Patent Publication Number: US-2023152821-A1

Title: Method and system for vehicle head direction compensation

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwanese application no. 110142553, filed on Nov. 16, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a method and a system for vehicle head direction compensation. 
     Description of Related Art 
     There are more than  23 , 000  bridges in Taiwan. If under bridge inspection is manually performed every year, it may be difficult to increase inspection efficiency because of time-consuming inspection operation, lack of inspection vehicles, and possible risks to public security. 
     The use of an unmanned vehicle for automated inspection operation can address the above issues. However, during the process of automated inspection operation using an unmanned vehicle, it is required to accurately know a head direction of the unmanned vehicle. Currently, an electronic compass (a magnetometer) is most frequently utilized to determine a head direction of an unmanned vehicle. However, when the electronic compass is utilized in an under bridge passage or in a tunnel, the magnetometer may be interfered with by electric power equipment or steel structures and become invalid. Therefore, how to design a method and a system for accurately obtaining the head direction of an unmanned vehicle in any environment is one of research topics for those skilled in the related field. 
     SUMMARY 
     The exemplary embodiments of disclosure provide a method and a system for vehicle head direction compensation, in which angle compensation is performed on a head direction angle of an unmanned vehicle in a local coordinate system by using a true north azimuth after the local coordinate system is established. 
     According to an exemplary embodiment of the disclosure, a method for vehicle head direction compensation includes the following. A relative position between each of a plurality of sensors disposed on a vehicle and a plurality of base stations is obtained through the sensors and a relative coordinate system is established by a processor to obtain a vehicle head direction of the vehicle in the relative coordinate system and a deviation angle between an X-axis of the relative coordinate system and a true north azimuth. An angle compensation is performed by the processor on the vehicle head direction of the vehicle in the relative coordinate system based on the deviation angle. 
     According to an exemplary embodiment of the disclosure, a system for vehicle head direction compensation includes a plurality of base stations, a vehicle, a plurality of sensors, and a processor. The sensors are disposed on the vehicle. The processor is coupled to the sensors, obtains a relative position between each of the sensors and the base stations through the sensors and establishes a relative coordinate system to obtain a vehicle head direction of the vehicle in the relative coordinate system and a deviation angle between an X-axis of the relative coordinate system and a true north azimuth, and performs an angle compensation on the vehicle head direction of the vehicle in the relative coordinate system based on the deviation angle. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG.  1    is a block diagram of a system for vehicle head direction compensation according to an exemplary embodiment of the disclosure. 
         FIG.  2    is a flowchart of a method for vehicle head direction compensation according to an exemplary embodiment of the disclosure. 
         FIG.  3    and  FIG.  4    are each a schematic diagram of a relative coordinate system according to an exemplary embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The exemplary embodiments of the disclosure provide a method and a system for accurately obtaining an unmanned vehicle head direction. In the method and the system, the head direction of the unmanned vehicle can be mapped to a world coordinate system through a local positioning system, and an angle difference between the local positioning system and the true north azimuth can be compensated instantly. Accordingly, with the method and the system of the exemplary embodiments of the disclosure, a head direction angle of an unmanned vehicle can be accurately obtained in any environment, thus achieving correctly and fully automated driving by the unmanned vehicle to perform inspection operation, and preventing risks in manual inspection operation. The method and the system of the exemplary embodiments of the disclosure may be applied to inspection operation such as drone bridge inspection, drone outdoor engineering inspection, and drone tunnel inspection. 
       FIG.  1    is a block diagram of a system for vehicle head direction compensation according to an exemplary embodiment of the disclosure. Nonetheless,  FIG.  1    is only for the ease of description, and is not intended to limit the disclosure. First,  FIG.  1    introduces all the member and configuration relationships of the system for vehicle head direction compensation, of which the detailed functions in combination with  FIG.  2    will be described. 
     With reference to  FIG.  1   , a system for vehicle head direction compensation  100  of this exemplary embodiment includes a plurality of base stations  120 , a vehicle  140 , a plurality of sensors  160 , and a processor  180 . The sensors  160  are disposed on the vehicle  140 . The vehicle  140  is, for example, an unmanned aerial vehicle, which may be a drone, but is not limited thereto. The processor  180  is coupled to the sensors  160 . 
     In an exemplary embodiment, the base stations  120  are set in the environment by the user in advance. In an exemplary embodiment, the processor  180  may be disposed on the vehicle  140 , or may be another device independent of the vehicle  140 . 
     It should be noted that the base stations  120  include at least three base stations, and the sensors  160  include at least two sensors. In addition, for simplicity of the description, in the system for vehicle head direction compensation  100  in this exemplary embodiment of  FIG.  1   , there are shown three base stations  122 ,  124 ,  126  and two sensors  162 ,  164  as examples. Nonetheless, those ordinarily skilled in the related field may appropriately adjust the numbers of base stations and sensors depending on the actual application circumstances, which are not limited by this exemplary embodiment. 
     The sensors  162  and  164  are, for example, radars, sonic sensing devices, or optical sensing devices, for example, optical radars, depth-of-field cameras, and image capture devices using light detection and ranging (LiDAR) among other devices having the function of sensing object distance. The sensors  162  and  164  are connected through a connection device (not shown) to the base stations  122 ,  124 ,  126  and the processor  180  in a wired or wireless manner. For the wired manner, the connection device may be an interface of Universal Serial Bus (USB), RS232, universal asynchronous receiver/transmitter (UART), internal integrated circuit (I2C), serial peripheral interface (SPI), display port, thunderbolt, or local area network (LAN), but is not limited thereto. For the wireless manner, the connection device may be a wireless fidelity (Wi-Fi) module, a wireless radio frequency identification (RFID) module, a Bluetooth module, an infrared module, a near-field communication (NFC) module, or a device-to-device (D2D) module, but is similarly not limited thereto. 
     The processor  180  is, for example, a central processing unit (CPU), or any other programmable general-purpose or special-purpose microprocessor, digital signal processor (DSP), programmable controller, application specific integrated circuit (ASIC), or other similar devices or a combination of these devices. In this exemplary embodiment, the processor  180  may load a computer program from a storage device (not shown) to execute a method for vehicle head direction compensation of an exemplary embodiment of the disclosure. 
       FIG.  2    is a flowchart of a method for vehicle head direction compensation according to an exemplary embodiment of the disclosure. With reference to  FIG.  2    together, the method of this exemplary embodiment is adapted for the system for vehicle head direction compensation  100  of  FIG.  1   . Detailed steps of a method for vehicle head direction compensation  200  of the exemplary embodiment of the disclosure accompanied with the actuation relationship between the elements in the system for vehicle head direction compensation  100  will be described hereinafter. 
     First, in step S 220 , in the process of vehicle head direction compensation, the processor  180  first obtains a relative position between each of the sensors  162 ,  164  and the base stations  122 ,  124 ,  126  through the sensors  162 ,  164  and establishes a relative coordinate system. Specifically, the processor  180  obtains the relative position between each of the sensors  162 ,  164  and the base stations  122 ,  124 ,  126  through the sensors  162 ,  164  and establishes the relative coordinate system using an ultra wideband positioning technology. 
     For example,  FIG.  3    and  FIG.  4    are each a schematic diagram of a relative coordinate system according to an exemplary embodiment of the disclosure. With reference to  FIG.  3    and  FIG.  4   , the direction from the base station  122  to the base station  124  is an X-axis of relative coordinate systems  300  and  400 , and the direction from the base station  122  to the base station  126  is a Y-axis of the relative coordinate systems  300  and  400 . A position coordinate of the base station  122  is ( 0 ,  0 ), a position coordinate of the base station  124  is (x 1 ,  0 ), and a position coordinate of the base station  126  is ( 0 , y 1 ). The sensor  162  and the sensor  164  are two coordinate points located in the relative coordinate systems  300  and  400 . 
     Then, in step S 240 , the processor  180  obtains a vehicle head direction of the vehicle  140  in the relative coordinate system and a deviation angle between the X-axis of the relative coordinate system and the true north azimuth. 
     In an exemplary embodiment, the specific implementation steps of step S 240  include step S 241 , step S 243 , and step S 245 , which accompanied with the relative coordinate system  300  of  FIG.  3    will be exemplarily described hereinafter. 
     In step S 241 , the processor  180  obtains position coordinates of the sensor  162  and the sensor  164  in the relative coordinate system to obtain a vector of the vehicle head direction. To be specific, the processor  180  obtains the position coordinates of the sensor  162  and the sensor  164  in the relative coordinate system by triangulation positioning. For example, with reference to  FIG.  3   , the sensor  162  and the sensor  164  are both disposed on the central axis of the vehicle  140  for ease of obtaining the axial direction of the central axis. Nonetheless, those ordinarily skilled in the related field may appropriately change the setting positions of the sensors depending on the actual application circumstances. Even if the setting positions of the sensor  160  and the sensor  164  are changed, the axial direction of the central axis can still be obtained through calibration, which is not limited by this exemplary embodiment. In particular, in this exemplary embodiment, a vector {right arrow over (V)} of the vehicle head direction is the same as a vector {right arrow over (A)} pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164 . Here, the position coordinate of the sensor  162  is (x 2 , y 2 ), and the position coordinate of the sensor  164  is (x 3 , y 3 ), so it follows that the vector {right arrow over (V)} of the vehicle head direction is (x 3 -x 2 , y 3 -y 2 ). 
     In step S 243 , the processor  180  calculates an angle between the vector of the vehicle head direction and the X-axis of the relative coordinate system to obtain a head direction angle of the vehicle head direction in the relative coordinate system. For example, with reference to  FIG.  3   , the processor  180  utilizes the function a tan 2 in the trigonometric functions to calculate and obtain that an angle between a ray pointing to (x 3 -x 2 , y 3 -y 2 ) on the coordinate plane and the positive direction of the X-axis is θ. 
     In step S 245 , the processor  180  calculates an angle between the X-axis of the relative coordinate system and the true north azimuth to obtain the deviation angle. For example, with reference to  FIG.  3   , the processor  180  utilizes the trigonometric functions to calculate and obtain that the angle between the positive direction of the X-axis of the relative coordinate system  300  and the true north azimuth is ∅, which is namely the deviation angle. 
     In another exemplary embodiment, the specific implementation steps of step S 240  include step S 242 , step S 244 , step S 246 , and step S 248 , which accompanied with the relative coordinate system  400  of  FIG.  4    will be exemplarily described hereinafter. 
     In step S 242 , the processor  180  obtains the position coordinates of the sensor  162  and the sensor  164  in the relative coordinate system to obtain a vector pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164 . To be specific, the processor  180  obtains the position coordinates of the sensor  162  and the sensor  164  in the relative coordinate system by triangulation positioning. For example, with reference to  FIG.  4   , the sensor  162  and the sensor  164  are both disposed on the central axis of the vehicle  140  for ease of obtaining the axial direction of the central axis. Nonetheless, those ordinarily skilled in the related field may appropriately change the setting positions of the sensors depending on the actual application circumstances. Even if the setting positions of the sensor  160  and the sensor  164  are changed, the axial direction of the central axis can still be obtained through calibration, which is not limited by this exemplary embodiment. It should be particularly noted that, in this exemplary embodiment, the vector {right arrow over (V)} of the vehicle head direction is different from the vector {right arrow over (A)} pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164 . Here, the position coordinate of the sensor  162  is (x 2 , y 2 ), and the position coordinate of the sensor  164  is (x 3 , y 3 ), so it follows that the vector A pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164  is (x 3 -x 2 , y 3 -y 2 ). 
     In step S 244 , the processor  180  calculates an angle between the vector pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164  and the X-axis of the relative coordinate system. For example, with reference to  FIG.  4   , the processor  180  utilizes the function a tan 2 in the trigonometric functions to calculate and obtain that the angle between the ray pointing to (x 3 -x 2 , y 3 -y 2 ) on the coordinate plane and the positive direction of the X-axis is θ. 
     In step S 246 , the processor  180  adds a predetermined angle to the angle between the vector pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164  and the X-axis of the relative coordinate system to obtain a head direction angle of the vehicle head direction in the relative coordinate system. In particular, the predetermined angle is the angle between the vector {right arrow over (A)} pointing from the position coordinate of the sensor  162  to the position coordinate of the sensor  164  and the vector {right arrow over (V)} of the vehicle head direction. In an exemplary embodiment, the predetermined angle may be preset, or may be calculated by the processor  180  based on information obtained by the sensor  162  and the sensor  164 , which is not limited by the disclosure. For example, with reference to  FIG.  4   , the predetermined angle is β, so the head direction angle is namely θ+β. 
     In step S 248 , the processor  180  calculates an angle between the X-axis of the relative coordinate system and the true north azimuth to obtain the deviation angle. For example, with reference to  FIG.  4   , the processor  180  utilizes the trigonometric functions to calculate and obtain that the angle between the X-axis of the relative coordinate system  400  and the true north azimuth is ∅, which is namely the deviation angle. 
     Next, in step S 260 , the processor  180  performs an angle compensation on the vehicle head direction of the vehicle  140  in the relative coordinate system based on the deviation angle. 
     In this exemplary embodiment, the specific implementation steps of step S 260  include step S 262 . 
     In step S 262 , the processor  180  performs a compensation on the head direction angle based on the deviation angle. For example, with reference to  FIG.  3   , the processor  180  utilizes the deviation angle ∅ to perform the compensation on the head direction angle θ. Accordingly, it follows that a head direction angle of the vehicle  140  in the world coordinate system is θ+∅. With reference to  FIG.  4    also, the processor  180  utilizes the deviation angle ∅ to perform the compensation on the head direction angle θ+β. Accordingly, it follows that a head direction angle of the vehicle  140  in the world coordinate system is θ+β+∅. 
     In an exemplary embodiment, after the angle compensation on the vehicle head direction, the vehicle  140  performs a destination navigation. 
     It is worth noting that the specific order and/or hierarchy of the steps in the method of the exemplary embodiment of the disclosure are only exemplary. Based on design preferences, the specific order or hierarchy of the steps of the disclosed method or process may be rearranged while remaining within the scope of the exemplary embodiments of the disclosure. Therefore, those of ordinary skill in the related field will understand that various steps or actions are presented in a sample order in the method and skills of the exemplary embodiments of the disclosure, and unless expressly stated otherwise, the exemplary embodiments of the disclosure are not limited to the specific order or hierarchy presented. 
     In summary of the foregoing, in the method and the system for vehicle head direction compensation of the exemplary embodiments of the disclosure, the relative positions between the sensors and the base stations are utilized to establish the local coordinate system, and the angle between the X-axis of the local coordinate system and the true north azimuth is utilized to compensate the head direction angle of the unmanned vehicle in the local coordinate system, to obtain the correct head direction angle of the unmanned vehicle (i.e., the head direction angle in the world coordinate system). Accordingly, in the method and the system for vehicle head direction compensation of the exemplary embodiments of the disclosure, the head direction angle of the unmanned vehicle can be accurately obtained in any environment, thus achieving fully automated inspection operation by the unmanned vehicle. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.