value SW3, as a result of which a low visual range (for example due to fog, rain, snowfall, etc.) is determined for the 3D distance sensor device. This can be the case, for example, in fog, in which case there is hardly any restriction in the visual range of the 3D sensor device for short distances, but a total number of measuring points can be considerably reduced for greater distances.

In one step 123 it is established that the named total number of points of the measurement points of the 3D point cloud is greater than the defined third threshold value SW3, in which case a visual blockage of the 3D distance sensor device is determined. This situation can exist, for example, when the vehicle equipped with the 3D distance sensor device is parked in front of a wall.

For a complete decision-making with regard to the visual range estimation of the 3D distance sensor device, an evaluation of all the aforementioned three threshold values SW1, SW2 and SW3 is necessary, which is why for this purpose in the steps 101 , 110 and 120 own detailed analyzes are carried out. The decision can be made using the decision tree from 1 to be hit. A quantitative value of the visual range can be determined by a decay rate of the distance histogram that is quantified by means of a calibration process. In this way, the distance histogram can advantageously also be used without the other two threshold values.

Advantageously, only the distance histogram can be evaluated for the estimation of the visual range, thereby enabling the detailed analyzes of the steps 101 , 120 can also be omitted. This advantageously saves computing time and in this way selected criteria or all of the proposed criteria for checking the visual range of the 3D distance sensor device can be checked.

The distance histograms are each suitably pre-calibrated for a specific type of 3D distance sensor device, whereby a specific decay rate is assigned to a visual range of the 3D distance sensor device. Due to the large number of different types of 3D sensor devices, it is not possible to specify generally valid numerical values for visual ranges, distances, numbers of measuring points of the 3D point cloud and threshold values SW1, SW2, SW3.

2 shows an exemplary distance histogram, the distance d being plotted on the x-axis and a logarithmic frequency H of the measuring points of the 3D point cloud on the y-axis. One recognizes two courses A, B of measuring points of a 3D point cloud. The course A represents a high visual range with a low exponential decay rate of the number of measuring points over the distance d and the course B a low visual range with a high exponential decay rate of the number of measuring points over the distance d. The second threshold value SW2 corresponds to the decay rate or the slope of the curves A, B.

The proposed 3D distance sensor device can advantageously be used to detect the surroundings in highly and fully automated vehicles (level 3-5).

The proposed method can preferably be carried out in a defined time pattern of the 3D distance sensor device, quasi in real time (e.g. with a cycle time of approx. 10 frames / s, i.e. approx. 10 Hz) in a background operation. It can be provided that the proposed method is implemented as software running in the 3D distance sensor device. Alternatively, it can also be provided that the software for executing the proposed method runs on an external computer device, which can be arranged in the cloud, for example.

Suitable measures can be derived from the determined visibility, e.g. an adaptation of one or more driver assistance functions of the vehicle, a speed of the vehicle, etc.

The proposed method is preferably carried out in normal operation of the 3D distance sensor device, in which the 3D distance sensor device is arranged in or on a highly or fully automated vehicle and is used to detect the surroundings while the vehicle is in motion. By determining the visual range of the 3D distance sensor device quasi in real time, a useful value of the 3D distance sensor device is significantly increased.

Although the invention was explained in connection with an optoelectronic 3D scanner in the form of a LiDAR sensor for a motor vehicle, it is also conceivable, for example, to use the proposed method for other 3D distance sensor devices, e.g. for a radar sensor.

The person skilled in the art will thus recognize that a large number of modifications are possible without departing from the essence of the invention.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19931825 A1 [0003]
• DE 102016014549 A1 [0004, 0005]
• EP 2101193 A1 [0006]
• US 6362773 B1 [0007]

Claims (13)

Method for operating a 3D distance sensor device, comprising the steps: - Provision of a defined number of detected measuring points; - Evaluation of the detected measuring points with the aid of at least one defined criterion; and - Estimating a visual range of the 3D distance sensor device from the evaluated measuring points. Procedure according to Claim 1 , wherein measurement points of a geometrically lowest level of the 3D distance sensor device are analyzed, the number of detected measurement points being compared with a defined first threshold value (SW1). Procedure according to Claim 2 , in the event that the proportion of the detected measuring points is defined below the first threshold value (SW1), a cover glass of the 3D distance sensor device is detected. Method according to one of the preceding claims, wherein an evaluation of a defined, calibrated distance histogram of the measurement points is carried out, a decay rate of a frequency of the measurement points being determined over the distance. Method according to one of the preceding claims, wherein in the event that the proportion of the detected measuring points is defined below a second threshold value (SW2) of the decay rate, a defined high visibility of the 3D distance sensor device is determined. Procedure according to Claim 5 , in the event that the proportion of recognized measuring points is defined below a second threshold value (SW2) of the decay rate, an evaluation of a total number of measuring points is carried out. Procedure according to Claim 6 , whereby when the total number of measuring points falls below a third threshold value (SW3) a defined low visual range of the 3D distance sensor device is determined and when the third threshold value (SW3) of the total number of measuring points is exceeded, a blockage of the 3D distance sensor device is determined. Method according to one of the preceding claims, wherein a driving function of a vehicle is adapted from the estimated visual range and / or cleaning of the 3D distance sensor device is initiated. Method according to one of the preceding claims, wherein the method is carried out in normal operation of the 3D distance sensor device. Method according to one of the preceding claims, wherein the method is carried out within the 3D distance sensor device or on an external computer device. 3D distance sensor device that is set up, a method according to one of the Claims 1 to 10 execute. Computer program comprising instructions which cause a computer to execute the computer program, a method according to one of the Claims 1 to 10 execute. Machine-readable storage medium on which the computer program is based Claim 12 is stored.

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