Method and apparatus for processing raw data from a UWB sensor

Abstract

A method for processing raw data from a UWB sensor (10), which is installed in a vehicle interior under the headliner for monitoring purposes, is described. The raw data comprises a multitude of radar echoes (RE1,..., REn) from a radar pulse repeatedly transmitted within a predefined time interval (ZS), as a function of the number of taps (TP), which represent a characteristic value for the range of the UWB sensor (10). After filtering, the multitude of radar echoes (RE1,..., REn) is transmitted to a processing unit (21) to be stored together as a radar image for further processing. The number of taps (TP) is varied depending on the evaluation of a subset of the radar echoes (RE1,..., REm).

Description

[0001] The invention relates to a method and a device for processing raw data from a UWB sensor (UWB = ultra-wideband) that is arranged under the roof of a motor vehicle for monitoring the vehicle interior. Such a UWB sensor is used for occupant detection in the motor vehicle.

[0002] The principle of a UWB sensor, which is a radar sensor, is to emit radar pulses and then receive radar echoes reflected from objects. Typically, a large number of radar pulses are emitted within a specified period of time, which are then received as radar echoes. The duration of a single radar pulse is usually in the range of a few nanoseconds to several hundred picoseconds. By appropriately evaluating the radar echoes, signs of life from vehicle occupants and thus their presence can be detected. Detection can be determined, for example, by the rise and fall of the vehicle occupant's chest as a result of breathing. Depending on the vehicle, one or more UWB sensors can be provided for complete monitoring of the vehicle interior.

[0003] The raw data to be processed comprises a multitude of radar echoes from a radar pulse repeatedly transmitted within a specified period of time, as a function of a number of so-called taps. A tap represents a characteristic value for the range of the UWB sensor. The higher the so-called tap number, the greater the distance between the UWB sensor and the object reflecting the signal. After being filtered by a sensor processing unit, the multitude of radar echoes are transmitted to a higher-level processing unit, where they are stored together as a radar image for further processing.

[0004] Storing the data as a radar image allows the higher-level processing unit to further process it using machine learning. For example, image analysis approaches from machine learning can be used. However, this requires sufficient processing resources on the higher-level processing unit.

[0005] It is an object of the invention to provide a method and a device which enables the processing of raw data from a UWB (radar) sensor with fewer resources.

[0006] These objects are achieved by a method according to the features of claim 1, a computer program product according to the features of claim 8 and a device according to the features of claim 9. Advantageous embodiments emerge from the dependent claims.

[0007] A method for processing raw data from a UWB sensor is proposed. The UWB sensor is an ultra-wideband radar sensor. It is arranged under the roof of a motor vehicle for monitoring the vehicle interior. The raw data comprises a plurality of radar echoes from a radar pulse repeatedly transmitted within a predetermined period of time as a function of a number of taps. The taps represent a characteristic value for the range of the UWB sensor. After each filtering, the plurality of radar echoes is transmitted to a computing unit in order to be stored together as a radar image in the computing unit for further processing. According to the invention, the number of taps is varied depending on an evaluation of a portion of the radar echoes.

[0008] The proposed approach enables the processing of raw data with fewer resources of the (higher-level) processing unit. Further processing of the radar image in the processing unit using machine learning methods requires the acquisition of the complete radar image and its storage in the processing unit before evaluation by the machine learning algorithm. For example, the evaluation can be performed using a so-called convolutional layer of a convolutional neural network (CNN). Since the memory requirements for the radar image can be considerable and the memory resources in the processing unit are generally limited, it is advisable to optimize them.

[0009] In order to optimize the storage requirements for the radar image required for evaluation, the invention varies the number of taps depending on the situation, specifically depending on the evaluation of a part of the radar echo. This makes it possible to reduce the radar image to the areas relevant for evaluation if, for example, no vehicle occupant could be detected in the monitored vehicle interior, e.g. in the seats further away from the UWB sensor (such as the rear seats in the case of a UWB sensor arranged in the front roof liner). This approach is based on the consideration that UWB sensors require a relatively large amount of storage space for the complete radar image, depending on the recording time and recording distance. This means that the greater the distance monitored by the UWB sensor, the greater the storage requirement for the radar image that must be saved for evaluation.Depending on the evaluation of a portion of the radar echoes, the number of taps is then varied such that information at a greater distance from the UWB sensor is no longer taken into account in the radar image.

[0010] Conveniently, the number of taps is varied depending on an evaluation of the portion of the radar echoes received at the beginning of the specified time period. In other words, the radar echoes received first (in time) are evaluated with respect to information that is the greatest distance from the UWB sensor. Depending on the result of the evaluation of a portion of the radar echoes at the beginning of the specified time period, the decision regarding the variation in the number of taps can then be made.

[0011] A further expedient embodiment provides that the evaluation of the portion of the radar echoes comprises a dynamic analysis separately for one or more selected taps. In particular, the evaluation comprises a dynamic analysis separately for one or more taps with a tap count greater than a predetermined value. The predetermined value can be specified once as part of a specification process that takes into account the arrangement of the UWB sensor in the vehicle interior and the conditions of the vehicle interior in the motor vehicle. Alternatively, the predetermined value can also be determined dynamically during runtime of the method based on the result of the analysis. According to this embodiment, the dynamic analysis focuses on taps with a "high" tap count, which means that those areas that have the greatest distance within the range that the UWB sensor can detect are taken into account.This makes it possible, for example, to use a UWB sensor located in the front area under the roof of the vehicle to sense the area on the back seat to determine whether children and / or animals are present there.

[0012] The evaluation expediently includes determining whether the amplitude of the portion of the radar echoes for taps whose tap count is greater than a predefined value is below a first predefined amplitude limit. Alternatively or additionally, the evaluation includes determining whether the mean amplitude of the portion of the radar echoes for taps whose tap count is greater than the predefined value is below a second predefined amplitude limit. These two criteria can be used to determine whether or not there are vehicle occupants in the areas distant from the UWB sensor. If at least one of the two criteria is met, the taps whose tap count is greater than the predefined value are expediently not transmitted to the computing unit. This can significantly reduce the memory requirements for the radar image stored in the computing unit.However, this reduction in the size of the radar image only occurs if the above criteria are met. If these criteria are not met, the radar image includes the entire number of taps for each radar echo.

[0013] According to a second aspect, a computer program product is proposed which comprises instructions which, when the program is executed by a computing unit, cause the computing unit to carry out the method according to one or more embodiment variants.

[0014] According to a further aspect, a device is proposed for processing raw data from a UWB sensor arranged in a vehicle interior under the roof of a motor vehicle for monitoring the vehicle. The raw data comprises a plurality of radar echoes from a radar pulse repeatedly transmitted within a predetermined period of time as a function of a number of taps, which represent a characteristic value for the range of the UWB sensor. After each filtering, the plurality of radar echoes is transmitted to a computing unit in order to be stored together as a radar image in the computing unit for further processing. According to the invention, the UWB sensor is designed to vary the number of taps depending on an evaluation of a portion of the radar echoes.

[0015] In further embodiments, the device is configured to carry out one or more embodiments of the method according to the invention.

[0016] The invention is explained in more detail below using an exemplary embodiment in the drawing. They show: Fig. 1 shows a schematic representation of an apparatus according to the invention for processing raw data from a UWB sensor; Fig. 2 a complete, unaltered radar image based on a plurality of radar echoes of a radar pulse repeatedly transmitted within a given time period as a function of a number of taps; and Fig. 3 that in Fig. 2, whose storage requirements are reduced by information reduction.

[0017] Fig. 1 shows a schematic representation of an inventive device for processing raw data from a UWB sensor 10. The UWB sensor 10 comprises, in a known manner, two antennas 11, 12 coupled to a transmitting / receiving unit 13. For example, the antenna 11 serves as a transmitting antenna (Tx) and the antenna 12 serves as a receiving antenna (Rx). The transmitting / receiving unit 13 is configured to repeatedly transmit radar pulses via the antenna 11 within a predetermined time period ZS and to transmit the radar echoes RE1, ..., REn received by the antenna 12 to a sensor processing unit 14 for processing. The sensor processing unit 14 is connected to a memory 15 for carrying out the processing steps it performs, in which memory data can be temporarily stored during processing. The radar echoes RE1, ..., REn are caused by reflection of the radar pulses from static or moving objects.The suffix “n” stands for the nth received radar echo.

[0018] The UWB sensor 10 is arranged in a vehicle interior (not shown in detail) under the roof of a motor vehicle for monitoring purposes. For example, the UWB sensor 10 is arranged near the interior mirror under the roof and oriented such that the radar pulses it emits are directed toward the front and rear seats. The presence of occupants can then be determined from the processing of the radar echoes RE1, .., REn reflected by the objects (static objects of the motor vehicle and / or vehicle occupants). For processing, the plurality of radar echoes RE1..., REn repeatedly emitted within the predetermined time period ZS are transmitted as a function of a number of taps TP to the sensor processing unit 14 of the UWB sensor 10 for preprocessing.

[0019] The radar image resulting from the preprocessing by the sensor processing unit 14, as shown for example in the Fig. 2 and Fig. 3, is then transmitted to a control unit 20 for further processing. The control unit 20 may be a (central) evaluation control unit that receives corresponding radar images from a plurality of UWB sensors and, if applicable, other sensors.

[0020] The control unit 20 comprises a computing unit 21, an image processing unit 22, and a data memory 23. The computing unit 21 serves to receive the radar image as a data stream and to store it in the data memory 23 for further processing. The radar image is then fed to the image processing unit 22, wherein the image processing unit 22 can also have direct access to the data memory 23 for this purpose. The image processing unit 22 comprises, for example, a machine learning algorithm, in particular a neural network (convolutional neural network, CNN), which is particularly suitable for evaluating images. During the evaluation, it is then determined whether or not an occupant is present in the vehicle interior. The type of image evaluation is not of central importance for the method described here, so reference is made to the analysis options known from the prior art.

[0021] Fig. 2 shows a complete radar image, as it must be stored in the data memory 23 without further preprocessing, in order to then be fed to the image processing unit for further processing. The radar image comprises a plurality of radar echoes RE1..., REn, which were recorded successively within a predetermined time period ZS from t = 0 to t ∼ 1200. The amplitude curve per time or radar echo REi (i = 1... n) is a function of a number of taps TP, where the taps are designated by a number from z = 0 to z = 65. The larger the tap number TPz, the greater the distance of the object from which a radar pulse was reflected. The tap or tap number thus represents a characteristic value for the range of the UWB sensor 10 and indicates the distance up to which the UWB sensor 10 records or can record data. The further the UWB sensor 10 “looks”, ieThe larger the tap number TPz, the more information must be stored for a radar echo RE1..., REn. The memory requirement for the radar image to be stored in the data memory 23 depends on the number n of radar echoes and the tap number TPz.

[0022] The invention therefore provides for varying the tap number TPz depending on an evaluation of a portion of the radar echoes RE1..., REm (with m < n), whereby the considered portion of the radar echoes RE1..., REm is selected at the beginning of the predetermined time period ZS. For example, radar echoes are selected within the time period from t = 0 to t = 200, where m corresponds to the mth radar pulse at t = 200.

[0023] For this portion of the radar echoes RE1, ... REm, a dynamic analysis is performed for a portion of the taps TP. In particular, a dynamic analysis is performed for taps with a tap count TPz greater than a specified value, e.g., 45. The specified value of the tap count TPz can optionally be specified once as part of a specification process that takes into account the type of UWB sensor, its installation location in the vehicle interior, and the size and / or volume of the vehicle interior. The specified value can also be set dynamically during runtime of the process based on the analysis result.

[0024] The evaluation includes whether the amplitude of the considered part of the radar echoes RE1, .... REm for the taps whose tap number is greater than the specified value, e.g. TPz = 45, is below a specified amplitude limit value AGW (see Fig. 2). Additionally or alternatively, it can also be determined whether an average value of the amplitude A of the considered part of the radar echoes RE1, ... REm for the taps whose tap number TPz is greater than the specified value is below a second specified amplitude limit.

[0025] If one or both criteria are met, those taps TP whose tap number TPz is greater than the specified value, in the example chosen here TPz ≥ 45, are not transmitted to the processing unit 21. This is shown schematically in Fig. 3, in which the taps with a tap count greater than TP 45 are illustrated with a hatched area and are not considered further. This type of preprocessing takes place in the sensor processing unit 14. The memory 15 is used by the sensor processing unit to temporarily store the observed portion of the radar echoes RE1, ... REm in order to determine whether the above-mentioned criteria are met or not.

[0026] As explained, if one or both of the criteria are met, only reduced data for generating the radar image are transmitted by the computing unit 21 in the control unit 20 and stored in the data memory 23 for further processing by the image processing unit 22.

[0027] If one or more of the criteria are not met, this indicates that, for example, living beings have been detected in the rear area of ​​the vehicle interior. Therefore, in this case, the complete information for generating the radar image is used according to Fig. 2 to the control unit 20.

[0028] The described procedure can be initiated, for example, when all doors have been closed in an exit scenario. In this scenario, a check is then made to determine whether any children and / or animals have been left behind in the vehicle. If the UWB radar sensor or the analysis of the radar echoes detects that an amplitude is present in the first radar echoes under consideration (also referred to as radar rounds) in the second row of seats, the full tap count for all radar echoes RE1, ... REn is transmitted to the control unit 20. If, however, the UWB sensor 10 does not detect any amplitude in the second row of seats in the part of the first radar echoes RE1, ... REm under consideration, the tap count is reduced, and the radar echoes with a lower tap count are transmitted to the control unit.

[0029] Due to the reduced number of taps, the need to store the entire radar image before transferring it to the image processing unit 22 is reduced. The unused storage space in the data memory 23 can then be used for other functions performed by the control unit. The smaller radar image also reduces the processing effort required for further image processing. List of reference symbols 10 UWB sensors 11 first antenna 12 second antenna 13 Transmitting / receiving unit 14 Sensor processing unit 15 storage 20 Control unit 21 computing unit 22 Image processing unit 23 data storage RE1,.., REm,..., REn radar echo ZS time span TP Tap TPz tap number with z=1...x AGW amplitude limit

Claims

[1] Method for processing raw data of a UWB sensor (10) which is arranged in a vehicle interior for monitoring the same under the roof of a motor vehicle, wherein the raw data comprise a plurality of radar echoes (RE1,..., REn) of a radar pulse repeatedly emitted within a predetermined time period (ZS) as a function of a number of taps (TP) which represent a characteristic value for the range of the UWB sensor (10), wherein the plurality of radar echoes (RE1,..., REn) are transmitted to a computing unit (21) after a respective filtering in order to be stored in the computing unit (21) together as a radar image for further processing, in which - the number of taps (TP) is varied depending on an evaluation of a part of the radar echoes (RE1,..., REm). [2] Method according to claim 1, characterized bythat the number of taps (TP) is varied depending on an evaluation of the part of the radar echoes (RE1,..., REm) received at the beginning of the specified time period. [3] Method according to claim 1 or 2, characterized by that the evaluation of the part of the radar echoes (RE1,..., REm) includes an analysis of the dynamics separately for one or more selected taps (TP). [4] Method according to claim 3, characterized by that the evaluation includes an analysis of the dynamics separately for one or more taps (TP) with a tap number (TPz) that is greater than a specified value. [5] Method according to claim 4, characterized by that the evaluation includes whether an amplitude (A) of the part of the radar echoes (RE1,..., REm) for the taps (TP) whose tap number (TPz) is greater than a predetermined value is below a first predetermined amplitude limit value (AGW). [6] Method according to claim 4 or 5, characterized bythat the evaluation includes whether an average value of the amplitude of the part of the radar echoes (RE1,..., REm) for the taps whose tap number (TPz) is greater than the specified value is below a second specified amplitude limit value. [7] Method according to claim 5 or 6, characterized by that the taps (TP) whose tap number (TPz) is greater than the specified value are not transmitted to the computing unit (21). [8] Computer program product comprising instructions which, when the program is executed by a computing unit, cause the computing unit to carry out the method according to one of claims 1 to 7. [9] Device for processing raw data of a UWB sensor (10) which is arranged in a vehicle interior for monitoring the same under the roof of a motor vehicle, wherein the raw data comprise a plurality of radar echoes (RE1,..., REn) of a radar pulse repeatedly emitted within a predetermined time period (ZS) as a function of a number of taps (TP) which represent a characteristic value for the range of the UWB sensor (10), wherein the plurality of radar echoes (RE1,..., REn) are transmitted to a computing unit (21) after a respective filtering in order to be stored together in the computing unit (21) as a radar image for further processing, wherein the UWB sensor (10) is designed to vary the number of taps (TP) depending on an evaluation of a part of the radar echoes (RE1,..., REm). [10] Device according to claim 9, characterized bythat it is adapted to carry out the method according to one of claims 2 to 7.

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