Aircraft control

Abstract

Aircraft Control The present invention relates to a computer implementation method for controlling an aircraft, wherein the aircraft has a plurality of control effectors, and the method comprises: determining a global force and / or moment allocation required to control the motion of the aircraft, wherein the global force and / or moment allocation is related to a net force and / or moment acting on the aircraft; determining a local force and / or moment allocation, wherein the local force and / or moment allocation is related to a force and / or moment contribution to a net force provided by at least one of the control effectors; and controlling at least one of the control effectors to generate the determined local force and / or moment. The present invention also relates to an aircraft comprising a processor and memory storing computer code that, when executed on the processor, performs the method.

Description

Technical Field

[0001] The present invention relates to the control of aircraft, and in particular to a computer-implemented method for controlling an aircraft, and an aircraft comprising a processor and a memory storing computer code for performing the method when executed on the processor.

Background Art

[0002] The allocation of force and moment commands in an aircraft with multi-purpose control effectors is a very complex and multi-dimensional problem. This is because multi-purpose control effectors can be used to simultaneously generate forces and moments in all six degrees of freedom. Also, the relationship between changes in the state of the control effector and the generation of forces and moments varies as a function of the airspeed, environmental conditions, and the state of the control effector itself. This problem becomes even more complex in the case of a vertical takeoff and landing aircraft associated with highly non-linear and coupled aerodynamic phenomena. These couplings and non-linearities need to be captured as accurately as possible by the allocation algorithm. The problem becomes even more complex when the control effector unit is controlled by a combination of actuators (e.g., propulsion units installed inside movable aerodynamic control surfaces).

[0003] The complexity of the control allocation algorithm requires storing a large amount of data in the flight control computer(s), potentially exceeding the memory limitations of the computer(s) or requiring additional computational hardware to be installed in the aircraft.

[0004] The present invention seeks to at least partially improve this problem.

Summary of the Invention

[0005] Aspects and embodiments of the present invention are set forth in the appended claims. These and other aspects and embodiments of the present invention are also described herein.

[0006] The problems described above are solved by a computer-implemented method for controlling an aircraft, the aircraft having a plurality of control effectors, the method comprising determining an allocation of global forces and / or moments required to control the movement of the aircraft, the allocation of global forces and / or moments being related to the net forces and / or moments acting on the aircraft, determining an allocation of local forces and / or moments, the allocation of local forces and / or moments being related to the contribution of forces and / or moments to the net force provided by at least one of the control effectors, and controlling at least one of the control effectors to generate the determined local forces and / or moments.

[0007] Thus, according to the present invention, global forces and / or moments (the contribution of all net forces, including gravity, propulsion, and aerodynamic forces acting on the aircraft) are decomposed and distributed to local forces (i.e., the contribution of the forces is generated by each of the respective control effectors to form the global force / moment). In this way, a complex global control allocation problem can be decomposed into several simpler local control allocation problems. The local control allocation problem can be solved by determining a set of parameters for each control effector that generates the contribution of the local force to the global force / moment.

[0008] Advantageously, the present invention results in a reduction of the data required by decomposing the global force / moment allocation problem into a plurality of local force / moment allocation problems. Thus, the method reduces the memory consumption of the control allocation algorithm, thereby complying with the memory limitations of the flight control computer(s). The method also reduces the complexity of the design of the control allocation algorithm and the complexity of testing the control allocation algorithm.

[0009] While the present invention can be applied to various aircraft configurations, it is particularly advantageous when applied to vertical take-off and landing (VTOL) aircraft. This is because such aircraft typically include multi-purpose control effectors that generate forces and moments in multiple degrees of freedom. Such multi-purpose control effectors, especially those that generate forces and moments in three or more degrees of freedom, are generally rarely, and sometimes never, found in civilian aircraft.

[0010] The method may also include determining at least two local force and / or moment assignments related to the force and / or moment contributions to the net force provided by at least two control effectors. In this way, the method involves decomposing a global force and / or moment assignment problem into at least two local force and / or moment assignment problems, e.g., one assignment problem for each wing of a pair of wings. Alternatively, the assignment problem may cover multiple control effectors, e.g., one local assignment problem for a pair of canards and another local assignment problem for a pair of wings. Decomposing a global assignment problem into multiple local assignment problems simplifies the control assignment algorithm and reduces the amount of data that needs to be stored in the flight control computer(s).

[0011] Each of at least two local force and / or moment assignments can correspond to a different degree of freedom of the aircraft. For example, each local force and / or moment assignment can correspond to one of the following: x-direction, z-direction, roll moment, pitch moment, and yaw moment. Decomposing the global assignment problem into multiple local assignment problems in this way further simplifies the control assignment algorithm.

[0012] Controlling at least one of the control effectors may involve adjusting at least one parameter of the control effector to generate a local force and / or moment. The parameters of the control effector may include, for example, flap angle or engine rotor speed (essentially, engine power). The parameters may be determined by referring to a simulation to solve the local control assignment problem, which provides information about the forces generated by the control effector as a function of the control effector parameters.

[0013] At least one parameter can be adjusted at least partially based on at least one external condition of the aircraft. Similarly, the assignment of local forces and / or moments can be determined at least partially based on at least one external condition of the aircraft. In particular, at least one parameter and the assignment of local forces and / or moments can be adjusted and determined at least partially based on at least one of the following: airspeed, ambient air density, aerodynamic angle of attack, and the effect of the canard's operating state on the local forces generated by the wing (e.g., canard flap downwash / canard wing interaction), which can be captured by scheduling the assignment of local forces to the wing through the canard's operating state (i.e., canard flap angle and / or canard rotor speed).

[0014] The local force and / or moment assignments for one control effector can be determined, at least partially, to compensate for forces and / or moments generated by another control effector. For example, a force x generated by one control effector located above the aircraft's center of gravity may generate a downward pitch moment. Therefore, another control effector must compensate for this pitch moment by generating a correction for the opposite moment. This concept will be explained in more detail below with reference to Figures 5a and 5b.

[0015] At least one control effector may comprise at least one engine. In particular, a control effector may comprise at least one propulsion engine. A control effector may include multiple engines, such as multiple engines arranged adjacent to one another. Multiple engines may be arranged in pairs. The engines may be, for example, ducted electric vectored thrust engines.

[0016] The propulsion engine could be an electric propulsion engine with a ducted fan. For example, an electric propulsion engine can generate load changes more quickly than an equivalent gas turbine engine. This is advantageous when controlling control effectors to generate local forces.

[0017] Controlling at least one of the control effectors may include adjusting the thrust of at least one propulsion engine. Depending on the angle of the engine relative to the aircraft's canards or wings, the propulsion engine may provide an x-force, a z-force, or a combination of both. The amount by which the engine thrust should be adjusted to produce a particular force may be determined by referencing simulations.

[0018] The control effector may comprise multiple propulsion engines, the thrust of at least one of the propulsion engines may be adjusted at least partially based on the distance between the propulsion engine and the aircraft's center of mass. For example, to generate a given moment, the method may increase the thrust of an engine closer to the center of gravity by a certain amount, or increase the thrust of another engine further from the center of gravity (due to a larger lever arm) by a smaller amount.

[0019] At least one control effector may comprise at least one control surface. Controlling at least one of the control effectors may involve adjusting the angle of at least one control surface. The control surface may be an aerodynamic surface of an aircraft, such as an aircraft canard and / or wing flaps. In particular, the control surface may be an adjustable flap of an aircraft. An adjustable flap may generate a local aerodynamic z-force to control the aircraft's motion in the z-direction and generate pitch and roll moments.

[0020] At least one control effector may comprise at least one engine mounted on or near the control surface, the engine's position being movable with the control surface to change the thrust vector, particularly to change the direction of the thrust vector. For example, the engine may be a propulsion engine mounted on or within an adjustable flap of an aircraft's canard or wing. As the angle of the flap (i.e., the control surface) is adjusted, the engine moves with the flap, thereby also adjusting the direction of the thrust vector. In one extreme position, the engine may be essentially horizontal to apply an x ​​force. In another extreme position, the engine may be essentially vertical to apply a z force. Between these extreme positions, the engine provides a force having x and z components.

[0021] Control effectors may be located on the wings and / or canards of an aircraft. In particular, a control effector may be an engine, such as a propulsion engine, mounted within the adjustable flaps of the aircraft's canards and / or wings. In this way, the control effector can generate multiple degrees of freedom by changing the angle of the flaps that generate aerodynamic forces, as well as by changing the angle of the thrust generated by the engine.

[0022] Another aspect disclosed herein provides an aircraft comprising a processor and a memory storing computer code that, when executed on the processor, performs the aforementioned method.

[0023] Features in one aspect of the present invention may be applied in any suitable combination to other aspects of the present invention. In particular, aspects of the method may be applied to aspects of the apparatus, and vice versa. Furthermore, any, some, and / or all features in one aspect may be applied in any, some, and / or all features in any other aspect to any suitable combination. It should also be recognized that certain combinations of the various features described and defined in any aspect of the present invention may be independently implemented and / or provided and / or used.

[0024] Features of one aspect of the present invention may be applied to other aspects of the present invention in any suitable combination. In particular, aspects of the method may be applied to aspects of the apparatus, and vice versa. Where used herein, means-plus-function features may be expressed alternatively with respect to their corresponding structures, such as preferably programmed processors and associated memory. Any apparatus features described herein may be provided as method features, and vice versa. Furthermore, features implemented in hardware may generally be implemented in software, and vice versa. Any references to software and hardware features herein should be interpreted appropriately.

[0025] The present invention extends to methods, systems, and apparatus, which are substantially described herein and / or illustrated with reference to the accompanying drawings.

[0026] Hereinafter, one or more embodiments of the present invention will be described with reference to the accompanying drawings, merely as examples. [Brief explanation of the drawing]

[0027] [Figure 1] This is a plan view of an exemplary aircraft with multiple control effectors. [Figure 2a] This shows an example of x-force distribution between control effectors. [Figure 2b] This shows an example of x-force distribution between control effectors. [Figure 3a] This shows an example of z-force distribution between control effectors that generate a roll moment. [Figure 3b] This shows an example of z-force distribution between control effectors that generate a roll moment. [Figure 4a] This shows an example of x-force distribution between control effectors that generate the yaw moment. [Figure 4b] This shows an example of x-force distribution between control effectors that generate the yaw moment. [Figure 5a] This shows the distribution of x-forces between control effectors that generate the pitch moment. [Figure 5b] This shows the distribution of x-forces between control effectors that generate the pitch moment. [Figure 6] This shows the distribution of z-forces between control effectors that do not generate an overall moment. [Figure 7] This shows the distribution of z-forces among the control effectors that generate the overall roll moment. [Figure 8] This shows the distribution of z-forces among the control effectors that generate the overall pitch moment. [Figure 9] This shows the distribution of x-forces among the control effectors that generate the overall yaw moment. [Figure 10] A flowchart of the steps of the method described herein is shown. [Modes for carrying out the invention]

[0028] Figure 1 shows a vertical take-off and landing (VTOL) aircraft 10. The aircraft 10 has a left canard 20 and a right canard 30, each equipped with a left canard control effector 22 and a right canard control effector 32, respectively. The aircraft 10 also has a left wing 40 and a right canard 50, each equipped with a left wing control effector 42 and a right wing control effector 52, respectively. The canards and wings extend from the fuselage of the aircraft, with the canards located forward of the wings on the fuselage. The aircraft has a center of gravity (CG), also referred to herein as the center of mass, which in this embodiment is located slightly aft of the center of the fuselage toward the wings.

[0029] The longitudinal axis of an aircraft is referred to herein as the "x" direction or "x" axis (as shown in Figure 1), and the term "x force" is used to refer to a force acting along the "x" direction. The horizontal axis of an aircraft is referred herein as the "y" direction or "y" axis (as shown in Figure 1), and the term "y force" is used to refer to a force acting along the "y" direction. The vertical axis of an aircraft is referred herein as the "z" direction or "z" axis (in or out of the plane of the paper in Figure 1), and the term "z force" is used to refer to a force acting along the "z" direction.

[0030] The control effectors (22, 32, 42, 52) are multi-purpose control effectors in that each of them generates aircraft motion in multiple degrees of freedom. Specifically, the control effectors include propulsion engines mounted within adjustable flaps on each of the canards and wings. Thus, each control effector includes an aerodynamic surface for generating aerodynamic forces on the aircraft and one or more propulsion units for generating thrust forces on the aircraft. For example, a propulsion unit may provide a thrust force in the forward direction ("x" as shown in Figure 1) when the aircraft is in a cruising configuration, or a propulsion unit may provide a thrust force in the vertical direction ("z", in or out of the plane of the paper in Figure 1) when the aircraft is in a takeoff or landing configuration.

[0031] Each control effector is located at a certain distance from the aircraft's center of gravity (CG). Therefore, any force generated by a control effector acts on the aircraft's center of gravity via a lever arm. As shown in Figure 1, the lever arms associated with each control effector are as follows: ·Δx C This is an effective canard lever arm in the x-direction relative to the center of gravity when generating a z-force. ·Δx W This is the effective wing lever arm in the x-direction relative to the center of gravity when generating the z-force. ·Δy C,L This is an effective canard lever arm in the y-direction relative to the center of gravity when generating a z-force to produce a roll moment. ·Δy W,L This is an effective wing lever arm in the y-direction relative to the center of gravity when generating a z-force to produce a roll moment. ·Δy C,N This is an effective canard lever arm in the y-direction relative to the center of gravity when generating an x-force to produce a yaw moment. ·Δy W,N This is an effective wing lever arm in the y-direction relative to the center of gravity when generating an x-force to produce a yaw moment.

[0032] Additional relevant lever arms, which are described herein but not shown in Figure 1, are as follows: ·Δz C This is an effective canard lever arm in the z-direction relative to the center of gravity that generates pitch coupling (requiring correction) when generating x-force, as described below with reference to Figures 5a and 5b. ·Δz W This is an effective wing lever arm in the z-direction relative to the center of gravity that generates pitch coupling (requiring correction) when generating x-forces, as described below with reference to Figures 5a and 5b.

[0033] As used herein, the subscript "C" refers to the canard, and the subscript "W" refers to the wing. The subscript "CL" refers to the left canard, "CR" refers to the right canard, "WL" refers to the left wing, and "WR" refers to the right wing. The subscript "L" refers to the roll moment, the subscript "M" refers to the pitch moment, and the subscript "N" refers to the yaw moment.

[0034] Due to the different characteristics of the underlying physical phenomena, the x force (Δy for generating a yaw moment C,N and Δy W,N ) and the z force (Δy for generating a roll moment C,L and Δy W,L ) may have different lateral lever arms for generation. In particular, when the adjustable flap rotates, the position of the engine with respect to the center of gravity moves. Therefore, the distance between the engine and the center of gravity can be different when the engine is used to generate a z force (e.g., when the engine points downward in the z direction and the aircraft is in a takeoff or landing configuration) and when the engine is used to generate an x force (e.g., when the engine points backward in the x direction and the aircraft is in a cruise configuration).

[0035] The weight coefficient of the canard As described above, the assignment of force and moment commands to an aircraft with multi-purpose control effectors is a very complex and multi-dimensional problem, in part because the multi-purpose control effectors can be used to simultaneously generate forces and moments in all six degrees of freedom. By the method of the present disclosure, the complexity of the control assignment algorithm is reduced by transforming the "global" force and moment assignment problem into a plurality of "local" force assignment problems. "Global" forces are the sum of the contributions of all forces acting on the center of gravity of the aircraft (including gravity, propulsion, and aerodynamic forces). "Local" forces are the individual force contributions provided by each control effector. In this embodiment, the global force consists of four local forces, and each of the local forces represents one of the four control effectors (left canard, right canard, left wing, right wing).

[0036] Decomposing global forces and moments into contributions to individual local force and moment commands can be related to the aircraft's geometric and aerodynamic characteristics, as well as the location of its center of gravity. For this reason, the pitch moment command must be decomposed in a specific manner into contributions to local canard and wing z force commands to avoid generating a net z force acting on the aircraft that affects its level. Similarly, the global z force command needs to be distributed in a specific manner into contributions to local canard and wing z force commands to avoid generating any unwanted pitch moments. However, with respect to the distribution of roll moment command, yaw moment command, and x force command, the force distribution between the canard and wing is arbitrary. To control this distribution, a weighting coefficient for the canard is used.

[0037] Figures 2a to 4b show exemplary force distribution between canards and wings with different canard weighting coefficients.

[0038] Figures 2a, 3a, and 4a show a distribution where the canard's force contribution is minimized and the wing's force contribution is maximized, in which case the canard's weighting coefficient is minimized. Figures 2b, 3b, and 4b show a distribution where the canard's force contribution is maximized and the wing's force contribution is minimized, in which case the canard's weighting coefficient is maximized. In the most extreme conditions, for the distribution of roll moment command, yaw moment command, and x force command, 100% of the global force may be provided by the canard and 0% by the wing, or vice versa.

[0039] Figures 2a and 2b show exemplary x-force distributions. In Figure 2a, the x-force is generated as much as possible by the control effectors 42 and 52 located on the wings 40 and 50, as indicated by the arrows in Figure 2a, while the control effectors 22 and 32 located on the canards 20 and 30 provide the minimum force contribution. In Figure 2b, the x-force is generated as much as possible by the control effectors 22 and 32 located on the canards 20 and 30, as indicated by the arrows in Figure 2b, while the control effectors 42 and 52 located on the wings 40 and 50 provide the minimum force contribution. The weighting coefficient for the canards regarding the global x-force distribution between the canards and wings is:

number

[0040] Figures 3a and 3b show exemplary x-force distributions for generating a roll moment. In Figure 3a, the z-force required to generate the roll moment is generated as much as possible by the control effectors 42 and 52 located on the wings 40 and 50, as indicated by the arrows in Figure 3a, while the control effectors 22 and 32 located on the canards 20 and 30 provide the minimum force contribution. In Figure 3b, the z-force required to generate the roll moment is generated as much as possible by the control effectors 22 and 32 located on the canards 20 and 30, as indicated by the arrows in Figure 3b, while the control effectors 42 and 52 located on the wings 40 and 50 provide the minimum force contribution. In both figures, the force contributions provided by the left and right control effectors are in opposite directions along the z-axis, thereby generating a roll moment around the x-axis without generating a net z-force relative to the aircraft's level. The weighting coefficient for the canard regarding the distribution of roll moment force between the canard and the wing is "k C,L This is indicated by ".

[0041] Figures 4a and 4b show exemplary distribution of x-forces to generate a yaw moment. In Figure 4a, the x-forces required to generate the yaw moment are generated as much as possible by the control effectors 42 and 52 located on the wings 40 and 50, as indicated by the arrows in Figure 4a, while the control effectors 22 and 32 located on the canards 20 and 30 provide the minimum force contribution. In Figure 4b, the x-forces required to generate the yaw moment are generated as much as possible by the control effectors 22 and 32 located on the canards 20 and 30, as indicated by the arrows in Figure 4b, while the control effectors 42 and 52 located on the wings 40 and 50 provide the minimum force contribution. In both figures, the force contributions provided by the left and right control effectors are in opposite directions along the x-axis, thereby generating a yaw moment around the z-axis without generating a net force in the x-direction. The weighting coefficient for the canard regarding the distribution of yaw moment force between the canard and the wing is "k C,N This is indicated by ".

[0042] Figures 2a to 4b show extreme cases where either the maximum or minimum force contribution is provided by the canard or wing, but in many cases, both the canard and wing provide some contribution to the global force that lies somewhere between the maximum and minimum contributions, and the force distribution between the canard and wing is determined by the weighting coefficient of the canard.

[0043] Distribution of global x-forces to local x-forces Figures 5a and 5b illustrate the exemplary distribution of global x-forces to local x-forces in each control effector. The distributed x-forces in this embodiment generate a pitch moment that requires correction.

[0044] As discussed above, the distribution of global x forces between the local x forces on the canard and the local x forces on the wing can generally be arbitrary, and the corresponding weight coefficient of the canard

number

[0045] The mathematical distributive property in vector form is obtained by the following equation:

number

[0046] In this formula,

number

number

[0047] Therefore, taking an example where the weighting coefficient of the canard is chosen to be 0.4 (i.e., 40% of the global x force is provided by the canard and 60% by the wing), the force command vector in the x direction is

number

number

[0048] The control effector may be offset in the z direction from the center of gravity, and the degree of offset may vary depending on the position of the flap (which changes with airspeed). In the embodiment shown in Figure 5b, the control effector located on the wing is offset Δz from the center of gravity (CG). W It is offset by a distance of . This offset means that the force contributions provided by the left and right wings also generate a downward pitch moment. To counteract this moment, pitch compensation may be introduced. Pitch moment compensation command

number

number

[0049] In the embodiments shown in Figures 5a and 5b, the control effectors located on the canard are not offset in the z-direction from the center of gravity, but in other embodiments, Δz c The offset can be by a distance of Δz, and this offset can contribute to or counteract the pitch coupling generated by the wing's control effector (Δz). c However, Δz W (Depending on whether it is in the same direction or the opposite direction.)

[0050] Distribution of global z-forces to local z-forces Figure 6 shows an exemplary distribution of global z forces to local z forces in each control effector. The distribution of z forces in this embodiment is determined to prevent the generation of arbitrary moments in the aircraft.

[0051] To avoid generating moments in the aircraft, the weighting of the z-force distribution between the canards and wings (i.e., the canard weighting coefficient) cannot be done arbitrarily, as in the case of x-force distribution. Since both the global z-force (which affects the aircraft's z-motion) and the pitch moment are ultimately distributed into local z-forces, it is not advisable to first apply an arbitrary canard weighting and then correct the moment in a second step (similar to the principle described for x-force distribution). Typically, because the center of gravity is located slightly closer to the wings than to the canards on the fuselage, the z-force component distributed to the canards is relatively smaller than the force component distributed to the wings.

[0052] Similar to global force commands, global moment commands can be expressed as contributions of local forces. A moment is always generated when a local force is generated by the control effector at the center of gravity and the position of the lever arm. The control method of this disclosure uses this relationship. Similar to the distribution of global x force commands, the decomposition of a global z force command into contributions of local z force commands can be explained in mathematical form. In particular, the equation for distributing a global z force into local z forces can be derived as follows.

[0053] Global z force (F) acting on an aircraft z,global,cmd ) is the z force (i.e., 2·F) generated by each of the two canards. z,local,C ), and the z force generated by each of the two wings (i.e., 2·F) z,local,W It is given by the sum of ). This can be mathematically shown by the following equation (I). F z,global,cmd =2·(F z,local,C +F z,local,W ) (I)

[0054] To avoid generating a residual pitch moment in the aircraft, the sum of the moments generated by the local z forces produced by the canards and wings must be zero, as given by equation (II) below. M residual=0=2·(-F z,local,C ·Δx C +F z,local,W ·Δx W ) (II)

[0055] Equation (II) can be rearranged and rewritten as shown in equation (III) below.

number

[0056] Substituting equation (III) into equation (I) and rearranging, we obtain the following two equations for the contributions of the local z-forces on the canard and the wing, respectively.

number

number

[0057] By vectorizing the two equations above, a single equation for distributing the z-force is provided, as follows:

number

number

[0058] In this formula,

number

number

number

[0059] In this case, the weight coefficient of the canard

number

number

number

[0060] Distribution of roll moment command to local z force Figure 7 shows an example distribution of the roll moment command to the local z force in each control effector.

[0061] Similar to the distribution to x-force commands described above, the distribution of roll moment commands to local z-forces is defined as a function of the weights of the corresponding canards. The local force commands for the left and right canards have the same magnitude but different signs. The same is true for the left and right wings. The local force commands on both sides of the aircraft (i.e., the left canard and left wing) have the same sign but may differ in magnitude. The same is true for the right side of the aircraft (i.e., the right canard and right wing).

[0062] Therefore, the mathematical expression for distributing the roll moment command to the contribution of the local z-force command is as follows:

number

[0063] In this formula, ·ΔF z,local,cmd,L (L cmd ) is a 4x1 command vector, where each vector element represents a local z-direction force command for each of the aircraft's four control effectors (i.e., left canard, right canard, left wing, and right wing).

number

[0064] The pitch moment generated by the left-side control effectors (left canard and left wing) is canceled out by the pitch moment generated by the right-side control effectors (right canard and right wing), so no pitch moment is generated by local forces.

[0065] Distribution of pitch moment command to local z force Figure 8 shows an example distribution of the pitch moment command to the local z force in each control effector.

[0066] The pitch moment is distributed as local z forces to both the canard and the wing. To avoid generating any residual net z forces relative to the aircraft level, the local z force command assigned to the canard must be the same magnitude as the z force command assigned to the wing, but in the opposite direction (i.e., with a different sign). Figure 8 shows an exemplary distribution of local z forces resulting from a positive pitch moment command.

[0067] The decomposition of the pitch moment command into contributions of local z-force commands can be explained in mathematical terms. In particular, the equation for distributing the global z-force into local z-forces can be derived as follows.

[0068] Firstly, the net z force (F) acting on the aircraft z,residual ) is the z force (i.e., 2·F) generated by each of the two canards. z,local,C ), and the z force generated by each of the two wings (i.e., 2·F) z,local,W It is given by the sum of ). In order to avoid generating residual z forces in the aircraft, the sum of the local z forces generated by the canards and wings must be zero. This is mathematically shown by equation (I) below. F z,residual =0=2·(F z,local,C +F z,local,W ) (I)

[0069] Secondly, the pitch moment generated by each of the two canards and the two wings is the force generated by each canard or wing (Δx each) by its lever arm from the center of gravity. C and Δx W It is given by multiplying by ). Considering the force in the opposite direction (and therefore the sign), the pitch moment (M cmd ) can be expressed in equation (II) as follows: M cmd =2·(-F z,local,C ·Δx C +F z,local,W ·Δx W ) (II)

[0070] From equation (I), we can show the following: F z,local,W =-F z,local,C (III)

[0071] Substituting equation (III) into equation (II) and rearranging, we obtain the following equation.

number

number

[0072] By vectorizing the above equation, a single equation is provided for distributing the pitch moment to the z force, as follows:

number

number

[0073] In this formula, ·ΔF z,local,cmd,M (M cmd) is a 4x1 command vector, where each vector element represents a local z-direction force command for each of the aircraft's four control effectors (i.e., left canard, right canard, left wing, and right wing).

number

[0074] In this embodiment, the pitch moment command M cmd This is considered to already include the correction of pitch coupling by the generation of global x forces (i.e.,

number

[0075] Distribution of yaw moment command to local x-force Figure 9 shows an example distribution of the yaw moment command to the local z force in each control effector.

[0076] The distribution of yaw moment command is very similar to the distribution of roll moment command. However, in contrast, the moment is distributed to local x forces rather than local z forces. Here again, the contributions of the two canards are equal in magnitude to each other, and the same is true for the wing contribution, but the contribution of the control effector on the left side is in the opposite direction to the contribution of the control effector on the right side. The contributions of the canards and wings on the same side of the aircraft have the same sign.

[0077] Therefore, the mathematical expression for distributing the yaw moment command to the contribution of the local x-force command is as follows:

number

[0078] In this formula, ·ΔF x,local,cmd,N (N cmd ) is a 4x1 command vector, where each vector element represents a local x-direction force command for each of the aircraft's four control effectors (i.e., left canard, right canard, left wing, and right wing).

number

[0079] Because the x-force generated by the left-side control effectors (left canard and left wing) is canceled out by the x-force generated by the right-side control effectors (right canard and right wing), no net x-force is generated by local forces. As a result, only the yaw moment rotates the aircraft around its center of gravity without generating a net x-force that moves the aircraft forward in the x-direction.

[0080] Sum of local force contributions Once all global forces and moments are distributed to local x and z forces in each control effector (as described above), it is necessary to sum the contributions of the individual local x and z force commands due to the distribution from global to local to determine the total (subscript t) local force command on each control effector. Each of the local force contributions described above is a 4×1 vector, where each of the four elements represents one of the two canards and two wings.

[0081] The sum of the contributions of local x-forces can be expressed as follows:

number

[0082] Therefore, the total x force command has two components, namely the total global x force command.

number

[0083] The sum of the contributions of local z-forces can be expressed as follows:

number

[0084] Therefore, the total z-force command has three components, namely the total global z-force command.

number

[0085] Consequently, the current need is to solve four individual control assignment problems—one for each canard and wing—rather than a single, more complex global control assignment problem. These problems are solved by finding the parameters of a control effector that generates the required combination of local x-forces and local z-forces according to the aircraft simulation model. In the embodiments described herein, the control effector is a propulsion engine mounted on an adjustable flap. Therefore, the parameters of the control effector include (a) the flap angle and (b) the engine output (essentially, the engine rotor speed). For a different aircraft configuration, a different control effector may be used, having different adjustable parameters for generating forces.

[0086] For simplicity, in some cases, each canard and each wing may apply the same flap angle command and rotor speed command to all flaps and engines within that wing / canard. As a result, the local force problem is deterministic and solved by finding combinations of two actuator states (i.e., one flap angle state and one rotor speed state) that produce the required combination of local x and local z forces.

[0087] In other cases, flap angle commands or rotor speed commands may differ for each different engine within the wing / canard. For example, the thrust (i.e., rotor speed) of at least one of the propulsion engines within the wing / canard may be adjusted, at least partially depending on the distance between that engine and the center of mass of the aircraft. In this embodiment, the moment can be increased by increasing the rotor speed of the engine located furthest from the center of mass.

[0088] Figure 10 shows a flowchart of the steps of the method described herein.

[0089] In the first step, the allocation of global forces and / or moments required to control the aircraft's motion is determined. The allocation of global forces and / or moments relates to the net forces and / or moments acting on the aircraft. For example, if it is necessary to move the aircraft forward and upward, the global forces relate to the net x force required to move the aircraft forward by the desired amount, and the net z force required to move the aircraft upward by the desired amount.

[0090] In the second step, the local force and / or moment assignments are determined. The local force and / or moment assignments relate to the force and / or moment contributions to the net force provided by at least one of the control effectors. Thus, the local force and / or moment assignments represent the individual local force contributions provided by each control effector. Global x and z forces are decomposed into individual local x and z force contributions, as described above in the sections titled “Distribution of Global x Forces to Local x Forces” and “Distribution of Global z Forces to Local z Forces.” Moments are decomposed into individual local x and z force contributions, as described above in the sections titled “Distribution of Roll Moment Command to Local z Forces,” “Distribution of Pitch Moment Command to Local z Forces,” and “Distribution of Yaw Moment Command to Local z Forces.”

[0091] In the third step, the local x and z force contributions from each control effector are summed to provide the total force contribution required by each control effector to provide the global force and moment required in the first step. As a result of this summation, there are four control assignment problems to be solved (one for each canard and wing).

[0092] In the fourth step, the control assignment problem is resolved to determine the control effector parameters that generate the required combination of local x and local z forces. As described above, these parameters can be the flap angles for each canard and wing, as well as the rotor speed for the engine located within the flap, and these generate the required x and z forces for each canard / wing.

[0093] In the fifth step, control effectors are activated according to the determined parameters to generate the determined local forces and / or moments. For example, flaps are adjusted to a determined flap angle, and engine rotor speed is adjusted to a determined level.

[0094] Although the present invention has been described above with reference to VTOL aircraft, the concept can be applied to other aircraft configurations. For example, the concept can be applied to an aircraft with means for directly generating lateral forces (in the y-direction) through appropriate control devices.

[0095] The present invention has been described above merely as an example, and it will be understood that further modifications can be made within the scope of the invention.

[0096] Each feature described herein and (as appropriate) in the claims and drawings may be provided independently or in any suitable combination.

[0097] The reference numbers appearing in the claims are for illustrative purposes only and do not have any limiting effect on the scope of the claims.

Claims

1. A computer implementation method for controlling an aircraft (10), wherein the aircraft has a plurality of control effectors (22, 32, 42, 52), and the method Determining the allocation of global forces and / or moments required to control the motion of the aircraft (10), wherein the allocation of global forces and / or moments is related to the net forces and / or moments acting on the aircraft (10), Determining a local force and / or moment assignment, wherein the local force and / or moment assignment relates to the contribution of force and / or moment to the net force provided by at least one of the control effectors (22, 32, 42, 52), A computer implementation method comprising controlling at least one of the control effectors (22, 32, 42, 52) to generate the determined local force and / or moment.

2. The method according to claim 1, comprising determining the assignment of at least two local forces and / or moments relating to the force and / or moment contributions to the net force provided by at least two control effectors (22, 32, 42, 52).

3. The method according to claim 2, wherein each of the at least two local force and / or moment assignments corresponds to a different degree of freedom of the aircraft (10).

4. The method according to any one of the prior claims, wherein controlling at least one of the control effectors (22, 32, 42, 52) includes adjusting the parameter of at least one of the control effectors to generate the local force and / or moment.

5. The method according to claim 4, wherein the at least one parameter is adjusted at least in part based on at least one external condition of the aircraft (10).

6. The method according to any one of the prior claims, wherein the local force and / or moment assignment is determined at least in part on at least one external condition of the aircraft (10).

7. The method according to any one of the prior claims, wherein the local force and / or moment assignment with respect to one control effector (22, 32, 42, 52) is determined at least partially to compensate for a force and / or moment generated by another control effector.

8. The method according to any one of the prior claims, wherein the at least one control effector (22, 32, 42, 52) comprises at least one propulsion engine.

9. The method according to claim 8, wherein the propulsion engine is an electric propulsion engine with a ducted fan.

10. The method according to claim 8 or 9, wherein controlling at least one of the control effectors (22, 32, 42, 52) includes adjusting the thrust of the at least one propulsion engine.

11. The method according to claim 10, wherein the control effectors (22, 32, 42, 52) comprise a plurality of propulsion engines, and the thrust of at least one of the propulsion engines is adjusted at least partially based on the distance between the propulsion engine and the center of mass of the aircraft.

12. The method according to any one of the prior claims, wherein the at least one control effector (22, 32, 42, 52) comprises at least one control surface, and preferably, controlling the at least one of the control effectors includes adjusting the angle of the at least one control surface.

13. The method according to claim 12, wherein the at least one control effector (22, 32, 42, 52) comprises at least one engine mounted on or near the control surface, the position of the engine being movable with the control surface to change the thrust vector.

14. The method according to any one of the prior claims, wherein the control effectors (22, 32, 42, 52) are located on the wings (40, 50) and / or canards (20, 30) of the aircraft (10).

15. An aircraft (10) comprising a processor and a memory storing computer code that, when executed on the processor, performs the method according to any one of the prior claims.

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