METHOD FOR DETERMINING A MANEUVERING RESERVE IN AN AIRCRAFT, FLIGHT CONTROL DEVICE IN AN AIRCRAFT AND APPROPRIATELY EQUIPPED AIRCRAFT

Abstract

A method for determining a maneuvering reserve in an aircraft having a number of propulsion units, preferably a multirotor VTOL aircraft, most preferably an aircraft with electrically operated drive units for the rotors, including the steps: a) Determining a control vector, τ, for the aircraft, τ=(L M N F).sup.T, the components of which represent control torques of the aircraft around the roll axis, L, the pitch axis, M, and the yaw axis, N, and a total thrust, F, b) Approximating an existing four-dimensional control volume, D, of the aircraft by a four-dimensional ellipsoid, E, the axes of which represent the control torques, L, M, N, of the aircraft and the total thrust, F, c) Determining a normalized control vector, τ.sub.ind=(L.sub.ind M.sub.ind N.sub.ind F.sub.ind).sup.T for the aircraft, using axis dimensions, L.sub.max, M.sub.max, N.sub.max, F.sub.max, of the ellipsoid, in particular semi-axis dimensions of the ellipsoid; and d) Outputting at least the normalized control vector, τ.sub.ind, for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume.

Claims

1. A method for determining a maneuvering reserve in an aircraft (1) with a number of propulsion units (3), comprising the steps of: a) determining a control vector, τ, for the aircraft (1), τ=(L M N F).sup.T, components of which represent control torques of the aircraft (1) around a roll axis, L, a pitch axis, M, and a yaw axis, N, and a total thrust, F, b) approximating an existing four-dimensional control volume, D, of the aircraft (1) by a four-dimensional ellipsoid, E, axes of which represent the control torques, L, M, N, of the aircraft (1) and the total thrust, F, c) determining a normalized control vector, τ.sub.ind=(L.sub.ind M.sub.ind N.sub.ind F.sub.ind).sup.T for the aircraft (1), using axis dimensions, L.sub.max, M.sub.max, N.sub.max, F.sub.max, of the ellipsoid; and d) outputting at least the normalized control vector, τ.sub.ind, for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume.

2. The method as claimed in claim 1, wherein in step a) for determining the control vector, τ, the components of the control vector are commanded by a pilot, directly measured and/or determined by a physical model of the aircraft (1).

3. The method as claimed in claim 1, wherein in step b) the axis dimensions of the ellipsoid are selected according to maximum permissible control torques and a maximum permissible total thrust of the aircraft (1).

4. The method as claimed in claim 1, wherein in step b) the axis dimensions of the ellipsoid are determined from maximum permissible thrust values, u.sub.min,u.sub.max; u.sub.min≤u≤u.sub.max, of individual ones of the propulsion units (3) according to:
τεD:={τ∈R.sup.4:τ=Mu}, with
u∈U:={u∈R.sup.m:U.sub.min≤u.sub.i≤u.sub.max}, where in symbolizes the number of propulsion units (3), with i=1, . . . , m, wherein M∈R.sup.4×m is a control-effectiveness matrix based on a linear relationship
τ=Mu

5. The method as claimed in claim 1, wherein in step c) all entries of the normalized control vector, τ.sub.ind, are each determined depending on the total thrust, F.

6. The method as claimed in claim 1, wherein in step c) the normalized control torque of the aircraft (1) around the yaw axis, N.sub.ind, is determined as a function of the determined total thrust, F.

7. The method as claimed in claim 1, wherein in step c) a normalized control torque of the aircraft (1) around the roll axis, L.sub.ind, and a normalized control torque of the aircraft (1) around the pitch axis, M.sub.ind, are each determined as a function of the determined total thrust, F, and as a function of a determined control torque of the aircraft (1) around the yaw axis, N.sub.ind.

8. The method as claimed in claim 1, wherein in step c) for the determination of the normalized control vector, τ.sub.ind, the following relationships are used: $F_{\mathrm{ind}}=\frac{F-F_0}{F_{\max }};$ $N_{ind}=\frac{N-N_0}{N_{\max }\sqrt{1-F_{ind}^2}};$ $L_{\mathrm{ind}}=\frac{L-L_0}{L_{\max }\sqrt{1-F_{ind}^2-\frac{{\left(N-N_0\right)}^2}{N_{\max }^2}}};$ $M_{\mathrm{ind}}=\frac{M-M_0}{M_{\max }\sqrt{1-F_{ind}^2-\frac{{\left(N-N_0\right)}^2}{N_{\max }^2}}};$ wherein components of τ.sub.0∈R.sup.4 are selected as values with index “0”, which corresponds to a center point of the ellipsoid.

9. The method as claimed in claim 1, wherein in step d) the normalized control vector, τ.sub.ind, is output as a data set having at least three data points, wherein i) a first data point indicates a normalized total thrust, F.sub.ind, ii) a second data point indicates a normalized control torque of the aircraft (1) about the yaw axis, N.sub.ind, and iii) a third data point indicates a normalized control torque of the aircraft (1) around the roll axis, L.sub.ind, as a function of the normalized control torque of the aircraft (1) around the pitch axis, M.sub.ind, or indicates the normalized control torque of the aircraft (1) around the pitch axis, M.sub.ind, as a function of the normalized control torque of the aircraft (1) around the roll axis, L.sub.ind.

10. The method as claimed in claim 1, wherein in step c) additionally a rate of change of the normalized control vector, {dot over (τ)}.sub.ind, or of components, {dot over (F)}.sub.ind, {dot over (L)}.sub.ind, {dot over (M)}.sub.ind, {dot over (N)}.sub.ind thereof, is determined and is at least partially output in step d).

11. The method as claimed in claim 1, wherein the output in step d) is carried out to at least one of a controller for the aircraft (1) or a display device (2a).

12. The method as claimed in claim 1, wherein the aircraft is a vertical take-off and landing multirotor VTOL aircraft, with electrically operated drive units for the rotors (3b).

13. A flight controller (2) in an aircraft (1) with a number of propulsion units (3), the flight controller comprising a computing unit (2b) which is configured for: a) determining a control vector, τ, for the aircraft (1), τ=(L M N F).sup.T, components of which represent control torques of the aircraft (1) around a roll axis, L, a pitch axis, M, and a yaw axis, N, and a total thrust, F, b) approximating an existing four-dimensional control volume, D, of the aircraft (1) by a four-dimensional ellipsoid, E, axes of which represent the control torques, L, M, N, of the aircraft and the total thrust, F, c) determining a normalized control vector, τ.sub.ind=(L.sub.ind M.sub.ind N.sub.ind F.sub.ind).sup.T, for the aircraft (1), using axis dimensions, L.sub.max, M.sub.max, N.sub.max, F.sub.max; and d) outputting at least a normalized control vector, τ.sub.ind, for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume.

14. The flight controller (2) as claimed in claim 13, wherein the computing unit (2b) is further configured such that, for determining the control vector, τ, the components of the control vector are adapted to be commanded by a pilot, directly measured and/or determined by a physical model of the aircraft (1).

15. The flight controller (2) as claimed in claim 12, further comprising a display device (2a), and the computing unit (2b) has a signaling connection to the display device (2a).

16. The flight controller (2), as claimed in claim 15, wherein the display device (2a) is configured to receive a normalized control vector, τ.sub.ind, from the computing unit (2b) and to display this, for which purpose the display device (2a) comprises three output segments (2aa-2ac), of which i) a first output segment (2aa) has a first, one-dimensional scale in order to display a normalized total thrust, F.sub.ind, ii) a second output segment (2ab) has a second, one-dimensional scale in order to display a normalized control torque of the aircraft (1) around the yaw axis, N.sub.ind, and iii) a third output segment (2ac) comprises a two-dimensional coordinate system in order to display the normalized control torque of the aircraft (1) around the roll axis, L.sub.ind, as a function of the normalized control torque of the aircraft (1) around the pitch axis, M.sub.ind, or to display the normalized control torque of the aircraft (1) around the pitch axis, M.sub.ind, as a function of the normalized control torque of the aircraft (1) around the roll axis, L.sub.ind.

17. The flight controller (2) as claimed in claim 13, further comprising at least one of a pilot input unit (5), a sensor (4), or a physical modeling unit, each of which is configured to determine the control vector, τ, and components thereof, wherein the computing unit has a working connection to the pilot input unit (5), the sensor (4), or the physical modeling unit.

18. The flight controller as claimed in claim 13, wherein the aircraft is a vertical take-off and landing multi-rotor VTOL aircraft, with electrically operated drive units for the rotors (3b).

19. An aircraft (1), comprising: a number of propulsion units (3), and a flight controller as claimed in claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further advantages and properties of the present invention result from the following description of exemplary embodiments based on the drawing.

[0044] FIG. 1 shows the control/regulation volume and its approximate representation as an ellipsoid for a generic eVTOL in a three-dimensional projection;

[0045] FIG. 2A shows an embodiment of the display device provided in the context of the flight control device according to the invention;

[0046] FIG. 2B shows a further development of the display device from FIG. 2A;

[0047] FIG. 3 shows a graphic representation to illustrate the relative limits mentioned in the introductory part in a two-dimensional representation; and

[0048] FIG. 4 shows a possible embodiment of the aircraft according to the invention.

DETAILED DESCRIPTION

[0049] In FIG. 1, the four-dimensional control/regulation volume, D, and its approximate representation as an ellipsoid, E, is shown in the form of a three-dimensional representation for a generic eVTOL. Vertically, the total thrust is plotted in units of Newtons. In the plane, the x-axis indicates the roll torque or the pitch torque (unit: Newton-meters), while the yaw torque is plotted perpendicularly to this (unit also Newton-meters). Reference character D in FIG. 1 denotes the convex polytope described at the beginning, while reference character E indicates the largest (hyper)ellipsoid which can be inscribed in the polytope. This ellipsoid is used in the context of the present invention as the basis for the described calculations or determinations.

[0050] FIG. 2A shows a possible embodiment of the display device 2a (see FIG. 4), which can be used for displaying the values output according to step d) of the method.

[0051] According to FIG. 2A, the display device 2a has three different output segments 2aa, 2ab and 2ac. The first output segment 2aa is in the form of an essentially one-dimensional scale and is used to display the normalized total thrust. The second output segment 2ab is also in the form of a substantially one-dimensional scale and is used to display the normalized control torque of the aircraft around the yaw axis. The third output segment 2ac is in the form of a polar coordinate system for displaying the normalized control torque of the aircraft around the roll axis together with the normalized control torque of the aircraft around the pitch axis.

[0052] The display mentioned is carried out according to the exemplary embodiment in FIG. 2A for the first output segment 2aa in the form of a diamond-shaped output element 2aa1 (without limitation), which moves along the scale depending on the value of the total thrust. The center marking line 2aa2 shown corresponds to the value F.sub.0. The upper, offset region 2aa3 of the scale indicates that the maneuvering reserve in relation to the thrust is practically exhausted and accordingly directs the pilot to change his flying behavior if possible.

[0053] The output segment 2ab for the yaw torque is essentially formed according to the output segment 2aa; however, there are marked areas 2ab3 at both ends of the scale. Reference character 2ab1 again denotes the display element (diamond-shaped), while reference character 2ab2 denotes the mentioned center line.

[0054] The third output segment 2ac is formed in the manner shown as a type of target. The display element 2ac1 is cross-shaped (without limitation), wherein the vertical and horizontal lines 2ac2 correspond to the already mentioned center lines 2aa2 and 2ab2. The colored area 2ac3 surrounds the entire third output segment 2ac.

[0055] In FIG. 2B (without reference characters) in addition to FIG. 2A the respective range of values of the scales is shown. In addition, FIG. 2B comprises a number of solid black arrows, which are used in the manner shown to represent rates of change against time of the normalized control vector or its components, {dot over (F)}.sub.ind, {dot over (L)}.sub.ind, {dot over (M)}.sub.ind, {dot over (N)}.sub.ind, —in particular to indicate to the pilot the immediate consequences of his current flying behavior and possibly to cause a countermeasure before a disaster or an accident can occur.

[0056] How the relative limits mentioned in the introductory part of the description can behave due to the mentioned coupling, for example for the yaw torque, in the event of the change of the thrust requirement, is shown in FIG. 3 in a two-dimensional representation.

[0057] In FIG. 3, the outer polygon again represents the polytope, D, in accordance with FIG. 1; the inscribed ellipse represents the ellipsoid E shown in FIG. 1. When the thrust requirement decreases as shown (thrust decrease), the maneuvering reserve expands relative to the yaw torque (relative yaw limits), because the ellipsoid or polytope becomes wider in the direction of the thrust decrease.

[0058] Finally, FIG. 4 shows a possible embodiment of the aircraft according to the invention as a multirotor eVTOL 1 with 18 propulsion units 3 in the present case, of which only one is explicitly designated in FIG. 1. According to the illustration shown, each propulsion unit 3 comprises an electric motor 3a and a propeller 3b. The propulsion units, in particular the propellers 3b, are not pivotable according to the design of the aircraft 1 in FIG. 1, so that the linear relationship described above results.

[0059] The aircraft 1 has a flight control unit with reference character 2 designed according to the invention. The flight control unit 2 comprises in addition to the display unit 2a, which has already been referred to above, a computing unit with reference character 2b, which is designed, preferably programmatically set up, in particular for carrying out the method according to the invention. Reference character 4 refers to an exemplary sensor; the aircraft 1 will usually comprise a large number of such sensors 4, which are in particular designed and suitable to determine a state of the aircraft 1 and in particular also the control vector. With reference character 5, a pilot input unit is shown, via which the pilot (not shown) transmits his control requirements to the aircraft 1, for example via a joystick or the like. The mentioned control vector can be determined or derived from this too. Alternatively or additionally, the flight control device 2 can use a physical model of the aircraft 1 for determining the control vector, which is not shown further in FIG. 4.

[0060] Preferably, the flight control unit 2 determines the normalized control vector by use of the computing unit 2b, as detailed above, and displays this to the pilot by the display device 2a, so that the pilot sees his maneuvering reserves at a glance and, if necessary, adjusts his flying behavior accordingly.