Method for automatically tracking the trajectory of an aircraft using an autopilot, and associated aircraft
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-08-13
Smart Images
Figure EP2025081582_13082026_PF_FP_ABST
Abstract
Description
[0001] METHOD FOR AUTOMATIC TRAJECTORY TRAJECTING OF AN AIRCRAFT USING AN AUTOPILOT AND ASSOCIATED AIRCRAFT
[0002] The present invention relates to a piloting assistance system for a rotary-wing aircraft.
[0003] According to a known teaching, an aircraft can include an autopilot to automatically follow a route, developed and known at the level of a flight management system generally referred to by the English expression "Flight Management System" or by its acronym "FMS".
[0004] When avionics system architectures are based on this functional distribution, the route remains known only at the flight manager level.
[0005] Therefore, in order to follow this route, the aircraft's autopilot receives instructions from the flight management system to change speed or altitude, and a roll command aimed at generating movements along a roll axis in order to change the direction of movement of the aircraft.
[0006] Indeed, assuming that the autopilot will perform a coordinated turn, for an aircraft speed V known to the flight management system, a commanded roll angle phi corresponds to a radius of gyration Rg of the aircraft within the air mass. The equation is given by the formula:
[0007] Rg=V 2 / (g*tan(phi))
[0008] g being the gravitational acceleration constant, and
[0009] tan(phi) the tangent function applied to the roll angle phi. Thus, by controlling the roll angle while taking into account the speed of the aircraft, the flight manager will effectively be able to control the trajectory along arcs of circles with variable radii or straight lines according to the route to be followed.
[0010] Depending on external disturbances, particularly those caused by wind, and the autopilot's response times to roll commands, the flight management system must constantly adjust its control to cancel out course deviations.
[0011] Thus, the flight management system can effectively control the horizontal trajectory with two important limitations which are, on the one hand, an approximate accuracy of the control of the trajectory on the route and not the following of a precise trajectory, and on the other hand, a disengagement of the autopilot when it is no longer able to coordinate the turn according to the roll, that is to say for a rotary-wing aircraft, only in the phases of cruise flight or the autopilot effectively coordinates the turn.
[0012] The aircraft's progress along this trajectory is then monitored by the flight management system. The aircraft's position, and in particular its deviation from the trajectory, is calculated by the flight management system.
[0013] Furthermore, the execution of such coordinated turns by applying a controlled roll angle is only performed by the autopilot from a minimum forward speed, on the order of 40 knots. In fact, automatic trajectory tracking is not possible from takeoff to landing inclusive, but only during level cruise flight phases. The documents US 2016 / 180716 A1 and "Path tracking for waypoint lists based on a pure pursuit method for fixed wing UAS" written by BALAMPANIS FOTIOS ET AL, 2017 WORKSHOP ON RESEARCH, EDUCATION AND DEVELOPMENT OF UNMANNED AERIAL SYSTEMS (RED-UAS) and published on October 3, 2017, are also known.
[0014] The present invention aims to provide an innovative method for overcoming the limitations mentioned above. In this way, the invention extends the level of assistance provided to the aircraft pilot by enabling trajectory tracking throughout the aircraft's entire flight envelope. In particular, when the architectures of an avionics system are based on a flight management system and an autopilot, the invention allows for controlling the trajectory of a vertical takeoff / landing aircraft throughout its entire flight envelope.
[0015] Furthermore, the invention makes it possible to improve the accuracy of control on the trajectory by an autopilot capable of taking into account and anticipating the performance of the aircraft and the wind conditions.
[0016] Furthermore, the invention also aims to enable control of the integrity of a trajectory transfer between a flight manager and an autopilot.
[0017] The invention therefore relates to a method for automatically tracking the trajectory of an aircraft using an aircraft autopilot. According to the invention, such a method is remarkable in that it comprises the following steps: - generation by an aircraft flight management system of a flight trajectory in at least two dimensions having a plurality of segments between a starting point and an arrival point, each segment comprising at least a set of points forming a line segment or a curve, each point being defined at least by a latitude and a longitude,
[0018] - Transfer of the trajectory from the flight management system to an autopilot computer of the aircraft,
[0019] - identification of a current aircraft position measured by an aircraft positioning system,
[0020] - extraction by the autopilot computer of a target position from the trajectory comprising at least a target latitude and a target longitude, the extraction being implemented at least as a function of the aircraft's current position, the target position being located downstream of the current position in a direction of aircraft movement along the trajectory, and
[0021] - control by the autopilot of at least one actuator enabling the movement of an aerodynamic control surface so that the aircraft heads towards the set position.
[0022] In other words, the aircraft's FMS flight management system provides the aircraft's autopilot with the flight path to follow, in its entirety, this flight path being defined by geographical coordinates of points belonging to straight or curved portions.
[0023] The flight management system therefore includes at least one controller configured to generate such a flight trajectory and transmit it to the autopilot computer. Once generated, this trajectory is therefore transmitted to the autopilot computer.
[0024] An aircraft positioning system such as an inertial navigation system or a satellite positioning system, for example one of the GPS, Glonass, Galileo... systems, allows the current position of the aircraft to be measured.
[0025] This aircraft positioning system is also connected by wired or wireless means to the autopilot computer and periodically transmits the current position of the aircraft to it at a frequency less than or equal to the repetition of the steps of extracting the setpoint position from the trajectory.
[0026] The extraction step consists of identifying in the trajectory the target position of a waypoint which is on the trajectory, downstream of the current position according to a direction of movement of the aircraft.
[0027] This waypoint can be located at a predetermined distance from the aircraft's current position. For example, this distance can be fixed or variable depending on at least one parameter, such as the aircraft's speed or the type of segment containing a line segment or curve. The target position is then defined by at least a target latitude and a target longitude for this waypoint located downstream of the aircraft's current position.
[0028] An autopilot is an electronic system that can automatically generate control signals to at least one actuator. This autopilot allows the control of one or more actuators to guide the movement of an aerodynamic control surface so that the aircraft heads towards the target position. Such an actuator might include, for example, a motor, a hydraulic or electric cylinder, and controlling this actuator could, in particular, generate the extension or retraction of a rod within a cylinder body, or the rotation of a shaft.
[0029] The aerodynamic control surface can, for example, include a rotor or propeller blade, a flap or a fin, and its movement allows for the modification of a roll angle, a pitch angle and / or a yaw angle so that the aircraft moves towards the set position, or even reaches the set position.
[0030] Such an aircraft can be, in particular, a rotorcraft or a helicopter and may include several actuators. The actuators are controlled by the autopilot to collectively or cyclically modify the pitch of the blades of a lift rotor forming such an aerodynamic control surface, either directly or via a mechanical system.
[0031] In practice, the actuator(s) can also be controlled to pilot aircraft movements while respecting flight constraints defining a flight domain of that aircraft, such as the execution of coordinated turns.
[0032] Therefore, the flight management system provides the trajectory to be followed to an autopilot system, rather than a roll command, for example, to the autopilot. The autopilot then deduces a series of target positions and controls one or more actuators accordingly, respecting the aircraft's capabilities. In this way, the invention extends the level of assistance provided to the pilot by enabling trajectory tracking across the entire flight envelope of the aircraft. The trajectory tracking method is then transferred to the aircraft's autopilot, which is able to combine commands on its actuators to control the different axes, not just the roll axis. Consequently, the autopilot is able to control the aircraft's movement throughout the entire flight envelope.
[0033] Advantageously, the process can include a check of the integrity of the transfer of the trajectory to the autopilot computer.
[0034] Such a verification of the integrity of the transfer makes it possible to ensure, for example before the flight, that the trajectory has been transferred without error or alteration in the autopilot computer.
[0035] In practice, verifying the integrity of the transfer may involve the following sub-steps:
[0036] - the first control calculation performed on the trajectory by the flight management system, the first calculation generating a first result,
[0037] - a second control calculation performed on the trajectory by the autopilot computer, the second calculation generating a second result, the second calculation being identical to the first calculation, and
[0038] - comparison between the first and second results, the integrity of the transfer being verified when a zero difference is identified between the first and second results.
[0039] Such a transfer integrity check can, for example, be implemented using a checksum, generally referred to by the English term "checksum," by means of a cyclic redundancy check known by the acronym "CRC." According to one embodiment of the invention, the transfer integrity check may include a substep of transferring the second result from the autopilot computer to the flight management system, with the comparison between the first and second results being performed by the flight management system. Consequently, the first and second results are compared by the flight management system.
[0040] According to another embodiment of the invention, the verification of the integrity of the transfer may include a substep of transferring the first result from the flight management system to the autopilot computer, the comparison between the first and second results being carried out by the autopilot computer.
[0041] Consequently, the first and second results are compared by the autopilot computer.
[0042] Preferably, the comparison between the first and second results can be performed by both the flight management system and the autopilot computer. Cross-checking substeps for transferring the first and second results are then implemented between the flight management system and the autopilot computer.
[0043] According to another aspect of the invention, the flight trajectory can be generated in at least three dimensions, the target position of the trajectory comprising at least a target latitude, a target longitude and a target altitude.
[0044] Consequently, each point of passage of the trajectory transmitted by the flight management system is defined at least by its latitude, its longitude and its altitude. According to another aspect of the invention, the flight trajectory can be generated in four dimensions, the target position of the trajectory comprising a target latitude, a target longitude, a target altitude and a target forward speed of the aircraft.
[0045] Thus, in addition to its latitude, longitude, and altitude, each waypoint along the trajectory transmitted by the flight management system is defined by a forward speed. The autopilot can then control the aerodynamic control surface actuator(s) to steer the aircraft toward, or even reach, the target position at that target speed.
[0046] Alternatively, the flight path can be generated in four dimensions, with the target position of the path comprising a target latitude, a target longitude, a target altitude, and a target vertical speed of the aircraft.
[0047] Similarly, in addition to its latitude, longitude, and altitude, each waypoint along the trajectory transmitted by the flight management system is defined by a vertical speed. The autopilot can then control the aerodynamic control surface actuator(s) so that the aircraft reaches the target position with that target vertical speed.
[0048] Advantageously, control of at least one actuator can be established to respect a corridor of variable precision around the trajectory.
[0049] In practice, the method may involve determining a current forward speed of the aircraft, with extraction being carried out according to the current position of the aircraft and the current forward speed of the aircraft. The present invention also relates to an aircraft comprising an aircraft flight management system and an autopilot for this aircraft.
[0050] According to the invention, such an aircraft is remarkable in that it is configured to implement the aforementioned trajectory tracking method.
[0051] Such an aircraft can thus take the form of a rotorcraft and more particularly a helicopter, and the aerodynamic control surface can include a blade of a lift rotor and / or a blade of a tail rotor.
[0052] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the attached figures, which represent: Figure 1, a schematic side view of an aircraft according to the invention,
[0053] Figure 2, a flowchart illustrating a first example of an automatic trajectory tracking method according to the invention,
[0054] Figure 3, a flowchart illustrating verification substeps, according to the invention,
[0055] Figure 4, a flowchart illustrating a second example of an automatic trajectory tracking method according to the invention, and Figure 5, a diagram of a two-dimensional trajectory used by an automatic trajectory tracking method according to the invention.
[0056] Elements present in several separate figures are assigned a single reference. As already mentioned, the invention relates to an aircraft equipped with an autopilot and aerodynamic control surfaces to control the movement of this aircraft in the air mass.
[0057] As shown in Figure 1, aircraft 1 may be in the form of a rotorcraft comprising at least one rotor 7, 17 equipped with blades forming such aerodynamic control surfaces 8, 18.
[0058] Aircraft 1 then includes at least one actuator 6, 16, such as a hydraulic or electric cylinder, controlled to move the aerodynamic control surfaces 8, 18. The actuator(s) 6, 16 can be connected respectively to at least one control surface directly or via a mechanical chain for example.
[0059] In practice, the actuator 6 can allow modification of a pitch of the blades of a main rotor participating in the lift, or even the propulsion, of the aircraft 1 and allowing control of the movements of the aircraft 1 along a roll axis and a pitch axis.
[0060] The actuator 16 can, for its part, allow a pitch of the blades of a rear rotor to be modified, enabling the movements of the aircraft 1 to be controlled along a yaw axis.
[0061] Aircraft 1 also includes a flight management system 3 enabling the generation of a flight trajectory T in at least two dimensions presenting a plurality of segments between a starting point D and an arrival point A.
[0062] Such a trajectory T is further represented in Figure 5 in two dimensions and presents a plurality of segments between a starting point D and an ending point A. According to another variant not shown, this trajectory T can also be in three dimensions. Each segment then comprises at least a set of points P1, P2, P3, P4 forming a segment S1, S2, S3 or a curve C1, C2, C3, each point P1, P2, P3, P4 being defined at least by a latitude and a longitude, or even an altitude when the trajectory T is in three dimensions.
[0063] Once the trajectory T is generated by the flight management system 3, it is transmitted to a computer 4 of an autopilot 2. Furthermore, the aircraft 1 also includes a positioning system 5 that allows the current position of the aircraft 1 to be identified, for example, in a ground-based reference frame. Such a positioning system 5 may include a position sensor, an inertial measurement unit, or a satellite positioning system. This current position may be defined by the current latitude, longitude, or even altitude of the aircraft 1.
[0064] The term "position sensor" here refers to both a physical sensor capable of directly measuring the position of aircraft 1 and a system that may include one or more physical sensors, as well as signal processing means to provide an estimate of aircraft 1's position based on the measurements provided by these physical sensors. Similarly, the term "position measurement" will refer to both a raw measurement from a physical sensor and a measurement obtained through more or less complex signal processing of raw measurements.
[0065] The computer 4 may include, for example, at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, at least one logic circuit; these examples do not limit the scope given to the expression "processing unit." The term processor can refer to a central processing unit known by the acronym CPU, a graphics processing unit (GPU), a digital signal processing unit (DSP), a microcontroller, etc.
[0066] The autopilot computer 4 is then configured to extract, at least as a function of the current position of the aircraft 1, a target position of the trajectory T comprising at least a target latitude and a target longitude.
[0067] Furthermore, such a setpoint designates a waypoint belonging to the trajectory T. This waypoint is located downstream of the current position of aircraft 1 according to a direction of movement of aircraft 1 along the trajectory T. Such a point may in particular be located at a distance from the current position fixed or defined by a stored law.
[0068] Consequently, such a computer 4 is connected by wired or wireless means, on the one hand, with the flight management system 3 and, on the other hand, with the positioning system 5.
[0069] Furthermore, the autopilot computer 4 is connected, either wired or wirelessly, to at least one actuator 6, 16 to control it so as to move an aerodynamic control surface 8, 18 in order to steer the aircraft 1 towards the set position. As shown in Figure 2, the invention also relates to a method 20 for automatically tracking the trajectory of the aircraft 1. Such a method 20 notably comprises a generation 21 by the flight management system 3 of the flight trajectory T in at least two dimensions, and then a transfer 22 of this trajectory T from the flight management system 3 to the autopilot computer 4.
[0070] Optionally, the process 20 may include a verification 23 of the integrity of the transfer 22 of this trajectory T to the computer 4. Such a verification step 23 may include a plurality of sub-steps, shown in more detail in Figure 3. Indeed, as shown in Figure 3, the verification 23 of the integrity of the transfer 22 includes a first calculation sub-step 231 of control performed on the trajectory T by the flight management system 3, this first calculation 231 generating a first result, and a second calculation sub-step 232 of control performed on the trajectory T by the computer 4, this second calculation 232 being identical to the first calculation 231. Such a second calculation 232 then generates a second result.
[0071] The verification 23 then includes a sub-step of transferring the second result from the computer 4 to the flight management system 3 and a comparison 234 between the first and second results carried out by the flight management system 3.
[0072] Such a verification 23 may also include in parallel a sub-step of transferring the first result from the flight management system 3 to the computer 4, then a comparison 234' between the first and second results carried out by the computer 4. The integrity of the transfer 22 can thus be verified when a zero difference is identified between the first and second results by the flight management system 3 and by the computer 4.
[0073] The method 20 also includes an identification 24 of the current position of the aircraft 1 measured by the positioning system 5 of the aircraft 1. The positioning system 5 transmits a signal to the computer 4 carrying this current position.
[0074] The process 20 then includes an extraction 25 implemented by the computer 4 of the autopilot 2 of the target position of the trajectory T. For example, the computer 4 is configured to determine a distance, fixed or variable depending for example on the speed of advance of the aircraft 1 and a stored time, and to consider that the target position corresponds to the point of passage of the trajectory located at said distance from the current position.
[0075] Therefore, the method 20 includes control 26 by the computer 4 of the actuator(s) 6, 16 allowing the movement of the aerodynamic control surfaces 8, 18 so that the aircraft 1 moves towards the set position, or even reaches this set position. As shown in Figure 4, the method 30 for automatically tracking the trajectory of the aircraft 1 may include a generation 31 by the flight management system 3 of the flight trajectory T in at least two dimensions, then a transfer 32 of this trajectory T from the flight management system 3 to the computer 4 of the autopilot 2.
[0076] The process 30 then includes a verification 33 of the integrity of the transfer 32 of this trajectory T to the computer 4. Such a verification step 33 may include a plurality of sub-steps as previously represented in figure 3.
[0077] The method 30 also includes an identification 34 of the current position of aircraft 1 measured by the positioning system 5 of aircraft 1 and a determination 37 of a current forward speed of aircraft 1.
[0078] The process 30 then includes an extraction 35 implemented by the computer 4 of the target position of the trajectory T, followed by a control 36 by the autopilot 2 of the actuator(s) 6 allowing the aerodynamic control surfaces 8, 18 to move the aircraft 1 towards the target position. Such an extraction 35 is then implemented both according to the current position of the aircraft 1 and the current forward speed of the aircraft 1.
[0079] The determination 37 of a current forward speed of aircraft 1 can be implemented by a speed sensor, an inertial measurement unit or a satellite positioning system.
[0080] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not possible to exhaustively identify all possible embodiments. It is, of course, conceivable to replace a described means with an equivalent means without departing from the scope of the present invention as defined by the claims.
Claims
DEMANDS 1. Method (20, 30) for automatically tracking the trajectory of an aircraft (1) using an autopilot (2) of said aircraft (1), characterized in that said process comprises the following steps: • generation (21, 31) by a flight management system (3) of the aircraft (1) of a flight trajectory (T) in at least two dimensions having a plurality of segments between a starting point (D) and an arrival point (A), each segment comprising at least a set of points (P1, P2, P3, P4) forming a segment (S1, S2, S3) or a curve (C1, C2, C3), each point (P1, P2, P3, P4) being defined at least by a latitude and a longitude, • transfer (22, 32) of said trajectory (T) from said flight management system (3) to a computer (4) of said autopilot (2) of said aircraft (1), • identification (24, 34) of a current position of the aircraft (1) measured by a positioning system (5) of said aircraft (1), • extraction (25, 35) by said computer (4) of said autopilot (2) of a setpoint position of said trajectory (T) comprising at least a setpoint latitude and a setpoint longitude, said extraction being implemented at least as a function of said current position of the aircraft (1), said setpoint position being located downstream of said current position in a direction of movement of said aircraft (1) along said trajectory (T), and • control (26, 36) by said autopilot (2) of at least one actuator (6, 16) enabling the movement of an aerodynamic control surface (8, 18) so that said aircraft (1) moves towards said setpoint position.
2. Method according to claim 1, characterized in that said method (20, 30) includes a verification (23, 33) of the integrity of said transfer (22, 32) of said trajectory (T) to said computer (4) of said autopilot (2).
3. Method according to claim 2, characterized in that said verification (23) of the integrity of said transfer (22) comprises the sub-steps of: • first calculation (231) of control performed on said trajectory (T) by said flight management system (3), said first calculation (231) generating a first result, • second calculation (232) of control performed on said trajectory (T) by said computer (4) of said autopilot (2), said second calculation (232) generating a second result, said second calculation (232) being identical to the first calculation (231), and • comparison (234, 234') between said first and second results, an integrity of said transfer (22) being verified when a zero difference is identified between said first and second results.
4. Method according to claim 3, characterized in that said verification (23) of the integrity of said transfer (22) comprises a sub-step of transferring (233) said second result from said computer (4) of said autopilot19 (2) to said flight management system (3), said comparison (234) between said first and second results being carried out by said flight management system (3).
5. A method according to any one of claims 3 to 4, characterized in that said verification (23) of the integrity of said transfer (22) comprises a substep of transferring said first result from said flight management system (3) to said computer (4) of said autopilot (2), said comparison (234') between said first and second results being carried out by said computer (4) of said autopilot (2).
6. Method according to any one of claims 1 to 5, characterized in that said trajectory (T) is generated in at least three dimensions, said setpoint position of said trajectory (T) comprising at least a setpoint latitude, a setpoint longitude and a setpoint altitude.
7. Method according to claim 6, characterized in that said trajectory (T) is generated in four dimensions, said setpoint position of said trajectory (T) comprising a setpoint latitude, a setpoint longitude, a setpoint altitude and a setpoint forward speed of said aircraft (1).
8. Method according to claim 6, characterized in that said trajectory (T) is generated in four dimensions, said setpoint position of said trajectory (T) comprising a setpoint latitude, a setpoint longitude, a setpoint altitude and a setpoint vertical velocity of said aircraft (1).20 9. Method according to claim 1 to 8, characterized in that said control of at least one actuator (6) is established to respect a corridor of variable precision around said trajectory.
10. A method according to any one of claims 1 to 9, characterized in that said method (30) comprises a determination (37) of a current forward speed of said aircraft (1), said extraction (35) being implemented as a function of said current position of the aircraft (1) and of said current forward speed of said aircraft (1).
11. Aircraft (1) comprising an aircraft flight management system (1) and an autopilot (2) of said aircraft (1), characterized in that said aircraft (1) is configured to implement said trajectory tracking method (T) according to any one of claims 1 to 10.