DE102019214567A1 - Method and device for operating a pulsed lidar sensor - Google Patents

Abstract

A method for operating a pulsed distance sensor (40) for a vehicle (50), comprising receiving a sequence of pulse signal groups which are emitted by the distance sensor (40) in a predefined spatial direction at a time spaced apart from one another in an environment (60) of the vehicle (50) ) objects (62) located are backscattered, each of the pulse signal groups comprising a plurality of pulse signals; Determining a histogram based on each of the obtained pulse signal groups to obtain a plurality of histograms; Determining a degree of similarity between two of the plurality of histograms, the two histograms belonging to two temporally adjacent pulse signal groups; and calculating a point cloud based on the histogram of the two histograms that is associated with the later of the two adjacent pulse signal groups if the degree of similarity falls below a predefined threshold value.

Description

TECHNICAL AREA

The present invention relates to the field of autonomous or partially autonomous vehicles. In particular, the present invention relates to a device, a method, a computer program product, a computer-readable storage medium and a data carrier signal.

TECHNICAL BACKGROUND

Distance sensors are used in autonomous or semi-autonomous vehicles in order to sense the surroundings of the vehicle and to recognize objects that are in the surroundings of the vehicle. Such a distance sensor normally comprises a transmitting unit for transmitting a sensor signal in a predefined spatial direction and a receiving unit for receiving the sensor signal after it has been scattered back on an object located in the vicinity of the vehicle. The length of time (time of flight or ToF) during which the sensor signal has moved in the space between the object and the distance sensor is measured and multiplied by the speed of the sensor signal in order to determine the distance to be measured between the object and the distance sensor receive.

In general, the sensor signal can have a pulse signal or a continuous signal. In the first case, the distance sensor is a pulsed distance sensor. Depending on the type of distance sensor, the pulse signal can be a light pulse, in particular a laser pulse, a radar pulse, a sound pulse or the like.

On the basis of the distance measurements, the surroundings of the vehicle can be analyzed quantitatively in order to reduce or avoid the risk of collision with objects located in the surroundings, in particular vehicles, people, buildings and / or plants.

Pulsed distance sensors are, for example, off EP 2 889 642 A1 known. The distance sensor disclosed there is designed to transmit a transmission pulse sequence with a known distance pattern and to receive a reception pulse sequence. In the received pulse train, a group of received pulses is determined, the pulse spacing of which is most similar to the known spacing pattern. The transit times between each transmit pulse and that particular receive pulse of said receive pulse group are based on this. This leads to a comparatively large amount of computation, which requires a correspondingly high computing capacity. This therefore places high computing power requirements on the processor used to evaluate the sensor data. The distance sensor and the entire environment recognition system are therefore costly.

The present invention is therefore based on the object of enabling environment recognition that requires less computing power and is therefore more cost-effective.

The object is achieved by a control device, a method, a computer program product, a computer-readable storage medium and a data carrier signal according to the independent claims.

A pulsed distance sensor can include a pulsed lidar sensor that sends and receives light pulse signals, in particular laser pulse signals, in order to measure the distance between the distance sensor and an object in the vicinity of the vehicle based on the flight time of the light pulse signal. Alternatively, however, it can also be a pulsed radar sensor, ultrasonic sensor or a pulsed time of flight (ToF) camera, the pulse signal being different depending on the type of sensor.

The distance sensor generates a sequence of pulse signal groups and sends them out in a predefined spatial direction at a time interval. This means that the pulse signal groups are transmitted with a group time interval between temporally adjacent pulse signal groups. Each pulse signal group comprises a plurality of pulse signals, which in turn are transmitted with a pulse time interval between temporally adjacent pulse signals. The group time interval is greater than the pulse time interval. The distance sensor is designed to transmit the sequence of pulse signal groups in a common, predefined spatial direction. The group time interval depends on the pulse rate of the distance sensor. With an exemplary pulse rate of 30 Hz, the group time interval is 30 ms. The pulse time interval can correspond to the length of time which the pulse signal needs to cover a distance which is twice the detection range of the distance sensor. In the case of a lidar sensor or radar sensor, the duration is based on the propagation speed of the light or the electromagnetic wave, which results in a pulse time interval of approximately 7 ns.

The transmitted sequence of pulse signal groups is scattered back in the direction of the distance sensor at an object located in the vicinity of the vehicle and received by the latter. Based on each of the pulse signal groups obtained an associated histogram is determined. The histogram represents a distribution of the intensity of the backscattered pulse signals as a function of the flight time between the transmission and reception of a pulse signal by the distance sensor. In this way, a sequence of histograms is obtained, each of which can be assigned a group time interval of the associated pulse signal group. The histograms are therefore spaced apart in time according to the pulse signal groups.

All histograms obtained in this way are subdivided into several groups of two chronologically adjacent histograms. Both histograms in each group are compared with one another to determine a degree of similarity. Based on the later histogram of the two histograms, which is associated with the later of the two adjacent pulse signal groups, a point cloud is then calculated, preferably only if the previously determined degree of similarity falls below a predefined threshold value. The point cloud contains at least the distance between the object and the distance sensor, which results from the flight time that is associated with the maximum of the intensity distribution in the later histogram.

A predefined threshold value for the degree of similarity can be set on a scale from 0 to 100% 80%, preferably 70%, more preferably 60% or 50%.

This means that a point cloud is not calculated for each individual histogram. This reduces the computational effort for the distance measurement. A degree of similarity that is higher than the predefined threshold value indicates that the detected object, from which the transmitted pulse signals were backscattered, is one of the objects that are located in the background of the surroundings of the vehicle at greater distances with a sufficient degree of probability ( e.g. sky, mountains, ... etc.). Such “background objects” have only a comparatively low relevance for the recognition of the surroundings. The quality of the environment recognition is therefore not impaired if such background objects are not taken into account, in that the histograms are not processed further to calculate point clouds.

Advantageous refinements and developments are specified in the subclaims.

According to one embodiment, the distance sensor is attached to the vehicle, the method further comprising checking whether the vehicle is in a static state at one of the times at which a pulse signal group is transmitted.

If the vehicle is in the static state during the period in which several pulse signal groups are transmitted, the calculated point cloud or the calculated point clouds are preferably used to detect moving objects. The point clouds relate to histograms that belong to those pulse signal groups at the times of origin (in particular at the times when the pulse signal groups are backscattered) the object that backscattered the pulse signals is movable relative to the vehicle. Since the vehicle is static in relation to a world coordinate system, it is a moving object in the world coordinate system. Such objects have a particularly high relevance for the recognition of the surroundings. The method according to the invention can therefore achieve a particularly reliable result of the environment recognition.

Otherwise, if the vehicle is not in a static state during the period in which several pulse signal groups are transmitted, it is checked whether a distance can be determined from the calculated point cloud or whether a distance can be determined from the calculated point clouds. If this is the case, the object detected by the distance sensor is within the detection range of the distance sensor. Thus, the calculated point cloud (s) can preferably be used to detect moving objects, since the detected object may be moving in the world coordinate system at the time the histograms were created from which the point cloud (s) is or are calculated. If no distance can be determined from the calculated point cloud or from the calculated point clouds, the objects can very likely be background objects that are outside the detection range of the distance sensor. In this case, the calculated point cloud or the calculated point clouds are preferably used to recognize static objects.

The computer program product according to the invention is designed to be loaded into a memory of a computer and comprises software code sections with which the method steps of the method according to the invention are carried out when the computer program product is running on the computer.

A program belongs to the software of a data processing system, for example an evaluation device or a computer. Software is a collective term for programs and associated data. The complement to software is hardware. Hardware denotes the mechanical and electronic alignment of a data processing system. A computer is an evaluation device.

Computer program products generally comprise a sequence of instructions which, when the program is loaded, cause the hardware to carry out a specific method that leads to a specific result. When the program in question is used on a computer, the computer program product produces the inventive technical effect described above.

The computer program product according to the invention is platform-independent. That means it can be run on any computing platform. The computer program product is preferably executed on an evaluation device according to the invention for detecting the surroundings of the vehicle.

The software code sections are written in any programming language, for example in Python, Java, JavaScript, C, C ++, C #, Matlab, LabView, Objective C.

The computer-readable storage medium is, for example, an electronic, magnetic, optical or magneto-optical storage medium.

The data carrier signal is a signal which the computer program product from a storage medium on which the computer program product is stored to another entity, for example another storage medium, a server, a cloud system, a wireless communication system 4G / 5G or a data processing facility, transmits.

• 1 eine schematische Darstellung einer Vorrichtung gemäß einer Ausführungsform;
• 2 eine schematische Darstellung eines Fahrzeugs mit einem gepulsten Entfernungssensor;
• 3 eine schematische Darstellung eines gepulsten Entfernungssensors; und
• 4 eine schematische Darstellung eines Verfahrens gemäß einer Ausführungsform.

Embodiments will now be described by way of example and with reference to the accompanying drawings. Show it:

• 1 a schematic representation of a device according to an embodiment;
• 2 a schematic representation of a vehicle with a pulsed distance sensor;
• 3rd a schematic representation of a pulsed distance sensor; and
• 4th a schematic representation of a method according to an embodiment.

In the figures, the same reference symbols relate to the same or functionally similar reference parts. The relevant reference parts are identified in the individual figures.

1 shows schematically a device 10 to operate a pulsed distance sensor 40 for a vehicle 50 . The device 10 includes an input interface 12th for obtaining a sequence of pulse signal groups generated by the range sensor 40 Sent out in a predefined spatial direction at a time interval and at one in an environment 60 of the vehicle 50 located object 62 (please refer 2 ) are scattered back. Each of the pulse signal groups includes a plurality of pulse signals. The device 10 further comprises a histogram unit 14th for determining a histogram based on each of the pulse signal groups obtained. Thus, a plurality of histograms are obtained. The device 10 further comprises a comparison unit 16 for determining a degree of similarity between any two of the plurality of histograms, the two histograms belonging to two temporally adjacent pulse signal groups. Finally, the device comprises 10 a point cloud unit 18th for calculating a point cloud based on the histogram of the two histograms that is associated with the later of the two adjacent pulse signal groups when the degree of similarity falls below a predefined threshold value.

2 shows a schematic representation of a vehicle 50 , on which a pulsed distance sensor 40 is appropriate. The distance sensor 40 may include a lidar sensor, a radar sensor, an ultrasonic sensor and / or a ToF camera. 3rd shows the distance sensor 40 in an enlarged schematic view. The distance sensor 40 includes a transmitter unit 42 for sending out pulse signals and a receiving unit 44 to receive the pulse signals after they have been sent to the one in the vicinity 60 of the vehicle 50 located object 62 has been scattered back.

4th shows schematically a method for operating the pulsed distance sensor 40 for the vehicle 50 . The method comprises a first step S1, in which a sequence of pulse signal groups are obtained which are generated by the distance sensor 40 Sent out in a predefined spatial direction at intervals and on in the vicinity 60 of the vehicle 50 located object 62 are scattered back. The method comprises a second step S2 in which a histogram is calculated based on each of the pulse signal groups obtained in order to obtain a plurality of histograms. The method comprises a third step in which a degree of similarity between two of the plurality of histograms is determined, the two histograms belonging to two temporally adjacent pulse signal groups. Finally, the method includes a fourth step S4 in which a point cloud based on the histogram of the two Histogram, which is associated with the later of the two adjacent pulse signal groups, is calculated when the degree of similarity falls below a predefined threshold value.

List of reference symbols

10

contraption

12th

Input interface

14th

Histogram unit

16

Comparison unit

18th

Point cloud unit

40

Distance sensor

42

Sending unit

44

Receiving unit

50

vehicle

60

environment

62

Object (human)

S1-S4

Procedural steps

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

• EP 2889642 A1 [0005]

Claims (13)

A method of operating a pulsed range sensor (40) for a vehicle (50), comprising: - Obtaining a sequence of pulse signal groups which are transmitted from the distance sensor (40) at a time spaced apart in a predefined spatial direction and which are backscattered at an object (62) located in an environment (60) of the vehicle (50), each of the pulse signal groups having a plurality of Pulse signals includes; Determining a histogram based on each of the pulse signal groups obtained to obtain a plurality of histograms; Determining a degree of similarity between two of the plurality of histograms, the two histograms belonging to two temporally adjacent pulse signal groups; and Calculation of a point cloud based on the histogram of the two histograms, which is associated with the later of the two adjacent pulse signal groups, if the degree of similarity falls below a predefined threshold value. Procedure according to Claim 1 , the threshold value of the degree of similarity on a scale from 0 to 100% being 80%, preferably 70%, more preferably 60% or 50%. Procedure according to Claim 1 or 2 , whereby the point cloud is only calculated if the degree of similarity falls below the predefined threshold value. Method according to one of the preceding claims, wherein the distance sensor (40) is attached to the vehicle (50), the method further comprising checking whether the vehicle (50) is in a static state at at least one of the times at which the pulse signal groups are transmitted State. Procedure according to Claim 4 wherein, when the vehicle (50) is in the static state, the calculated point cloud is used to detect moving objects. Procedure according to Claim 4 wherein those of the plurality of histograms are used to detect moving objects based on which no point cloud has been calculated when the vehicle (50) is not in the static state. Method according to one of the preceding claims, wherein the distance sensor (40) has a pulsed lidar sensor, the pulse signals comprising light pulses, in particular laser pulses. Device (10) for operating a pulsed lidar sensor (40), the device (10) for carrying out the method according to one of the Claims 1 to 7th is trained. A pulsed lidar sensor (40) comprising: - a transmitter unit (42) for transmitting a sequence of pulse signal groups in a predefined spatial direction, so that the pulse signal groups are spaced apart in time, each of the pulse signal groups comprising a plurality of pulse signals; - A receiver unit (44) for receiving the sequence of pulse signal groups after they have been scattered back on an object (62) located in an environment (60) of the vehicle (50); and - a device (10) according to Claim 8 . Use of the device (10) after Claim 8 and / or the pulsed lidar sensor (40) in a vehicle. Computer program product, comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to one of the Claims 1 to 7th to execute. Computer-readable storage medium on which the computer program product is based Claim 11 is stored. Data carrier signal that the computer program product according to Claim 11 transmits.

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