Patent Publication Number: US-2023140422-A1

Title: Radar self-calibration device and method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to self-calibration techniques, and more particularly, to a radar self-calibration device and method thereof. 
     2. Description of the Related Art 
     A vehicle radar is calibrated in advance before being installed on the vehicle body. However, when the vehicle radar is practically installed on the vehicle, due to the poor accuracy of the initial operation of the radar installation, reference axis of the radar deviates from the originally designed direction, causing an issue of an incorrect direction angle of the object obtained after the echo processing operation of the radar. 
     Also, even if the deviation of the radar reference axis does not occur in the initial installation stage, in the subsequent use of the radar, the long-term driving, age, and possible collision of the vehicle body will affect the radar, causing an abnormal detection due to the deviation of the radar reference axis. 
     When an abnormal object detection occurs, because the object status is misjudged and the correct observation value is unable to be obtained, a stationary object may be detected as a moving object. Besides, due to the incorrect position of the object relative to the vehicle body, the applications such as blind spot detection (BSD), rear cross traffic alert (RCTA), and door open warning (DOW), may suffer from false alarms, missed alarms, and abnormal real-time alarms. 
     SUMMARY OF THE INVENTION 
     The present invention aims at providing a radar self-calibration device and method thereof for promptly determining the deviation of radar angle and carrying out the calibration process. 
     For achieving the aforementioned objectives, an embodiment of the present invention provides a radar self-calibration device, which is installed on a vehicle body and configured to carry out an angular error detection according to an object on one side of the vehicle body, the radar self-calibration device comprising: 
     an antenna transceiver module having a detection range; and 
     a processor coupled with the antenna transceiver module and configured to obtain a relative velocity and a relative angle of the object with respect to the antenna transceiver module in a period of time, the relative angle being an angle included between the object and the driving direction of the vehicle body with respect to the vehicle body, the processor determining if the relative angle is equal to an ideal angle according to a detection model; 
     wherein, a detection condition of the detection model comprises that when the relative velocity is 0, the ideal angle is 90 degrees. 
     An embodiment of the present invention provides a radar self-calibration method, wherein a vehicle body comprises an antenna transceiver module, and the antenna transceiver module is configured to detect an object on one side of the vehicle body, the radar self-calibration method comprising following steps: 
     a capturing step, a processor obtaining a relative velocity and a relative angle of the object with respect to the antenna transceiver module in a period of time, the relative angle being an angle included between the object and the driving direction of the vehicle body with respect to the vehicle body; 
     a processing step, the processor inputting the relative velocity and the relative angle into a detection model; and 
     a determining step, the processor determining if the relative angle is equal to an ideal angle according to the detection model for confirming if the angle detected by the antenna transceiver module is correct. Therein, the detection condition of the detection model includes that when the relative velocity is 0, the ideal angle is 90 degrees. 
     With such configuration, after obtaining the relative velocity and the relative angle of the object with respect to the antenna transceiver module in a period of time, the radar self-calibration device of the present invention is able to confirm the correctness of the angle detected by the antenna transceiver module. When the detection shows error, the detection model and promptly carries out the subsequent process, so as to prevent the abnormal detection caused by the deviation of the reference axis of the antenna transceiver module, thereby specifically determining the status of the object and obtaining a correct observation value, ensuring the driving safety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a structural block view of the radar self-calibration device in accordance with an embodiment of the present invention. 
         FIG.  2    is a flow chart of the radar self-calibration method in accordance with an embodiment of the present invention. 
         FIG.  3 A  is a schematic view of the relative positions of the vehicle body and the object, illustrating the vehicle body not moving pass the object yet. 
         FIG.  3 B  is another schematic view of the relative positions of the vehicle body and the object, illustrating the vehicle body currently moving pass the object, and the object being right next to the vehicle body. 
         FIG.  3 C  is another schematic view of the relative positions of the vehicle body and the object, illustrating the vehicle body already moved pass the object. 
         FIG.  4    is a schematic view of the detection curve in accordance with an embodiment of the present invention. 
         FIG.  5    is a schematic view of the driving model in accordance with an embodiment of the present invention. 
         FIG.  6    is another schematic view of the driving model in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The aforementioned and further advantages and features of the present invention will be understood by reference to the description of the preferred embodiment in conjunction with the accompanying drawings where the components are illustrated based on a proportion, size, modification or displacement amount for explanation but not subject to the actual component proportion. 
     Referring to  FIG.  1    to  FIG.  6   , the present invention provides a radar self-calibration device  100  and a radar self-calibration method  200 . The radar self-calibration device  100  is installed on a vehicle body  1  and is configured to carry out an angular error detection according to an object  2  on one side of the vehicle. 
     The radar self-calibration device  100  comprises an antenna transceiver module  10 , a processor  20 , and a record module  30  that are coupled with each other. The processor  20  is communicatively connected with the controller area network bus (CAN bus) of the vehicle body  1 . In the embodiment, the antenna transceiver module  10  is disposed on a lateral side of the vehicle body  1 . Alternatively, the antenna transceiver module  10  is allowed to be installed on the front or rear side of the vehicle body  1  as long as it is capable of carrying out the radar detection operation toward the lateral side of the vehicle. The processor  20  is a digital signal processor (DSP). Alternatively, the processor  20  is allowed to be a chip or model capable of carrying out a signal calculation. 
     The antenna transceiver module  10  has a detection range. As shown by  FIG.  3 A , the driving direction D 2  is the moving direction of the vehicle body  1 , and the perpendicular detection direction D 1  is the detection direction perpendicular to the driving direction D 2  in the detection range of the antenna transceiver module  10 . The antenna transceiver module  10  emits an electromagnetic signal toward the detection range and receives the echo signal reflected by the object  2  in the detection range. 
     The processor  20  obtains a relative velocity V r (θ) and a relative angle θ of the object  2  with respect to the antenna transceiver module  10  in a period of time, and accordingly confirms if the relative angle θ is equal to an ideal angle according to a detection model  21 . 
     The detection model  21  is saved in the processor  20  in advance. In the embodiment, the detection model  21  is V r (θ)=V obj *cos(θ). Therein, the relative velocity V r (θ) represents the relative velocity between the vehicle body  1  and the object  2  with the directionality thereof taken into consideration. The parallel velocity V obj  represents the velocity of the object  2  in a direction parallel to the driving direction D 2  with respect to the vehicle body  1 . The relative angle θ is the angle included between the object  2  and the driving direction D 2  of the vehicle body  1  with respect to the vehicle body  1 . 
     Obviously in the embodiment, a detection condition of the said detection model  21  is set as: when the relative velocity V r (θ) is 0, the ideal angle is 90 degrees. In other words, when the vehicle body  1  moves pass the object  2 , and the direction of V r (θ) is equal to the perpendicular detection direction D 1 , the relative angle θ is equal to 90 degrees, and theoretically, the V r (θ) does not have a velocity. Therefore, such property is used for determining if the detection angle of the antenna transceiver module  10  is correct. 
     Also, the record module  30  is allowed to be, for example, a storage hard disk or flash memory for recording the immediate value of the relative velocity V r (θ) and the relative angle θ in the certain period of time. The processor  20  is able to obtain a driving model  22  of the vehicle body  1  with respect to the object  2  through the recording module  30 , so as to carry out a comparison between the information provided by the driving model  22  and the detection model  21 , thereby confirming the correctness of the detected angle of the antenna transceiver module  10 . 
     The foregoing content is to illustrate an embodiment of the radar self-calibration device  100  of the present invention. The following content is to illustrate a radar self-calibration method  200  of the radar self-calibration device  100 . Referring to  FIG.  2   , the method comprises a capturing step S 1 , a processing step S 2 , a determining step S 3 , and a calibrating step S 4 . Also, the embodiment further comprises a recording step P 1 . 
     In the capturing step S 1 , the processor  20  obtains the relative velocity V r (θ) and the relative angle θ of the object  2  with respect to the antenna transceiver module  10  in a period of time. To further explain, during the moving process of the vehicle body  1 , the antenna transceiver module  10  emits an electromagnetic signal toward the detection range through the antenna and receives the echo signal reflected by the object  2  in the detection range. The processor  20  obtains the echo signal of the antenna transceiver module  10  and carries out an analog-to-digital conversion and Fourier transform with the echo signal, thereby obtaining the relative velocity V r (θ) and the relative angle θ. 
     In the embodiment, when the object  2  is stationary, and the driving direction D 2  of the vehicle body  1  and the object  2  are not on the same straight line, the processor  20  is able to respectively apply two error-detection methods for confirming if the detected angle of the antenna transceiver module  10  is correct based on the fact that the vehicle body  1  moves pass the object  2  or not. 
     If the vehicle body  1  will move pass the object  2  (as shown by  FIG.  3 A  to  FIG.  3 C ), in the capturing step S 1 , the processor  20  obtains the relative velocity V r (θ) and the relative angle θ of the object  2  with respect to the antenna transceiver module  10  in a period of time. 
     In the processing step S 2 , the processor  20  inputs the relative velocity V r (θ) and the relative angle θ into the detection model  21 , so as to draw an actual detection curve L′. In the processing step S 2  of the embodiment, when the antenna transceiver module  10  is correctly installed with any angular errors, the actual detection curve L′ drawn by the processor  20  according to the pre-stored detection model  21  is an ideal detection curve L (as shown by  FIG.  4   ). 
     In the detection curve drawn by the processor  20 , the relative velocity V r (θ) varies according to the angle of the vehicle body  1  with respect to the object  2 . According to the detection condition set in the detection model  21 , at the moment the vehicle body  1  moves pass the object  2 , in which the direction of V r (θ) is the perpendicular detection direction D 1  (as shown by  FIG.  3 B ), the ideal relative angle θ is 90 degrees, and the relative velocity V r (θ) is equal to 0. 
     In other words, when the relative velocity V r (θ) actually obtained by the processor  22  is 0, the relative angle θ is theoretically equal to the ideal angle, which is 90 degrees. Therefore, when the relative velocity V r (θ) obtained by the processor  22  is 0, but the corresponding relative angle θ is not equal to 90 degrees, the angle detected by the antenna transceiver module  10  is incorrect. 
     In the determining step S 3 , at the moment of the vehicle body  1  moving pass the object  2  and the relative velocity V r (θ) in the actual detection curve L′ being 0, the processor  20  confirms if the corresponding relative angle θ is equal to the ideal angle which is 90 degrees based on the detection model  21 , so as to determine if the detected angle of the antenna transceiver module  10  has any error. If the relative angle θ is not equal to the ideal angle which is 90 degrees, the detected angle of the antenna transceiver module  10  is incorrect, and the method  200  proceeds to the subsequent calibrating step S 4 . 
     Besides, there is another situation that the vehicle body  1  will not move pass the object  2 . Before the vehicle body  1  moves pass the object  2 , the vehicle body  1  may possibly turn or faces other conditions. Therefore, in the embodiment, the present invention is still capable of carrying out the angular error detection operation when the vehicle body  1  does not move pass the object  2 . Therein, the recording step P 1  is added after the capturing step S 1 . In the recording step P 1 , the record module  30  records the immediate values of the relative velocity V r (θ) and the relative angle θ of the object  2  obtained by the processor  20 , so as to carry out the angular error detection operation by establishing the driving model  22 . 
     In the processing step S 2 , the processor  20  inputs the relative velocity V r (θ) and the relative angle θ recorded by the recording module  30  into the detection model  21 , so as to obtain the driving model  22  of the vehicle body  1  with respect to the object  2 . 
     In the embodiment, based on the relative velocity V r (θ) in a certain range of the relative angle θ recorded by the recording module  30 , the processor  20  converts the relative velocity V r (θ) and the relative angle θ into a linear curve for establishing the driving model  22  (as shown by  FIG.  5   ), so as to estimate the value of the relative angle θ when the relative velocity V r (θ) is 0 through the driving model  22 . Therein, the X axis of the driving model  22  is the relative angle θ, and the Y axis is the relative velocity V r (θ). 
     Next, in the determining step S 3 , the processor  20  compares the information provided by the driving model  22  with the detection model  21 , so as to confirm the correctness of the detection angle of the antenna transceiver model  10 . If the corresponding relative angle θ is not the ideal angle which is 90 degrees, it means that the detected angle of the antenna transceiver module  10  is incorrect, and the method  200  proceeds to the subsequent calibrating step S 4 . 
     For example, when the vehicle body  1  does not move pass the object  2 , in the recording step P 1 , the record module  30  records the relative angle θ and the relative velocity V r (θ) between the vehicle body  1  and the object  2  once per 0.1 seconds in a 5-second period of time during the driving process of the vehicle body  1 . In the processing step S 2 , according to the record module  30 , the processor  20  converts the recorded instant values of the relative velocity V r (θ) with respect to the relative angle θ ranging from 50 degrees to 70 degrees into a linear curve for establishing the driving model  22  (as shown by  FIG.  5   ). Based on this driving model  22 , at the moment the vehicle body  1  moving pass right next to the object  2  where the direction of V r (θ) is equal to the perpendicular detection direction D 1  and the relative velocity V r (θ) is 0, the processor  20  is able to estimate the value of the corresponding relative angle θ. In this driving model  22 , the processor  20  estimates that when the relative velocity V r (θ) is 0, the value of the corresponding relative angle θ is 90 degrees. In the determining step S 3 , from the driving model  22 , the processor  20  obtains the fact that when the relative velocity V r (θ) is 0, the value of the corresponding relative angle θ is 90 degrees. After the comparison with the detection model  21 , it is confirmed that the antenna transceiver module  10  is correctly installed, and the detected angle is correct. 
     Also, when the object  2  is a moving object, and the driving direction D 2  of the vehicle body  1  is parallel to and not on the same straight line of the moving direction of the object  2 , the processor  20  is still able to apply the two aforementioned error detection ways to confirm if the detected angle of the antenna transceiver module  10  based on the fact that the vehicle body  1  moves pass the object  2  or not. 
     In the situation where the vehicle body  1  will move pass the object  2  (as shown by  FIG.  3 A  to  FIG.  3 C ), in the capturing step S 1 , the processor  20  obtains the relative velocity V r (θ) and the relative angle θ of the object  2  with respect to the antenna transceiver module  10  in a period of time. 
     In the processing step S 2 , the processor  20  inputs the relative velocity V r (θ) and the relative angle θ into the detection model  21  to draw an actual detection curve L′. 
     In the determining step S 3 , according to the detection condition of the detection model  21 , even if the object  2  is in a moving status, as long as a velocity difference exists between the vehicle body  1  and the object  2 , the processor  20  confirms if the relative angle θ is equal to the 90-degree ideal angle at the moment the vehicle body  1  moving pass right next to the object  2  where the direction of V r (θ) is equal to the perpendicular detection direction D 1  (as shown by  FIG.  3 B ) and the relative velocity V r (θ) in the actual detection curve L′ is 0, thereby determining if the antenna transceiver module  10  have any angular errors. If the relative angle θ is not equal to the 90-degree ideal angle, it means that the detected angle of the antenna transceiver module  10  is incorrect, and the method  200  proceeds to the subsequent calibrating step S 4 . 
     Even the velocity difference between the vehicle body  1  and the object  2  is not sufficient for the vehicle body  1  to move pass the object  2 , in the embodiment, a recording step P 1  is able to be added after the capturing step S 1 . In the recording step P 1 , the record module  30  records the instant values of the relative velocity V r (θ) and the relative angle θ of the object  2  obtained by the processor  20 , so as to establish the driving model  22  for angular error detection. The detailed process is described as follows. 
     In the processing step S 2 , the processor  20  inputs the relative velocity V r (θ) and the relative angle θ recorded by the record module  30  into the detection model  21 , so as to obtain the driving model  22  of the vehicle body  1  with respect to the object  2  (as shown by  FIG.  6   ). 
     In the embodiment, because the parallel velocity V obj  of the object  2  would not stay unchanged, the processor  20  is able to draw out the relative velocity V r (θ) and the relative angle θ according to the relative velocity V r (θ) corresponding to a certain range of the relative angle θ recorded by the record module  30  when the object  2  is moving, so as to form a plurality of linear curves and establish the driving model  22 . Therein, the X axis of the driving model  22  is the relative angle θ, and the Y axis is the relative velocity V r (θ). 
     Therein, the relative velocity V r (θ) of the plurality of linear curves in the driving model  22  changes based on the parallel velocity V obj  of itself with respect to the object  2 , so as to present a linear curve having a corresponding slope. Because the processor  20  obtains the relative angle θ through an identical antenna transceiver module  10 , the values of the corresponding relative angle θ are theoretically the same at the moment the vehicle body  1  moving pass right next to the object  2  where the relative velocity V r (θ) is 0. In other words, the linear curves will cross at the same relative angle θ when the relative velocity V r (θ) is 0. 
     Then, in the determining step S 3 , the processor  20  compares the information provided by the driving model  22  and the detection model  21  to confirm if the angle detected by the antenna transceiver module  10  is correct. If the corresponding relative angle θ is not the ideal angle which is 90 degrees, it means that the detected angle of the antenna transceiver module  10  is incorrect, and the method  200  proceeds to the subsequent calibrating step S 4 . 
     For example, during the process of the vehicle body  1  approaching the object  2 , the object  2  moves at a velocity of 30 m/s for a period of time, and then accelerates to 40 m/s and keeps moving for a period of time, and then reduces to 20 m/s and keeps moving for a period of time. In the recording step P 1 , the record module  30  records the actually detected relative velocity V r (θ) and relative angle θ of the vehicle body  1  with respect to the object  2  once per 0.1 seconds in a 5-second period of time during the moving process of the vehicle body  1  approaching the object  2 . In the processing step S 2 , as shown by  FIG.  6   , according to the instant values of the relative velocity V r (θ) corresponding to three moving velocities with respect to the relative angle θ ranging from 50 degrees to 80 degrees recorded by the record module  30 , the processor  20  draws out the three linear curves established by relative velocity V r (θ) and the relative angle θ to establish the driving model  22 . Based on the driving model  22 , the processor  20  estimates that the value of the corresponding relative angle θ is 94 degrees at the moment the vehicle body  1  moving pass the object  2  where the relative velocity V r (θ) is 0. In the determining step S 3 , based on the driving model  22 , the processor  20  obtains the fact that when the relative velocity V r (θ) is 0, the value of the corresponding relative angle θ at which the three linear curves cross is 94 degrees. After comparing to the detection model  21 , the corresponding relative angle θ is not the 90-degree ideal angle. Therefore, it is determined that the angle detected by the antenna transceiver module  10  is incorrect, and the method  200  needs to proceed to the subsequent calibrating step S 4 . 
     In the calibrating step S 4 , the processor  20  subtracts the relative angle θ obtained when the relative velocity V r (θ) is 0 from the 90-degree ideal angle to get a deviation amount ε, so as to carry out the calibration of the detected angle according to the deviation amount ε. 
     In the embodiment, the calibration of the detected angle comprises a passive calibration and an active calibration. 
     Regarding the passive calibration, the processor  20  carries out a self-compensation through a software according to the deviation amount ε, so as to ensure that the subsequently obtained relative angle θ is correct. For example, as shown by  FIG.  4   , the relative angle θ obtained by the processor  20  according to the actual detection curve L′ is 85 degrees, so that the processor  20  subtracts 85 degrees from 90 degrees to get a 5-degree deviation amount ε. Thus, in the subsequent capturing step S 1 , the processor  20  immediately adds 5 degrees to the obtained relative angle θ, so that the relative angle θ is the correct detected angle. 
     Regarding the active calibration, the processor  20  applies a physical adjustment method, using a gyroscope and a servo motor with a movable bracket to rotate the reference axis of the antenna transceiver module  10  according to the deviation amount ε, thereby mechanically adjusting the detected angle of the antenna transceiver module  10 , ensuring that the relative angle θ is correctly detected. 
     With the foregoing configuration, the present invention achieves following advantages. 
     With the detection model  21  of the present invention, if the relative angle θ obtained by the processor  20  is not equal to 90 degrees when the relative velocity V r (θ) is 0, it can be determined that the angle detected by the antenna transceiver module  10  is incorrect. Thus, the present invention efficiently and accurately determines if the angle detected by the antenna transceiver module  10  is correct. 
     The object  2  used for error detection by the present invention is not limited to stationary objects. Because the ideal angle of the detection model  21  has an only solution, as long as the driving direction D 2  of the vehicle body  1  is parallel to and not on the same straight line with the moving direction of the object  2 , the error detection operation of the angle is able to be carried out. 
     Also, when the processor  20  determines that the angle detected by the antenna transceiver module  10  is incorrect, the processor  20  is able to immediately carry out the calibration, so as to prevent the detection abnormality caused by deviation of the reference axis of the antenna transceiver module  10 , thereby specifically determining the status of the object  2 , obtaining the correct observation value, and ensuring the driving safety. 
     Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.