Method for detecting degradation of lidar sensor

Abstract

The invention relates to a method for detecting degradation of a lidar sensor, in which the method-emits a laser pulse by the lidar sensor,-detects a reflection of the emitted lidar pulse by the lidar sensor,-detects an object (O) from which the lidar pulse is reflected in the environment of the lidar sensor, -tracking the detected object (O) over a plurality of clock cycles,-determining which lidar pulses have to be reflected on during tracking of the object (O), taking into account the distance (d) of the tracked object (O) from the lidar sensor and the geometry of the tracked object (O),-determining a failure rate (a), the failure rate (a) is indicative of a frequency at which no expected reflections are detected within a predetermined period of time, and inferring degradation of the lidar sensor based on the failure rate (a) and the distance (d) to the tracked object (O). The invention also relates to a method for operating a vehicle and / or a robot.

Description

Technical Field

[0001] The present invention relates to a method for detecting degradation of a lidar sensor.

[0002] The invention also relates to a method for operating a vehicle and / or a robot. Background Art

[0003] DE 10 2018 008 903 A1 discloses a method for determining the visibility of a beam-based sensor of a vehicle for detecting an environment. A sensor beam with a known intensity is emitted by means of the beam-based sensor, wherein a reflection of the sensor beam is detected by means of the sensor and the reflection intensity is evaluated. The measured distance and the reflection intensity are correlated with each other and it is determined whether the visibility of the sensor has decreased compared to its maximum visibility. Summary of the invention

[0004] The object of the present invention is to provide a novel method for detecting degradation of a LiDAR sensor and a novel method for operating a vehicle and / or a robot.

[0005] According to the invention, this object is achieved by a method for detecting degradation of a lidar sensor having the features of claim 1 and by a method for operating a vehicle and / or a robot having the features of claim 6 .

[0006] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0007] In a method for detecting degradation of a lidar sensor, according to the invention, laser pulses are emitted by the lidar sensor, and reflections of the emitted lidar pulses are detected by the lidar sensor. In addition, objects reflecting the lidar pulses are detected in the environment of the lidar sensor, wherein the detected objects are tracked over a plurality of clock cycles. Taking into account the distance of the tracked object to the lidar sensor and the geometry of the tracked object, it is determined which lidar pulses must have been reflected on the object during tracking of the object. In addition, a failure rate is determined, which indicates how often the expected reflections are not detected within a predetermined time period. The degradation of the lidar sensor is inferred based on the failure rate and the distance to the tracked object.

[0008] In addition to determining the current degradation of the lidar sensor (e.g. due to environmental influences or contamination), the method also allows the aging and wear of individual transmitter-receiver pairs of the lidar sensor to be reliably determined. This information enables particularly reliable and safe operation of vehicles and / or robots with automatic, in particular highly automatic or autonomous driving, since with the help of this information, on the one hand the current driving mode of the vehicle and / or robot can be adapted to the degradation of the lidar sensor and on the other hand the aging state of the lidar sensor can be determined.

[0009] In one possible design of the method, a reduction in the range of the lidar sensor is determined as degradation. Thus, the current driving mode of the vehicle and / or the robot can be adapted to the current range of the lidar sensor. For example, the driving speed of the vehicle and / or the robot can be reduced as the degradation of at least one lidar sensor increases.

[0010] In another possible embodiment of the method, the failure rate of each receiver pixel of the lidar sensor is determined. This allows, in the event of partial degradation of the lidar sensor, information detected by receiver pixels located outside the degradation area to continue to be used in a reliable manner for the autonomous operation of the vehicle, thereby minimizing restrictions on the autonomous operation.

[0011] In another possible embodiment of the method, a comparison of the determined failure rate of each receiver pixel with the determined failure rates of adjacent receiver pixels is performed as a function of the distance to the tracked object in order to determine defects and / or aging of the respective receiver pixel. The reliability of the method can thus be further increased.

[0012] In another possible embodiment of the method, the range of the lidar sensor is determined based on the reflection intensity of the lidar pulse reflected from the object and the distance of the lidar sensor from the object. Such a determination of the range is particularly simple, reliable and precise.

[0013] In the method for operating a vehicle and / or a robot according to the invention, the environment of the vehicle and / or the robot is detected with the aid of at least one lidar sensor, and based on the data detected with the aid of the lidar sensor, automatic, in particular highly automatic or autonomous driving operation of the vehicle and / or the robot is performed, taking into account the degradation of at least one lidar sensor detected with the aid of the aforementioned method.

[0014] Due to the reliable detection of degradation of the lidar sensor, the method enables equally reliable operation of autonomous vehicles and thus makes it possible to increase traffic safety.

[0015] In one possible design of the method, during autonomous driving operation, the driving speed of the vehicle and / or robot is reduced as the degradation of at least one lidar sensor increases, so that depending on the degradation of the lidar sensor, safe operation of the vehicle and therefore high traffic safety is always possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present invention are explained in more detail below with reference to the accompanying drawings.

[0017] in:

[0018] Figure 1 schematically illustrates a receiver of a lidar sensor when an object at a first distance is detected,

[0019] Figure 2 Schematically shows that when the object is detected at a second distance reduced compared to the first distance, Figure 1 The receiver,

[0020] Figure 3 schematically shows a receiver of a lidar sensor when an object is detected, and

[0021] Figure 4 The failure rate of a receiver of a lidar sensor as a function of the distance to a detection object is schematically shown.

[0022] In all the figures, parts which correspond to one another are provided with the same reference numerals. DETAILED DESCRIPTION

[0023] Figure 1 A receiver 1 of a lidar sensor is schematically shown detecting an object O at a first distance d. Figure 2 shows that when the object O is detected at a second distance d that is reduced compared to the first distance d, Figure 1 Receiver 1. Distance d at Figure 4 is shown in more detail in .

[0024] The lidar sensor detects its environment with light in the infrared range and detects the spacing or distance d and information about the backscattered light for each measuring point or receiver pixel 1.1 to 1.n respectively. This information is, for example, the intensity of the backscattered light. Due to the measuring principle, the number of measuring points or receiver pixels 1.1 to 1.n per unit area decreases as the distance d increases, because the receiver 1 of the lidar sensor measures in polar coordinates.

[0025] Therefore, if Figure 1 As shown schematically, at an object O at a large distance d (e.g., 150 m), the number of receiver pixels 1.1 to 1.n receiving signals is smaller than that according to Figure 2There are fewer detection cases of objects O, where the distance d of the object O to the receiver 1 is significantly smaller. If the object O has been measured multiple times and tracked over time, a comparison of the failure rates of the individual receiver pixels 1.1 to 1.n can be performed, although a signal is expected at the receiver pixels 1.1 to 1.n due to the size of the objects present.

[0026] Figure 3 The receiver 1 of the lidar sensor is shown when detecting an object O. In this case, the object O is constructed such that it must be detected by the receiver pixels 1.3 to 1.5, 1.12 to 1.14, 1.21 to 1.23 and 1.30 to 1.32. Figure 4 The failure rate a of different receiver pixels 1 . 1 to 1 . n of a lidar sensor is shown as a function of the distance d to a detected object O.

[0027] If an object O is detected for the first time at a first point in time t_0 and is continuously tracked in the further course of time through further points in time t_k until a further point in time t_m, a failure rate a can be determined for each receiver pixel 1.1 to 1.n of the lidar sensor based on the known geometry. Here, the failure rate a can be combined with a distance d of the object O between the first point in time t_0 and a further point in time t_m. Thus, a failure rate a can be determined for each receiver pixel 1.1 to 1.n as a function of the distance d.

[0028] Comparison of the determined failure rates a based on the spacing between different receiver pixels 1.1 to 1.n allows conclusions to be drawn about possibly defective or aged receiver pixels 1.1 to 1.n. ​​Possible temporary interfering influences, such as rain or a dirty windshield of the lidar sensor, can be detected by different temporal accumulations.

[0029] If the failure rate a as a function of distance d at the beginning of the life cycle of a lidar sensor is determined in the laboratory, these values ​​can be used as a basis for determining temporary or permanent changes.

[0030] In the example, Figure 3 It is shown that during the inspection of object O, a deviation occurs between receiver pixel 1.13 and defective receiver pixel 1.22. Figure 4 The shown failure rate a of 100% corresponds to a non-existent measurement, ie the receiver 1 of the lidar sensor did not detect the object O.

[0031] The determined failure rate a as a function of the distance d allows the following conclusions to be drawn. The relationship between the maximum range of the lidar sensor and the failure rate a is based on

[0032] d 最大 = β ·d(t k), when β=f(a), (1)

[0033] The factor β can be determined based on laboratory measurements or previous sensor measurements and depends on the failure rate a.

[0034] For example, it follows that

[0035] d 最大 = 1,25 ·d(t k ), where a(d(t k ))=25% and β=f(a)=f(25%)=1.25. (2)

[0036] In this case, the difference in the failure rate curves between two different receiver pixels 1.1 to 1.n may be caused permanently by defective or aged electronic and / or optical components and / or temporarily by dirty windshield of the lidar sensor or external disturbances (e.g. rain or fog). Figure 4 The failure rate a(1.22) for the defective receiver pixel 1.22 and the failure rate a(1.13) for the adjacent receiver pixel 1.13 are shown in FIG.

Claims

1. A method for detecting degradation of a lidar sensor, wherein - emitting laser pulses by means of said lidar sensor, - detecting reflections of the emitted LiDAR pulses by means of the LiDAR sensor, - detecting an object (O) reflecting a LiDAR pulse in the environment of said LiDAR sensor, - tracking the detected object (O) over a number of clock cycles, - determining which LiDAR pulses must have been reflected on the object (O) being tracked, taking into account the distance (d) of the object (O) being tracked from said LiDAR sensor and the geometry of the object (O) being tracked, - determining a failure rate (a) indicating how often an expected reflection is not detected within a predetermined period of time, and - Inferring the degradation of the LiDAR sensor based on the failure rate (a) and the distance (d) to the tracked object (O).

2. The method according to claim 1, It is characterized in that A reduction in the range of the lidar sensor is determined as degradation.

3. The method according to claim 1 or 2, It is characterized in that The failure rate (a) is determined for each receiver pixel (1.1 to 1.n) of the lidar sensor.

4. The method according to claim 3, It is characterized in that In order to determine defects and / or aging of the respective receiver pixels (1.1 to 1.n), a comparison of the determined failure rate (a) of each receiver pixel (1.1 to 1.n) with the determined failure rates (a) of adjacent receiver pixels (1.1 to 1.n) is performed depending on the distance (d) to the tracked object (O).

5. The method according to any one of the preceding claims, It is characterized in that The range of the lidar sensor is determined based on the reflection intensity of the lidar pulse reflected by the object (O) and the distance (d) from the lidar sensor to the object (O).

6. A method for operating a vehicle and / or a robot, wherein - detecting the environment of the vehicle and / or the robot by means of at least one lidar sensor, and - Performing automatic, in particular highly automatic or autonomous driving operations of the vehicle and / or the robot based on the data detected with the aid of the lidar sensor, taking into account degradation of the at least one lidar sensor detected with the aid of the method according to any of the preceding claims.

7. The method according to claim 6, wherein: In autonomous driving operation, the driving speed of the vehicle and / or the robot decreases as degradation of the at least one lidar sensor increases.

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