Patent ID: 12216193

DETAILED DESCRIPTION

The above-described aspects and other aspects are embodied through embodiments described below with reference to the accompanying drawings. It will be understood that components of each of the embodiments may be combined in various ways within one embodiment unless otherwise stated or contradicted by one another. Each of blocks in a block diagram may be a representation of a physical part in some cases but may be a logical representation of a portion of a function of one physical part or a function of a plurality of physical parts in other cases. In some cases, the block or an entry of a portion of the block may be a set of program instructions. All or some of the blocks may be implemented as hardware, software, or a combination thereof.

FIG.1illustrates an example of a related art in which a Doppler velocity of a target is obtained with a single radar. A radar shown inFIG.1may process a signal reflected by a target to obtain a position of the target, a Doppler velocity, and the like. Unlike a single channel radar that can only obtain a radial distance to a target, the radar shown inFIG.1may have a multi-channel to obtain an angular component and may calculate a position of a target as coordinates on a corresponding radar coordinate system using a distance to the target and the angular component. In addition, the radar shown inFIG.1may obtain a Doppler velocity. However, with the radar ofFIG.1, the Doppler velocity is obtained in a direction away from or toward the radar. Accordingly, when the target ofFIG.1moves while maintaining a distance from the radar, the radar ofFIG.1does not detect movement of the target well. This is because, even though the radar ofFIG.1is a multi-channel radar, when a size of a radar device is taken into consideration, an interval between receiving antennas is extremely narrow, and thus directions of Doppler velocities are almost the same for each channel. Therefore, in a method of detecting a target using the single radar ofFIG.1, since the radar can only detect movement in a direction of the radar in relation to target tracking and cannot detect movement in a direction horizontal to the radar, a separate prediction model for horizontal movement should be used to predict movement of a target.

FIG.2illustrates an example in which a Doppler velocity of a target is obtained with multiple radars. As shown inFIG.2, by using two radars, movement of a target may be accurately predicted using a Doppler velocity of the target obtained by each radar. That is, a Doppler velocity of a target in a direction of a first radar may be obtained through the first radar, a Doppler velocity of the target in a direction of the second radar may be obtained through the second radar, and then, a velocity vector of the target may be obtained using the two Doppler velocities. Like that shown inFIG.1, the first radar and the second radar shown inFIG.2are also multi-channel radars. Unlike the example ofFIG.1, after a measurement value through the second radar is transformed to a second radar coordinate system, movement of the target in a direction parallel to the first radar can be accurately detected based on the first radar. In addition, when a method ofFIG.2is used, it is possible to detect movement of a target of which a direction is changed irregularly.

Therefore, since a method of a detecting a target using the multiple radars as shown inFIG.2can also detect movement in a direction horizontal to a radar in relation to target tracking, in order to predict movement of a target, there is no need to use a separate prediction model for horizontal movement.

FIG.3is a block diagram of an apparatus for detecting a target according to the present invention. As shown inFIG.3, an apparatus10for detecting a target using a radar according to an aspect of the present invention includes a first radar100_1, a second radar100_2, a position information combination unit110, and a velocity vector information calculation unit120.

The first radar100_1is a multi-channel radar including a plurality of transmitting antennas and a plurality of receiving antennas. The first radar100_1may be a frequency modulated continuous wave (FMCW) radar.

The FMCW radar calculates a distance to a target and a Doppler velocity of the target from a beat frequency obtained from a transmission signal transmitted by being linearly frequency-modulated and a reception signal received when the transmission signal is reflected by the target.

FIG.4is a block diagram of an FMCW radar usable in an apparatus for detecting a target according to the present invention. The block diagram shown inFIG.4is a block diagram of a general FMCW radar, and each component will be briefly described. A voltage-controlled oscillator (VCO) generates and outputs an oscillation signal of which a frequency is linearly modulated, and a power amplifier PA amplifies a signal excluding noise and then transmits a radar signal through a transmitting antenna. Then, a low-noise amplifier LNA amplifies a signal received through a receiving antenna, and a frequency mixer mixes the amplified signal with an output signal of the VCO to generate a mixed signal that is to be used to generate a beat frequency signal. A low-pass filter (LPF) filters only a signal in a low frequency band of a signal output from the frequency mixer and removes noise of a high-frequency component thereof, and then, an analog-to-digital converter (ADC) converts the signal in the low frequency band into a digital signal. The converted digital signal is subjected to a first range fast Fourier transform (FFT) (range FFT), a second FFT (Doppler FFT), constant false alarm rate (CFAR) detection, and an angle component calculation (angle estimation) to calculate a distance, a velocity, and an angle of a target. A radar output ofFIG.4may be a set of distances, velocities, and angles of point clouds detected as a target or a set of coordinates (coordinates on a radar coordinate system) and velocities of the point clouds.

The first radar100_1processes a received signal and outputs first position information and first velocity information of a target. In this case, the first position information is a set of distances and angles of points detected as a target or a set of coordinates (coordinates on a radar coordinate system) of the points. The first velocity information is a set of Doppler velocities of points detected as a target.

Although a case in which the first radar100_1is the FMCW radar has been described, the present invention is not limited thereto, and the first radar100_1may be another type of radar.

The second radar100_2is also a multi-channel radar including a plurality of transmitting antennas and a plurality of receiving antennas. The second radar100_2may be an FMCW radar. However, the present invention is not limited thereto, and the second radar100_2may be another type of radar. The second radar100_2is installed to be spaced apart from the first radar100_1by a predetermined distance. The second radar100_2may be installed to be spaced apart from the first radar100_1by 50 cm or more.

In this case, the first radar100_1and the second radar100_2may be installed such that a surface on which the first radar100_1is installed and a surface on which the second radar100_2is installed form a predetermined inclination angle of θ. For the purpose of increasing a direction deviation between a Doppler velocity of a target obtained through the first radar100_1and a Doppler velocity obtained through the second radar100_2, the first radar100_1and the second radar100_2may be installed to be spaced apart from each other so as to form an inclination angle.

The second radar100_2processes a received signal to output second position information and second velocity information of a target. The second position information is also a set of distances and angles of points detected as a target or a set of coordinates (coordinates on a radar coordinate system) of the points. The second velocity information is also a set of Doppler velocities of points detected as a target.

The first radar100_1and the second radar100_2are multi-channel radars and detect one target as a plurality of points, that is, a point cloud. Since a target is generally an object having volume, the first radar100_1and the second radar100_2detect the same target as different point clouds due to a difference in installation positions thereof.

The position information combination unit110calculates combined position information of the target from the first position information and the second position information. The first position information is position information acquired by the first radar100_1and is position information on a first radar coordinate system. The second position information is position information acquired by the second radar100_2and is position information on a second radar coordinate system. Since the first position information and the second position information have different coordinate systems, a point cloud cannot be created by simply combining two pieces of position information.FIG.5is a diagram illustrating a concept in which the second radar coordinate system is transformed into the first radar coordinate system. As shown inFIG.5, the first radar100_1and the second radar100_2form an inclination angle of θ between installation surfaces thereof and are spaced apart from each other by xr along a horizontal axis and yr along a vertical axis. In the example ofFIG.5, the position information combination unit110rotates and transforms position information (x, y) acquired through the second radar100_2by θ ({circle around (1)}) and shifts and transforms the position information (x, y) in consideration of xr and yr which are distance differences between radar centers. That is, a target point at a position (x, y) based on second radar coordinates is reversely rotated by an angle between the two radars and transformed to obtained coordinates (xθ, yθ) (xθ=x sin θ+y cos θ, and yθ=x cos θ−y sin θ) and then obtain shifted and transformed coordinates (x′, y′) (x′=xr−xθ, and y′=yθ−yr). A target detected by the second radar100_2may be transformed to the first radar coordinate system, and a corresponding point may be a point detected by the first radar100_1or a point not detected by the first radar100_1.

When the first position information and the second position information are combined by the position information combination unit110, a point for a target detected by the second radar100_2is transformed to the first radar coordinate system and then is combined with a point for a target detected by the first radar100_1, thereby generating a point cloud. A point cloud generated by combining two coordinate systems may be a set of a target point detected by the first radar100_1and a target point detected by the second radar100_2, and some points may be points detected by both of two radars.

In the above-described example, coordinates are transformed to the first radar coordinate system, but of course, it is also possible to transform coordinates based on the second radar coordinate system.

The velocity vector information calculation unit120calculates velocity vector information of the target from the first velocity information and the second velocity information. The first velocity information is a Doppler velocity of the target detected by the first radar100_1, that is, a Doppler velocity in a direction toward or away from the first radar100_1, and is Doppler velocity information on the first radar coordinate system. The second velocity information is a Doppler velocity of the target detected by the second radar100_2, that is, a Doppler velocity in a direction toward or away from the second radar100_2, and is Doppler velocity information on the second radar coordination system. Movement of the target may be predicted using the first velocity information and the second velocity information. In this case, the second velocity information may be utilized by being transformed to the first coordinate system.FIG.6illustrates a velocity vector of a target being calculated using a Doppler velocity detected by the first radar100_1and a Doppler velocity detected by the second radar100_2. As shown inFIG.6, an actual velocity vector (vector3) of a target is calculated as a Doppler velocity vector (vector1) directed to the first radar100_1by the first radar100_1. In this case, since all vectors reaching a point on a straight line a from the target are calculated as the Doppler velocity vector (vector1) directed to the first radar100_1by the first radar100_1, an actual velocity of the target cannot be known only by the Doppler velocity calculated by the first radar100_1. In addition, the actual velocity vector (vector3) of the target may be calculated as a Doppler velocity vector (vector2) directed to the second radar100_2by the second radar100_2, and all vectors reaching a point on a straight line b from the target may be calculated as the Doppler velocity vector (vector2) directed to the second radar100_2by the second radar100_2. Accordingly, inversely, for the target, the actual velocity vector (vector3) can be obtained from the Doppler velocity (vector1) calculated by the first radar100_1and the Doppler velocity (vector2) calculated by the second radar100_2.

According to an additional aspect of the present invention, the apparatus10for detecting a target may further include a target detection unit130.

The target detection unit130may detect a target by clustering a point cloud of the target from combined position information of the target and velocity vector information of the target. The target detection unit130clusters points detected by the first radar100_1into groups of adjacent points and clusters points detected by the second radar100_2into groups of adjacent points. The position information combination unit110may transform a target position of the second radar100_2based on the first radar coordinate system to cluster points again on the first radar coordinate system. However, according to aspects of the present invention, a point cloud may be generated by first performing a coordinate transformation and then clustering points on the first radar coordinate system. In this case, as a clustering algorithm, a density based spatial clustering of application with a noise (DBSCAN) algorithm for calculating a Euclidean distance of adjacent points may be used, or other clustering algorithms may be used. In addition, the target detection unit130may accurately detect a target using velocity vector information of points calculated by the velocity vector information calculation unit120. For example, since two point clouds are adjacent, even when the two point clouds are detected as one point cloud in an Euclidean distance or the like (when two targets are actually adjacent), points clouds may be separated again into groups of points with pieces of velocity vector information of points which are the same or similar to each other.

In addition, the target detection unit130may detect a continuously tracked point cloud as an accurate target. That is, the target detection unit130may continuously track and remove a ghost target that appears temporarily and disappears.

According to an additional aspect of the present invention, the apparatus10for detecting a target may further include a target tracking unit140.

The target tracking unit140may track a target from combined position information of the detected target and velocity vector information of the target. The target tracking unit140may register a point cloud detected by the target detection unit130in a target candidate group and then may track the corresponding point cloud. The target tracking unit140may predict a next position of the target using the combined position information of the target and the velocity vector information of the target.

More specifically, the target tracking unit140may predict a position of movement of the target from the combined position information of the target detected in a previous frame and the velocity vector information of the target. The target tracking unit140may re-detect and track the target by clustering a point cloud of the target calculated from a currently input radar signal based on the predicted position. That is, the target tracking unit140re-detects the target by combining point clouds again using an algorithm such as a DBSCAN algorithm for points around the predicted position. Such a process is repeated until the target deviates from a designated region of interest (ROI).

FIG.7illustrates a concept in which a position of a target is predicted and the target is re-detected based on the predicted position. As shown inFIG.7, a position of a target is predicted using a velocity vector of the target from a previously detected position of the target, and the target is re-detected by performing clustering again based on the predicted position.

According to another aspect of the present invention, the number of radars used in the apparatus10for detecting a target may be increased to N (wherein N is a natural number greater than or equal to three). That is, the apparatus10for detecting a target may include N radars (wherein N is a natural number greater than or equal to three), and all of the radars may be multi-channel radars each including a plurality of transmitting antennas and a plurality of receiving antennas. In addition, the N radars (wherein N is a natural number greater than or equal to three) may be installed to be spaced apart from each other to output position information and velocity information of a target.

A position information combination unit110of the present aspect may calculate combined position information of a target from pieces of position information output by respective radars. A coordinate system of one radar may be set as a common coordinate system, and a separate global coordinate system may also be used as a common coordinate system.

A velocity vector information calculation unit120of the present aspect may calculate velocity vector information of the target from pieces of velocity information output by the respective radars.

A method of detecting a target according to one embodiment of an apparatus10for detecting a target of the present invention includes an operation of acquiring first position information and first velocity information of a target through a first radar100_1, an operation of acquiring second position information and second velocity information of the target through a second radar100_2installed to be spaced apart from the first radar100_1, an operation of calculating combined position information of the target from the first position information and the second position information, and an operation of calculating velocity vector information of the target from the first velocity information and the second velocity information. The first radar100_1and the second radar100_2may be multi-channel radars each including a plurality of transmitting antennas and a plurality of receiving antennas and may be FMCW radars.

The operation of acquiring the first position information and the first velocity information is an operation of processing a signal received through the first radar100_1and outputting the first position information and the first velocity information of the target. In this case, the first position information is a set of distances and angles of points detected as the target or a set of coordinates (coordinates on a radar coordinate system) of the points. The first velocity information is a set of Doppler velocities of points detected as the target.

The operation of acquiring the second position information and the second velocity information is an operation of outputting the second position information and the second velocity information through the second radar100_2installed to be spaced apart from the first radar100_1. The second position information is also a set of distances and angles of points detected as the target or a set of coordinates (coordinates on a radar coordinate system) of the points. The second velocity information is also a set of Doppler velocities of points detected as the target.

The first radar100_1and the second radar100_2are multi-channel radars and detect one target as a plurality of points, that is, a point cloud. Since a target is generally an object having volume, the first radar100_1and the second radar100_2detect the same target as different point clouds due to a difference in installation positions thereof.

The operation of calculating the combined position information of the target is an operation of calculating the combined position information of the target from the first position information and the second position information. The first position information is position information acquired by the first radar100_1and is position information on a first radar coordinate system, and the second position information is position information acquired by the second radar100_2and is position information on a second radar coordinate system. Since the first position information and the second position information have different coordinate systems, a point cloud cannot be created by simply combining two pieces of position information.FIG.15illustrates a concept in which the second radar coordinate system is transformed into the first radar coordinate system, and a description ofFIG.5is the same as that described above.

When the first position information and the second position information are combined through the operation of calculating the combined position information of the target, a point for the target detected by the second radar100_2is transformed to the first radar coordinate system and then is combined with a point for the target detected by the first radar100_1, thereby generating a point cloud. A point cloud generated by combining two coordinate systems may be a set of a target point detected by the first radar100_1and a target point detected by the second radar100_2, and some points may be points detected by both of two radars.

The operation of calculating the velocity vector information of the target is an operation of calculating the velocity vector information of the target from the first velocity information and the second velocity information. The first velocity information is a Doppler velocity of the target detected by the first radar100_1, that is, a Doppler velocity in a direction toward or away from the first radar100_1, and is Doppler velocity information on the first radar coordinate system. The second velocity information is a Doppler velocity of the target detected by the second radar100_2, that is, a Doppler velocity in a direction toward or away from the second radar100_2, and is Doppler velocity information on the second radar coordination system. Movement of the target may be predicted using the first velocity information and the second velocity information. In this case, the second velocity information may be utilized by being transformed to the first coordinate system.FIG.6illustrates a velocity vector of the target being calculated using the Doppler velocity detected by the first radar100_1and the Doppler velocity detected by the second radar100_2, and a description ofFIG.6is the same as that described above.

The method of detecting a target according to the present invention may further include an operation of clustering a point cloud of the target from the combined position information of the target and the velocity vector information of the target to detect the target.

The operation of detecting the target is an operation of clustering the point cloud of the target from the combined position information of the target and the velocity vector information of the target to detect the target. In the operation of detecting the target, points detected by the first radar100_1are clustered into groups of adjacent points, and points detected by the second radar100_2are clustered into groups of adjacent points. In the operation of detecting the target, a target position of the second radar100_2may be transformed based on the first radar coordinate system in the operation of calculating the combined position information of the target, and points may be clustered again on the first radar coordinate system. However, according to aspects of the present invention, a point cloud may be generated by first performing a coordinate transformation and then clustering points on the first radar coordinate system. In this case, as a clustering algorithm, a DBSCAN algorithm for calculating a Euclidean distance of adjacent points may be used, or other clustering algorithms may be used. In addition, in the operation of detecting the target, the target may be accurately detected using velocity vector information of points calculated through an operation of calculating a velocity vector of the target. For example, since two point clouds are adjacent, even when the two point clouds are detected as one point cloud in an Euclidean distance or the like (when two targets are actually adjacent), points clouds may be separated again into groups of points with pieces of velocity vector information of points which are the same or similar to each other.

In addition, in the operation of detecting the target, a continuously tracked point cloud may be detected as an accurate target. That is, in the operation of detecting the target, it is possible to continuously track and remove a ghost target that appears and disappears temporarily.

The method of detecting a target of the present invention may further include tracking the target from the combined position information of the target additionally detected and target velocity vector information of the target.

The operation of tracking the target is an operation of tracking the target from the combined position information of the detected target and the velocity vector information of the target. In the operation of the tracking the target, a point cloud detected in the operation of detecting the target may be registered in a target candidate group, and then, the corresponding point cloud may be tracked. In the operation of tracking the target, a next position of the target may be predicted using the combined position information of the target and the velocity vector information of the target.

Specifically, the operation of tracking the target may include an operation of predicting a position of movement of the target from the combined position information of the target previously detected and the velocity vector information of the target and an operation of clustering a point cloud based on the predicted position to re-detect and track the target. In the operation of tracking the target, for points around the predicted position, point clouds are combined again using an algorithm such as a DBSCAN algorithm to re-detect the target. Such a process is repeated until the target deviates from a ROI.

FIG.8is a flowchart of a method of detecting a target according to one embodiment of the present invention. Referring toFIG.8, an apparatus for detecting a target acquires first position information and first velocity information of a target through a first radar100_1(S8000) and acquires second position information and second velocity information of the target through a second radar100_2installed to be spaced apart from the first radar100_1(S8010). The apparatus10for detecting a target calculates combined position information of the target based on a first radar coordinate system from the first position information and the second position information (S8020) and calculates velocity vector information of the target from the first velocity information and the second velocity information (S8030). The apparatus10for detecting a target clusters a point cloud of the target from the combined position information and the velocity vector information of the target to detect the target (S8040), predicts next position of movement of the target using the combined position information and the velocity vector information of the target previously detected (S8050), and then clusters a point again based on the predicted position to re-detect and track the target (S8060). The tracking of the target is repeated until the target deviates from a ROI.

According to the present invention, velocity information of a target can be acquired as two-dimensional or more information to increase target detection precision, and a movement direction of the target can be predicted to increase target tracking performance.

Although the present invention has been described above using embodiments with reference to the accompanying drawings, the present invention is not limited thereto. The present invention should be interpreted as including various modified embodiments that may be evidently derived from the above embodiments by one of ordinary skill in the art. The claims below are intended to include such modified embodiments.