Abstract:
Systems and methods for generating approach information for a first vehicle approaching a second dynamic vehicle. An example method determines motion information of the second vehicle and generates approach information based on the determined motion information and the approach centerline. The method generates at least one of an approach path or a plurality of approach path reference points based on at least one of a center of motion of the second vehicle or a touchdown point on the second vehicle and generates at least one of a synthetic path or a plurality of synthetic path reference points by filtering the generated at least one approach path or plurality of approach path reference points.

Description:
BACKGROUND OF THE INVENTION 
     Landing a vehicle onto a dynamic vehicle, such as an aircraft carrier, requires some respect for dynamics that do not exist when the landing is performed onto a stable environment, such as ground or a building. Some systems presently provide for flight deck motion compensation when an approaching aircraft is close to the aircraft carrier. However, at range the system still provides navigation relative to a reference landing beam that varies to a great extent when the dynamic vehicle is experiencing motion. For example, when the carrier is changing heading and an aircraft is on approach, the reference landing beam skews by a great amount thereby causing any aircraft at distance to perform quite dynamic maneuvers to get back to the centerline of the touchdown point. 
     SUMMARY OF THE INVENTION 
     The present invention provides systems and methods for generating approach information for a first vehicle approaching a second dynamic vehicle. An example method determines motion information of the second vehicle and generates approach information based on the determined motion information and the approach centerline. 
     In one aspect of the invention, the method generates at least one of an approach path or a plurality of approach path reference points based on at least one of a center of motion of the second vehicle or a touchdown point on the second vehicle and generates at least one of a synthetic path or a plurality of synthetic path reference points by filtering the generated at least one approach path or plurality of approach path reference points. 
     In another aspect of the invention, navigation signals are generated based on one of the generated synthetic path or plurality of reference points 
     In still another aspect of the invention, filtering includes damping out variations of the at least one approach path or plurality of approach path reference points. 
     In yet another aspect of the invention, the second vehicle is a ship and the first vehicle is an aircraft. The ship includes a plurality of touchdown points. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  illustrates a block diagram of an example system formed in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates an example process performed by the system shown in  FIG. 1 ; 
         FIGS. 3A and 3B  illustrate top view and side views of approach information formed in accordance with an embodiment of the present invention; 
         FIGS. 3C and 3D  illustrate top view and side views of final approach information formed in accordance with an embodiment of the present invention; and 
         FIGS. 4A and 4B  illustrate top and side views of an alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates an example system  20  that provides approach guidance information. The system  20  includes a dynamic vehicle  28  that is in data communication with a plurality of approaching vehicles  30 . The dynamic vehicle  28  is any of a number of moving vehicles, such as land, sea (e.g. aircraft carrier, subsurface vehicle) and space vehicle. 
     The dynamic vehicle  28  includes a processing device  40  that is in data communication with a database  42  and a communication device  44 . The approaching vehicles  30  include a processing device  50  that is in data communication with database  52 , a communication device  56 , a navigation system  58 , and control surfaces  60 . The control surfaces  60  may optionally be in data communication with the navigation system  58  or can be in direct data communication with both the processing device  50  and the navigation system  58 . 
     The dynamic vehicle  28  also includes sensors  46  for supplying the processing device  40  with motion information of the dynamic vehicle  28 . The approaching vehicle  28  includes sensors  54  that provide aircraft positional information to either one of or both the processing device  50  and the navigation system  58 . 
     In one embodiment, the processing device  40  of the dynamic vehicle  28  generates a multi-segmented synthetic approach path based on information stored in the database  42  and/or received from the sensors  46 . The determined synthetic approach path is then wirelessly communicated to the approaching vehicle  30  via the communication device  44 . In another embodiment, the dynamic vehicle  28  communicates motion information generated by the sensors  46  and/or information stored in the database  42  to the approaching vehicle  30  and the approaching vehicle  30  generates the synthetic approach path based on the received information and/or information stored in the local database  52 . 
     When the approaching vehicle  30  either receives the synthetic path information via the communication device  56  or generates the synthetic path information, either the processing device  50  or navigation system  58  outputs navigation information, such as in the form of approach crosshair (e.g. Instrument Landing System (ILS) crosshairs), or controls operation of the control surfaces  60  (e.g. autopilot) according to the received or generated synthetic path. Navigation performed by an autopilot can be accomplished by navigating relative to glideslope and alignment information associated with the synthetic approach path or by navigating between reference points (i.e., waypoints) included in the synthetic approach path. 
       FIG. 2  illustrates an example process  100  performed by the system  20  shown in  FIG. 1 . First, at a block  102  a three-dimensional (3-D) fixed path having reference points is generated relative to the dynamic vehicle  28 . At a block  106 , a synthetic stabilized path is generated based on the fixed path and dynamic vehicle motion information. The synthetic path is a dampened version of the fixed path. Next, at a block  108 , navigation signals are generated and outputted based on the generated synthetic path. At a block  112 , autopilot controls are provided and/or navigation displays are controlled based on the outputted navigation signals. 
       FIGS. 3A-D  illustrate top and side views of the present invention described above that is used in generating navigation signal information for approach to landing on a aircraft carrier  210  in both approach and final segments. In this embodiment, the approach segment is defined as the portion of an approach to landing greater than three nautical miles (NM). The final segment is the approach from 3 NM to touchdown.  FIGS. 3A and 3B  are top and side views of approach navigation information generated by both the prior art and the present invention in the approach segment. The prior art generates a fixed reference landing beam  214  that extends away from the centerline of the touchdown area of the aircraft carrier  210 . The reference landing beam  214  is comprised of reference points  216  that is shown visually connected by lines. As the heading of the aircraft carrier  210  moves even slightly, the fixed reference landing beam  214  generates large distance swings in the approach segment. In accordance with the present invention, a synthetic stabilized landing beam  220  is generated. The synthetic stabilized landing beam  220  is comprised of damped reference points  222  and lines that link the points  222 . The synthetic landing beam  220 , if viewable by a pilot, would appear to be stable in space while the aircraft carrier  210  is in motion. The synthetic landing beam and the reference points  222  are calculated according to a damping technique, such as “lag filter” damping or lead prediction of the reference landing beam  214 . The number of reference points  222  generated can vary depending upon system designer&#39;s/operator&#39;s choice. In one embodiment, the three-dimensional position of the reference points  222  are generated and used by the systems of the aircraft when presenting either navigational information for use in navigational displays or for use in automatic controls. 
     As shown in  FIG. 3B , the altitude value for the synthetic landing beam  220  and reference points  222  is stable because it is associated with sea level. Therefore, what the aircraft experiences during the approach segment is damped-out navigation information that compensates for horizontal movements of the aircraft carrier  210  while also rounding out large changes in heading of the aircraft carrier  210 . The greater the distance the aircraft is from the aircraft carrier  210  the more damping of the dramatic changes of the reference landing beam  214 . 
       FIGS. 3C and 3D  illustrate top and side views of the environment  200  when a synthetic landing beam  220  is determined in the final segment of an approach. In the final segment of the approach, the stabilized path is determined relative to a touchdown point on the carrier  210  with an inclusion of deck motion compensation. In the final segment, the synthetic path is damped relative to the motion of the centerline of the canted deck of the carrier  210  and the touchdown point. The closer to the touch down point the less will be the damping of the synthetic path. Deck motion compensation is also used to generate the final synthetic path that may include lead compensation to estimate the position of the touch down point at the instance of landing. Examples of deck motion compensation algorithms are used in coupled approach systems that are presently being used with the F/A-18. 
       FIGS. 4A and 4B  illustrate an alternate embodiment of the present invention. A dynamic vehicle, such a helicopter carrier  250  (such as an Landing, Helicopter, Assault (LHA) ship), includes multiple landing pads  252   a - c  (static reference points). If a selection is made as to which landing pad an approaching aircraft is to land at, then during the final segment of flight, the synthetic approach path  256  is altered according to the selected landing position. Also, reference points for the newly created synthetic path are generated (see synthetic path  256   a, c  and reference points  258   a ,  258   c ). The reference points  258   a ,  258   c  are selected in order to comply with regard to a published approach, such as Carrier Vessel Nuclear (CVN) and LHA approaches. 
     In one embodiment, stabilized or synthetic path reference points are broadcasted at a generally low broadcast rate of 1 typically 1 Hz to the approaching vehicle  30  when the vehicle  30  is within the approach segment. But when the approaching vehicle  30  is in the final segment of an approach, the reference points are transmitted at a higher rate to the vehicle  30 . The higher rate will be dependant on the dynamics of the carrier  250  and the capabilities of the vehicle  30 . Typical rates for the final segment would be between 10 and 20 Hz, other rates may be used. 
     In one embodiment the data link between the dynamic vehicle  28  and the approaching vehicle  30  is a bidirectional transmission information between vehicles. 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.