Abstract:
A mobile navigation system includes a directive beamforming antenna carried by the vehicle, emitting first and second sensing beams in first and second directions at first and second time points, respectively; an electromagnetic wave reflector installed in the target zone, receiving the first and second sensing beams, and transmitting first and second retro waves back; and a processor electrically coupled to the directive beamforming antenna, receiving the first and second retro waves, and determining a direction where the vehicle will be guided to move according to information of the first and second retro waves. A coverage area of the first sensing beam and a coverage area of the second sensing beam partially overlaps with each other, and the direction where the vehicle will be guided to move lies between the first direction and the second direction.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to navigation means, and more particularly to mobile navigation method and system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Generally, an electronic radar positioning process is conducted by emitting an electromagnetic wave from an emitter and calculating relative distance and speed of a target object according information of a reflected electromagnetic wave, which is reflected from the target object back to the emitter. In practice, not only the target object but also other objects might reflect the electromagnetic wave. When the electromagnetically positioning process is performed in such an environment, detection errors are likely to occur since more than one reflected electromagnetic wave might be received. For example, if the radar positioning is implemented with a frequency-modulated continuous wave (FMCW), the scattering behavior of objects might happen to form multi-directional reflected waves, and different reflective paths would result in a multi-path electromagnetic wave. In the FMCW radar positioning method, electromagnetic waves in different paths would show different distances, so the multi-path electromagnetic wave would make the detection of the position of the target object unreliable. 
       SUMMARY OF THE INVENTION 
       [0003]    Therefore, the present invention provides mobile navigation system for precisely guiding a vehicle toward a target zone. 
         [0004]    In an aspect of the present invention, a mobile navigation system for guiding a vehicle toward a target zone, comprises: a directive beamforming antenna carried by the vehicle, emitting a first sensing beam in a first direction at a first time point and emitting a second sensing beam in a second direction at a second time point toward the target zone; an electromagnetic wave reflector installed in the target zone, receiving the first sensing beam and the second sensing beam, and transmitting a first retro wave corresponding to the first sensing beam back and a second retro wave corresponding to the second sensing beam back; and a processor electrically coupled to the directive beamforming antenna, receiving the first retro wave and the second retro wave, and determining a direction where the vehicle will be guided to move according to information of the first retro wave and information of the second retro wave. A coverage area of the first sensing beam and a coverage area of the second sensing beam partially overlaps with each other, and the direction where the vehicle will be guided to move lies between the first direction and the second direction. 
         [0005]    In another aspect of the present invention, a mobile navigation method for guiding a vehicle toward a target zone, comprises: emitting a first sensing beam from the vehicle in a first direction at a first time point and emitting a second sensing beam from the vehicle in a second direction at a second time point toward the target zone, wherein a coverage area of the first sensing beam and a coverage area of the second sensing beam partially overlaps with each other; using an electromagnetic wave reflector installed in the target zone to receive the first sensing beam and the second sensing beam, and transmit a first retro wave corresponding to the first sensing beam and a second retro wave corresponding to the second sensing beam back; and receiving the first retro wave and the second retro wave, and determining a direction where the vehicle will be guided to move according to information of the first retro wave and information of the second retro wave. The direction where the vehicle will be guided to move lies between the first direction and the second direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0007]      FIG. 1  is a functional block diagram schematically illustrating a mobile navigation system according to an embodiment of the present invention; 
           [0008]      FIG. 2A  is a schematic flowchart illustrating a mobile navigation method according to an embodiment of the present invention; 
           [0009]      FIG. 2B  is a schematic flowchart illustrating a mobile navigation method according to another embodiment of the present invention; and 
           [0010]      FIG. 3  is a schematic diagram exemplifying paths of wave beams for illustrating an operating principle according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    The invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
         [0012]    Please refer to  FIG. 1 , in which a mobile navigation system for guiding a vehicle according to an embodiment of the present invention is schematically shown. In this embodiment, the mobile navigation system  10  includes a directive beamforming antenna  100 , a retro-directive antenna  110 , and a processor  120 . The directive beamforming antenna  100  is carried by the vehicle  102  and sequentially emits sensing beams  100   a ,  100   b ,  100   c  or more in a variety of directions. The retro-directive antenna  110 , which is an antenna that transmits the signal back to where it came from, is installed in a target zone  112  for receiving one of the sensing beams which are emitted by the directive beamforming antenna  100 , and in response to the received sensing beam, e.g. the wave  100   a , returning a corresponding wave, which is so called as a retro wave, e.g.  110   a , in a direction correlating to the direction of the wave  100   a . Likewise, if the retro-directive antenna  110  receives the wave  100   b  or  100   c , a corresponding retro wave, e.g.  110   b  or  110   c , would be transmitted back in a direction correlating to the direction of the wave  100   b  or  100   c . According to the information revealed by the returned retro wave, the vehicle  102  is guided toward the target zone  112 . 
         [0013]    In this embodiment, the directive beamforming antenna  100  changes emitting directions of sensing beams with time. For example, the directive beamforming antenna  100  emits a first sensing beam in a first direction at a first time point, and then emits a second sensing beam in a second direction at a second time point. The processor  120 , which is carried by the vehicle  102  or disposed at a network node that can control the vehicle  102 , and electrically coupled to the directive beamforming antenna  100  for receiving the retro wave  110   a ,  110   b  or  110   c , processes the information revealed by the retro waves corresponding to the first sensing beam and the second sensing beam to determine the direction where the vehicle  102  will be guided. 
         [0014]    The operating principle of the present invention will be described hereinafter, using the system, the flowchart, and the scheme as shown in  FIGS. 1, 2A, 2B and 3  as examples. In the embodiment illustrated in  FIG. 3 , the major axial direction n of the directive beamforming antenna  100  is defined as a normal direction of the directive beamforming antenna  100 , where the vehicle  102  will be guided to move, but the implementation of the present invention is not limited hereto. For example, the moving direction of the vehicle  102  may be different from the major axial direction n, and there could be a non-zero angle between the major axial direction n and the moving direction of the vehicle  102 . Furthermore, the included angle between the major axial direction n and the moving direction of the vehicle  102  may dynamically change. For example, the directive beamforming antenna  100  may be rotatable, and the vehicle  102  will be guided in response to a received retro wave in a direction determined according to current orientation of the vehicle  102  and the major axial direction n of the directive beamforming antenna  100 , which are recorded by the processor  120 . 
         [0015]    The flowchart of  FIG. 2A  schematically illustrates steps of a mobile navigation method based on the above-described operational principle according to an embodiment of the present invention. A sensing beam is first emitted at a specified time point (Step S 200 ). Then in Step S 210 , whether a retro wave is received in response to the sensing beam is determined. If no retro wave in response to the sensing beam is received within a default period of time, wherein the default period of time is determined according to an intensity of the sensing beam and a detected area, proceed to Step S 250  to adjust a direction of the sensing beam, and then to Step S 200  to re-emit a sensing beam. The wave remission cycle will be repeated until a corresponding retro wave is received. 
         [0016]    On the other hand, if a retro wave is received in Step S 210 , proceed to Step S 220  to further check whether there is another retro wave in response to another emitted sensing beam is received or not. If no further retro wave is received, proceed to Step S 250  to adjust a direction of the sensing beam. If two retro waves have been received, a position of the retro-directive antenna  110  can be derived according to the information carried by the two retro waves (Step S 230 ). Once the position of the retro-directive antenna  110  is realized, whether the moving direction of the vehicle  102  need be changed can be determined (Step S 240 ). If the moving direction of the vehicle  102  needs to be changed, necessary adjustment is made (Step S 260 ). Otherwise, proceed to Step S 270  to clear information of the retro waves (Step S 270 ). Meanwhile, enter next operation cycle if necessary. 
         [0017]    Please refer to  FIG. 2B , in which another embodiment of mobile navigation method according to the present invention is schematically illustrated. The steps included in this embodiment of mobile navigation method are similar to those illustrated in  FIG. 2A  except modifications between Step S 220  and Step S 250 . In this embodiment, if there is no additional retro wave received in Step S 220 , a distance of a target object is estimated according to the information carried by the previously received retro wave, and compared with a default value (Step S 222 ). If the distance of the target object is greater than the default value, guide the vehicle  102  to move toward the major axial direction n of the directive beamforming antenna  100  (Step S 224 ), and subsequently, adjust the direction of the sensing beam (Step S 250 ). If the distance of the target object is not greater than the default value, directly proceed to Step S 250  to adjust the direction of the sensing beam. 
         [0018]    It is to be noted that the major axial direction n of the directive beamforming antenna  100 , i.e. the moving direction of the vehicle  102  in this embodiment, is not necessarily an orientation toward the retro-directive antenna  110 . Instead, it is required that the sensing beam emitted in a specified direction at a specified time point can be transmitted back as a retro wave from the retro-directive antenna  110  within a default period of time. For example, as illustrated in  FIG. 1 , in which the directive beamforming antenna  100  rotates with time, the sensing beam  100   a  is emitted by the directive beamforming antenna  100 . Then a retro wave  110   a  is returned to the directive beamforming antenna  100  from the retro-directive antenna  110  in response to the sensing beam  100   a  within a default period of time. Likewise, another sensing beam  100   b  is emitted by the directive beamforming antenna  100  just subsequent to the emission of the sensing beam  100   a . Another retro wave  110   b  is returned to the directive beamforming antenna  100  from the retro-directive antenna  110  in response to the sensing beam  100   b  within the default period of time. Afterwards, the processor  120  processes the received wave signals and estimates a distance r between the directive beamforming antenna  100  and the retro-directive antenna  110  according to a time difference between the transmission of the sensing beam and the receiving of the retro wave. 
         [0019]    Since both the retro wave corresponding to the sensing beam  100   a  emitted in a direction A 1  and the retro wave corresponding to the sensing beam  100   b  emitted in a direction A 2  are returned from the retro-directive antenna  110 , it is inferable that the retro-directive antenna  110  is present at a position covered by a wave range of the sensing beam  100   a  and also a wave range of the sensing beam  100   b . That is, the retro-directive antenna  110  must be disposed at an overlapping area of the wave ranges of the sensing beams  100   a  and  100   b , as exemplified in  FIG. 3 . The term “wave range” used herein is defined as an area where an intensity of the sensing beam is high enough for the retro-directive antenna  110  to recognize. The wave range is generally a cone shape with projected edge lines  300  and  302  for the sensing beam  100   a , and projected edge lines  310  and  312  for the sensing beam  100   b . More specifically, the retro-directive antenna  110  is disposed at an intersection of a wavefront of the sensing beam  100   a  and a wavefront of the sensing beam  100   b , and has an orientation A from the directive beamforming antenna  100 . 
         [0020]    With the two parameters, i.e. the orientation A and the distance r, the processor  120  can estimate the position of the retro-directive antenna  110 . Subsequently, the processor  120  determines whether the moving direction of the vehicle  102  needs to change or not with reference to the current orientation of the vehicle  102  and one or more proper logic operations. If it is determined that the moving direction of the vehicle  102  does not follow an expected one, the moving direction of the vehicle will be adjusted, and the vehicle will be guided toward the expected direction. On the other hand, if it is determined that no adjustment is required, clear the information of the retro waves to avoid interference with operations in next cycle. 
         [0021]    The above-mentioned “one or more proper logic operations” may be any proper algorithm or combination of algorithms applicable for navigation. For example, with reference to  FIG. 1  and  FIG. 3 , when the orientation A is determined, the processor  120  may directly control the vehicle  102  to rotate with an angle S so as to have the major axial direction n of the directive beamforming antenna  100 , i.e. the moving direction of the vehicle  102  in this embodiment, consistent to the direction A between the direction A 1  to the direction A 2 . It is understood that other operations may be alternatively adopted. 
         [0022]    As described above, a retro-directive antenna  110 , which functions for focusing and amplifying electromagnetic waves received from the directive beamforming antenna  100 , is installed in the target zone  112 . The focused and amplified retro waves are transmitted along the reverse direction, i.e. toward where it came from. Since the electromagnetic waves are amplified by the retro-directive antenna  110 , the corresponding retro waves is supposed to be more intense than waves reflected by other objects. In other words, if one sensing beam is emitted but two or more reflected waves are sent back, it is inferable that the most intense one is the corresponding retro wave returned by the retro-directive antenna  110 . Furthermore, the other reflected waves will show the presence of objects which might become obstacles to the movement of the vehicle and can be referred to for estimating the positions of the obstacles. Possible collision with the obstacles can thus be avoided by, for example, guiding the vehicle to deviate from the path of the sensing beam. Whether a reflected wave is the corresponding retro wave sent back from the retro-directive antenna  110  or not can be further checked by estimating the distance of the reflective object and determining whether the reflective object is disposed in the target zone according to the distance data. 
         [0023]    In a case that the mobile navigation is conducted in an area where multi-path reflection is not an issue, e.g. an open space, a specific electromagnetically reflective object can be used in lieu of the retro-directive antenna  110  to accomplish the guidance of the vehicle. The omission of the retro-directive antenna  110  facilitates reduction of the cost of the navigation system. 
         [0024]    To sum up, the mobile navigation method and system according to the present invention use electromagnetic waves to implement positioning and navigation of a vehicle, and use a directive sensing beam and a retro-directive antenna in a target zone to enhance precisions of the positioning and navigation. Furthermore, information of the reflected waves can be referred to for dodging obstacles. An example of the directive beamforming antenna  100  is a radar. The mobile navigation method and system according to the present invention can be used to guide a car on a road, and in addition, guide a vehicle, a vessel or an aircraft to park into a garage, a dock or an apron safely. Accordingly, human laboring and cost can be saved, and mobile safety can be improved. 
         [0025]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures. For example, in spite hardware devices are exemplified as above in order to practice the redundancy power supply system and the power control circuit according to the present invention, hardware/software hybrid modules or firmware designs may also adopted as alternatives of the devices when appropriate.