Method for determining a maneuvering reserve in an aircraft, flight control device in an aircraft and appropriately equipped aircraft

1. A method for determining a maneuvering reserve in an aircraft with a number of propulsion unit, comprising the steps of:

a) determining a control vector, τ, for the aircraft, τ=(L M N F) T , components of which represent control torques L, M, and N of the aircraft around a roll axis, a pitch axis, and a yaw axis, respectively, and a total thrust, F;

b) approximating an existing four-dimensional control volume, D, of the aircraft by a four-dimensional ellipsoid, E, axes of which represent the control torques, L, M, and N, of the aircraft and the total thrust, F;

c) determining a normalized control vector, τ ind =(L ind M ind N ind F ind ) T for the aircraft, using axis dimensions, L max , M max , N max , F max , of the ellipsoid, L ind , M ind , N ind , and F ind representing a normalized control torque of the aircraft around the roll axis, a normalized control torque of the aircraft around the pitch axis, a normalized control torque of the aircraft around the yaw axis, and a normalized total thrust, respectively;

d) outputting at least the normalized control vector, τ ind , for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume; and

e) controlling, using a flight controller or flight control device for the aircraft, the number of propulsion units of the aircraft to perform the permissible flight maneuver based at least in part on the normalized control vector, τ ind .

2. The method as claimed in claim 1 , wherein the components of the control vector are commanded by a pilot, directly measured by a physical model of the aircraft, or determined by the physical model of the aircraft.

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.

4. The method as claimed in claim 1 , wherein in step b) the axis dimensions of the ellipsoid are determined from minimum and maximum permissible thrust values, u min , u max ; u min ≤u≤u max , of individual ones of the number of propulsion units according to:

τ=D:={τ∈R 4 :τ=Mu}, with

u∈U:={u∈R m : u min ≤u i ≤u max },

where u symbolizes thrust values, u i symbolizes thrust values of the individual ones of the number of propulsion units, U symbolizes a total thrust for the number of propulsion units, m symbolizes the number of propulsion units, with i=1, . . . , m, wherein M∈R 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 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 around the yaw axis, N ind , is determined as a function of the total thrust, F.

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

8. The method as claimed in claim 1 , wherein in step c) for the determination of the normalized control vector, τ ind , the following relationships are used:

F

ind

=

F

-

F

0

F

max

;

N

i

⁢

n

⁢

d

=

N

-

N

0

N

max

⁢

1

-

F

i

⁢

n

⁢

d

2

;

L

ind

=

L

-

L

0

L

max

⁢

1

-

F

i

⁢

n

⁢

d

2

-

(

N

-

N

0

)

2

N

max

2

;

M

ind

=

M

-

M

0

M

max

⁢

1

-

F

i

⁢

n

⁢

d

2

-

(

N

-

N

0

)

2

N

max

2

;

wherein components of τ 0 ∈R 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 ind , is output as a data set having at least three data points, wherein

i) a first data point indicates the normalized total thrust, F ind ;

ii) a second data point indicates the normalized control torque of the aircraft about the yaw axis, N ind ; and

iii) a third data point indicates the normalized control torque of the aircraft around the roll axis, L ind , as a function of the normalized control torque of the aircraft around the pitch axis, M ind , or indicates the normalized control torque of the aircraft around the pitch axis, M ind , as a function of the normalized control torque of the aircraft around the roll axis, L 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)} ind , or of components, {dot over (F)} ind , {dot over (L)} ind , {dot over (M)} ind , {dot over (N)} 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 output to a display device.

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 rotors.

13. A flight controller in an aircraft with a number of propulsion units, the flight controller comprising a computing unit which is configured for:

a) determining a control vector, τ, for the aircraft, τ=(L M N F) T , components of which represent control torques L, M, and N of the aircraft around a roll axis, a pitch axis, and a yaw axis, respectively, and a total thrust, F;

b) approximating an existing four-dimensional control volume, D, of the aircraft by a four-dimensional ellipsoid, E, axes of which represent the control torques, L, M, and N, of the aircraft and the total thrust, F;

c) determining a normalized control vector, τ ind =(L ind M ind N ind F ind ) T , for the aircraft, using axis dimensions, L max , M max , N max , F max of the ellipsoid, Lind, M ind , N ind , and F ind representing a normalized control torque of the aircraft around the roll axis, a normalized control torque of the aircraft around the pitch axis, a normalized control torque of the aircraft around the yaw axis, and a normalized total thrust, respectively;

d) outputting at least the normalized control vector, τ ind , for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume; and

e) controlling the number of propulsion units of the aircraft to perform the permissible flight maneuver based at least in part on the normalized control vector, τ ind .

14. The flight controller as claimed in claim 13 , wherein the computing unit 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 by a physical model of the aircraft, or determined by the physical model of the aircraft.

15. The flight controller as claimed in claim 13 , wherein the flight controller further comprises a display device with a signaling connection to the computing unit.

16. The flight controller as claimed in claim 15 , wherein the display device is configured to receive, from the computing unit, and display the normalized control vector, τ ind , and comprises three output segments, of which

i) a first output segment has a first, one-dimensional scale in order to display the normalized total thrust, F ind ;

ii) a second output segment has a second, one-dimensional scale in order to display the normalized control torque of the aircraft around the yaw axis, N ind ; and

iii) a third output segment comprises a two-dimensional coordinate system in order to display the normalized control torque of the aircraft around the roll axis, L ind , as a function of the normalized control torque of the aircraft around the pitch axis, M ind , or to display the normalized control torque of the aircraft around the pitch axis, M ind , as a function of the normalized control torque of the aircraft around the roll axis, L ind .

17. 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 rotors.

18. An aircraft, comprising:

a number of propulsion units; and

a processor configured to:

a) determine a control vector, τ, for the aircraft, τ=(L M N F) T , components of which represent control torques L, M, and N of the aircraft around a roll axis, a pitch axis, and a yaw axis, respectively, and a total thrust, F;

b) approximate an existing four-dimensional control volume, D, of the aircraft by a four-dimensional ellipsoid, E, axes of which represent the control torques, L, M, and N, of the aircraft and the total thrust, F;

c) determine a normalized control vector, τ ind =(L ind M ind N ind F ind ) T , for the aircraft, using axis dimensions, L max , M max , N max , F max of the ellipsoid, L ind , M ind , N ind , and F ind representing a normalized control torque of the aircraft around the roll axis, a normalized control torque of the aircraft around the pitch axis, a normalized control torque of the aircraft around the yaw axis, and a normalized total thrust, respectively;

d) output at least the normalized control vector, τ ind , for determining a permissible flight maneuver in at least one dimension of the four-dimensional control volume; and

e) control the number of propulsion units of the aircraft to perform the permissible flight maneuver based at least in part on the normalized control vector, τ ind .

19. The aircraft of claim 18 , wherein the aircraft is a vertical take-off and landing (VTOL) multi-rotor aircraft with electrically operated drive units for rotors.