Method and apparatus for identifying a wobble object in radar data

Abstract

The present application relates to a method and apparatus for identifying a wobble object in radar data. A method is disclosed for determining, based on a plurality of range-Doppler maps provided by a radar system, that one or more wobble objects are present within a range interval of the plurality of range intervals. Each of the plurality of range-Doppler maps corresponds to a time interval of a sequence of time intervals and includes a respective energy value for a plurality of velocity intervals within each of the plurality of range intervals. For each time interval, a difference between a statistical measure of energy values for a set of velocity intervals having positive velocities of the plurality of velocity intervals within a range interval and a statistical measure of energy values for a set of velocity intervals having negative velocities of the plurality of velocity intervals within the range interval is computed from the range-Doppler map corresponding thereto. A spectrum is then determined from the computed sequence of differences. In a condition that a peak is present in the spectrum for a frequency above a frequency threshold, it is determined that one or more wobble objects are present at the range interval.

Description

Technical Field

[0001] The present invention relates to identifying swaying objects in radar data, and more specifically, to determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler maps provided by a radar system. Background Technology

[0002] When monitoring a scene using a radar-based surveillance system, it may be desirable to detect and / or render only moving objects within the scene. However, a problem with existing technologies is the lack of differentiation between moving objects such as cars or people and objects that are swaying due to wind, such as grass, trees, and poles, which are generally of little interest. Therefore, it is desirable to be able to identify these swaying objects, for example, so that swaying objects are not identified as being detected, or so that any detections associated with swaying objects are not further processed (e.g., by tracking algorithms or classifiers). Summary of the Invention

[0003] The purpose of this invention is to overcome or at least mitigate the problems and defects of the prior art.

[0004] According to a first aspect, a method is provided for determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler maps provided by a radar system. Each range-Doppler map in the multiple range-Doppler maps corresponds to a time interval in a time interval sequence and includes corresponding energy values ​​for multiple velocity intervals within each range interval. The method includes: for each time interval in the time interval sequence, calculating, based on the range-Doppler map corresponding to that time interval, a difference sequence of energy values ​​between a set of velocity intervals with positive velocities within that range interval and a set of velocity intervals with negative velocities within that range interval, thereby calculating the difference sequence of the time interval sequence. The method further includes: determining the spectrum of the calculated difference sequence of the time interval sequence; and determining the presence of one or more swaying objects at that range interval if a peak exists in the spectrum for frequencies above a frequency threshold.

[0005] Oscillating objects typically exhibit periodic motion, causing their motion to vary between positive and negative velocities. Therefore, the energy values ​​in multiple range-Doppler graphs usually vary, such that within the distance intervals in which the oscillating object exists, the energy values ​​are periodically higher for positive velocities and periodically higher for negative velocities. Consequently, the difference in statistical measurements of the energy values ​​for positive and negative velocities in multiple range-Doppler graphs also typically varies periodically. This difference in statistical measurements varies at the same frequency as the frequency at which the oscillating object is oscillating. Therefore, by calculating the sequence of differences in the statistical measurements of the energy values ​​for positive and negative velocities over a time interval sequence and then determining the spectrum of the calculated difference sequence, the oscillating object at a specific frequency can be identified as a peak in the spectrum at that specific frequency.

[0006] Identifying the presence of one or more swaying objects within a distance interval prevents further processing (such as by tracking algorithms or classifiers) of detections associated with one or more swaying objects. Furthermore, it avoids presenting trajectories associated with one or more swaying objects.

[0007] Statistical measurement refers to numerical values ​​that summarize the characteristics of a dataset.

[0008] The spectrum refers to the representation of a signal, in this case, the calculated difference sequence in the frequency domain. Specifically, it can refer to the amplitude spectrum, which describes the distribution of the amplitudes of the frequency components in the signal.

[0009] In an embodiment, the method according to the first aspect further includes: upon determining that one or more swaying objects exist at a distance interval, filtering out any detections in a velocity interval having an absolute velocity less than a first velocity threshold from a plurality of velocity intervals within the distance interval.

[0010] By filtering out detections within a distance interval based on the determination that one or more swaying objects exist at that distance interval, detections related to one or more swaying objects (which are typically unrelated to the radar system user, such as operators of surveillance systems including the radar system) are not used in subsequent processing or visualization. Furthermore, by filtering out any detections in velocity intervals within the multiple velocity intervals that have an absolute velocity less than a first velocity threshold, any detections with an absolute velocity greater than or equal to the velocity threshold are not filtered out. Such detections may, for example, involve moving objects other than one or more swaying objects.

[0011] Detection here typically refers to the energy value within a velocity interval at a certain distance interval being considered relevant to an object. For example, this can be determined based on an energy value exceeding an energy threshold, which in this context generally means that the energy value is considered high enough to be relevant to the object. For example, the energy threshold can be based on noise levels, and an energy value exceeding the energy threshold can mean that the signal-to-noise ratio (SNR) of the energy value exceeds the SNR threshold. The energy threshold (SNR threshold) can be different for different velocity intervals, and the energy threshold (SNR threshold) for one velocity interval can depend on the energy values ​​of other velocity intervals. The energy threshold (SNR threshold) can be selected to provide a probability of detecting a moving object higher than the desired detection probability and a false detection probability lower than the desired false detection probability.

[0012] In an embodiment, the method according to the first aspect further includes: filtering out the energy values ​​of velocity intervals with absolute velocities less than a first velocity threshold from among a plurality of velocity intervals within the distance interval, provided that a swaying object is determined to exist at the distance interval and there are no peaks in the spectrum for frequencies below a frequency threshold.

[0013] By setting a condition that there are no peaks in the spectrum for frequencies below a frequency threshold for the detections to be filtered out, it is possible to prevent the filtering out of detections associated with objects other than one or more swaying objects. For example, such other objects might be objects moving at a low radial velocity relative to the radar. The frequency threshold can be set, for example, based on the lowest expected frequency at which one or more swaying objects sway.

[0014] The first velocity threshold can be fixed. The velocity threshold can be set, for example, based on the maximum expected velocity of one or more swaying objects. Then, detections associated with absolute velocities above the first velocity threshold will be considered associated with moving objects that are not swaying.

[0015] In an embodiment, the method according to the first aspect further includes: for each velocity interval at a distance interval, aggregating the energy values ​​of at least a subset of multiple range-Doppler maps based on an aggregation function to obtain an aggregated energy value for each velocity interval at that distance interval. Then, identifying the maximum absolute velocity such that among the multiple velocity intervals within that distance interval, there exists a velocity interval with a positive velocity and a velocity interval with a negative velocity, which has a maximum absolute velocity and an aggregated energy value exceeding an aggregated energy threshold. Then, setting a first velocity threshold based on the maximum absolute velocity.

[0016] By identifying the maximum absolute velocity that exists both a velocity interval with negative velocity and a velocity interval with positive velocity that exceeds the aggregation energy threshold, this maximum absolute velocity is considered to be associated with one or more swinging objects, and the maximum absolute velocity can be used as an estimate of the maximum absolute velocity of one or more swinging objects.

[0017] In an embodiment, the method according to the first aspect further includes: dividing velocity intervals within multiple velocity intervals in each of the multiple range-Doppler maps into multiple groups, depending on their absolute velocities. These groups are ordered such that velocity intervals in higher-order groups have larger absolute velocities than velocity intervals in lower-order groups. The multiple groups are then processed sequentially by the following steps: For the currently processed group: For each time interval in the time interval sequence, based on the range-Doppler map corresponding to that time interval, a difference sequence of the time interval sequence is calculated between a statistical measurement of the energy value of the velocity interval with positive velocity in that group of velocity intervals within that range interval and a statistical measurement of the energy value of the velocity interval with negative velocity in that group of velocity intervals within that range interval. Then, the spectrum of the calculated difference sequence of the time interval sequence is calculated. If a peak exists in the spectrum for frequencies above a frequency threshold, the next group in the sequence is processed. If no peak exists in the spectrum for frequencies above a frequency threshold, a first velocity threshold is set to a value corresponding to the maximum absolute velocity of the velocity interval in the previous group in the sequence.

[0018] By identifying the group with the highest absolute velocity that has a peak in the spectrum for frequencies above a frequency threshold, this group is considered to be associated with the highest group, which is associated with one or more swinging objects, and the highest absolute velocity of this group can be used as an estimate of the maximum absolute velocity of one or more swinging objects.

[0019] In an embodiment, during the calculation of the difference, the difference between a statistical measurement of the energy value of a set of velocity intervals with positive velocity and absolute velocity less than the second velocity threshold within the distance interval and a statistical measurement of the energy value of a set of velocity intervals with negative velocity and absolute velocity less than the second velocity threshold within the same distance interval is calculated.

[0020] The computational load is reduced by calculating the difference based solely on the energy values ​​of this set of speed intervals with absolute speeds less than the second speed threshold.

[0021] Statistical measurements can be one of the following: standard deviation, variance, mean, median, and sum of squares.

[0022] According to the second aspect, a non-transitory computer-readable storage medium is provided thereon having instructions stored thereon, which, when executed in a processing-capable device, cause the device to perform the method according to the first aspect.

[0023] The optional additional features described above in the method according to the first aspect may also be applied, where appropriate, to non-transitory computer-readable storage media according to the second aspect. To avoid repetition, refer to the foregoing.

[0024] According to a third aspect, an apparatus is provided for determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler images provided by a radar system. Each range-Doppler image corresponds to a time interval in a time interval sequence and includes corresponding energy values ​​for multiple velocity intervals within each range interval. The apparatus includes circuitry configured to perform a calculation function, a first determination function, and a second determination function. The calculation function is configured, for each time interval in the time interval sequence, to calculate, based on the range-Doppler image corresponding to that time interval, a difference between a statistical measurement of the energy values ​​of a set of velocity intervals with positive velocities within that range interval and a statistical measurement of the energy values ​​of a set of velocity intervals with negative velocities within that range interval. The first determination function is configured to determine the spectrum of the calculated difference sequence. The second determination function is configured to determine the presence of one or more swaying objects at that range interval if a peak exists in the spectrum for frequencies above a frequency threshold.

[0025] The optional additional features described above in the method according to the first aspect may also be applied, where appropriate, to the apparatus according to the third aspect. To avoid repetition, refer to the foregoing.

[0026] Therefore, it should be understood that the present invention is not limited to the specific components of the described system or the operation of the described method, as such systems and methods can be modified. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and appended claims, the articles “a,” “the,” and “the” are intended to refer to one or more of the elements present, unless the context clearly specifies otherwise. Thus, for example, a reference to “unit” or “the unit” can include several means, etc. Furthermore, the words “comprising,” “including,” “containing,” and similar wording do not exclude other elements or steps. Attached Figure Description

[0027] The above and other aspects of the invention will now be described in more detail with reference to the accompanying drawings. The drawings should not be considered limiting, but rather for explanation and understanding.

[0028] Figure 1a and Figure 1b A flowchart is shown relating to an embodiment of a method for determining the presence of one or more swinging objects within a range interval based on multiple range-Doppler images provided by a radar system.

[0029] Figure 2 An example of a distance-Doppler plot is shown.

[0030] Figure 3a and Figure 3b Plots showing the differences between the standard deviations of the energy values ​​for the positive velocity intervals and the standard deviations of the energy values ​​for the negative velocity intervals, respectively, and plots of the discrete Fourier transforms of these differences.

[0031] Figure 4 The diagram illustrates an embodiment of a device for determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler images provided by a radar system. Detailed Implementation

[0032] The invention will now be described with reference to the accompanying drawings, in which presently preferred embodiments of the invention are illustrated. However, the invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0033] Embodiments of the present invention are applicable to scenarios where a radar system is used to monitor an area, for example, to identify moving objects based on range-Doppler maps of time interval sequences. Some of these moving objects may be swaying objects such as grass, trees, poles, etc., due to wind, and these swaying objects are generally of little interest for monitoring purposes; therefore, it is of interest to identify these swaying objects and the associated radar data. The identified swaying objects and associated radar data can be used to avoid visualizing such swaying objects to the user, so as to avoid distracting the user when such swaying objects are of little or no interest to them. Additionally or alternatively, such radar data can be excluded from further processing in the monitoring system in order to reduce the computational load in the monitoring system.

[0034] A swaying object is an object that moves left and right and / or forward and backward relative to the radar.

[0035] A radar system is a type of radar capable of determining the velocity of an object detected by the radar device. For example, a radar system could be a frequency-modulated continuous wave (FMCW) radar that uses a short transmitted signal (chirp) whose frequency varies over time, typically increasing or decreasing gradually. As another example, a radar could be a phase-modulated continuous wave (PMCW) radar device.

[0036] A radar system is further capable of determining the type of direction vector from the radar device of the radar system to the object being detected by the radar. For example, the radar can be a multiple-input multiple-output (MIMO) radar device.

[0037] A range-Doppler map for a time interval is a two-dimensional matrix of radar data, presented as energy values ​​reflected from objects at different distances (radial distances) along a first axis (dimension), such as the y-axis, and having different radial velocities along a second axis (dimension), such as the x-axis. More specifically, for each range interval in a sequence of consecutive range intervals along the first axis, such as from 0 to the maximum distance, energy values ​​are provided for each velocity interval in a sequence of consecutive velocity intervals, such as from the maximum negative velocity to the maximum positive velocity. For example, the maximum negative velocity and the maximum positive velocity have the same absolute velocity. Regarding the range-Doppler map, the velocity intervals within a range interval can be represented as “bins,” and zero velocity can be represented as “DC Doppler.” A range interval is an interval from lower to higher distances. Similarly, a velocity interval is an interval from lower to higher velocities. Therefore, the energy value of a velocity interval at a range interval is related to all velocities from lower to higher velocities within all distances from lower to higher distances in that range interval.

[0038] Furthermore, the energy value is the signal value in the range-Doppler graph. Therefore, the energy value of the velocity interval at the range interval is related to the signal values ​​detected for all velocities in that velocity interval at all distances within that range interval.

[0039] Since swaying objects are identified based on range-Doppler images, only swaying objects with a swaying component in the radial direction relative to the radar will be identified. On the other hand, swaying objects that do not have any radial component of swaying motion in the range-Doppler image are considered static objects and therefore will not result in any detection. For example, for FMWC radar, each time interval may correspond to a radar frame and is typically 10 ms.

[0040] Now we will combine Figure 1a and Figure 1bThe flowchart describes an embodiment of a method 100 for determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler maps provided by a radar system. Each range-Doppler map in the multiple range-Doppler maps corresponds to a time interval i in a time interval sequence. For example, the time interval sequence can be a sequence of N time intervals prior to the current time, where N is chosen to be high enough to enable identification of swaying objects in their presence. Preferably, the time intervals should have the same length. Furthermore, the time intervals can be arranged such that the start of each time interval directly follows the end of the previous time interval in the time interval sequence. Alternatively, the start of each time interval can follow an intermediate time after the end of the previous time interval in the time interval sequence. In the latter case, the intermediate times between time intervals in the sequence should have equal lengths.

[0041] Each range-Doppler plot includes the corresponding energy values ​​for multiple velocity intervals within each of multiple range intervals. The velocity intervals within each range interval can be, for example, a continuous velocity interval from a negative velocity with the maximum absolute velocity to a positive velocity with the maximum absolute velocity. Figure 2 An example of a range-Doppler plot is shown, featuring velocity intervals (Doppler cells) along the horizontal axis and range intervals (range cells) along the vertical axis. The energy value of the velocity interval at each range interval is indicated, such that higher energy values ​​within the velocity interval are indicated by brighter white. A brighter velocity interval at zero velocity indicates an object with no radial velocity relative to the radar. A brighter velocity interval to the left of zero velocity indicates an object with a negative radial velocity relative to the radar, and a brighter velocity interval to the right of zero velocity indicates an object with a positive radial velocity relative to the radar.

[0042] Method 100 is executed for each distance interval to determine whether one or more swaying objects exist within that distance interval. To determine whether one or more swaying objects exist in other distance intervals, method 100 is repeated for those intervals. Below, speed intervals with positive velocities will be denoted as positive speed intervals, and speed intervals with negative velocities will be denoted as negative speed intervals.

[0043] Method 100 includes calculating a difference sequence of time intervals S120 (i = 1 to N). Starting from the first time interval (i = 1) S110, the difference of S120 is calculated based on the distance-Doppler plot corresponding to the first time interval (i = 1). The calculated difference is the difference between a statistical measurement of the energy values ​​of a set of positive velocity intervals within the distance interval and a statistical measurement of the energy values ​​of a set of negative velocity intervals within the distance interval.

[0044] The calculated statistical measure can be, for example, standard deviation, variance, mean, median, or sum of squares. Preferably, a second-order or higher-order statistical measure is used.

[0045] When calculating the difference for each time interval i in S120, a set of positive velocity intervals can consist entirely of positive velocity intervals, and a set of negative velocity intervals can consist entirely of negative velocity intervals. However, to reduce the required computation, the set of positive velocity intervals can be only a subset of all positive velocity intervals, and the set of negative velocity intervals can be only a subset of negative velocity intervals. For example, a subset of all positive velocity intervals can be all or a subset of positive velocity intervals with an absolute velocity less than a second velocity threshold, and a subset of all negative velocity intervals can be all or a subset of negative velocity intervals with an absolute velocity less than the second velocity threshold. The second velocity threshold can be selected based on the expected maximum absolute velocity of the oscillating object. If the expected oscillating object always has an absolute velocity lower than the maximum absolute velocity, the second velocity threshold can be set to the maximum absolute velocity, because the expected oscillating object does not contribute to the energy values ​​of the positive and negative velocity intervals when its absolute velocity is greater than the expected maximum absolute velocity. The second velocity threshold can also be set to a value lower than the maximum absolute velocity expected for the swinging object, as this will include at least some velocity intervals in the velocity intervals that the swinging object will contribute to the energy values ​​of at least some of the distance-Doppler graphs in the distance-Doppler graph. This set of positive intervals can also be a subset of positive velocity intervals, such as every other positive velocity interval or every two positive velocity intervals, or other alternatives, and this set of negative velocity intervals can also be a subset of negative velocity intervals, such as every other negative velocity interval or every two negative velocity intervals, or other alternatives.

[0046] As long as the number of the next time interval is not higher than the total number of time intervals (i>N)C128, the difference of each next time interval (i=i+1)S125 is repeated and calculated in S120. Under the condition that the next time interval is higher than the total number of time intervals (i>N)C128, the difference sequence of the time intervals (i=1 to N) has been calculated.

[0047] Go to Figure 3a The figure shows the difference sequence of statistical measurements of the standard deviation of energy values ​​for a set of positive velocity intervals and the difference of energy values ​​for a set of negative velocity intervals within a range interval, each with a corresponding frame number and associated with a corresponding time interval in the time interval sequence. As can be seen in the figure, the difference in standard deviation alternates between positive and negative values. This indicates the presence of alternating motion relative to the radar in the positive and negative radial directions within the range interval. This alternating motion relative to the radar in the positive and negative radial directions would be, for example, the swaying motion of an object at the range interval.

[0048] Return to Figure 1a Then, method 100 continues to determine the spectrum of the calculated difference sequence of the S130 time interval sequence. In this spectrum, the amplitude at each frequency is given based on the difference sequence calculated for the time interval sequence. In this graph, the amplitude peak associated with the difference at a certain frequency indicates the oscillation of the difference at that frequency. This amplitude may also be referred to as the oscillation.

[0049] The spectrum can be computed by a transformation to the frequency domain (e.g., by performing a Fast Fourier Transform (FFT) on the difference sequence). For example, the spectrum computed by the FFT can be plotted as a graph with frequencies along a first axis (e.g., the x-axis) and amplitudes of the transformed values ​​along a second axis (e.g., the y-axis). In such a graph, the peak of the amplitude at a certain frequency indicates the oscillation of the difference at that frequency.

[0050] Under condition C140, where a peak exists in the spectrum for frequencies above a frequency threshold, it is determined that S145 indicates the presence of one or more swaying objects at a distance interval.

[0051] If the amplitude at a frequency related to the noise level of the spectrum is higher than a threshold—that is, if the signal-to-noise ratio (SNR) at that frequency is higher than a threshold—then a peak exists at that frequency in the spectrum. The noise level in the spectrum can be determined based on the amplitude of each frequency. For example, the noise level can be determined as the median of the amplitudes across all frequencies. In an embodiment where the spectrum is calculated using an FFT, the amplitude at each frequency is the transformed value of the amplitude at that frequency.

[0052] Go to Figure 3b , showing Figure 3a The graph is a plot of the difference between the FFT values. In this plot, a peak at approximately 1 Hz is shown corresponding to one or more rocking objects.

[0053] Return to Figure 1a Under the condition C140, where there are no peaks in the spectrum for frequencies above the frequency threshold, it is determined that there are no swaying objects at the distance interval in S148.

[0054] Once it is determined in S145 that one or more swaying objects exist within the distance interval, further processing of the energy values ​​of the velocity interval at the distance interval can be modified, for example, to reduce computational load and / or reduce visualization clutter in the monitoring system. For example, energy values ​​identified or assumed to be associated with one or more swaying objects can be identified and optionally filtered out from further processing, i.e., removed, for example, so that they are not used for object detection, visualization in the monitoring system, object tracking, object type identification, etc.

[0055] For example, go to Figure 1bUnder the condition C150 where one or more swaying objects exist at a distance interval, any detection in a speed interval with an absolute velocity less than a first speed threshold can be filtered out S158.

[0056] Detection here typically refers to the energy value within a velocity interval at a given distance interval being considered relevant to an object. For example, this can be determined based on an energy value exceeding an energy threshold, which in this context generally means that the energy value is considered sufficiently high to be relevant to the object. For instance, the energy threshold can be based on noise levels, and an energy value exceeding the energy threshold can mean that the signal-to-noise ratio (SNR) of the energy value exceeds the SNR threshold. The energy threshold (SNR threshold) can vary for different velocity intervals, and the energy threshold (SNR threshold) for one velocity interval can depend on the energy values ​​of other velocity intervals. The energy threshold (SNR threshold) can be selected such that the probability of a moving object resulting in detection is higher than the desired detection probability, and the probability of false detection is lower than the desired false detection probability. Typically, detection identification is performed across all velocity intervals within the distance interval, ensuring that any further processing in the monitoring system and any visualization to the user is based on the detection.

[0057] The first velocity threshold can be a fixed threshold. The fixed first velocity threshold can be set based on the maximum expected speed at which a swaying object will move while swaying. More specifically, the fixed first velocity threshold can be set without considering a specific distance-Doppler map (based on which one or more swaying objects are determined within a distance interval). For example, the fixed first velocity can be set to the maximum expected speed at which a swaying object will move while swaying. The fixed first velocity threshold can be set to a value such that it is equal to the maximum expected speed at which all types of swaying objects will move while swaying. Alternatively, a corresponding maximum expected speed at which each type of swaying object will move while swaying can be determined. The fixed first velocity threshold can then be set to a value such that it is equal to the highest of the maximum speeds of all types of swaying objects present in the monitored area.

[0058] In addition to the condition C150 that determines the presence of a swaying object at the distance interval, a further condition C155 may need to be met to ensure that there are no peaks in the spectrum for frequencies below a frequency threshold, in order to perform the step of filtering out the energy values ​​of velocity intervals with absolute velocities less than a first velocity threshold from among the multiple velocity intervals within the distance interval in S158. This further condition is included because peaks in the spectrum for frequencies below the frequency threshold indicate the presence of at least one moving object within the distance interval that is not a swaying object. Therefore, filtering out detections within the distance interval may risk filtering out detections associated with at least one moving object at the distance interval that is not a potentially undesirable swaying object. Therefore, filtering is performed only if the further condition C155 that there are no peaks in the spectrum for frequencies below the frequency threshold is also met.

[0059] Detections within multiple velocity intervals (denoted as protective chambers) can be filtered out based on DC Doppler across all distance intervals to remove detections associated with static objects. When one or more swaying objects are determined to exist within a distance interval, rather than a distance interval where one or more swaying objects are determined to be absent, a larger number of velocity intervals (i.e., all velocity intervals with absolute velocities less than a first velocity threshold) will typically be filtered out. Therefore, filtering out any detections in velocity intervals with absolute velocities less than the first velocity threshold within the multiple velocity intervals of the S158 distance interval can also be considered as increasing the number of protective chambers around the DC Doppler for that distance interval.

[0060] The first velocity threshold can be further set by considering a specific distance-Doppler graph, based on which one or more swaying objects are determined within the distance interval.

[0061] In one embodiment, when it is determined that one or more swaying objects exist at a distance interval, at least a subset of multiple distance-Doppler graphs is used to determine a first velocity threshold for that distance interval. Energy values ​​are then aggregated over the at least subset of the multiple distance-Doppler graphs. Specifically, for each velocity interval at that distance interval, the energy values ​​of the at least subset of the multiple distance-Doppler graphs are aggregated based on an aggregation function. This results in an aggregated energy value being derived for each velocity interval at that distance interval. The aggregation function can be, for example, a mean, the number of times an energy value exceeds an energy threshold, etc. The aggregated energy values ​​of the velocity intervals at that distance interval are then examined to identify the maximum absolute velocity such that there exists at least one positive velocity interval with a maximum absolute velocity and an aggregated energy value exceeding the aggregated energy threshold, and at least one negative velocity interval with the maximum absolute velocity and an aggregated energy value exceeding the aggregated energy threshold. If the aggregation function is a mean function, the aggregated energy value of the velocity intervals is the average energy value of the velocity intervals over the at least subset of the multiple distance-Doppler graphs. Then, the aggregated energy value of a velocity interval exceeding the aggregated energy threshold can mean that the signal-to-noise ratio of the mean energy value of the velocity interval on at least a subset of multiple range-Doppler maps exceeds the SNR threshold. If the aggregation function is a count of the number of range-Doppler maps on at least a subset of the range-Doppler maps where the energy value of the velocity interval exceeds the energy threshold, then the aggregated energy value of the velocity interval is the count value of the velocity interval. Then, the energy value of a velocity interval exceeding the velocity interval energy threshold can mean that the signal-to-noise ratio of the energy value of the velocity interval exceeds the SNR threshold. Then, the aggregated energy value of a velocity interval exceeding the aggregated energy threshold means that the count of the velocity intervals exceeds the count threshold. This can be achieved, for example, by checking the aggregated energy values ​​of positive velocity intervals to identify positive velocity intervals where the aggregated energy value exceeds the aggregated energy threshold and checking the aggregated energy values ​​of negative velocity intervals to identify negative velocity intervals where the aggregated energy value exceeds the aggregated energy threshold. Then, the maximum absolute velocity is identified such that both positive and negative velocity intervals where the aggregated energy value exceeds the aggregated energy threshold exist. Then, a first velocity threshold can be set, for example, based on this maximum absolute velocity. This embodiment is based on the assumption that one or more swaying objects have the same or similar maximum positive and negative velocities during the swaying process. At least a subset of multiple range-Doppler images is selected based on the lowest expected frequency of the object's swaying. For example, if the number of range-Doppler images per second is 10, and it should be possible to determine a first velocity threshold for an object swaying at 1 Hz, then the subset of multiple range-Doppler images should cover a time range of at least one second, i.e., one cycle of the swaying. For example, 10 consecutive range-Doppler images could be selected for this subset. Depending on the number of range-Doppler images per second and the lowest frequency at which it should be possible to determine the first velocity threshold, not all consecutive range-Doppler images are required.Conversely, subsets such as every other distance-Doppler plot, every two distance-Doppler plots, or other subsets can be used. By selecting multiple subsets of distance-Doppler plots based on the lowest frequency of the expected object's swaying, it can be ensured that the distance-Doppler plots cover at least one cycle of the lowest frequency, such that the swaying object at the lowest frequency will have its highest positive and highest negative velocities within the subsets of multiple distance-Doppler plots. The time covered and the number of distance-Doppler plots selected can further depend on the aggregation function used.

[0062] In another embodiment, when it is determined that one or more swaying objects exist at distance intervals, the velocity intervals within multiple velocity intervals in each distance-Doppler plot are divided into multiple groups based on their absolute velocities. Therefore, each group of velocity intervals will include both positive and negative velocity intervals. These groups are ordered such that the velocity intervals in higher-order groups have larger absolute velocities than the velocity intervals in lower-order groups. In other words, the positive axis is divided into n positive intervals. Furthermore, the negative axis is divided into n negative intervals that are mirror images of the positive intervals around zero Doppler. Each positive interval includes multiple positive velocity intervals, and each negative interval includes multiple corresponding negative velocity intervals. Therefore, the group of velocity intervals in sequence k is a positive interval. and negative interval Yes. Then, multiple groups are processed sequentially by performing the following actions on the current group: calculating the difference sequence of velocity intervals in the group, determining the spectrum of the calculated difference sequence, and continuing to process the next group in the sequence if there is a peak in the spectrum for frequencies above a frequency threshold. The difference sequence of velocity intervals in the group is calculated as follows: for each time interval in the time interval sequence, the difference between the statistical measurement of the energy value of the velocity interval with positive velocity in the group of velocity intervals within the distance interval and the statistical measurement of the energy value of the velocity interval with negative velocity in the group of velocity intervals within the distance interval is calculated based on the distance-Doppler plot corresponding to the time interval. This calculation continues until, for the current group of velocity intervals, the condition that there is no peak in the spectrum for frequencies above a frequency threshold is met. Then, the first velocity threshold is set to a value corresponding to the maximum absolute velocity of the velocity interval in the previous group in the sequence, for example, equal to the maximum absolute velocity. This embodiment is based on a subset of the steps of a method for determining the presence of one or more swaying objects at a distance interval using each velocity interval in a group of velocity intervals at a distance interval. By performing these steps on the groups in ascending order, that is, in order of increasing absolute velocity, the last group in that order where a peak exists in the spectrum for frequencies above a frequency threshold can be identified. In other words, for each group (i.e., interval...) The processing is performed in ascending order until the first group is found, for which there are no peaks in the spectrum for frequencies above the frequency threshold. Therefore, the last group with peaks in the spectrum for frequencies above the frequency threshold is the group that appears just below in the order. Since peaks in the spectrum for frequencies above the frequency threshold indicate the presence of one or more swaying objects, this is the group that determines the velocity interval with the highest absolute velocity where one or more swaying objects exist. In this embodiment, the statistical measurement used to determine the first velocity threshold can be, for example, one of the following: standard deviation, variance, mean, median, and sum of squares. Furthermore, it can be combined with the above... Figure 1a The statistical measures used in the calculation action S210 for each time interval in the time interval sequence in the described method 100 may be the same or different.

[0063] Figure 4 A block diagram is shown relating to an embodiment of an apparatus for determining the presence of one or more swaying objects within a range interval based on multiple range-Doppler images provided by a radar system. Each range-Doppler image corresponds to a time interval in a time interval sequence and includes corresponding energy values ​​for multiple velocity intervals within each of the multiple range intervals. The apparatus 400 may, for example, be included in a radar system.

[0064] Device 400 includes circuitry 410. Circuitry 410 is configured to perform the functions of image processing system 400. Circuitry 410 may include processor 412, such as a central processing unit (CPU), graphics processing unit (GPU), tensor processing unit (TPU), microcontroller, or microprocessor. Processor 412 is configured to execute program code. The program code may, for example, be configured to perform the functions of device 400.

[0065] Device 400 may further include memory 420. Memory 420 may be one or more of a buffer, flash memory, hard disk drive, removable media, volatile memory, non-volatile memory, random access memory (RAM), and other suitable devices. In a typical arrangement, memory 420 may include non-volatile memory for long-term data storage and volatile memory used as device memory for circuit 410. Memory 420 may exchange data with circuit 410 via a data bus. Additional control lines and address buses may also exist between memory 420 and circuit 410.

[0066] The functionality of device 400 can be implemented as an executable logic program (e.g., lines of code, software program, etc.) stored on a non-transitory computer-readable medium (e.g., memory 420) of device 400 and executed by circuitry 410 (e.g., using processor 412). Furthermore, the functionality of device 400 can be a standalone software application or part of a software application that performs additional tasks associated with device 400. The described functionality can be considered as a method configured to be executed by a processing unit (e.g., processor 410 of circuitry 412). Moreover, although the described functionality can be implemented in software, it can also be executed via dedicated hardware or firmware, or a combination of hardware, firmware, and / or software.

[0067] Circuit 410 is configured to perform calculation function 431, first determination function 433, and second determination function 433. Circuit 410 is further optionally configured to perform filtering function 434 and setting function 435.

[0068] The calculation function 431 is configured to, for each time interval in the time interval sequence, calculate, based on the distance-Doppler graph corresponding to that time interval, the difference between a statistical measurement of the energy value of a set of velocity intervals with positive velocity among the multiple velocity intervals within the distance interval and a statistical measurement of the energy value of a set of velocity intervals with negative velocity among the multiple velocity intervals within the distance interval.

[0069] The first determining function 432 is configured to determine the spectrum of the calculated difference sequence.

[0070] The second determination function 433 is configured to determine the presence of one or more swinging objects at a distance interval, provided that a peak exists in the spectrum for frequencies above a frequency threshold.

[0071] Circuit 410 may be further configured to perform filtering function 434. Filtering function 434 is configured to filter out any detections in a velocity interval having an absolute velocity less than a first velocity threshold from a plurality of velocity intervals within the distance interval, provided that a swaying object is determined to exist at the distance interval.

[0072] The filtering function 434 can be further configured to filter out the energy values ​​of velocity intervals with absolute velocities less than a first velocity threshold from among multiple velocity intervals within the distance interval, under the further condition that there are no peaks in the spectrum for frequencies below a frequency threshold.

[0073] The first speed threshold can be fixed.

[0074] Circuit 410 may be further configured to perform setting function 435, which is configured to, for each speed interval at a distance interval, aggregate the energy values ​​of at least a subset of multiple range-Doppler maps based on an aggregation function, thereby deriving an aggregated energy value for each speed interval at a distance interval, identify the maximum absolute speed of a speed interval with a maximum absolute speed and an aggregated energy value exceeding an aggregated energy threshold among the multiple speed intervals within the distance interval, and a speed interval with a positive speed and a speed interval with a negative speed, and set a first speed threshold based on the maximum absolute speed.

[0075] Alternatively, setting function 435 can be configured to: divide velocity intervals within multiple velocity intervals in each range-Doppler chart of multiple range-Doppler charts into multiple groups based on their absolute velocity, wherein these groups are ordered such that velocity intervals in higher-order groups have larger absolute velocities than velocity intervals in lower-order groups; process the multiple groups sequentially by the following steps: for the currently processed group: for each time interval in the time interval sequence, calculate the difference between a statistical measurement of the energy value of the velocity interval with positive velocity in the group of velocity intervals within the range interval and a statistical measurement of the energy value of the velocity interval with negative velocity in the group of velocity intervals within the range interval, based on the range-Doppler chart corresponding to the time interval, thereby calculating a difference sequence of the time interval sequence; determine the spectrum of the calculated difference sequence of the time interval sequence; and, if there is a peak in the spectrum for frequencies above a frequency threshold, proceed to the next group in the sequence, and if there is no peak in the spectrum for frequencies above a frequency threshold, set a first velocity threshold to a value corresponding to the maximum absolute velocity of the velocity interval in the previous group in the sequence.

[0076] In the first determining function 432, the difference between the statistical measurement of the energy value of a set of velocity intervals with positive velocity and absolute velocity less than the second velocity threshold within the distance interval and the statistical measurement of the energy value of a set of velocity intervals with negative velocity and absolute velocity less than the second velocity threshold within the distance interval can be calculated.

[0077] Statistical measurements can be one of the following: standard deviation, variance, mean, median, and sum of squares.

[0078] The above text combines Figure 1a and Figure 1b The detailed description of the actions of method 100 also applies to the corresponding functions of device 400. Furthermore, where appropriate, the above description is combined with... Figure 1a and Figure 1b The optional additional features of the described method 100 also apply to the corresponding optional additional features of the device 400.

[0079] Those skilled in the art will recognize that the present invention is not limited to the embodiments described above. Instead, many modifications and variations can be made within the scope of the appended claims. These modifications and variations can be understood and implemented by those skilled in the art in practicing the claimed invention through a study of the drawings, the disclosure, and the appended claims.

Claims

1. A method for determining the presence of one or more swaying objects within a range interval in a plurality of range intervals based on multiple range-Doppler maps provided by a radar system, wherein, Each of the plurality of range-Doppler maps corresponds to a time interval in a time interval sequence, and includes corresponding energy values ​​for multiple velocity intervals within each of the plurality of range intervals, the method comprising: For each time interval in the time interval sequence, the difference between the statistical measurement of the energy values ​​of a set of velocity intervals with positive velocities within the plurality of velocity intervals within the distance interval and the statistical measurement of the energy values ​​of a set of velocity intervals with negative velocities within the plurality of velocity intervals within the distance interval is calculated based on the distance-Doppler plot corresponding to the time interval, thereby calculating the difference sequence of the time interval sequence. Determine the spectrum of the calculated difference sequence of the time interval sequence; and Given that there is a peak in the spectrum for frequencies above a frequency threshold, it is determined that one or more swaying objects exist at the distance interval.

2. The method according to claim 1, further comprising: If it is determined that one or more swaying objects exist at the distance interval, any detections in the velocity intervals with an absolute velocity less than a first velocity threshold are filtered out from the plurality of velocity intervals within the distance interval.

3. The method according to claim 1, further comprising: If it is determined that one or more swaying objects exist at the distance interval and there are no peaks in the spectrum for frequencies below the frequency threshold, then any detections in the velocity intervals within the plurality of velocity intervals that have an absolute velocity less than a first velocity threshold are filtered out.

4. The method according to claim 2, wherein, The first speed threshold is fixed.

5. The method of claim 2, further comprising: For each velocity interval at the distance interval, the energy values ​​of at least a subset of the plurality of distance-Doppler maps are aggregated based on an aggregation function to derive the aggregated energy value for each velocity interval at the distance interval; Among the plurality of velocity intervals within the distance interval, identify the maximum absolute velocity, which includes velocity intervals with positive velocities and velocity intervals with negative velocities, such that there exists a velocity interval with a maximum absolute velocity and a polymerization energy value exceeding a polymerization energy threshold; and The first speed threshold is set based on the maximum absolute speed.

6. The method of claim 2, further comprising: Based on their absolute velocities, the velocity intervals within the multiple velocity intervals of each distance-Doppler map within the multiple distance-Doppler maps are divided into multiple groups, wherein the groups are ordered such that the velocity intervals in higher-order groups have larger absolute velocities than the velocity intervals in lower-order groups. The multiple groups are processed sequentially using the following steps: For the currently processed group: For each time interval in the time interval sequence, the difference between the statistical measurement of the energy value of the velocity interval with positive velocity in the group of velocity intervals within the distance interval and the statistical measurement of the energy value of the velocity interval with negative velocity in the group of velocity intervals within the distance interval is calculated based on the distance-Doppler plot corresponding to the time interval, thereby calculating the difference sequence of the time interval sequence; Determine the spectrum of the calculated difference sequence of the time interval sequence; and If a peak exists in the spectrum for frequencies above the stated frequency threshold, proceed to the next group in the processing sequence. If there are no peaks in the spectrum for frequencies above the frequency threshold, the first speed threshold is set to a value corresponding to the maximum absolute speed of the speed interval in the previous group of the sequence.

7. The method according to claim 1, wherein, In the operation of calculating the difference, the difference is calculated between the statistical measurement of the energy value of a set of velocity intervals with positive velocity and absolute velocity less than the second velocity threshold within the distance interval and the statistical measurement of the energy value of a set of velocity intervals with negative velocity and absolute velocity less than the second velocity threshold within the distance interval.

8. The method according to claim 1, wherein, The statistical measure is one of the following: standard deviation, variance, mean, median, and sum of squares.

9. A non-transitory computer-readable storage medium having instructions stored thereon, the instructions causing the apparatus to perform the method according to claim 1 when executed in a processing-capable device.

10. An apparatus for determining the presence of one or more swaying objects within a range interval in a plurality of range intervals based on a plurality of range-Doppler images provided by a radar system, wherein, Each of the plurality of range-Doppler maps corresponds to a time interval in a time interval sequence and includes corresponding energy values ​​for multiple velocity intervals within each of the plurality of range intervals. The device includes circuitry configured to perform: The calculation function is configured to, for each time interval in the time interval sequence, calculate, based on the distance-Doppler plot corresponding to the time interval, the difference between a statistical measurement of the energy value of a set of velocity intervals with positive velocity among the plurality of velocity intervals within the distance interval and a statistical measurement of the energy value of a set of velocity intervals with negative velocity among the plurality of velocity intervals within the distance interval; The first determining function is configured to determine the spectrum of the computed difference sequence; as well as The second determination function is configured to determine the presence of one or more swaying objects at the distance interval if a peak exists in the spectrum for frequencies above a frequency threshold.

11. The apparatus according to claim 10, wherein, The circuit is further configured to perform: The filtering function is configured to: upon determining that a swaying object exists at the distance interval, filter out any detections in the velocity intervals within the plurality of velocity intervals that have an absolute velocity less than a first velocity threshold.

12. The apparatus according to claim 10, wherein, The circuit is further configured to perform: The filtering function is configured to: filter out any detections in the velocity intervals within the plurality of velocity intervals that have an absolute velocity less than a first velocity threshold, provided that a swaying object is determined to exist at the distance interval and there are no peaks in the spectrum for frequencies below the frequency threshold.

13. The apparatus according to claim 11, wherein, The first speed threshold is fixed.

14. The apparatus according to claim 11, wherein, The circuit is further configured to perform: The settings function is configured as follows: For each velocity interval at the stated distance interval, the energy values ​​of at least a subset of the multiple range-Doppler maps are aggregated based on an aggregation function, thereby deriving the aggregated energy value for each velocity interval at the stated distance interval. Among the plurality of velocity intervals within the distance interval, the maximum absolute velocity is identified such that there exists a velocity interval with a positive velocity and a velocity interval with a negative velocity, which have a maximum absolute velocity and a polymerization energy value exceeding the polymerization energy threshold. The first speed threshold is set based on the maximum absolute speed.

15. The apparatus according to claim 11, wherein, The circuit is further configured to perform: The settings function is configured as follows: Based on their absolute velocities, the velocity intervals within the multiple velocity intervals of each distance-Doppler map within the multiple distance-Doppler maps are divided into multiple groups, wherein the groups are ordered such that the velocity intervals in higher-order groups have larger absolute velocities than the velocity intervals in lower-order groups. The multiple groups are processed sequentially using the following steps: For the currently processed group: For each time interval in the time interval sequence, the difference between the statistical measurement of the energy value of the velocity interval with positive velocity in that group of velocity intervals within the distance interval and the statistical measurement of the energy value of the velocity interval with negative velocity in that group of velocity intervals within the distance interval is calculated based on the distance-Doppler plot corresponding to the time interval, thereby calculating the difference sequence of the time interval sequence. Determine the spectrum of the calculated difference sequence of the time interval sequence, and If a peak exists in the spectrum for frequencies above the stated frequency threshold, proceed to the next group in the processing sequence. If there are no peaks in the spectrum for frequencies above the frequency threshold, the first speed threshold is set to a value corresponding to the maximum absolute speed of the speed interval in the previous group of the sequence.

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