MX2008006166A - Control system for automatic circle flight - Google Patents

Abstract

A flight control system for an aircraft is configured for receiving command signals representing commanded values of a location of a geospatial point and a radius about the geospatial point for defining a circular groundtrack. A sensor determines a geospatial location of the aircraft and provides a location signal representing the location of the aircraft. A controller for commanding flight control devices on the aircraft controls the flight of the aircraft and is configured to receive the command signals and the location signal. The controller uses the command signals and location signal to operate the flight control devices to control the flight of the aircraft for directing the aircraft generally toward a tangent point of the circular groundtrack and then maintaining a flight path along the circular groundtrack.

Description

SYSTEM OF CONTROL FOR AUTOMATIC FLIGHT IN CIRCLE TECHNICAL FIELD The present invention relates generally to the field of flight control systems for aircraft and is particularly related to a system for achieving and maintaining a circular flight path around the selected fixed or mobile point.

DESCRIPTION OF THE PREVIOUS TECHNIQUE It is often desirable to fly an aircraft in a trajectory describing a closed-cycle surface path around a particular area of interest, such as an accident site or an area that is searched. One of the benefits is that the aircraft maintains a distance from the area, providing a continuous line of sight from the aircraft to the area of interest. When the aircraft is being flown in manual control, either by a pilot on board the aircraft or by a pilot operating the aircraft remotely, the pilot can maintain the desired trajectory around the area by observing the area of interest and controlling the flight of the aircraft. the aircraft in response to the observation. One way this can be achieved is for the pilot to fly the aircraft in a laterally inclined flight position, maintaining a generally constant turn to circle the area of interest. The pilot may attempt to fly the aircraft on a circular path around a particular point, which could be located by conventional navigation means such as radio signals or using the Global Positioning System. To maintain a circular path, the pilot must maintain a constant radial distance from the selected point. An alternative method to fly a closed cycle is to fly to the reference points and turn the aircraft to the next reference point in a looping sequence. This method is illustrated in Figure 1, which represents a trajectory 13 generally circular about an area of interest 11. The trajectory 13 is defined by a number of reference points and the flight segments connecting the adjacent reference points. . As shown, the path 13 comprises eight reference points, labeled from A to H, although the path 13 may comprise more or less reference points. The pilot flies the aircraft from each reference point to the adjacent reference point, and the trajectory can be flown in any direction. For example, an aircraft can start the trajectory 13 at a reference point A and fly along the segment 15 straight to the reference point B. At the reference point B, the pilot rotates the aircraft in a straight line towards the reference point C, flying the aircraft along the segment 17. The pilot continues to fly towards a subsequent reference point along the straight segments and completes the trajectory 13 flying from the reference point H to the reference point A along segment 19. The pilot can then continue on trajectory 13 by flying again at reference point B. The requirement for the on-board or remote pilot to manually fly the aircraft in the desired path increases the workload of the aircraft. pilot and reduces the pilot's ability to observe the area of interest. Also, it can be difficult for the pilot to maintain a desired distance from the site while circling, especially in windy conditions. For the reference point method to describe a circular path, the path must have a large radius or many reference points. Selecting this group of reference points can be difficult and time consuming. Many modern aircraft, including manned and unmanned aircraft, have flight control systems to maintain the selected flight parameters at or near the selected values. These parameters can include: altitude, course, surface trajectory, altitude and / or speed, and the control system maintains each parameter through the commands sent to the flight control systems of the aircraft. The speed can be controlled as the speed of flight or the inertial speed of the aircraft. The speed of flight is defined as the frontal velocity of the aircraft with respect to the mass of air in which the aircraft is flying, while the inertial velocity is defined as the velocity of the aircraft with respect to ground over which the aircraft it's flying. The existing flight control systems provide an automatic flight along the closed cycle path flying towards the reference points. Alternatively, an aircraft can be commanded to fly aimlessly around or near an area, in which flight control systems fly the aircraft in complicated patterns or landing paths. For example, some systems will control the aircraft to fly over a selected point on the ground, which can be given as GPS coordinates or through other coordinate systems, then rotate the aircraft around to fly over the same point again. The runways of these trajectories may be of regular patterns, such as a "figure 8" pattern, or the trajectories may be irregular in shape. The disadvantage of these systems is that they can not provide a continuous line of sight or may require a replenishment of observers or devices in the aircraft to continue observations of the area of interest.

BRIEF DESCRIPTION OF THE INVENTION There is a need for a flight control system that provides automatic flight around a circle of a center and ordered radio at an ordered altitude and speed. Therefore, it is an object of the present invention to provide a flight control system that provides automatic flight around a circle of a center and radio arranged at an ordered altitude and speed. A flight control system for an aircraft is configured to receive command signals representing ordered values of a site of a geospatial point and a radius on the geospatial point to define a circular surface path. A sensor determines a geospatial site of the aircraft and provides a signal from the site that represents the site of the aircraft. A controller for controlling the flight control devices in the aircraft controls the flight of the aircraft and is configured to receive the command signals and the signal from the site. The controller uses the command signals and the site signal to operate the flight control devices to control the flight of the aircraft to direct the aircraft generally towards a tangential point of the surface trajectory and then maintain a flight path throughout of a circular surface path. The present invention provided for various advantages, including: (1) the ability for a system to automatically operate the aircraft to fly in a circle having a selected center and radius; and (2) the ability to intercept and fly a circle from an initial point located inside or outside the circle.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, including these features and advantages, reference is now made to the detailed description of the invention taken in conjunction with the accompanying drawings in which similar numbers identify similar parts, and in which Figure 1 is a schematic view of the flight path of an aircraft when a prior art reference point method is used to fly an aircraft around an area of interest; Figure 2A is a schematic view of a flight control system in accordance with the present invention and configured to be used with a remotely piloted aircraft; Figure 2B is a flowchart view of a portion of the flight control system of Figure 2A. Figure 3 is a perspective view of an aircraft having the flight control system shown in Figure 2A; Figure 4 is a graph of a surface trajectory of the flight of an aircraft, the flight of an aircraft being controlled by the system of Figure 2A to fly in a circular path in a clockwise direction, the aircraft has initiated outside the pre-written circle; Figure 5 is a diagram of a surface trajectory of the flight of an aircraft, the flight of the aircraft is controlled by the system of Figure 2A to fly in a circular path in a clockwise direction, the aircraft has initiated outside the pre-written circle; Figure 6 is a diagram of a surface trajectory of the flight of an aircraft, the flight of an aircraft is controlled by the system of Figure 2A to fly in a circular path clockwise, the aircraft has started within the prescribed circle, Figure 7 is a diagram of a surface trajectory of a flight of an aircraft, the flight of the aircraft is controlled by the system of Figure 2A to fly in a circular path in a counterclockwise direction, the aircraft has started within the preset circle, and Figure 8 is a diagram of a surface trajectory of the flight of an aircraft, the flight of the aircraft is controlled by the system of Figure 2A to fly in a circular path in the opposite direction to the hands of the clock, the aircraft has started from a position towards the center of the prescribed circle DESCRIPTION OF THE PREFERENTIAL MODALITY The present invention is directed to a flight control system configured to automatically control the flight of an aircraft, so that the aircraft flies to a selected area of interest and circumvents a selected point in the area at a specified radius, altitude and speed. Specifically , the system generates a cross-slope order or list to tilt the aircraft in a turn and uses the list order with the speed and altitude error signals to fly the selected circular path The control system requires only one point in space and a radius to define the circle and is useful for controlling the flight of the manned or unmanned aircraft of all types, including helicopters, tilt-rotor aircraft and fixed-wing aircraft. The system is particularly suitable for use on an aircraft that performs reconnaissance missions. surveillance, search, rescue and military For example, a medical evacuation helicopter used to transport patients in trauma could use the system when it is sent to the scene of the accident. The dispatcher could provide the helicopter crew with the coordinates of the accident, and the system could allow the helicopter to get there in the fastest time possible without the need to follow the marks on the ground. Similarly, a helicopter to which the law applies could be sent to a specific site and encircle the site without the requirement of the pilot's entry. Another example is the use of the system for a helicopter used to provide traffic reports, the helicopter is able to quickly and easily obtain the site of a specific accident or traffic and then circle the area. The military ships can use the invention system for the gunboat, which allows the aircraft to surround the identified objectives. The system of the invention commands an aircraft to automatically fly in a circular path over any selected point (longitude and latitude, or specify in another reference system that has been programmed in the flight control system) by selecting the following parameters: (1 ) central point of the circle, or point of the circle; (2) radius of the circle; (3) flight speed or inertial velocity to be flown; (4) altitude to be flown; and (5) direction of rotation on the circle to be flown. It should be noted that the circle pattern can easily be changed to a spiral of any dimension by continuously changing the radius and / or the speed of flight commanded. It is also not necessary for the center point of the circle to remain fixed. The center point can be a moving target as well as the speed of the center point is less than the command speed of the aircraft. Referring to the figures, Figure 2A is a schematic view of one embodiment of the control system according to the invention. The control system 21 is specifically configured to be used with a remotely piloted, unmanned aircraft, such as an aircraft 23 of Figure 3, although the system 21 may alternatively be configured to be used with any type of manned or unmanned aircraft. The aircraft 23 is an inclined rotor aircraft driven by rotors 25, which are rotatably mounted to mobile pods 27. Each nacelle 27 is capable of pecking with respect to an associated wing 29 between a position corresponding to the flight mode of an airplane, shown in the figure, and a position corresponding to a helicopter mode, wherein the propulsion rotors 25 rotate in a generally horizontal plane. The propulsion rotors are driven by one or more engines (not shown) carried within a fuselage 31 or in each nacelle 27. A turret 33 is rotatably mounted on the fuselage 31 to provide a rotary assembly for the sensors (not shown) ), which may include optical, infrared or other types of sensors. E system 21 of Figure 2 is based on a computer and preferably carried within aircraft 23, although portions of system 21 may be remotely located from the aircraft. Referring again to Figure 2A and Figure 2B, the system 21 comprises an automatic circle flight control system 35 that receives the transmitted command data from a Ground Control Station (GCS) 36 through a receiver 37 carried in aircraft 23, the command data represent the parameters for the command circle maneuver. In addition, the system 35 is also provided with the data representing the site, speed, and altitude of the aircraft 23. The site data is provided by at least one position sensor 39, such as an inertial navigation sensor (INS), a RADAR system, or a sensor capable of calculating a position from the signals of the Global Positioning System (GPS). At least one speed sensor 41 provides the data representing the speed of the aircraft 23, and this speed can be measured as the flight speed and / or the inertial velocity for the comparison of the control speed to be flown during the maneuver. in a circle. In the embodiment shown, the measured and commanded speed is the speed of flight or of the aircraft 23. An altitude sensor 43 provides the altitude data, which can be provided as altitude above sea level or as altitude above the altitude. local terrain. The system 35 uses the data provided by the sensors 39, 41, 43 and the command data from the receiver 37 to operate the flight control devices 45 on the aircraft 23 to cause the aircraft 23 to fly in accordance with the parameters commanded Figure 2B is a view of a flow diagram of a circle flight control system 35, which comprises three sections of the system 47, 49, 51, each section 47, 49, 51 performs the calculations to affect a aspect of the flight of the aircraft 23. Section 47 generates an inclination command signal 53, section 49 generates an error signal of flight speed 55, and section 51 generates an altitude error signal 57. The combination of signals 53, 55, 57 shows the system 35 for commanding the flight control devices 45 for maneuvering the aircraft 23 in the ordered path. In operation, the section 47 of the system 35 calculates in step 59 the range and is oriented towards the point of the ordered circle. These calculations are computed by comparing the position of the point of the circle 100, which is provided through the receiver 37, to the site of the aircraft 101, which is provided by the position of the sensor 39. These calculations are then used in step 61 to determine a surface path, which is a two-dimensional projection of the flight path of the aircraft 23 as seen from the top of the aircraft 23, from the current position of the aircraft 23 to the point where it is tangent to the ordered circle. The surface path is calculated using the selected radius 102, which indicates the distance from the center point of the circle to the tangential point 103, and using the direction of travel around the circle 104, which determines which side of the circle of the surface path it will be intercepted. The surface path is preferably a straight path that is perpendicular to the radius of the circle at the tangential point, although other paths can be used when necessary, such as to avoid terrain or evade detection. The selected radius and the direction of travel (clockwise or counterclockwise 105) are also provided to the system 35 through the receiver 37. The circle can be focused either externally or internally to the circle, depending on the speed of the aircraft and the position with respect to the circle when the commands are given to the system 21. When the distance to the tangential point is greater than the radius of the ordered circle 106, section 47 controls the flight of aircraft 23 to the tangential point. Once step 63 is carried out as aircraft 23 intercepts tangent 107 (or is within the selected range of the tangential point), section 47 will begin to generate the tilt command 53 to continuously fly aircraft 23 to along the circumference of the circle. In step 65, the site of the aircraft 23 is continuously compared to the site of the radius in a circle to determine the distance of the aircraft 23 from the center of the circle. If the distance is greater than the commanded radius, an error radius will be indicated, step 65 alters the tilt control 53 to blow the control devices 45 in order to drive the error radius to zero. In the embodiment of Figure 2B, section 49 of the system 35 calculates the error of the flight speed 55, which is used to control the throttles or other devices on the aircraft 23 to preserve the selected flight speed. The selected flight speed is either a commanded flight speed when the aircraft 23 is flying towards the tangential point of the desired circle (the air velocity in flight) or the commanded flight speed at which the aircraft 23 is maintained when it flies around of the circle (speed of flight in a circle). In addition, section 49 includes an increment function to change the flight speed of aircraft 23 from the "in flight" flight speed to the circle flight speed, if the flight speed values are different. The rate of increase is expressed as an index of change in flight speed, such as 1 kt / sec. At the beginning of section 49, step 67 is provided for the computation of the distance from the circle where the rate of increase from the command of the existing flight speed 108 which must start for the aircraft 23 to travel to the circle flight speed 109 selected at approximately the same time as aircraft 23 intercepts the circle. This distance output, shown as "B" in the figure, is compared to the output of step 69, which determines the range of the tangential point using the selected radius and the range towards the center of the circle, which is produced at starting from step 59 of section 47. The value of the output represents the range of the tangential point as shown in figure "A". In step 71, the values A and B are compared to determine if A is less than B. If not, this means that aircraft 23 is still too far from the intercept point of the tangent to begin the increase in flight speed , and the system 35 continues to use the flight speed command in previous flight 110 as the flight speed command 11 produces a node 73. The production of the flight speed command is summed with a flight speed command. feedback 1 12 which represents the current flight speed of the aircraft 23 to produce the error in the flight speed 55, which is used to operate the devices on the aircraft 23 to control the flight speed in such a way that the error of the flight Flight speed 55 is minimized. If A is less than B, this means that the aircraft 13 is at or within the distance from the tangential point necessary to increase the flight speed at the selected index. Step 75 produces a new flight speed output command to increase the flight velocity output at the index selected from the command prior to the circle flight speed command, and this output from the velocity command flight is added to node 73 with the flight speed feedback signal to calculate the flight speed error 55. In the same way as that used in section 49 to calculate the error of the flight speed in section 51 the error of altitude 57 is calculated, which is used to operate the flight control surfaces or other devices of the aircraft 23 to maintain the selected altitude. The selected altitude is either a commanded altitude when aircraft 23 is flying towards the tangential point of the desired circle (at an altitude "in flight") or the commanded altitude that aircraft 23 maintains when flying around the circle (altitude in a circle) . In addition, section 51 includes an increment function to change the altitude of aircraft 23 from the altitude "in flight" to the altitude in a circle, if the altitude values are different. The rate of increase is expressed as the rate of change in altitude, such as, for example, 1000ft / min. At the beginning of section 51, step 77 provides for computation of the distance of the circle where the rate of increase from the existing altitude command 113 must begin such that the aircraft 23 travels at the selected circle altitude 1 14 at approximately the same time that the aircraft intercepts the circle. This distance produced is shown as "C" in the figure and is compared in step 79 to produce "A" in step 69 to determine if A is less than C. If not, aircraft 23 is still too far away from the point. intercept of the tangent to begin altitude increment, and system 35 continues to use the previous "in flight" altitude command 115 as altitude command 116 produces node 81. The production of the altitude command is added with a feedback signal 117 representing the current altitude of aircraft 23 to produce altitude error 57, which is used to operate aircraft devices 23 to control altitude so that altitude error 57 is minimized. If A is less than C, aircraft 23 is at or within the distance from the tangential point necessary to increase the altitude at the selected index. Step 83 produces a new altitude command to increase the production of the altitude command in the index selected from the selected index of the command prior to the circle altitude command, and this production of the altitude command is added to node 81 with the altitude feedback signal to calculate altitude error 57. It should be noted that the modality shown in the figures includes the use of flight speed commands to control the speed of the aircraft, although the inertial speed of the commands may also or alternatively be used to command the speed of an aircraft controlled with the system 35. Also, certain limitations must be observed in order to achieve the ordered circle. For example, the specific speed and radius must be compatible to prevent the aircraft from continuously exceeding the circumference of the circle. In system 21, system commands 35 are shown as being transmitted to the aircraft from a ground control station (GCS), although other methods for entering commands may be used. For example, all commands can be entered into the system 35 before the flight of the aircraft, and this method can be used when the aircraft is going to fly to a predetermined route to a circle, fly the circle using the parameters commanded for the amount selected time, then return to the launch site or land on an alternate site. Alternatively, only the selected commands can be entered before the flight, such as the "in flight" speed and / or altitude values. Also, it should be noted that the system 35 can easily be used to fly the aircraft in a spiral of a specified dimension by continuously changing the selected radius. For a piloted aircraft, the locations of interest can be pre-programmed in the system 35, the pilot can enter the data as the objectives are identified, or locations of interest can be sent to the pilot from any number of sources. In a fully automated system, the pilot might not have to fly the aircraft. The system 35 could also be used in a piloted aircraft with or without the ability to fly the circle fully automatically. With the help of a flight director, the pilot can be given the necessary information by following the visual cues provided by the system 35 to manually fly the aircraft to the intercept point of the designated circle and to keep the flight around the circle. There are two types of situations in which the system 35 acts to intercept a circle: 1) when an aircraft is out of the command circle as the command circle is given to the system 35; and 2) when an aircraft is within the ordered circle as the ordered circle is given to the system 35. Figures 4 to 8 illustrate the surface trajectory for an aircraft using the system 35 for situations where the aircraft is flying towards the aircraft. north (a heading of 0 degrees) when the circle command is received (or acts on, if it is entered before the flight). Figures 4 and 5 illustrate the situations where the aircraft is outside the ordered circle, and Figures 6 to 8 illustrate the situations where the aircraft is inside the ordered circle. The tracks on the ground do not show the altitude of the aircraft, since are two dimensional top views of the flight path When they approach the circle from the outside of the circle, the system 35 performs the following sequence 1 Compute the distance and direction of the aircraft to the tangential point of the ordered circle 2 Command the flight path of the aircraft to intercept the circle at the tangential point corresponding to the commanded direction of rotation around circle 3 Compute the velocity / distance profile (using the speed specified in the rate of increments) to produce the velocity circle when Intercept the circle 4 Keep the current command speed until it is necessary to change the speed to intercept the circle in the circle speed, and then follow the computed speed / distance profile 5 Compute the altitude / distance profile (using the specified altitude of the increment index) to produce the altitude of the circle when intercepting the circle 6 Keep the altitude currently commanded until it is necessary to change the altitude to intercept the circle at the altitude of the circle, and then follow the computed altitude / distance profile 7 When the aircraft reaches the point where the specified range limit of the tangential point, provides a dashboard to cause an instant spin index to keep the aircraft in a circle radius above the center of the circle. 8. Continue commanding the speed, altitude and the rate of turn to continue flying the ordered circle. 9. If the speed is too high when the circle parameters are given and the aircraft passes the calculated tangential point, the aircraft will try another approach by recalculating the tangential point from its current location and fly the appropriate trajectory at that point and achieve the circle. Figure 4 shows a surface path 85 for an aircraft that is commanded by the system 35 to intercept and fly around the circle 87 having the center 89 and a radius 91. The surface trajectory 85 is determined in a distance plot, which indicates that the radius of circle 91 is 1000 feet and that the center of circle 89 is located 2000 feet east of the starting position and guides the aircraft and 2000 feet north of the initial position of the aircraft. Initially, the aircraft is flying by the portion 93 of the surface path 85, the portion 93 is directed to the north and along the vertical line indicating the east. The circle command is turned on when the aircraft has flown approximately 500 feet, and the aircraft turns to fly to the northwest portion "in flight" 95 to intercept the west section of circle 87 and fly around circle 87 in the direction of the hands of the aircraft. clock. When the aircraft is within the selected distance from the tangential point 97, the system 35 provides a dashboard that acts to maintain the flight path of the aircraft in a radius 91 around the center 89. As shown in the figure, the The aircraft can initially fly to a curved path that deviates slightly from the circumference of the circle 87, although this is corrected as the system 35 that acts to minimize the error using the control panel. Figure 5 shows a surface path 99 for an aircraft commanded by a system 35 to intercept and maintain a circle 101 from the outer circle 101. As the circle 87 of Figure 4, circle 101 has a radius 103 of 1000 feet and a center 105 located at 2000 feet east of the starting position and directs the aircraft and 2000 feet north of the initial position of the aircraft. In this example, the aircraft will fly around circle 101 in an anti-clockwise direction, and the initial turn of the aircraft from portion 107 to the "in flight" portion 109 that directs the aircraft toward the tangential point 111, which is in a south section of the circle 101. Once the aircraft is within a specific range of the tangential point 1 1 1, the system 35 provides a dashboard for flying the aircraft around the circle 101 in the altitude and speed selected. An aircraft can receive a command to circumvent when the aircraft is within the circumference of the desired circle. When approaching the circle from inside the circle, the system 35 carries out the following sequence: 1. Compute the speed and direction to approach the radius of the circle from inside the circle - if the initial velocity is too high, it will be necessary pass out of the circle and approach from the outside. 2. Command the speed and direction to intercept the radius of the circle. 3. Start increasing or decreasing to achieve the altitude of the circle - if the radius of the circle is achieved before the altitude is reached, it continues to increase or decrease until the desired altitude is reached. 4. When the aircraft reaches the point within a limit of the specific range of the radius of the circle, a dashboard is provided to cause the instantaneous turning rate to keep the aircraft in the radius of the circle. 5. Continue commanding the speed, altitude and turning rate to continue flying the ordered circle. Figure 6 shows the surface trajectory 113 for an aircraft commanded by the system 35 to fly to circle 1 15. Circle 115 has a radius 117 of 4000 feet and a center 1 19 located 3,000 feet east of the aircraft's initial site , which places the aircraft at 1000 feet within the circle 115. In this example, the aircraft will fly around circle 155 counterclockwise, and the initial turn of the aircraft from the initial portion 121 to the inclined portion 123 which directs the aircraft to intercept point 125, which is in a northwestern section of circle 1 15. The aircraft may have been flown at a speed sufficiently greater than the aircraft exceeding circle 115, in which case the aircraft will continue with the tilt maneuver to achieve the desired radius. During this time, the system 35 will command the aircraft to accelerate or decelerate to achieve the desired circle speed. Also, the system 35 will command the aircraft to ascend or descend to achieve the altitude of the desired circle. Figure 7 shows a surface path 127 for an aircraft commanded by the system 35 to fly in circle 129 in a counter-clockwise direction. As the example shown in Figure 6, the surface trajectory of Figure 7 shows that the initial position of the aircraft is within circle 129 which has a radius 131 of 4000 feet and a center 133 located at 3000 feet east of the initial position of the aircraft. The initial turn of the aircraft from the initial portion 135 to the inclination portion 137 directs the aircraft to the intercept point 139, which is in a southwestern section of the circle 129. Since the system 35 commands the aircraft for Curving the circle 129 in the 137th portion, the aircraft can fly to intercept the 139th point with very little over-boost or not and then the tilt is achieved and retains the radius of the desired circle. During this time, the system 35 will command the aircraft to accelerate or decelerate and achieve the speed of the desired circle. Also, system 35 will command the aircraft to ascend or descend to achieve the desired circle altitude. Figure 8 also shows a surface path 141 commanded by the system 35 to fly in circle 143 counterclockwise from an initial position within circle 143. Circle 143 has a radius of 145 of 1000 feet and a center 147 located approximately 800 feet north of the initial position of the aircraft. In the example shown, the aircraft has an initial velocity that is high enough so that the aircraft can over-propel the circumference of the circle 143 if the aircraft were to make a turn toward the tangential point 149 from the initial portion 151. both, the system 35 commands the aircraft to initially turn east at the inclination portion 153 to reduce the speed of the aircraft before turning toward the tangential point at the inclined portion 155. This allows the aircraft to intercept the circle 143 at or near the tangential point 149 with little or no over-pulse or sub-pulse, then for the system 35 to command an angle of inclination to maintain the radius of the desired circle. During this time, the system 35 will command the aircraft to accelerate or decelerate and achieve the speed of the desired circle. Also, system 35 will command the aircraft to ascend or descend and achieve the desired circle altitude. As described above as used with an unmanned aircraft, the system of the invention is applicable to all types of aircraft, including manned aircraft. The system of the invention may also incorporate additional features, including: automatic or autonomous search patterns; the ability to detect, follow and circumvent the objective, ability to avoid a collision; and invalidate the methods for returning control to a pilot.

The present invention provides several advantages, including: (1) the ability for a system to automatically operate an aircraft to fly a circle having a selected center and a radius; and (2) the ability to intercept and fly a circle from an initial point located inside or outside the circle. While this invention has been described with respect to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative modalities, as well as other embodiments of the invention, will be apparent to those skilled in the art with reference to the description.

Claims (18)

1. A flight control system for an aircraft, the system comprises: means for receiving the command signals representing the command values of a site of a geospatial point and a radius around the geospatial point to define a circular surface path; means for determining a geospatial site of the aircraft and providing a signal from the site representing the site of the aircraft; and a controller for controlling the flight control devices in the aircraft to control the flight of the aircraft, the controller also being configured to receive the command signals and the site signal; characterized in that the controller uses the command signals and the site signal to operate the flight control devices to control the flight of the aircraft to direct the aircraft to a tangential point of the circular surface path to intercept the circular surface path and then generally maintain a flight path along the circular surface path.

The flight control system according to claim 1, characterized in that it further comprises: means for determining the speed of the aircraft and providing a speed signal representing the speed of the aircraft; wherein the command signals also represent an ordered value of a speed in a circle; and wherein the controller is also configured to receive the speed signal and operate the flight control devices to achieve and generally maintain the speed in a circle along the circular surface path.

3. The flight control system according to claim 2, further characterized in that the controller comprises an increment function to change the current speed of the aircraft to the speed in a circle based on a distance of the aircraft from the tangential point.

4. The flight control system according to claim 1, characterized in that it further comprises: means for determining an altitude of the aircraft and providing an altitude signal representing the altitude of the aircraft; wherein the command signals also represent an ordered value of a circle altitude; and wherein the controller is also configured to receive the altitude signal and operate the flight control devices to achieve and generally maintain the altitude of the circle along the circular surface path.

5. The flight control system in accordance with the claim 4, further characterized in that the controller comprises an increment function to change the current altitude of the aircraft to the altitude of the circle based on the distance of the aircraft from the tangential point.

The flight control system according to claim 1, further characterized in that the means for receiving the control signals is a receiver located in the aircraft and configured to receive command signals transmitted from a remote site of the aircraft.

The flight control system according to claim 1, further characterized in that the means for receiving the control signals is a receiver located in the aircraft and configured to receive the control signals transmitted from a remote site of the aircraft, and wherein the command signals are transmitted from a ground control station.

8. The flight control system according to claim 1, further characterized in that the means for receiving the control signals is an input device located in the aircraft.

9. A method to control the flight of an aircraft, the method comprising: a) entering the command values in a flight controller, the values represent a geospatial site and a radius, characterized in that the site and the radius define a surface trajectory circular mandated; b) compute with the controller a distance and direction from a current site of the aircraft to a tangential point of the circular surface trajectory commanded; c) operating with the controller at least one flight control device of the aircraft to direct the aircraft to the tangential point; d) when the aircraft reaches a site within a specified range of the tangential point, operating with the controller at least one flight control device to cause an instantaneous turning value of the aircraft that generally maintains a flight path of the aircraft in the circular surface trajectory commanded.

The method according to claim 9, further characterized in that it comprises entering in the flight controller a command value representing an ordered circle speed; and operating with the controller at least one flight control device to cause the aircraft to generally maintain the speed of the circle commanded along the commanded circular surface path.

11. The flight control system according to claim 10, further characterized in that it comprises: increasing the speed of the aircraft from the current speed of the aircraft to the speed of the ordered circle based on the distance of the aircraft from the tangential point.

The method according to claim 9, further characterized in that it comprises: entering in the flight controller a command value representing the altitude of the ordered circle; and operating with the controller at least one flight control device to cause the aircraft to generally maintain the altitude of the circle ordered along the ordered circular surface path.

The flight control system according to claim 12, characterized in that it further comprises: increasing the altitude of the aircraft from the current altitude of the aircraft to the altitude of the ordered circle based on the distance of the aircraft to from the tangential point.

14. An aircraft, comprises: flight control devices to control a flight path, speed, the altitude of the aircraft; and a flight control system, comprising: means for receiving command signals representing the commanded values of a site of a geospatial point and a radius on the geospatial point to define a circular surface path; means for determining a geospatial site of the aircraft and providing a signal from the site representing the site of the aircraft; and a controller for controlling the flight control devices, the controller is also configured to receive the command signals and the site signal; characterized in that the controller uses the command signals and the site signal to operate the flight control devices to control the flight of the aircraft to direct the aircraft to a tangential point of the circular surface path to intercept the circular surface path and then generally maintain a flight path in the circular surface path.

15. The aircraft according to claim 14, further characterized in that the aircraft is an unmanned aerial vehicle.

16. The aircraft according to claim 14, further characterized in that the means for receiving the command signals is a receiver located in the aircraft and the command signals are transmitted to the receiver from a remote location of the aircraft.

17. The aircraft according to claim 14, characterized in that it further comprises: means for determining the speed of the aircraft and providing a speed signal representing the speed of the aircraft; wherein the command signals also represent a control value of the speed of the circle; and wherein the controller is also configured to achieve the speed of the signal and operate the flight control devices to achieve and generally maintain the speed of the circle in the circular surface path. The aircraft according to claim 14, further characterized in that it comprises: means for determining the altitude of the aircraft and providing an altitude signal representing the altitude of the aircraft; wherein the command signals also represent a commanded value of a circle altitude; and where the controller is also configured to receive the altitude signal and operate the flight control devices to achieve and generally maintain the altitude of the circle in the circular surface path.