Object detection by means of ultrasound for a vehicle

Abstract

The invention relates to the operation of an ultrasonic sensor device (10) for a vehicle (1) for detecting objects in surroundings (U). In the process, an ultrasonic sensor (11) is used to transmit at least two ultrasonic pulses (P1, P2), which are provided as mutually different chirp signals, into the surroundings (U). An associated echo pulse (E1, E2) is determined for each of the at least two ultrasonic pulses (P1, P2) from a reception pulse (E) that was received by the ultrasonic sensor device (10) in response to a reflection of the at least two ultrasonic pulses (P1, P2) off the object (2). A predetermined object detection algorithm is used to determine an object height (H), a relative speed (vr) and / or an absolute distance (a) of the object (2) relative to the vehicle (1) from a difference in the echo pulses (E1, E2).

Description

[0001] Ultrasonic object detection for a vehicle

[0002] The invention relates to a method for operating an ultrasonic sensor device for a vehicle for detecting objects in an environment. Furthermore, the invention relates to an ultrasonic sensor device for a vehicle for detecting objects in an environment. The invention also relates to a vehicle with a corresponding ultrasonic sensor device.

[0003] In modern vehicles, ultrasonic sensor devices with ultrasonic sensors are used, for example, for environmental monitoring. The sensor signals, i.e., ultrasonic pulses, are used to detect and / or classify objects in the environment. Objects can be people, animals, vehicles, or other obstacles, for example. In response to the detected object, a driving maneuver can be performed using the vehicle's driver assistance system, for example. Some well-known applications in which such an ultrasonic sensor device is used are distance warning systems, parking space detectors, and / or parking aids. Corresponding environmental monitoring systems are already known in various forms from the state of the art.

[0004] For example, DE 20 2018 103 861 U1 discloses a sensor with an acoustic transducer that emits so-called composite bursts with a burst signature and receives the resulting echo signals. The received echo signals are categorized by source based on the respective burst signature, so that only the self-generated echoes are considered.

[0005] EP 2 171 495 B1 discloses a method and a device for detecting an environment, in which a measurement rate is increased and data quality is improved by means of a pulse-echo method using at least two acoustic transducers. Different pulses are generated by the transducers by modulating a carrier wave to make the individual pulses distinguishable.

[0006] EP 2 569 650 B1 discloses a method for determining the position of an object relative to a vehicle. An ultrasonic sensor emits a first ultrasonic pulse with several predetermined transmission frequencies, which lead to a variation in the directional characteristic of the ultrasonic sensor. From a frequency spectrum of an echo pulse of the ultrasonic pulse, an absolute value of a relative offset angle of an object in the surroundings of the vehicle is determined depending on the frequency spectrum and the directional characteristic.

[0007] The current state of the art therefore allows for the use of multiple ultrasonic sensors, each generating an ultrasonic pulse, to detect the environment. Alternatively, it is possible to use a single ultrasonic sensor that generates multiple pulses. This has the advantage of requiring less space in the vehicle, and systems with a single sensor can be manufactured more cost-effectively overall.

[0008] It is the object of the present invention to cost-effectively improve the application possibilities of an ultrasonic sensor device for a vehicle for object detection in an environment.

[0009] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are disclosed by the dependent patent claims, the description, and the figures.

[0010] According to one aspect, the invention relates to a method for operating an ultrasonic sensor device for a vehicle for object detection in an environment. "Object detection" in this case refers in particular to object detection or classification. This involves determining or recognizing the presence of an object mentioned above and / or its properties and / or its condition. This can include, for example, an object height, a relative speed, and / or a real distance. The information or data about the detected object can be used or utilized, for example, in a driver assistance system mentioned above for obstacle detection or collision detection.

[0011] In the method, at least two ultrasonic pulses are emitted into the environment by means of an ultrasonic sensor. This means that the ultrasonic sensor is operated as a transmitter or in a transmission mode. In particular, the ultrasonic sensor provides the two or more pulses together in a single measuring process or operating process. The respective ultrasonic pulses are provided as different chirp signals in which the signal frequency changes in different ways over the pulse duration. In this case, a chirp or chirp signal refers to a signal composed of a frequency spectrum with multiple frequencies that are arranged and output in ascending or descending order. To make the chirp signals distinguishable, the signals comprise, for example, different center frequencies or the frequencies are output, for example, inversely to one another.For example, one signal can be provided as low chirp (frequency descending) and the other signal as high chirp (frequency ascending).

[0012] Subsequently, in the method, an associated echo pulse is determined for each of the at least two ultrasonic pulses emitted by a sensor from a received pulse that the ultrasonic sensor device receives in response to a reflection of the at least two ultrasonic pulses by an object. The received pulse thus comprises, in particular, a mixed signal of ultrasonic pulses reflected by the object. From the superimposed received pulse, the individual echo pulses, each associated with one of the ultrasonic pulses of one of the sensors, are to be determined. The signature of the respective chirp signal in the received pulse can therefore be determined or ascertained. From this, exactly one echo pulse can be assigned to each of the two or more emitted ultrasonic pulses.

[0013] For receiving, the ultrasonic sensor device can use the transmitting ultrasonic sensor and / or one or more further or additional ultrasonic sensors. The receiving ultrasonic sensor is operated as a receiver or in a receive mode. The ultrasonic sensor device can thus comprise one or more ultrasonic sensors. Each of the ultrasonic sensors can be operated or used as a transmitter or receiver, but preferably as a so-called transceiver (transmitter-receiver device). The respective ultrasonic sensor can comprise one or more (electro-)acoustic transducers or ultrasonic transducers. The transducer preferably comprises a piezoelectric element and a membrane coupled to it. Based on the piezoelectric effect, the transducer can convert electrical signals into ultrasonic pulses (acoustic signals in the ultrasonic frequency range) in transmit mode and vice versa in receive mode.The design and operation of a corresponding ultrasonic sensor are generally known. In the method, an object height, a relative speed, and / or an absolute distance between the object and the vehicle are determined for object detection according to a predetermined object detection algorithm from a difference in the detected echo pulses. In this case, the object height refers in particular to the vertical extent of the object relative to the vehicle. The object height thus indicates how high the object or obstacle is relative to the vehicle along a vehicle's vertical axis. The object height is relevant, for example, for planning an obstacle crossing. The relative speed describes how quickly the object is moving towards the vehicle or vice versa.Based on the relative speed, driving maneuvers such as braking, accelerating, maintaining speed, and / or steering can be planned. The absolute distance refers to the actual distance of the vehicle from the object. If the absolute distance is known, collision avoidance, for example, can be effectively planned and executed.

[0014] In other words, the object detection algorithm is applied to the two or more resulting echo pulses. In this process, the echo pulses, for example, and in particular their amplitude curves, are compared with each other. The comparison result provides an echo pulse difference or echo pulse deviation, which represents the difference between the echo pulses. The determined difference provides a measure or indication of the respective object property, i.e., the object height, the relative speed, and the absolute distance. The desired object property can thus be determined or detected from the difference between the echoes. Depending on the object property to be determined, a time difference, a time of flight difference, and / or an amplitude difference can be taken into account. Specific examples of the evaluation to determine the object height, the relative speed, and / or the absolute distance are described in more detail later.

[0015] Overall, multi-channel signal generation and measurement can be performed in a single operation using a single ultrasonic sensor. This has the advantage that there is at most a slight signal delay between the ultrasonic pulses, resulting in essentially similar propagation times for the echo pulses. This increases the probability of detecting a real object rather than noise or interference. The evaluation can thus be more precise overall, and the measurement results are more reliable. This allows the described application possibilities for object detection to be improved overall and implemented particularly cost-effectively. The invention includes embodiments that result in additional advantages.

[0016] According to one embodiment, in a first variant, the at least two ultrasonic pulses are transmitted simultaneously with the ultrasonic sensor. This means that the chirp signals can be provided and transmitted in a temporally overlapping or superimposed manner. This requires an ultrasonic transducer that can provide a higher bandwidth for signal frequencies. Thus, two channels are controlled essentially simultaneously to emit the chirps.

[0017] Alternatively, in a second variant, the at least two ultrasonic pulses are emitted sequentially using the ultrasonic sensor. This means that the chirp signals are provided sequentially or one after the other. Thus, two channels are triggered at different times to emit the chirps. However, the transmitter of the ultrasonic pulses cannot receive the echo pulse during the second channel if the second channel is triggered for transmission after the first channel. During this time, only one measurement result is available. Preferably, the pause time and / or delay time between the two pulses is no more than one to two milliseconds.

[0018] According to one embodiment, signal filtering or signal correlation is performed to distinguish the echo pulses for the received pulse. Known digital and / or analog filtering or correlation techniques can be used for this purpose. The ultrasonic sensor device can comprise, for example, a so-called correlator or a filter circuit. A so-called bandpass filter, for example, is suitable as a filter circuit.

[0019] According to one embodiment, to determine the object height, the ultrasonic pulses are generated as chip signals with different center frequencies, with the respective center frequencies being selected such that the respective ultrasonic pulses have different vertical aperture angles relative to the vehicle, i.e., in the vehicle's vertical direction. According to the object detection algorithm, the resulting echo pulse amplitudes are compared to determine the object height.

[0020] This means that height classification takes advantage of the fact that the directional characteristic of an ultrasonic sensor changes in a known way depending on the signal frequency used, in this case the center frequency. The directional characteristic describes the angular dependence of the strength of received and / or transmitted signals. Thus, the amplitude of the ultrasonic pulse directed toward the object, and thus also the amplitude of the echo pulse reflected from the object in the received echo pulse, depends on the transmitted frequency or signal frequency.

[0021] The center frequency is thus set or used for so-called beamforming in the vertical direction of the vehicle. The different beam angles result in different echo amplitudes of the at least two echo pulses. For example, the echo amplitudes can be of different widths or lengths. By comparing the echo amplitudes, the edges of the object and its distance relative to the road surface can be detected particularly easily.

[0022] Preferably, a membrane of the ultrasonic sensor or a piezo element of the ultrasonic sensor can be shaped so that vertical differences can be adjusted with the respective center frequency. The horizontal directional characteristic is preferably independent of the selected center frequency. This allows beamforming to be realized in which the same horizontal aperture angle is always created, regardless of the center frequency, and different vertical aperture angles are created depending on the center frequency.

[0023] According to one embodiment, the echo amplitudes to be compared are normalized according to a known sensitivity curve as a function of the respective signal frequency of the associated ultrasonic pulse. The sensitivity curve is preferably horizontally normalized. This allows distortions in the received pulses, which may arise, for example, due to different center frequencies, to be eliminated.

[0024] According to one embodiment, a position and / or a horizontal offset angle of the object relative to the ultrasonic sensor is determined by trilateration of the echo pulse's travel time, and the echo amplitude is corrected to determine the object's height according to a known sensitivity curve. The amplitude correction can improve overall height classification. Trilateration is a well-known measurement method for distance measurement. Since multiple signals or signal paths must be present for trilateration, the evaluation can be carried out, for example, across multiple signal paths of the emitted ultrasonic pause and / or in conjunction with the ultrasonic pulses emitted by other ultrasonic sensors of the ultrasonic sensor device.

[0025] According to one embodiment, to determine the relative speed and / or the absolute distance, the at least two ultrasonic pulses are generated as chirp signals with mutually different frequency responses from high to low signal frequencies and vice versa, and differences in the time of flight of the echo pulses are evaluated according to the object detection algorithm. This means that the ultrasonic pulses are provided as counter-rotating or inverse chirp signals, for example as chirp up (high chirp) and chirp down (low chirp). Preferably, the chirp signals can also have different center frequencies. For the evaluation, a time-of-flight analysis of the echo pulses is performed. This means that the time it takes from the transmission of the ultrasonic pulse to the detection of the respective received pulse is examined in a known manner.

[0026] To determine the relative speed and / or the absolute distance, the Doppler effect is used to influence the signals differently depending on the modulation of the ultrasonic pulses, which are emitted as chirps. When counter-rotating pulses are used, the Doppler effect causes the emitted chirp signals to shift in different directions relative to each other when the object and / or vehicle are moving. The Doppler shift, particularly by correcting the Doppler effect, allows the absolute distance or relative speed to be estimated.

[0027] According to one embodiment, the relative velocity according to the object detection algorithm is determined from the difference in the propagation time, i.e., the temporal separation of the resulting echo amplitudes of the echo pulses. This means, for example, that the temporal separation of the maxima of the echo amplitudes can be compared.

[0028] According to one embodiment, the chirp signals have a mutually inverse frequency response, and the absolute distance is determined according to the object detection algorithm from an average value corresponding to the travel times of the echo pulses. The travel times of the echo pulses are therefore averaged to obtain the absolute distance. According to one embodiment, the position of the object relative to the ultrasonic sensor or the vehicle is determined by trilateration of the travel time of the echo pulses, and based on this, a velocity vector of the object relative to the ultrasonic sensor is determined. In other words, the object position can be used to determine the velocity vector in the x / y direction, i.e., in the horizontal direction relative to the vehicle. The velocity vector indicates the velocity of the object relative to the vehicle's own motion, in lines from the sensor to the object.

[0029] According to one embodiment, the speed vector is used to adapt at least one vehicle function of the vehicle. This means that a vehicle function can be controlled depending on the speed vector. For example, a vehicle occupant can be warned of a collision with an object or an appropriate driving maneuver can be initiated. However, if the speed vector indicates, for example, that the object is moving with the vehicle, there is no need to issue a warning or perform the appropriate driving maneuver.

[0030] According to one embodiment, the echo pulses are compared with each other according to a predetermined filter algorithm to detect and filter, i.e., suppress, interference signals. In other words, the echo comparison thus enables interference signal filtering. During the comparison, for example, the echo amplitudes of the echo signals are compared with each other. In particular, only if the two echoes have components with identical or similar amplitude comparisons is an object assumed. If the object components in the echoes differ, however, this can indicate interference.

[0031] According to one aspect, the invention relates to an ultrasonic sensor device for a vehicle for object detection in an environment, comprising at least one, i.e., one or more ultrasonic sensors and at least one computing unit. The at least one ultrasonic sensor is configured to emit at least two ultrasonic pulses into the environment, wherein the at least two ultrasonic pulses are provided as different chirp signals in which the signal frequency changes in different ways for the pulse duration. The ultrasonic sensor device is configured to determine an associated echo pulse for each of the at least two ultrasonic pulses from a received receive pulse in response to a reflection of the at least two ultrasonic pulses by an object in the environment.The at least one computing unit is configured to determine an object height, a relative speed, and / or the absolute distance of the object from the vehicle based on a difference in the echo pulses according to a predetermined object recognition algorithm. This means that the computing unit can execute or perform the object recognition algorithm to obtain the desired information about the object in the environment, for example, its condition or properties.

[0032] A computing unit can be understood, in particular, as a data processing device that contains a processing circuit. The computing unit can then process data, in particular, to carry out computing operations. The computing unit can therefore, in particular, process data to carry out computing operations. The computing unit can, in particular, contain one or more computers, one or more microcontrollers and / or one or more integrated circuits, for example one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and / or one or more single-chip systems (SoCs).The computing unit may also include one or more processors, for example one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs), and / or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit may also include a physical or virtual network of computers or other of the aforementioned units.

[0033] In various embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more memory units.

[0034] A memory unit can be a volatile data memory, for example a dynamic random access memory (DRAM) or a static random access memory (SRAM), or a non-volatile data memory, for example a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory or flash EEPROM, a ferroelectric random access memory (FRAM), a magnetoresistive random access memory,MRAM (magnetoresistive random access memory) or phase-change random access memory (PCRAM).

[0035] According to one aspect, the invention relates to a vehicle with a corresponding special ultrasonic device, as described above by way of example. The vehicle is preferably designed as a motor vehicle, in particular as a motor vehicle, such as a passenger car or a truck, passenger bus, or motorcycle. The ultrasonic sensor device can be part of a driver assistance system of the vehicle, with which a predetermined driver assistance function can be executed or performed depending on the results of the evaluation based on the object detection. For example, a distance warning system, a parking space detector, and / or a parking aid, as are known to be used in vehicles, can be implemented with the driver assistance system.

[0036] Further embodiments of the ultrasonic sensor device according to the invention and of the vehicle according to the invention follow directly from the various embodiments of the method according to the invention, and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the ultrasonic sensor device according to the invention and the vehicle according to the invention can be transferred analogously to corresponding embodiments of the method according to the invention, and vice versa. In particular, the ultrasonic sensor device is designed or programmed to carry out the method according to the invention. In particular, the ultrasonic sensor device carries out the method according to the invention.

[0037] The invention is explained in more detail below using specific exemplary embodiments with associated schematic drawings. In the figures, identical or functionally equivalent elements may be provided with the same reference numerals. The description of identical or functionally equivalent elements may not necessarily be repeated for different figures.

[0038] The figures show:

[0039] Fig. 1 is a schematic representation of a vehicle with an ultrasonic sensor device for environmental detection; Fig. 2 is a schematic process flow diagram for a method for operating a corresponding ultrasonic sensor device;

[0040] Fig. 3 is a schematic representation of the vehicle with the ultrasonic sensor device operated according to a first embodiment for determining an object height of an object in an environment; and

[0041] Fig. 4 is a schematic representation of the vehicle with the ultrasonic sensor device, which is operated according to a second embodiment for determining a relative speed and / or an absolute distance of an object in the environment.

[0042] Fig. 1 shows a schematic representation of a vehicle 1 from a side view. Vehicle 1 is shown as an example of a passenger car. The vehicle 1 is moving on a road surface, not shown, in a direction of travel F. In the direction of travel F in front of the vehicle 1, i.e. in its surroundings U, there is an object 2. In this case, the object 2 is, for example, another vehicle. Alternatively to the embodiment as a vehicle, the object 2 could be another object, such as another road user, for example a person or a cyclist or a motorcyclist or another type of obstacle for the vehicle 1.

[0043] The other vehicle or other vehicle is moving in the same direction as vehicle 1. The other vehicle is therefore driving in front of vehicle 1, for example, at a lower speed. The other vehicle could therefore potentially pose an obstacle for vehicle 1.

[0044] Vehicle 1 is intended to be able to react automatically to objects in the environment. This reaction can include, for example, issuing a notification to a driver of vehicle 1 or automatically or autonomously performing a driving maneuver, such as a braking or acceleration maneuver, maintaining a driving speed, and / or a steering maneuver. This enables vehicle 1 to warn the driver of collisions with object 2, for example, in road traffic, or even prevent them. For this purpose, vehicle 1 includes, for example, a driver assistance system (not shown in detail) or an electronic vehicle guidance system.The driver assistance system can provide a control signal to one or more actuators of the vehicle in response to the detected object 2 in the environment U, for example, to initiate or execute the respective driving maneuver, or to alert the driver to the object 2 so that the driver can initiate the respective driving maneuver by intervening in a vehicle control system. Such driver assistance systems are generally known. They can be, for example, a parking aid, a distance warning system, and / or a parking space detector.

[0045] To detect or identify the environment U and thereby also the object 2 in the environment U, the driver assistance system uses a suitable sensor device. In this case, the sensor device is, for example, an ultrasonic sensor device 10. Using ultrasonic signals or ultrasonic pulses, the object 2 in the environment U can be detected or classified. This includes, for example, checking whether the object 2 is present and / or identifying its object properties or object state.

[0046] For this purpose, the ultrasonic sensor device 10 uses one or more ultrasonic sensors, the structure and mode of operation of which are generally known. For example, the respective ultrasonic sensor comprises an ultrasonic transducer designed as an electroacoustic transducer. The transducer can thus generate a sound signal, in particular an ultrasonic signal, whose frequency range is specified for applications in the vehicle sector (transmit mode) by excitation with an electrical signal, for example by suitable control electronics. Typically, the operating principle of an ultrasonic transducer is reciprocal, so that upon excitation with a corresponding sound signal, i.e., the ultrasonic signal, a corresponding electrical signal can be generated (receive mode). In particular, each ultrasonic sensor can thus fundamentally be used as a transmitter and receiver (transceiver).Alternatively, it is of course also possible to use an ultrasonic sensor exclusively as a transmitter, i.e. to operate it in transmit mode, or to use it as a receiver and thus operate it in receive mode.

[0047] Fig. 1 shows an embodiment in which the ultrasonic sensor device 10 comprises precisely one ultrasonic sensor 11. The ultrasonic sensor 11 is preferably designed as a transceiver. The ultrasonic sensor 11 is, for example, installed in the region of a radiator grille of the vehicle 1. This makes it possible to implement front-end monitoring, i.e. monitoring in the direction of travel F in front of the vehicle. Of course, other installation locations are also conceivable, particularly depending on the respective application or area to be monitored. Of course, the ultrasonic sensor device 10 could also comprise a plurality of corresponding ultrasonic sensors 11, which are installed, for example, at different installation locations in the vehicle, for example in the region of a bumper and / or a vehicle rear and / or on the sides of the vehicle doors.

[0048] In the present embodiment, the ultrasonic sensor device 10 also includes a filter circuit 12. The filter circuit can be designed, for example, as a bandpass filter. Alternatively, the use of a correlator would be conceivable.

[0049] Furthermore, the ultrasonic sensor device 10 comprises a computing unit 13. The computing unit 13 can, for example, comprise one or more microcontrollers or microprocessors. The computing unit 13 can, for example, be part of the control electronics for the ultrasonic sensor 11 and / or form the control electronics.

[0050] The operation of the ultrasonic sensor device 10 for environmental detection, in particular object detection, can now be described in more detail using Fig. 2 as an example. Fig. 2 shows a schematic process flow diagram with individual process steps for a method for operating the ultrasonic sensor device 10.

[0051] In a step S1, at least two ultrasonic pulses P1, P2, in this case for example precisely these, are emitted into the environment U by means of the ultrasonic sensor 10. The ultrasonic pulses P1, P2 are the ultrasonic signals mentioned above. An ultrasonic pulse P1, P2 can also be referred to below as a burst. The two or more ultrasonic pulses P1, P2 are provided as different chirp signals, the signal frequency of which changes in different ways over the pulse duration. For example, the signal frequency can be output as an increase (chirp up) or a decrease (chirp down) and / or chirp signals with different center frequencies can be output. The type of chirp signal depends in particular on which properties of the object 2 in the environment U are to be detected or determined. The suitable pulse selection will be discussed in more detail later.In connection with the transmission of ultrasonic pulses P1, P2, two different variants are shown schematically in Fig. 1. For example, ultrasonic pulses P1 and P2 can be transmitted one after the other. This means that the generated chirp signals are emitted one after the other, i.e., sequentially. The pulse interval between the ultrasonic pulses P1, P2 is preferably no more than one to two milliseconds.

[0052] Alternatively, the at least two ultrasonic pulses P1, P2 can be emitted simultaneously as a superimposed signal, which is designated P1+P2 in Fig. 1 for clarity. This means that the generated chirp signals are emitted simultaneously, in particular simultaneously, by the ultrasonic sensor 11.

[0053] In total, multiple ultrasonic signals can be transmitted in a single transmission process using the ultrasonic sensor 11. This provides advantages in the subsequent evaluation for object detection.

[0054] If the object 2 is located in the environment U, in particular in a predetermined reception range of the ultrasonic sensor device 10, which can in particular be up to eight or ten meters away from the vehicle 1, the respective ultrasonic pulse P1, P2 is reflected by the object 2. The reflection causes the respective ultrasonic pulse P1, P2 to be thrown back to the ultrasonic sensor device 10 as an echo. The ultrasonic sensor 11 can receive this echo as a received pulse E. The received pulse E contains respective echo pulses E1, E2, which result from the reflection of the respective ultrasonic pulse P1, P2 by the object 2.

[0055] In a step S2, an associated echo pulse E1, E2 is determined for each of the ultrasonic pulses P1, P2 from a received pulse E, which the ultrasonic sensor device 10 receives in response to a reflection of the respective ultrasonic pulses P1, P2 or chirps from the object 2. This involves extracting the echoes of the chirp signals from the received pulse E and reusing them in the form of echo pulses E1, E2.

[0056] Each echo pulse E1, E2 thus represents one of the transmitted chirp signals. For example, the ultrasonic sensor device 10 uses the filter circuit to detect the echo pulses E1, E2. By applying known digital or analog filtering or correlation techniques, the filter circuit 12 can be used to filter or correlate the signals to distinguish between the echo pulses E1, E2 for the received pulse. For this purpose, the known frequency spectrum and frequency response of the originally transmitted chirp signals can be used, for example.

[0057] The extracted echo pulses E1, E2 are then transferred or forwarded to the computing unit 13 for evaluation. According to a step S3 of the method, the computing unit 13 can apply a predetermined object recognition algorithm to the echo pulses E1, E2. The object recognition algorithm can be implemented as a computer algorithm. When applying the object recognition algorithm, a difference between the echo pulses E1, E2 can be determined. The echo pulses E1, E2 are compared with one another to obtain a deviation or a difference between the echo pulses E1, E2. From the comparison result, object properties, in particular an object height H, a relative speed vr and / or a distance a of the object 2 from the vehicle 1 or from the ultrasonic sensor device 10, can be estimated.

[0058] A concrete exemplary embodiment for determining the object height H can be explained in more detail with reference to Fig. 3. Fig. 3 shows a schematic representation of the vehicle 1 with the ultrasonic sensor device 10. The vehicle 1 is also shown from a side view. In the present exemplary embodiment, the object 2 is, for example, a curb 4 which is raised relative to a driving surface 3 on which the vehicle 1 is moving. The curb 4 thus, in contrast to the road surface 3, has a vertical extension in the vehicle's vertical direction R, which can be specified by the object height H. This height difference can represent an obstacle for the vehicle 1 that the vehicle 1 cannot or should not drive over.

[0059] For height classification, i.e. detecting the object height H, exploitation is now made of the fact that a directional characteristic of an ultrasonic sensor 11 changes depending on the signal frequency. For this purpose, the ultrasonic pulses P1, P2 are generated as chirp signals, each with a different center frequency, wherein the center frequency is selected such that the ultrasonic pulses P1, P2 have different vertical opening angles, α, β in the vertical direction to the vehicle 1, i.e. in the vehicle's vertical direction R, as shown in Fig. 3. Both chirp signals can be designed, for example, as chirp-up or chirp-down or in opposite directions to one another. Beamforming can therefore be carried out using the selected signal frequency. Fig. 3 shows, as an example, the directional characteristic R1 for the ultrasonic pulse P1 and the directional characteristic R2 for the ultrasonic pulse P2. The directional characteristic R1 has an elevation opening angle α that is smaller than the elevation opening angle β of the directional characteristic R2.In order to obtain the difference in the directional characteristics R1, R2 shown in Fig. 3, the ultrasonic pulse P1 can, for example, have a higher center frequency than the ultrasonic pulse P2.

[0060] According to the object detection algorithm, the resulting echo amplitudes of the echo pulses E1, E2 are compared to determine the object height H. The height of the object can be determined from the ratio of the echo amplitudes. For this purpose, a position and a horizontal offset angle of the object 2, in this case the curb 4, relative to the ultrasonic sensor 11 can be determined, for example, using trilateration or triangulation from the transit time of the ultrasonic pulses P1, P2 or the echo pulses E1, E2.

[0061] Additionally or alternatively, the echo pulse(s) E1, E2 of an additional or different ultrasonic sensor of the ultrasonic sensor device 10 can also be used for the evaluation, or, for example, a previous measurement can be used. Subsequently, for example, the echo amplitudes can be corrected or normalized based on a predetermined horizontal sensitivity curve, taking into account the respective signal frequencies and the determined position and / or the horizontal deviation angle. This normalization can ensure that horizontal influences on the echoes are not taken into account for the subsequent evaluation. Subsequently, the amplitudes of the two measurements, i.e. of the two ultrasonic pulses P1, P2, normalized to the vertical direction R, can be compared with each other. The comparison provides a reliable result regarding the height of the object 2.For example, it is possible to distinguish whether object 2 can be driven over or not.

[0062] A concrete embodiment for determining the relative speed vr and / or the absolute distance a can be explained in more detail with reference to Fig. 4. Fig. 4 shows the vehicle 1 with the ultrasonic sensor device 10 from a top view or bird's eye view. Analogous to the embodiment in Fig. 1, the vehicle is again moving in the direction of travel F, with the other vehicle being located in front of the vehicle 1 in the direction of travel F as object 2, which in particular is traveling in the same direction of travel F as the vehicle 1. The vehicle 1 is moving at its own speed, which is represented by the speed vector v1. The other vehicle is moving at an external speed, which is represented by the speed vector v2.In the present embodiment, the external speed is reduced compared to the vehicle's own speed, so that vehicle 1 would collide with the external vehicle if it maintained its current own speed. This results in a relative speed vr for the external vehicle, which, as represented by the speed vector vr in Fig. 4, acts opposite to the direction of travel F.

[0063] To determine the relative speed vr and / or the absolute distance a, the ultrasonic pulses P1, P2 are generated as chirp signals with different, in particular inverse, frequency responses from high to low signal frequencies and vice versa. This means that one pulse is output, for example, as a chirp-up and the other pulse as a chirp-down. According to the object detection algorithm, differences in the propagation time of the echo pulses E1, E2 are evaluated. The speed or distance measurement between the sensor and object 2 is thus carried out using the so-called time of flight. This exploits the fact that the Doppler effect acts on the chirp signals due to the relative speed vr of the object 2 to the vehicle, resulting in different distances in the wave crests or troughs of the chirp signals for moving objects 2 or a moving vehicle 1.In particular, the Doppler effect causes a compression or stretching of the echo pulses E1, E2 depending on the relative velocity, in different directions to each other, since inverse chirps were chosen.

[0064] To determine the relative speed, the position of object 2 relative to ultrasonic sensor 11 can be determined, for example, by trilateration or triangulation of the echo pulse travel time. Depending on this, the speed vector that indicates the relative speed vr of object 2 relative to the ultrasonic sensor can be determined. As shown in Fig. 4, the speed vector is located in an indirect connecting line to sensor 11 and object 2 and indicates the direction of movement of the other vehicle relative to the vehicle's own movement.

[0065] From the mean value of the corresponding travel times of the echo pulses E1, E2, i.e. from the time interval of the resulting echo amplitudes of the echo pulses, the real distance, i.e. the absolute distance a, between vehicle 1 and object 2 can be determined. The difference in the distances between the echo amplitudes can also be used to determine the Doppler frequency and thus the relative speed of object 2. Depending on this, an absolute speed can also be determined. The absolute speed of object 2 can be determined using trilateration and the resulting offset angle, as well as the known vehicle speed.

[0066] Preferably, the determined velocity vector of the relative velocity vr can be used to adapt at least one vehicle function of the vehicle. For this purpose, the velocity vector can be output, for example, to the driver assistance system. If the other vehicle is moving, for example, at the same speed as vehicle 1 or a higher speed, the vehicle function can be, for example, to maintain the current speed. The driver therefore does not need to be warned or the vehicle braked. If the other vehicle is traveling more slowly, as in the present exemplary embodiment, for example, a braking maneuver or an overtaking maneuver can be initiated.

[0067] In addition to the described object classification, the computing unit 13 can also be used, for example, to compare the echo pulses E1, E2 according to a predetermined algorithm to determine and filter out interference signals. For this purpose, the time-of-flight of the echo signals can be compared, for example, and, depending on this, common interference in the signals can be filtered out or suppressed.

[0068] Overall, the exemplary embodiments demonstrate multi-channel ultrasound measurement and processing. This involves using only a single ultrasound sensor 11 to output multiple channels, and thus multiple ultrasound pulses P1, P2, together in order to classify or categorize objects 2 in the environment U.

Claims

Patent claims 1. A method for operating an ultrasonic sensor device (10) for a vehicle (1) for object detection in an environment (U), wherein - at least two ultrasonic pulses (P1, P2) are emitted into the environment (U) by means of an ultrasonic sensor (11) of the ultrasonic sensor device (10), wherein the at least two ultrasonic pulses (P1, P2) are provided as different chirp signals in which the signal frequency changes in different ways over the pulse duration, - from a reception pulse (E) which the ultrasonic sensor device (10) receives in response to a reflection of the at least two ultrasonic pulses (P1, P2) at the object (2), an associated echo pulse (E1, E2) is determined for each of the at least two ultrasonic pulses (P1, P2), and - according to a predetermined object recognition algorithm, an object height (H), a relative speed (vr) and / or an absolute distance (a) of the object (2) to the vehicle (1) is determined from a difference between the echo pulses (E1, E2).

2. Method according to claim 1, wherein the at least two ultrasonic pulses (P1, P2) are emitted simultaneously as a superimposed signal with the ultrasonic sensor (11) or the at least two ultrasonic pulses (P1, P2) are emitted one after the other with the ultrasonic sensor (11).

3. Method according to one of the preceding claims, wherein signal filtering or signal correlation is carried out to distinguish the echo pulses (E1, E2) for the received pulse (E).

4. Method according to one of the preceding claims, wherein, for determining the object height (H), the at least two ultrasonic pulses (P1, P2) are generated as chirp signals with different center frequencies, wherein the respective center frequency is selected such that the at least two ultrasonic pulses (P1, P2) have different height opening angles (α, ß) in the vertical direction to the vehicle (1), and according to the object recognition algorithm for determining the object height (H), resulting echo amplitudes of the echo pulses (E1, E2) are compared with each other.

5. The method according to claim 4, wherein the echo amplitudes are normalized according to a known sensitivity curve as a function of the respective signal frequency of the associated ultrasonic pulse (P1, P2).

6. Method according to one of claims 4 or 5, wherein a position and / or a horizontal offset angle of the object (2) to the ultrasonic sensor (11) is determined by means of trilateration of the travel times of the echo pulses (E1, E2), and the echo amplitudes are corrected in accordance with a known sensitivity curve to determine the object height (H).

7. Method according to one of the preceding claims, wherein, in order to determine the relative speed (vr) and / or the absolute distance (a), the at least two ultrasonic pulses (P1, P2) are generated as chirp signals with mutually different frequency profiles from high to low signal frequencies and vice versa, and differences in the propagation time of the echo pulses (E1, E2) are evaluated according to the object recognition algorithm.

8. The method according to claim 6, wherein the relative speed (vr) is determined according to the object detection algorithm from the difference in the propagation time of resulting echo amplitudes of the echo pulses (E1, E2).

9. Method according to one of the preceding claims 6 or 7, wherein the chirp signals have a mutually inverse frequency characteristic and the absolute distance (a) is determined according to the object recognition algorithm from an average value of the corresponding propagation times of the echo pulses (E1, E2).

10. Method according to one of the preceding claims 8 or 9, wherein by means of trilateration of the transit times of the echo pulses (E1, E2) a position of the object (2) relative to the ultrasonic sensor (11) is determined and, depending thereon, a Velocity vector of the object (2) relative to the ultrasonic sensor (11) is determined.

11. Method according to claim 10, wherein the velocity vector is used to adapt at least one vehicle function of the vehicle (1).

12. Method according to one of the preceding claims, wherein the echo pulses (E1, E2) are compared according to a predetermined filter algorithm to determine and filter interference signals.

13. Ultrasonic sensor device (10) for a vehicle (1) for object detection in an environment (U) with at least one ultrasonic sensor (11) and at least one computing unit (13), wherein - the at least one ultrasonic sensor (11) is designed to emit at least two ultrasonic pulses (P1, P2) into the environment (U), wherein the at least two ultrasonic pulses (P1, P2) are provided as different chirp signals in which the signal frequency changes in different ways over the pulse duration, - the ultrasonic sensor device (10) is designed to determine an associated echo pulse (E1, E2) for each of the at least two ultrasonic pulses (P1, P2) from a received reception pulse (E) in response to a reflection of the at least two ultrasonic pulses (P1, P2) at the object (2), and - the at least one computing unit (13) is designed to determine an object height (H), a relative speed (vr) and / or an absolute distance (a) of the object (2) from the vehicle (1) from a difference in the echo pulses (E1, E2) according to a predetermined object recognition algorithm.

14. Vehicle (1) with an ultrasonic sensor device (10) according to claim 10.

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