Patent Publication Number: US-2018046202-A1

Title: Point-and-shoot automatic landing system and method

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with United States Government (“USG”) support under Contract Number H92241-11-D-0001-0001-0007 awarded by the Department of Defense. The USG has certain rights in the invention. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure is generally related to automatic landing systems for aircraft and more particularly, to a point-and-shoot automatic landing system for aircraft. 
     2. Related Art 
     Many fixed-wing aircraft feature autopilot systems and pilot-aids for takeoffs and landings. The primary purpose of such systems is to enhance the capability for and the safety of takeoff and landing. In the case of rotary-wing aircraft, operational conditions in secluded locations have led to the need for the Degraded Visual Environment (DVE) operating capabilities. This refers to flight operations under severe conditions where downwash generates a cloud of airborne dust, sand, snow, debris, and other obscurants that may partially reduce or fully impair the pilot&#39;s ability to see outside the aircraft. Inability to see outside removes important visual cues for the pilot to control aircraft attitude, speed, altitude, and clearance to terrain features and obstacles. The loss of pilot visual cues in DVE is compensated for using navigation sensors, graphical displays of information, and automatic control of vehicle attitude, speed, and altitude. 
     In general, any equipment that reduces pilot workload or improves pilot situational awareness during critical phases of flight can result in safer operation with greater probability of mission success. One example is the replacement of mechanical needle-based flight instruments with multi-function and moving map displays, which may include various gauges, symbols, and text that indicate sensor data and system status to the pilot. 
     An example of such equipment may be found in the U.S. Army&#39;s advanced model CH-47F Chinook, which has digital avionics with large color displays interfacing with a Digital Automatic Flight Control System (DAFCS). These systems provide an autopilot function that allows pilots to program an approach profile to a waypoint prior to takeoff or during the flight using a keypad. Programming an approach profile to a waypoint may include the following steps:
         a. The pilot keys-in GPS coordinates of a hover point (17 keystrokes);   b. The pilot keys-in GPS coordinates of a final approach fix (17 keystrokes);   c. The pilot keys-in glideslope (2 keystrokes or more);   d. The pilot keys-in hover altitude (3 keystrokes or more);   e. The pilot keys-in terrain altitude (2 keystrokes or more);   f. Once in-flight, the pilot may engage visual steering cues made available to the pilot via a multi-function display (MFD) in the cockpit, to execute the programmed approach (3 buttons);   g. The pilot makes flight control inputs to satisfy visual steering cues;   h. The pilot may optionally engage the autopilot to keep visual steering cues satisfied (1 button); and   i. The pilot may terminate the preprogrammed mission at any time (1 button).       

     There are several drawbacks with this traditional autopilot concept, with primary drawbacks being that the process requires extensive programming in advance of performing a maneuver and inability to alter parameters during the maneuver. While this may be acceptable in the case of fixed-wing aircraft that fly stabilized approach profiles at a constant airspeed and a constant flight-path-angle to a desired touchdown point on a prepared runway, in the case of vertical takeoff and landing (VTOL) aircraft, i.e., rotary-wing helicopters and other powered-lift aircraft capable of hovering, a VTOL approach is highly dynamic with changing airspeed, changing engine power demand, changing flight path, and changing angle-of-attack. Thus the VTOL approach may trace either a line or an arc through the sky to a touchdown or hover point, and manually performing such an approach requires pilot inputs in all four primary axes of control to both cause and compensate for the changing conditions. Moreover, the VTOL aircraft landing in confined, unprepared, landing zones without fences may discover other vehicles or obstructions fouling the intended aim point upon arrival and therefore may be forced to divert to an alternate location in the immediate vicinity. 
     To realize the safety and mission effectiveness benefits of fixed-wing transports in VTOL aircraft, there is a need for an improved point-and-shoot automatic landing system that provides a pilot of an aircraft with the capability of quickly selecting an aim point while in-flight, and once selected, the navigation systems of the aircraft will automatically guide the aircraft to that selected aim point, while still allowing the pilot to repeatedly change the aim point and to adjust or override automatic flight control inputs. The pilot may be physically located inside the aircraft or remotely located when controlling an Unmanned Aerial Vehicle (UAV). 
     SUMMARY 
     A point-and-shoot automatic landing system (“P-A-S ALS”) and method of utilizing the P-A-S ALS are disclosed. In general, the P-A-S ALS comprises:
         a. An inceptor device to receive force inputs from a pilot for selecting an aim point that represents the termination of a planned mission segment;   b. An aiming device that shows the pilot the selected aim point;   c. A ranging device to determine the aircraft&#39;s position relative to the selected aim point;   d. An approach profile guidance algorithm that governs the aircraft&#39;s altitude, speed, and direction into the selected aim point based on ranging device input; and   e. One or more devices that confirm deceleration to landing at the selected aim point is possible.       

     The inceptor device receives force inputs from the pilot that command movement of an aim point symbol to the desired aim point. Example inceptor devices may include:
         a. Primary flight control sticks;   b. A dedicated secondary control joystick;   c. A trackball;   d. A mouse; and   e. A four-way switch to slew the desired aim point.       

     The aiming device provides visual indication of the selected aim point to the pilot. Example aiming devices may include:
         a. A gimbaled laser pointer directed at the selected aim point and viewable outside the aircraft;   b. A camera directed at the selected aim point and displayed inside the aircraft; and   c. A mark on an overhead moving-map display inside the aircraft.       

     The ranging device detects distance, azimuth, and elevation from the aircraft to the selected aim point. Alternatively, multiple sensors may provide the geometric equivalent. Example ranging devices may include:
         a. Laser range finders;   b. Radar range finders;   c. Radar altimeters limited to operation over flat terrain; and   d. Radar altimeters combined with digital terrain elevation data.       

     The approach profile guidance algorithm calculates the desired flight path to the selected aim point utilizing aiming commands generated from the aiming device and ranging device data. The approach profiles may have fixed or programmable characteristics. In an example implementation, the approach profiles may comprise horizontal and vertical commands that include horizontal groundspeed and vertical velocity commands that may be computed from ranging device distance and elevation data, respectively. A commanded ground track may be computed from ranging device azimuth data. A radar altimeter may be used to compute a vertical velocity command during a final vertical descent to landing at the selected aim point. Example approach profiles may include:
         a. Constant flight path angles;   b. A constant vertical speed;   c. A constant deceleration rate of horizontal groundspeed; and   d. Combinations of the above.       

     The approach profiles may have fixed or programmable characteristics which may be entered into the P-A-S ALS by the pilot through a keypad, touch screen, buttons, or soft (configurable) buttons. Example programmable characteristics may include:
         a. Flight path angle;   b. Profile vertical speed;   c. Vertical deceleration rate;   d. Horizontal deceleration rate; and   e. Vertical speed at touchdown.       

     Once the P-A-S ALS determines an approach to the selected aim point is achievable, the pilot may relinquish control to the P-A-S ALS all the way to landing at the selected aim point, or in the alternative, hovering above the selected aim point or tracking a moving aim point. At any time during an approach, the pilot may terminate the approach and select a new aim point, whereupon the P-A-S ALS will immediately compute an approach profile to the new aim point and control the aircraft into that aim point. If the pilot attempts to select an aim point that is not achievable, then the P-A-S ALS may provide immediate feedback to the pilot. Example feedback devices may include:
         a. Tactile cues from the inceptor;   b. Visual indication; and   c. Aural indication.       

     Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention may be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a system block schematic diagram illustrating an example of an implementation of a point-and-shoot automatic landing system (P-A-S ALS) in accordance with the present disclosure. 
         FIG. 2  is a schematic diagram of an aiming device utilizing a gimbaled laser pointer for the pilot to view an aim point outside the aircraft in accordance with the present disclosure. 
         FIG. 3  is a schematic diagram of an aiming device utilizing a multi-function display inside the aircraft to present the pilot with a crosshair symbol superimposed over a camera video of the aim point. 
         FIG. 4  is a schematic diagram of an aiming device utilizing an overhead moving map with an aim point symbol. 
         FIG. 5  is a graph of a horizontal approach profile in accordance with the present disclosure that uses ranging device distance remaining data and a constant deceleration rate in horizontal groundspeed to command horizontal groundspeed. 
         FIG. 6  is a graph of several possible vertical approach profiles using ranging device distance remaining and elevation data to command vertical speed. 
         FIG. 7  is a flow diagram of an example of a process whereby a pilot of an aircraft selects an aim point on a display using flight controls and a P-A-S ALS in accordance with the present disclosure and determines an approach profile to the selected aim point. 
     
    
    
     DETAILED DESCRIPTION 
     A point-and-shoot automatic landing system (“P-A-S ALS”) and method are disclosed.  FIG. 1  is a system block schematic diagram illustrating an example of an implementation of a P-A-S ALS  100  in accordance with the present disclosure. 
     The P-A-S ALS  100  operation may be engaged manually by a force input  162  from a pilot  160  or automatically by the Autopilot System  140 . Once the P-A-S ALS is engaged, the Aiming Device(s)  130  are configured to provide a visual indication  132  of the P-A-S ALS aim point over signal path  134 . The visual indication  132  of the aim point may be a gimbaled laser pointer viewable outside the aircraft, a camera directed at the aim point for an internal display inside the aircraft, or a mark on an overhead moving map display inside the aircraft. The Aiming Device(s)  130  receive the P-A-S ALS aim point data  174  from the Approach Profile Guidance Algorithm  120  over signal path  172 . 
     Once the Aiming Device(s)  130  provide the pilot  160  with visual indication  132  of the aim point, the pilot  160  may select the desired aim point through force inputs  162  to Inceptor Device(s)  110  over signal path  164  that move an aim point symbol on the gimbaled laser pointer, the internal display, or the overhead moving map display to the desired aim point, whereupon the pilot  160  may then select the aim point. The pilot  160  may also select a desired speed and altitude at the desired aim point through force inputs  162 . The Inceptor Device(s)  110  send the Approach Profile Guidance Algorithm  120  aiming commands  126  based on force inputs  162  over signal path  122 . The pilot  160  can modify the aim point in this manner at any time once the P-A-S ALS  100  is engaged. The Inceptor Device(s)  110  may be the primary flight controls of an aircraft, a dedicated secondary control joystick, a trackball, a mouse, or a 4-way switch to slew an aim point. 
     The Ranging Devices  102  provide distance, azimuth and elevation data  104  to the Approach Profile Guidance Algorithm  120  over signal path  106 . The Ranging Devices may include a laser range finder, radar range finders, radar altimeters limited to operation over flat terrain and radar altimeters combined with digital terrain elevation. The ranging device may be a single device or a suite of devices. 
     The Approach Profile Guidance Algorithm  120  uses the aiming commands  126  and the ranging data  104  to calculate an approach profile to the aim point selected by the pilot  160 . These calculated approach profiles generated by the Approach Profile Guidance Algorithm  120  may include constant flight path angle, constant vertical speed, constant horizontal deceleration rate or any combination thereof. The calculated approach profile may also include fixed or programmable characteristics, which may include flight path angle, profile vertical speed, vertical deceleration rate, horizontal deceleration rate and vertical speed at touchdown. 
     Once the desired approach profile is generated, the Approach Profile Guidance Algorithm  120  transmits a plurality of approach profile commands  142  to the Autopilot System  140  over signal path  144 , whereupon the Autopilot System  140  commences to automatically control the flight of the aircraft to a desired speed and altitude at the aim point selected by the pilot  160 . In an example operation, the Approach Profile Guidance Algorithm  120  computes controls in three to five axes of control for position, altitude, heading and pitch attitude, and the plurality of approach profile commands  142  include distance data, aircraft speed data, aircraft elevation data, and aircraft azimuth data relative to the selected aim point. 
     The Approach Profile Guidance Algorithm  120  will continuously receive ranging data  104  and aiming commands  126  to generate a plurality of approach profile horizontal and vertical commands  142  that are updated in real-time and transmitted to the Autopilot System  140 . This process continues until the aircraft reaches the selected aim point unless the automatically-controlled approach profile is earlier terminated by the pilot  160 . 
     In computing the desired approach profile, the Approach Profile Guidance Algorithm  120  may determine that an approach profile to the selected aim point is not achievable within pre-determined aircraft performance and passenger comfort limits. Examples of aircraft performance limits include engine power, rotor speed, sideslip envelope, and maximum descent rate. Examples of passenger comfort limits include maximum angular accelerations and maximum linear accelerations. The Approach Profile Guidance Algorithm  120  will continuously compute if the approach profile is achievable within these limits. 
     The Approach Profile Guidance Algorithm  120  may communicate aim point status to the pilot  160  through the Audio/Visual Device(s)  150 , the Inceptor Device(s)  110  or the Aiming Device(s)  130 . 
     The Approach Profile Guidance Algorithm  120  may transmit warnings  152  via signal path  154  to Audio/Visual Device(s)  150  to present aural or visual cues  156  via signal path  158  to the pilot  160  that indicate that there is no achievable approach profile and another aim point must be selected. Other cues that may be presented to the pilot  160  by the Approach Profile Guidance Algorithm  120  through the Audio/Visual Device(s)  150  may include distance-to-go and time-to-go to the aim point. 
     The Inceptor Device(s)  110  may provide tactile cues  112  to the pilot  160  over signal path  114  informing the pilot  160  that a calculated approach profile is not achievable or possible. Such tactile cues may include softstops on or shaking of the flight controls. The Approach Profile Guidance Algorithm  120  may transmit aim point status information  124  to the Inceptor Device(s)  110  via signal path  122 . 
     The Approach Profile Guidance Algorithm  120  may also communicate with the pilot  160  through the Aiming Device(s)  130 , which are configured to display the visual indication  132  of the aim point to the pilot  160 . The Aiming Device(s)  130  may indicate to the pilot  160  that the calculated approach profile is not achievable. The Aiming Device(s)  130  may also indicate to the pilot  160  the nearest achievable aim point(s), recommended aim points(s), and time-to-go or distance-to-go to aim point(s). The Aiming Device(s)  130  may indicate this information to the pilot  160  through text, color or symbols. 
     If the pilot  160  wishes to terminate the automatically-controlled flight by the Autopilot System  140  for whatever reason, he may do so at any time through force inputs  162  to the Inceptor Device(s)  110 . 
     The circuits, components, modules, and/or devices of, or associated with, the P-A-S ALS  100  are described as being in signal communication with each other, where signal communication refers to any type of communication and/or connection between the circuits, components, modules, and/or devices that allows a circuit, component, module, and/or device to pass and/or receive signals and/or information from another circuit, component, module, and/or device. The communication and/or connection may be along any signal path between the circuits, components, modules, and/or devices that allows signals and/or information to pass from one circuit, component, module, and/or device to another and includes wireless or wired signal paths. The signal paths may be physical, such as, for example, conductive wires, electromagnetic wave guides, cables, attached and/or electromagnetic or mechanically coupled terminals, semi-conductive or dielectric materials or devices, or other similar physical connections or couplings. Additionally, signal paths may be non-physical such as free-space (in the case of electromagnetic propagation) or information paths through digital components where communication information is passed from one circuit, component, module, and/or device to another in varying digital formats without passing through a direct electromagnetic connection. 
       FIG. 2  is a schematic diagram of an aiming device using a gimbaled laser  202  mounted on the aircraft  200  and viewable outside the aircraft. In this display example the aim point  204  is on a prepared runway  206  in a controlled airspace  208 . With a prepared landing surface and controlled airspace, many approach profiles are achievable, which is not always the case for VTOL aircraft. A few example approach profiles  210 ,  212  and  214  to the aim point  204  are shown. 
       FIG. 3  is a schematic diagram of an aiming device utilizing a multi-function display inside the aircraft with the aim point marked at the center of a crosshair symbol  302  superimposed over a display of an aircraft-mounted camera directed at the aim point. The content displayed in  FIG. 3  may include information retrieved from aircraft sensors, helicopter-mounted cameras, radars and any other available sensors. The sensor data can be fused together with information from on-board databases and data links to external sources, such as off-board databases. In this display example, the aircraft is responding to an emergency situation. Pre-planning a detailed approach profile is unlikely in this scenario due to uncertainty of exact aim-point coordinates and exact object locations within the landing zone. While the location and required clearance height of some stationary obstacles, such as power lines  320 , trees  322 A and  322 B, and housing structure  324 , may be known in advance, the exact location and clearance height of moving obstacles such as the ambulance  314 , truck  316  or fire  318  would not be known until observing the area. These obstacles may eliminate the use of a pre-programmed approach, requiring a piloted approach to an unprepared landing surface  332  where slope and dust conditions pose safety risks and may reduce mission effectiveness. With the P-A-S ALS system, the pilot only has to select an aim point, e.g., unprepared landing surface  332 , using crosshair symbol  302 , which is a safe distance from obstacles, and the system will automatically land the aircraft at unprepared landing surface  332 . If the situation requires the pilot to change the original aim point, the pilot can change the aim point with only force inputs  162  to Inceptor Device(s)  110 ,  FIG. 1 . 
       FIG. 4  is a schematic diagram of an aiming device utilizing an overhead moving map with crosshair  402  marking the aim point. The Moving Map Display  400  shows a portion of an overhead moving map selected by the pilot. The Moving Map Display  400  shows a river  410  and several mountains  420  which must be avoided. In some cases, as the pilot approaches the aim point, it may be necessary for the pilot to switch from an overhead moving map display to a display that shows the aim point in greater detail, e.g., a visual display like  FIG. 3 . In any situation, the pilot may use force inputs to select a new aim point in order to complete his assigned mission. 
       FIG. 5  is a graph of a horizontal approach profile in accordance with the present disclosure that uses ranging device distance remaining data and a constant deceleration rate in horizontal groundspeed to calculate desired horizontal groundspeed where the y-axis  502  of graph  500  represents horizontal groundspeed (in knots) and the x-axis  504  represents horizontal distance of an aircraft to an aim point (in nautical miles). Profile  510  represents a horizontal approach profile in accordance with the present disclosure, such that the horizontal groundspeed of the aircraft is decelerating at a constant rate as the aircraft approaches the aim point. 
       FIG. 6  is a graph of several possible vertical approach profiles using ranging device distance remaining and elevation data to calculate desired vertical speed. Graph  600  shows Height-Above-Aim-Point (in feet) on the y-axis  602  versus distance remaining to an aim point (in nautical miles) on the x-axis  604 . Profiles  610 ,  612 ,  614 , and  616  represent constant flight path angle approaches at angles of 3, 4, 5, and 6°, respectively. Profile  620  represents a constant vertical speed approach of 240 feet-per-minute sink rate. 
       FIG. 7  is a flow diagram of an example of a process whereby a pilot of a VTOL aircraft selects an aim point with a P-A-S ALS, which automatically calculates an approach profile to the selected aim point and allows an Autopilot System to automatically fly the aircraft along the calculated approach profile in accordance with the present disclosure. Starting at step  702 , the pilot selects a display with which to begin planning an approach profile for his assigned mission in step  704 . Generally, the pilot will have numerous displays available to him in his aircraft, where these displays may provide real-time images and/or data received from on-board aircraft sensors, on-board aircraft radars, on-board aircraft cameras, on-board aircraft databases, and data links connected to off-board databases, and where the displays may include any type of multi-function display (MFD) such as overhead moving map displays, heads-down displays, heads-up displays, and helmet displays. 
     In step  706 , the pilot, using flight control inputs, may view the selected display and search for a suitable aim point for the assigned mission. Once satisfied with the aim point, the pilot selects the aim point in step  708 . The aim point may be selected by the pilot placing a symbol, such as a crosshair or aircraft icon, of the display on the desired aim point and clicking or pressing a button. 
     In step  710 , the P-A-S ALS automatically calculates an approach profile to the aim point. The desired approach profile parameters may be fixed, may be programmable, or may have been selected earlier. In decision step  712 , the P-A-S ALS determines if the approach profile is achievable. If the approach profile is achievable, the process continues to step  714 , where the P-A-S ALS commences to automatically fly the aircraft to the selected aim point using the approach profile calculated by the P-A-S ALS. In decision step  720 , at any time during the automatically-controlled flight, the pilot has the option to terminate the flight and select a new aim point. If the pilot chooses this option, the process returns to step  706 . An approach profile guidance algorithm continuously updates the approach profile at step  710  and confirms that the approach profile is achievable in decision step  712 . As more information is collected by the sensors of the P-A-S ALS, it may be determined that the approach profile is no longer achievable in decision step  712 . Once the aim point is reached, the automatically-controlled flight is terminated  730 . 
     Returning to decision step  712 , if the P-A-S ALS determines the approach profile is not achievable, the process proceeds to step  722 , where the P-A-S ALS may provide the pilot with tactile, visual or aural cues that inform the pilot that the selected aim point is not achievable. The process then returns to step  706 , where the pilot can reinitiate the process. 
     It will be understood that various aspects or details of the invention may be changed without departing from the scope of the invention. It is not exhaustive and does not limit the claimed inventions to the precise form disclosed. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation. Modifications and variations are possible in light of the above description or may be acquired from practicing the invention. The claims and their equivalents define the scope of the invention.