DETERMINING THE PITCH ANGLE POSITION OF AN ACTIVE OPTICAL SENSOR SYSTEM

Description

[0001] The invention relates to a method for determining a pitch angle position of an active optical sensor system mounted on a motor vehicle located on a roadway. The invention further relates to a corresponding active optical sensor system for mounting on a motor vehicle, a motor vehicle, a computer program, and a computer-readable storage medium.

[0002] Active optical sensor systems, such as lidar systems, can be mounted on motor vehicles to implement a wide range of functions in electronic vehicle guidance systems or driver assistance systems. These functions include distance measurements, adaptive cruise control algorithms, lane departure warning systems, object tracking functions, and so on. Deviations in the sensor system's installation position or orientation from a nominal orientation affect the accuracy of the measured values, their interpretation and evaluation, and thus the reliability and robustness of the corresponding functions. Therefore, it is necessary to calibrate the active optical sensor system to compensate for corresponding orientation or position deviations.

[0003] Document US 9,052,721 B1 describes a method for correcting the alignment of a vehicle-mounted laser scanner. The method is based on comparing a three-dimensional point cloud of the laser scanner with a three-dimensional reference point cloud to calculate an incorrect alignment of the laser scanner. The reference point cloud is recorded in advance by driving the vehicle or another vehicle along the roadway.

[0004] As a result, the misalignment of the laser scanner can only be compensated based on measurement points if reference measurement points are available for the corresponding road section. However, the number of available measurement points or the frequency with which calibration can be performed significantly influences the accuracy of the compensation for orientation or position deviations. Another disadvantage is that the reference point cloud must be recorded in advance. Methods for determining the alignment of an optical sensor system are also known from JP 2015-75382 A and WO 2018 / 166956.

[0005] Against this background, it is an object of the present invention to provide an improved concept for determining a pitch angle position of an active optical sensor system, which does not require a pre-recorded reference point cloud and with which, in particular, a higher accuracy can be achieved.

[0006] According to the invention, this object is achieved by the respective subject matter of the independent patent claims. Advantageous developments and further embodiments are the subject matter of the dependent patent claims.

[0007] The improved concept is based on the idea of generating two different subsets of sample points from a road surface and determining a pair of sample points from the different subsets whose connecting vector, projected into a transmission plane of the sensor system, is parallel to a longitudinal axis of the sensor system. The angle that the connecting vector forms with the longitudinal axis of the sensor system serves as a measure of the pitch angle.

[0008] According to a first independent aspect of the improved concept, a method is provided for determining a pitch angle position of an active optical sensor system, wherein the sensor system is mounted on a motor vehicle located on a roadway. The sensor system generates a point cloud containing a first subset of sample points of the roadway and a second subset of sample points of the roadway. A computing unit of the sensor system identifies a first pair of sample points, one point of the first pair being part of the first subset and another point of the first pair being part of the second subset. A projection of a first connecting vector of the first pair into a transmission plane of the sensor system is parallel to a longitudinal axis of the sensor system.The computing unit determines a first angle that the first connecting vector encloses with the longitudinal axis of the sensor system in order to determine the pitch angle position.

[0009] The fact that a point is part of a subset can be understood in such a way that the subset contains the corresponding point.

[0010] The connection vector is given in particular by a vector that has the point as the starting point and the other point as the end point.

[0011] Here and below, an active optical sensor system can be defined as such by having a transmitting unit with a light source, in particular for emitting light or light pulses. The light source can be configured, in particular, as a laser. Furthermore, an active optical sensor system has a receiving unit with at least one optical detector, in particular for detecting light or light pulses, in particular reflected portions of the emitted light. The active optical sensor system is configured, in particular, to generate and output one or more sensor signals based on the detected light.

[0012] Here and in the following, the term "light" can be understood to include electromagnetic waves in the visible, infrared, and / or ultraviolet spectral ranges. Accordingly, the term "optical" can also be understood to refer to light in this sense.

[0013] The light emitted by the active optical sensor system may, in particular, include infrared light, for example, with a wavelength of 905 nm, approximately 905 nm, 1,200 nm, or approximately 1,200 nm. This may refer to a wavelength range with a broader distribution that is typical for the corresponding light source.

[0014] In the present case of the active optical sensor system, the light source can be, for example, a laser light source. The wavelengths mentioned can, within the usual tolerances, correspond, for example, to peak wavelengths of the laser spectrum.

[0015] The fact that the point cloud is generated by means of the sensor system can be understood, for example, in such a way that at least one sensor signal is generated by means of the receiving unit based on detected portions of the reflected light and the computing unit generates corresponding sampling points of the point cloud based on the at least one sensor signal, wherein each sampling point contains a three-dimensional coordinate tuple of spatial coordinates, in particular in a sensor coordinate system of the sensor system.

[0016] The sensor system may, for example, include a deflection device, for example with a movable or rotatably mounted mirror, by means of which light beams generated by the transmitting unit can be deflected in a controlled manner.

[0017] In particular, the longitudinal axis of the sensor system, which defines, for example, an X-axis of the sensor coordinate system, corresponds to an emission direction of the light rays at an emission angle of zero degrees, for example, when the deflection device is in a neutral position. The deflection device can assume positions deviating from the neutral position to deflect the light rays so that the light rays exit the sensor system within the emission plane.

[0018] A transverse axis of the sensor system, which defines, for example, a Y-axis of the sensor coordinate system, lies within the transmission plane and is perpendicular to the longitudinal axis, which, by design, also lies within the transmission plane. A normal axis of the sensor system is perpendicular to the longitudinal axis and the transverse axis of the sensor system. The normal axis of the sensor system defines, for example, a Z-axis of the sensor coordinate system.

[0019] In other words, the viewing direction or emission direction of the sensor system in the neutral position is equal to the X-axis of the sensor coordinate system. The emission plane is defined by the XY plane of the sensor coordinate system. The sensor system can emit light at different emission angles within the emission plane.

[0020] The reflected portions of the light can be received spatially resolved by the receiving unit, for example, so that not only the different emission angles but also the different reception angles can be recorded and determined. Furthermore, the distance between the sensor system and a point or object at which the light was reflected can be determined, for example, using a time-of-flight (TOF) measurement. This makes it possible to generate the point cloud as a three-dimensional point cloud, i.e., a point cloud composed of three-dimensional spatial coordinate tuples.

[0021] The spatial resolution of the receiving unit can be achieved, for example, by having at least two optical detectors. The sample points captured by one of the detectors are also referred to as layers. Layers resulting from reflections from the road surface are also referred to as ground layers, ground layers, or touchdown lines.

[0022] The first and second subsets are, in particular, different soil layers.

[0023] A longitudinal axis of the motor vehicle, which in particular defines an X-axis of a vehicle coordinate system, is given, for example, by a direction of travel of the motor vehicle when a steering system of the motor vehicle is in the neutral position or when the steering angle, in particular a wheel angle or steering wheel angle, of the motor vehicle is zero degrees. A transverse axis of the motor vehicle is perpendicular to the longitudinal axis of the motor vehicle and lies in a plane that is parallel to the roadway or parallel to a plane within which the contact points of the wheels of the motor vehicle on the roadway lie. The transverse axis defines, in particular, a Y-axis of the vehicle coordinate system. A normal axis of the motor vehicle, which in particular defines a Z-axis of the vehicle coordinate system, is perpendicular to the longitudinal axis and the transverse axis of the motor vehicle.

[0024] The overall angular position of the sensor system can be defined, for example, by the pitch angle, the yaw angle, and the roll angle of the sensor system. A pitch angle, a yaw angle, and a roll angle of the sensor system are defined as the rotation angle or Euler angle of the sensor coordinate system with respect to the vehicle coordinate system according to a predefined convention.

[0025] For example, the convention can be such that the sensor coordinate system results from the vehicle coordinate system through the following three rotations, assuming that the sensor coordinate system and the vehicle coordinate system are initially identical: The sensor coordinate system is rotated by the yaw angle around the Z-axis of the vehicle coordinate system. The resulting sensor coordinate system is then rotated by the pitch angle around the resulting Y-axis of the resulting sensor coordinate system. The resulting sensor coordinate system is then rotated by the roll angle around the resulting X-axis of the resulting sensor coordinate system. Other conventions are also possible.

[0026] If the yaw and roll angles are zero, the pitch angle corresponds in particular to a rotation angle of the sensor coordinate system around the Y-axis of the vehicle coordinate system.

[0027] The pitch angle position corresponds in particular to an estimated or measured value for the pitch angle of the sensor system.

[0028] To implement the method for determining the pitch angle position according to the improved concept, it is assumed, for example, that the yaw angle is zero or negligibly small, or that the sensor system has been previously calibrated with respect to the yaw angle. If a calibration with respect to the yaw angle was carried out beforehand, the yaw angle position of the sensor system was determined in advance, for example using the computing unit. To generate the point cloud, the yaw angle position was then taken into account by normalizing the spatial coordinates of the sampled points accordingly, so that they appear to have been generated by a sensor system with a vanishing yaw angle. Accordingly, it can be assumed here and in the following, without loss of generality, that the yaw angle is zero.

[0029] In various embodiments, the method for determining the pitch angle position according to the improved concept includes the method steps for calibrating the sensor system with respect to the yaw angle.

[0030] The same may apply to the roll angle. However, the roll angle does not influence the determination of the pitch angle in the manner described in the improved concept. Therefore, it is not necessary for the roll angle to be determined in advance. Accordingly, it can be assumed here and in the following, without loss of generality, that the roll angle is zero.

[0031] Under the assumptions explained above, the longitudinal axis of the sensor system lies along the XZ axis of the vehicle coordinate system. The pitch angle can therefore also be understood as the angle formed by the longitudinal axis of the sensor system with the longitudinal axis of the vehicle.

[0032] The fact that the sensor system is mounted on the motor vehicle can be understood, for example, to mean that the sensor system is attached to the motor vehicle and can, in particular, also mean that the sensor system is partially or completely installed within the motor vehicle. In this case, it is ensured in any case that the transmitting unit can transmit the light into an environment outside the motor vehicle and the receiving unit can receive the reflected components.

[0033] The fact that the motor vehicle is on the roadway can be understood in particular to mean that it is moving on the roadway or is standing on it.

[0034] The first and second subsets each contain at least two sampling points. Preferably, the subsets each contain a plurality of sampling points, for example, a number of sampling points on the order of a few tens, a few hundred, or a few thousand sampling points. In particular, the number of sampling points in a subset corresponds to the number of different emission angles for the light that can be set by means of the transmission unit or the deflection device.

[0035] According to at least one embodiment, the deflection device includes a mirror mounted for rotation about a rotation axis. The transmitting unit, which can be fixedly mounted relative to the sensor coordinate system, for example, emits the light, which strikes a defined point on the mirror and, depending on the angular or rotational position of the mirror, is emitted according to a defined emission angle within the transmission plane. The respective angular position of the mirror can be detected, for example, by means of a rotary encoder arranged on a shaft or coupled to the shaft aligned along the rotation axis of the mirror.

[0036] In alternative embodiments, the deflection device can comprise a mirror element that can be tilted or pivoted about one or two axes to deflect the light in the transmission plane. The mirror element can be configured, for example, as a microelectromechanical system (MEMS).

[0037] The first pair of sampling points consists, in particular, of the point and the other point of the first pair. The same applies to the pairs of sampling points introduced later, namely that a pair of sampling points always consists of two sampling points.

[0038] Identifying the first pair by means of the computing unit can be understood, for example, as meaning that the point and the further point of the first pair are selected by means of the computing unit in such a way that the described condition for the projection of the first connection vector is met. In particular, for a given pair of sampling points, the computing unit can calculate the corresponding connection vector and its projection into the transmission plane, and determine whether the projection is parallel to the longitudinal axis of the sensor system by calculating an angle between the projection and the longitudinal axis of the sensor system and comparing it with zero. The projection of the first connection vector can in particular be considered parallel to the longitudinal axis of the sensor system if the corresponding angle is equal to zero or smaller than a predetermined tolerance angle.

[0039] In particular, by the spatial resolution of the receiving unit, for example by using different optical detectors, such a pair of sampling points can be found whose connecting vector, projected into the transmission plane, is parallel to the longitudinal axis of the sensor system.

[0040] The projection p of the first connection vector v can be expressed, for example, as follows: p = v - ( v * z S) z S . Here, z S is the direction vector of the Z-axis of the sensor coordinate system.

[0041] The first angle corresponds, in particular, to an estimated value for the pitch angle. From this, possibly with further estimated values for the pitch angle, the pitch angle position can be determined, for example, by averaging. Alternatively, the pitch angle position can be equal to the first angle.

[0042] The first angle δ can be calculated in particular according to the equation δ = arctan([ZB - ZA ] / [XB - XA ]), where XA denotes the X-coordinate of the point of the first pair, ZA its Z-coordinate, XB the X-coordinate of the further point of the first pair and ZB its Z-coordinate, each in the sensor coordinate system.

[0043] According to the improved concept, the pitch angle position of the sensor system can be determined online, i.e., while the motor vehicle is in operation and without a dedicated calibration template, also known as a calibration target. By using various subsets of sample points on the roadway, in particular from different ground surfaces, to determine the first angle, no reference data is required that, for example, must be recorded in advance. Furthermore, the improved concept does not require any reference objects in the vicinity of the motor vehicle, such as road markings or lane boundaries, other than the roadway itself to determine the pitch angle position. This is particularly advantageous because the roadway is naturally always available and, accordingly, the ground surfaces are also permanently or almost permanently available.

[0044] Compared to methods based on reference data or reference objects, the method based on the improved concept can be performed at virtually any time during vehicle operation. This allows the pitch angle position to be determined more or less continuously, resulting in a much larger number of measurement points and, accordingly, a much higher accuracy in determining the pitch angle position.

[0045] Furthermore, the improved concept eliminates the need to know the sensor system's installation height. This is particularly advantageous because, in most cases, the sensor system's installation height is unknown or only known with limited accuracy. This also results in increased accuracy in determining the pitch angle position.

[0046] According to at least one embodiment of the method, to generate the point cloud, light is emitted into the environment of the sensor system by means of the transmitting unit of the sensor system. Reflected portions of the light are detected by the receiving unit of the sensor system. At least one sensor signal is generated by the receiving unit based on the detected reflected portions. The point cloud is generated by the computing unit based on the at least one sensor signal.

[0047] The transmitting unit contains, for example, the light source, which is designed in particular as a laser light source, for example, a laser diode. The laser light source is designed in particular as an infrared laser. The peak wavelength of the corresponding laser spectrum can be, for example, 905 nm or 1,200 nm.

[0048] According to at least one embodiment, the sampling points of the first subset are generated by means of a first optical detector of the sensor system, in particular the receiving unit, and the sampling points of the second subset are generated by means of a second optical detector of the sensor system, in particular the receiving unit.

[0049] The detectors can, for example, each contain a photodiode, for example, exactly one photodiode. In various embodiments, the photodiode can be configured as an avalanche photodiode.

[0050] According to at least one embodiment, the first and second detectors are arranged along the Z-axis of the sensor coordinate system or along an axis parallel to the Z-axis of the sensor coordinate system. Accordingly, the first angle is, by design, equal to or approximately equal to the pitch angle.

[0051] According to at least one embodiment, a second pair of sample points is identified by means of the computing unit, wherein one point of the second pair is part of the first subset, another point of the second pair is part of the second subset, and a projection of a second connecting vector of the second pair into the transmission plane is parallel to the longitudinal axis of the sensor system. The computing unit determines a second angle that the second connecting vector encloses with the longitudinal axis of the sensor system. The computing unit determines an average value depending on the first angle and the second angle in order to determine the pitch angle position. The first pair differs in particular from the second pair.

[0052] The fact that the mean value is determined as a function of the first and second angles can be understood, in particular, to mean that the mean value is determined from a set of angles that includes the first and second angles. In particular, the mean value can also be determined based on additional angles, in particular estimated values for the pitch angle. By calculating the mean value, a higher accuracy of the pitch angle position can be achieved, in particular by partially compensating for random errors or interference.

[0053] In further embodiments, as described for the second pair, further pairs are identified whose projections of the respective connection vectors in the transmission plane are each parallel to the longitudinal axis of the sensor system. The mean value can then be determined depending on the correspondingly determined angles.

[0054] According to at least one embodiment, the point cloud contains a third subset of sample points of the roadway, which in particular also corresponds to a ground position. The third subset can be generated, for example, using a third optical detector of the receiving unit, which is arranged, for example, linearly with respect to the first and second detectors.

[0055] According to at least one embodiment, the point cloud contains a fourth subset of sample points of the roadway, which in particular also represents a ground layer. The fourth subset can be generated, for example, by means of a fourth optical detector of the receiving unit, which is arranged, for example, linearly with respect to the first, second, and third detectors.

[0056] According to at least one embodiment, a third pair of sample points is identified by means of the computing unit, wherein one point of the third pair is part of the first subset, another point of the third pair is part of the third subset, and a projection of the third connecting vector of the third pair into the transmission plane is parallel to the longitudinal axis of the sensor system. The computing unit determines a third angle that the third connecting vector encloses with the longitudinal axis of the sensor system, and the computing unit determines the mean value as a function of the first and third angles, for example, the first, second, and third angles, in order to determine the pitch angle position.

[0057] According to at least one embodiment, a fourth pair of sample points is identified by means of the computing unit, wherein one point of the fourth pair is part of the third subset and another point of the fourth pair is part of the fourth subset. A projection of a fourth connecting vector of the fourth pair into the transmission plane is parallel to the longitudinal axis of the sensor system. The computing unit determines a fourth angle that the fourth connecting vector encloses with the longitudinal axis of the sensor system, and the mean value is determined as a function of the first angle and the fourth angle, in particular as a function of the first, second, third, and fourth angles, in order to determine the pitch angle position.

[0058] According to at least one embodiment, the sensor system generates a further point cloud containing a first further subset of sample points of the roadway and a second further subset of sample points of the roadway, wherein the point cloud and the further point cloud are generated during different time periods. The computing unit identifies a further pair of sample points, wherein one point of the further pair is part of the first further subset, another point of the further pair is part of the second further subset, and a projection of a further connecting vector of the further pair into the transmission plane is parallel to the longitudinal axis of the sensor system. The computing unit determines a further angle that the further connecting vector encloses with the longitudinal axis of the sensor system.By means of the computing unit, an average value, in particular the average value, is determined depending on the first angle and the further angle in order to determine the pitch angle position.

[0059] For example, the mean value can be determined depending on the first angle, the further angle and the second, the third and / or the fourth angle.

[0060] Because the point clouds are generated during different time periods, they generally correspond to different vehicle positions and thus to different sampling points on the road. This allows for better consideration and compensation of different external interference. This ultimately leads to further increased accuracy in determining the pitch angle.

[0061] The various embodiments described with respect to the second and third pairs or the third and fourth subsets of sample points can be directly transferred to the further point cloud and corresponding further third and fourth subsets of sample points or further second and third pairs of sample points.

[0062] According to at least one embodiment, the yaw angle position of the sensor system is determined or provided, for example, by means of the computing unit or provided to the computing unit. Determining the yaw angle position can, for example, involve estimating, measuring, or neglecting the yaw angle.

[0063] According to at least one embodiment, the point cloud is determined by means of the sensor system as a function of the yaw angle position.

[0064] In other words, the point cloud is generated by the computing unit in such a way that the coordinates of the sample points are calibrated or normalized coordinates with respect to the yaw angle. In other words, according to the improved concept, a point cloud calibrated with respect to the yaw angle is used to determine the pitch angle position.

[0065] According to at least one embodiment, the further point cloud is also generated by means of the sensor system as a function of the yaw angle position.

[0066] The yaw angle can be determined, for example, by determining an initial sensor coordinate system based on at least two of the sampling points generated with the first detector. A reference coordinate system can be determined based on two corresponding sampling points from different detectors. The two sampling points correspond, for example, to the same emission angle. The yaw angle can be determined by comparing the initial sensor coordinate system with the reference coordinate system.

[0067] Any other method for determining the yaw angle can be used.

[0068] In particular, it is not necessary for the yaw angle to be determined online like the pitch angle. The yaw angle can be determined, for example, using a predefined calibration target or calibration template in a test environment.

[0069] According to a further independent aspect of the improved concept, an active optical sensor system for installation in a motor vehicle is specified. The sensor system has a transmitting unit, a receiving unit, and a computing unit. The transmitting unit is configured to emit light into an environment of the sensor system. The receiving unit is configured to detect reflected portions of the light and to generate at least one sensor signal based on the detected reflected portions. The computing unit is coupled to the receiving unit in order to receive the at least one sensor signal. The computing unit is configured to generate a point cloud based on the at least one sensor signal, said point cloud containing a first subset of sample points of a roadway on which the motor vehicle is located and a second subset of sample points of the roadway.The computing unit is configured to identify a first pair of sample points, wherein one point of the first pair is part of the first subset, another point of the first pair is part of the second subset, and a projection of a first connecting vector of the first pair into a transmission plane of the sensor system is parallel to a longitudinal axis of the sensor system. The computing unit is configured to determine a first angle that the first connecting vector encloses with the longitudinal axis of the sensor system in order to determine a pitch angle position of the sensor system.

[0070] The sensor system is designed specifically as a lidar system.

[0071] The transmitting unit includes in particular a laser source, for example a semiconductor laser, in particular an infrared laser.

[0072] According to at least one embodiment of the active optical sensor system, the receiving unit has a first optical detector, in particular a first photodiode, for example a first avalanche photodiode, wherein the first optical detector is configured to detect first reflected portions of the light and, based thereon, to generate a first sensor signal of the at least one sensor signal. The receiving unit has a second optical detector, in particular a second photodiode, for example a second avalanche photodiode, wherein the second optical detector is configured to detect second reflected portions of the light and, based thereon, to generate a second sensor signal of the at least one sensor signal. The computing unit is configured to generate the first subset based on the first sensor signal and to generate the second subset based on the second sensor signal.

[0073] The first reflected portions and the second reflected portions are in particular each part of the reflected portions of the light that are detected by the receiving unit.

[0074] According to at least one embodiment, the first optical detector and the second optical detector are arranged along the normal axis or along an axis parallel to the normal axis of the sensor system.

[0075] In particular, spatial positions of the optical detectors in the sensor coordinate system differ only by their Z coordinates.

[0076] According to at least one embodiment, the computing unit is configured to identify a second pair of sample points, wherein one point of the second pair is part of the first subset, another point of the second pair is part of the second subset, and a projection of a second connecting vector of the second pair into the transmission plane is parallel to the longitudinal axis of the sensor system. The computing unit is configured to determine a second angle that the second connecting vector encloses with the longitudinal axis of the sensor system and to determine an average value depending on the first angle and the second angle in order to determine the pitch angle position.

[0077] According to at least one embodiment, the computing unit is configured to generate, based on the at least one sensor signal, a further point cloud containing a further first subset of sample points of the roadway and a further second subset of sample points of the roadway, wherein the point cloud and the further point cloud are generated during different time periods. The computing unit is configured to identify a further pair of sample points, wherein one point of the further pair is part of the first further subset, another point of the further pair is part of the second further subset, and a projection of a further connecting vector of the further pair into the transmission plane is parallel to the longitudinal axis of the sensor system.The computing unit is configured to determine a further angle that the further connection vector encloses with the longitudinal axis of the sensor system and to determine an average value depending on the first angle and the further angle in order to determine the pitch angle position.

[0078] According to at least one embodiment, the computing unit is configured to generate the point cloud as a function of a yaw angle position of the sensor system.

[0079] Further embodiments of the active optical sensor system according to the improved concept arise directly from the various embodiments of the method according to the improved concept, and vice versa. In particular, the active optical sensor system can be configured or programmed to perform a method according to the improved concept, or the sensor system according to the improved concept performs a method according to the improved concept.

[0080] According to a further independent aspect of the improved concept, a motor vehicle with an active optical sensor system according to the improved concept is provided.

[0081] According to a further independent aspect of the improved concept, a computer program with instructions is specified. When the computer program is executed by an active optical sensor system according to the improved concept, in particular by the computing unit of the sensor system, the instructions cause the sensor system to perform a method according to the improved concept.

[0082] According to a further independent aspect of the improved concept, a computer-readable storage medium is provided on which a computer program according to the improved concept is stored.

[0083] Further features of the invention emerge from the claims, the figures and the description of the figures.

[0084] The figures show: Fig. 1 shows a motor vehicle with a schematic representation of an exemplary embodiment of an active optical sensor system according to the improved concept; Fig. 2 shows a transmitting unit of an exemplary embodiment of an active optical sensor system according to the improved concept; Fig. 3 shows a receiving unit of a further exemplary embodiment of an active optical sensor system according to the improved concept; Fig. 4 shows a schematic representation of a point cloud in an exemplary embodiment of a method according to the improved concept; Fig. 5 shows a further representation of the point cloud from Fig. 4 ; Fig. 6 another representation of the point cloud from Fig. 4 und Fig. 5 ; and Fig. 7 another representation of the point cloud from Fig. 4, Fig. 5 and Fig. 6 .

[0085] In Fig. 1 a motor vehicle 1 is shown which has an active optical sensor system 2 according to the improved concept.

[0086] The sensor system 2 is designed as a lidar system. A nominal orientation of the sensor system 2 is given, for example, by a longitudinal axis 17 of the motor vehicle 1, a transverse axis 18 of the motor vehicle 1, and a (not shown) normal axis of the motor vehicle 1, which is perpendicular to its longitudinal and transverse axes 17, 18.

[0087] In the top view of the Fig. 1 1 shows a projection of a longitudinal axis 15 of the sensor system 2 into the plane spanned by the longitudinal axis 17 and the transverse axis 18 of the motor vehicle 1. In particular, it is assumed that the longitudinal axis 15 of the sensor system 2 lies in a plane spanned by the longitudinal axis 17 of the motor vehicle 1 and the normal axis of the motor vehicle 1, so that the projection of the longitudinal axis 15 of the sensor system 2 is parallel to the longitudinal axis 17 of the motor vehicle 1. This assumption does not represent a limitation of generality, since it is assumed that yaw angle compensation has already been performed beforehand or that the yaw angle of the sensor system is approximately zero with respect to the nominal orientation.

[0088] The sensor system 2 has a transmitting unit 8, for example, with a laser source, for emitting light at different emission angles within a transmission plane of the sensor system 2. Accordingly, the emission direction at an emission angle of zero degrees is equal to the longitudinal axis 15 of the sensor system 2.

[0089] The transmission plane is defined in particular by the plane spanned by the longitudinal axis 15 of the sensor system 2 and a transverse axis of the sensor system 2. The transverse axis of the sensor system 2 can be regarded, without loss of generality, as identical or parallel to the transverse axis 18 of the motor vehicle 1. Deviations of the transverse axis of the sensor system 2 from the transverse axis of the motor vehicle 1 correspond to a roll angle of the sensor system 2 that is different from zero. However, the method steps described below for determining a pitch angle of the sensor system 2 are independent of the roll angle.

[0090] The transmission plane therefore corresponds to the plane spanned by the longitudinal axis 17 of the motor vehicle 1 and the transverse axis 18 of the motor vehicle 1, rotates by an angle, namely the pitch angle, around the transverse axis 18 of the motor vehicle 1.

[0091] In other words, the longitudinal axis 15 of the sensor system 2 encloses the pitch angle with the longitudinal axis 17 of the motor vehicle 1.

[0092] The active optical sensor system 2 also has a computing unit 4 and a receiving unit 9. The computing unit 4 is connected to the receiving unit 9 and, for example, to the transmitting unit 8. In particular, the computing unit 4 can control the transmitting unit 8 to emit the light 3. The receiving unit 9 can detect reflected portions 5 of the light 3 and, based thereon, generate at least one sensor signal and transmit it to the computing unit 4.

[0093] In Fig. 2 The transmitting unit 8 of the sensor system 2 is shown schematically. Light 3, in particular laser beams, emitted by the transmitting unit 8 is also shown. Furthermore, Fig. 2 schematically shows an object 19 in an environment of the sensor system 2.

[0094] The upper figure in Fig. 2 corresponds, for example, to a viewing direction parallel to the transverse axis 18 of the motor vehicle 1 to the transmitting unit 8 and the lower figure in Fig. 2 corresponds, for example, to a viewing direction parallel to the normal axis of the sensor system 2 to the transmitting unit 8.

[0095] As shown in the illustrations of the Fig. 2 As can be seen, the respective beam expansion of the laser beams can be different in different planes.

[0096] In Fig. 3 The receiving unit 9, a lens 16 and a mirror 20 of the sensor system 2 are shown schematically.

[0097] The receiving unit 9 contains at least two, in the example of Fig. 3 three optical detectors 10, 11, 12, which are arranged, in particular, side by side linearly along an axis parallel to the normal axis of the sensor system 2 and are designed, for example, as avalanche photodiodes. The receiving unit 9 also has a shaft 21 that is rotatably mounted and connected to the mirror 20, so that the mirror 20 can rotate about the axis of rotation.

[0098] The view of the Fig. 3 can be understood, for example, as a top view of the sensor system 2, i.e., according to a viewing direction parallel to the normal axis of the sensor system 2. The detectors 10, 11, 12 are shown with a distorted perspective for the purpose of clarity. In an actual top view, the detectors 10, 11, 12 would lie on top of one another and, for example, obscure one another.

[0099] The transmitter unit 8 is in Fig. 3 not shown, but can be arranged with respect to the mirror 20 such that the emission angle of the light 3 can be varied upon rotation of the mirror 20 about the axis of rotation. The axis of rotation and the shaft 21 are thus aligned in particular perpendicular to the transmission plane.

[0100] A reception path for the reflected portions 5 of the light beams 3, which were reflected, for example, by the object 19, leads via the mirror 20 and the lens 16 to the reception unit 9. The reflected portions 5 are then detected by at least one of the detectors 10, 11, 12.

[0101] By rotating the mirror 20 about the rotation axis, each of the detectors 10, 11, 12 can detect reflected portions 5 of the light 3 incident from different directions. The instantaneous position of the mirror 20 can be determined, for example, via a rotary encoder (not shown) coupled to the shaft 21.

[0102] By knowing the instantaneous position of the mirror 20 at any given time, for example, a set of sample points, also referred to as a point cloud 6, can be generated from the temporal sequence of the detected light beams. A subset of the sample points or a subset of the point cloud 6 is generated using each detector 10, 11, 12. A subset of sample points generated for different emission angles or angular positions of the mirror 20, and accordingly for different times, can also be referred to as the position of sample points. If the object 19 is a roadway on which the motor vehicle 1 is located, the position is also referred to as the ground layer.

[0103] Point cloud 6 is exemplary in Fig. 4 and is in particular a three-dimensional point cloud, since in addition to the respective emission angles and the information about which detector 10, 11, 12 the respective scanning point is based on, the distance of the object 19 can also be determined via a light propagation time measurement.

[0104] Different positions of the point cloud 7a, 7b, 7c, 7d, 7e, 7f are shown in Fig. 4 represented by different line types. The sample points shown in point cloud 6 were generated, for example, based on reflected portions of light 3, which were reflected from roadway 13. Accordingly, layers 7a, 7b, 7c, 7d, 7e, and 7f are ground layers. Further layers of point cloud 6, which may be present and do not represent ground layers, are not shown for the sake of clarity. Fig. 4 A total of six layers 7a, 7b, 7c, 7d, 7e, 7f are shown as examples, so that the receiving unit 9 has at least six detectors in this case.

[0105] In addition, Fig. 4 The sensor coordinate system is shown. An X-axis XS of the sensor coordinate system corresponds to the longitudinal axis 15 of sensor system 2, a Y-axis YS corresponds to the transverse axis of sensor system 2, and a Z-axis ZS corresponds to the normal axis of sensor system 2.

[0106] In Fig. 5 Two of the ground positions 7a, 7b are shown in the sensor coordinate system. For illustration purposes, only a few sampling points of the positions 7a, 7b are shown. To determine a pitch angle position of the sensor system 2 according to the improved concept, the computing unit 4 identifies a point A of the first ground position 7a and a point B of the second ground position 7b. Fig. 5 a connection vector 14 is shown which leads from point A to point B.

[0107] In Fig. 6 is the same situation as in Fig. 5 shown, but from a viewing direction parallel to the Z-axis ZS . Here, a projection 14' of the connecting vector 14 into the XS -YS plane is shown. The points A, B are identified by the computing unit 4 in such a way that the projection 14 is parallel or approximately parallel to the longitudinal axis 15 of the sensor system 2, i.e., to the XS axis.

[0108] In Fig. 7 is the same situation as in Fig. 5 and Fig. 6 also shown, but in the vehicle coordinate system, which has an X-axis X 0 , a Y-axis Y 0 and a Z-axis Z 0 . The X-axis X 0 corresponds to the longitudinal axis 17 of the motor vehicle 1, the Y-axis Y 0 to the transverse axis 18 of the motor vehicle 1 and the Z-axis Z 0 to the normal axis of the motor vehicle 1.

[0109] In Fig. 7 also schematically shows the sensor system 2 with the transmitting unit 8 and the receiving unit 9, as well as the longitudinal axis 15 of the sensor system 2. As explained above, the longitudinal axis 15 of the sensor system 2 and the longitudinal axis 17 of the motor vehicle 1 enclose an angle which corresponds to the pitch angle δ.

[0110] It can generally be assumed with a high degree of accuracy that the roadway 13 is an approximately flat surface. Furthermore, the plane spanned by the longitudinal axis 17 of the motor vehicle 1 and the transverse axis 18 of the motor vehicle 1 is parallel to the surface of the roadway 13. Accordingly, it follows that the connecting vector 14 does not enclose any angle with the X0-Y0 plane of the vehicle coordinate system, i.e., it is approximately parallel to this plane. In other words, the connecting vector 14 encloses the same angle δ with the XS-YS plane of the sensor coordinate system, in particular with the XS direction of the sensor coordinate system or the longitudinal axis 15 of the sensor system 2, as the longitudinal axis 15 of the sensor system 2 encloses with the longitudinal axis 17 of the motor vehicle 1.

[0111] The pitch angle can therefore be approximately determined by the computing unit 4 as the angle that the connecting vector 14 forms with the XS axis. In particular, the pitch angle δ is given by δ = arctan([ZB - ZA ] / [XB - XA ]), where XA denotes the X coordinate of point A, ZA its Z coordinate, XB the X coordinate of point B, and ZB its Z coordinate.

[0112] The described steps for determining the pitch angle δ can be repeated for different pairs of sample points from the different ground positions 7a, 7b, 7c, 7d, 7e, 7f. The determined angle values can, for example, be averaged to achieve greater accuracy.

[0113] As an example, in the Fig. 5 , Fig. 6 und Fig. 7Another pair of sampling points A', B' is shown, whose connecting vector also lies approximately in the XS -ZS axis of the sensor coordinate system. Accordingly, the pitch angle can also be determined here in the manner described.

[0114] The steps described can, for example, be repeated at different times to further increase accuracy.

[0115] The improved concept provides a method for determining the pitch angle position of an active optical sensor system, enabling increased accuracy. One advantage of the improved concept is that the installation height of the sensor system in the motor vehicle does not need to be known, eliminating corresponding inaccuracies and resulting measurement errors. Since the ground positions used to determine the pitch angle position are generally constantly present during vehicle operation, the number of possible measurements for determining the pitch angle position can be greatly increased, resulting in a significant increase in the accuracy of determining the pitch angle position.

[0116] The improved concept takes particular advantage of the fact that at a pitch angle as realistically expected, there are always several ground layers in the corresponding point cloud.

Claims

1. Method for determining a pitch angle position of an active optical sensor system (2), which is mounted on a motor vehicle (1) located on a roadway (13), wherein - a point cloud (6) containing a first subset (7a) of scanning points of the roadway (13) and a second subset (7b) of scanning points of the roadway (13) is generated by means of the sensor system (2); characterized in that - a first pair (A, B) of scanning points is identified by means of a computation unit (4) of the sensor system (2), wherein one point (A) of the first pair (A, B) is part of the first subset (7a), a further point (B) of the first pair (A, B) is part of the second subset (7b), and a projection (14') of a first connection vector (14) of the first pair (A, B) into a transmission plane of the sensor system (2) is parallel to a longitudinal axis (15) of the sensor system (2); and - a first angle (δ), which the first connection vector (14) encloses with the longitudinal axis (15) of the sensor system (2), is determined by means of the computation unit (4) in order to determine the pitch angle position.

2. Method according to Claim 1, characterized in that, for generating the point cloud (6), - light (3) is emitted into a surrounding area of the sensor system (2) by means of a transmission unit (8) of the sensor system (2); - reflected components (5) of the light (3) are detected by a reception unit (9) of the sensor system (2); - at least one sensor signal is generated by means of the reception unit (9) based on the detected reflected components (5); and - the point cloud (6) is generated by means of the computation unit (4) based on the at least one sensor signal.

3. Method according to either of Claims 1 and 2, characterized in that - the scanning points of the first subset (7a) are generated by means of a first optical detector (10) of the sensor system (2); and - the scanning points of the second subset (7b) are generated by means of a second optical detector (11) of the sensor system (2).

4. Method according to one of Claims 1 to 3, characterized in that - a second pair (A', B') of scanning points is identified by means of the computation unit (4), wherein one point (A') of the second pair (A', B') is part of the first subset (7a), a further point (B') of the second pair (A', B') is part of the second subset (7b), and a projection of a second connection vector of the second pair into the transmission plane is parallel to the longitudinal axis (15) of the sensor system (2); - a second angle, which the second connection vector encloses with the longitudinal axis (15) of the sensor system, is determined by means of the computation unit (4); and - a mean value is determined by means of the computation unit (4) as a function of the first angle (δ) and the second angle in order to determine the pitch angle position.

5. Method according to one of Claims 1 to 4, characterized in that - the sensor system (2) is used to generate a further point cloud, which contains a first further subset of scanning points of the roadway (13) and a second further subset of scanning points of the roadway (13), wherein the point cloud (6) and the further point cloud are generated during different time periods; - the computation unit (4) is used to identify a further pair of scanning points, wherein one point of the further pair is part of the first further subset, a further point of the further pair is part of the second further subset, and a projection of a further connection vector of the further pair into the transmission plane is parallel to the longitudinal axis (15) of the sensor system (2); - a further angle, which the further connection vector encloses with the longitudinal axis (15) of the sensor system (2), is determined by means of the computation unit (4); and - a mean value is determined by means of the computation unit (4) as a function of the first angle (δ) and the further angle in order to determine the pitch angle position.

6. Method according to one of Claims 1 to 5, characterized in that the point cloud (6) is generated by means of the sensor system (2) as a function of a yaw angle position of the sensor system (2).

7. Active optical sensor system for mounting on a motor vehicle (1), having - a transmission unit (8), which is configured to emit light (3) into a surrounding area of the sensor system (2); - a reception unit (9), which is configured to detect reflected components (5) of the light (3) and to generate at least one sensor signal based on the detected reflected components (5); and - a computation unit (4), which is coupled to the reception unit (8) in order to receive the at least one sensor signal; wherein the computing unit (4) is configured - to generate, based on the at least one sensor signal, a point cloud (6), which contains a first subset (7a) of scanning points of a roadway (13) on which the motor vehicle (1) is located, and a second subset (7b) of scanning points of the roadway (13); characterized in that the computing unit is furthermore configured - to identify a first pair (A, B) of scanning points, wherein one point (A) of the first pair (A, B) is part of the first subset (7a), a further point (B) of the first pair (A, B) is part of the second subset (7b), and a projection (14') of a first connection vector (14) of the first pair (A, B) into a transmission plane of the sensor system (2) is parallel to a longitudinal axis (15) of the sensor system (2); and - to determine a first angle (δ), which the first connection vector (14) encloses with the longitudinal axis (15) of the sensor system (2), in order to determine a pitch angle position of the sensor system (2).

8. Active optical sensor system according to Claim 7, characterized in that - the reception unit (9) has a first optical detector (10), which is configured to detect first reflected components of the light (3) and, based thereon, to generate a first sensor signal of the at least one sensor signal; - the reception unit (9) has a second optical detector (11), which is configured to detect second reflected components of the light (3) and, based thereon, to generate a second sensor signal of the at least one sensor signal; and - the computation unit (4) is configured to generate the first subset (7a) based on the first sensor signal and to generate the second subset (7b) based on the second sensor signal.

9. Active optical sensor system according to Claim 8, characterized in that the first optical detector (10) and the second optical detector (11) are arranged along a direction parallel to a normal axis of the sensor system (2).

10. Active optical sensor system according to one of Claims 7 to 9, characterized in that the computing unit (4) is configured - to identify a second pair (A', B') of scanning points, wherein one point (A') of the second pair (A', B') is part of the first subset (7a), a further point (B') of the second pair (A', B') is part of the second subset (7b), and a projection of a second connection vector of the second pair into the transmission plane is parallel to the longitudinal axis (15) of the sensor system; - to determine a second angle, which the second connection vector encloses with the longitudinal axis (15) of the sensor system (2); and - to determine a mean value as a function of the first angle (δ) and the second angle in order to determine the pitch angle position.

11. Active optical sensor system according to one of Claims 7 to 10, characterized in that the computing unit (4) is configured - to generate, based on the at least one sensor signal, a further point cloud, which contains a first further subset of scanning points of the roadway (13) and a second further subset of scanning points of the roadway (13), wherein the point cloud (6) and the further point cloud are generated during different time periods; - to identify a further pair of scanning points, wherein one point of the further pair is part of the first further subset, a further point of the further pair is part of the second further subset, and a projection of a further connection vector of the further pair into the transmission plane is parallel to the longitudinal axis (15) of the sensor system; - to determine a further angle, which the further connection vector encloses with the longitudinal axis of the sensor system (2); and - to determine a mean value as a function of the first angle (δ) and the further angle in order to determine the pitch angle position.

12. Active optical sensor system according to one of Claims 7 to 11, characterized in that the computation unit (14) is configured to generate the point cloud (6) as a function of a yaw angle position of the sensor system (2).

13. Motor vehicle with an active optical sensor system (2) according to one of Claims 7 to 12.

14. Computer program with instructions which, when the computer program is executed by an active optical sensor system (2) according to one of Claims 7 to 12, cause the sensor system (2) to carry out a method according to one of Claims 1 to 6.

15. Computer-readable storage medium on which a computer program according to Claim 14 is stored.