Method and device for piloting an aircraft about a piloting axis

A method for piloting an aircraft about a piloting axis, said aircraft comprising a plurality of N controllable aerodynamic surfaces (2A to 2N) capable of producing a movement of the aircraft about said piloting axis, according to which method the following series of successive operations is carried out in an automatic and repetitive manner:

• a) an overall piloting command relating to said piloting axis is produced;
• b) on the basis of this overall piloting command, individual control commands are determined, intended for said N controllable aerodynamic surfaces (2A to 2N);
• and
• c) said individual control commands are applied to said aerodynamic surfaces (2A to 2N), wherein:
• in step b), on the basis of said overall piloting command, N individual piloting commands relating respectively to said N aerodynamic surfaces (2A, 2N) are formed by multiplying on each occasion said overall piloting command by at least one gain Ki which is positive or negative, i being an integer varying from 1 to N and N being an integer greater than 1, said gains Ki being such that:
• ∑
• i
• 
• 
• Ki
• 
• =
• N
• ;
• they make it possible to reduce the excitation of N−1 flexible modes of the aircraft, which are responsible for a discomfort of the latter, these N−1 flexible modes being chosen as a function of the current values of parameters related to the aircraft;
• and
• applied together, said N individual piloting commands produce effects which correspond overall to the effect of said overall piloting command, as regards the piloting of the aircraft about said piloting axis,
• these N commands being obtained by solving a linear system of N−1 equations with N unknowns;
• in step b), said individual control commands are thereafter deduced from said individual piloting commands;
• and
• in step c), to said aerodynamic surfaces (2A to 2N) are applied:
• initially, solely the individual control commands which have been deduced from individual piloting commands obtained on the basis of positive gains Ki;
• and
• after a predetermined duration, all said individual control commands deduced in step b).

A device for piloting an aircraft about a piloting axis, said aircraft comprising a plurality of N controllable aerodynamic surfaces (2A to 2N) capable of producing a movement of the aircraft about said piloting axis, said device (1) comprising:

• first means (3) for producing an overall piloting command relating to said piloting axis;
• second means (4A to 4N) for determining, on the basis of this overall piloting command, individual control commands intended for said N controllable aerodynamic surfaces (2A to 2N);
• and
• third means (6A to 6N) for applying said individual control commands to said aerodynamic surfaces (2A to 2N),
• wherein:
• said second means (4A to 4N) comprise means (8A to 8N) for forming, on the basis of said overall piloting command, N individual piloting commands relating respectively to said N aerodynamic surfaces (2A to 2N), by multiplying on each occasion said overall piloting command by at least one gain Ki which is positive or negative, i being an integer varying from 1 to N and N being an integer greater than 1, said gains Ki being such that:
• ∑
• i
• 
• 
• Ki
• 
• =
• N
• ;
• they make it possible to reduce the excitation of N−1 flexible modes of the aircraft, which are responsible for a discomfort of the latter, these N−1 flexible modes being chosen as a function of the current values of parameters related to the aircraft;
• and
• applied together, said N individual piloting commands produce effects which correspond overall to the effect of said overall piloting command, as regards the piloting of the aircraft about said piloting axis, these N commands being obtained by solving a linear system of N−1 equations with N unknowns;
• said second means (4A to 4N) comprise, moreover, means (9A to 9N) for deducing said individual control commands from said individual piloting commands;
• and
• said third means (6A to 6N) are formed so as to apply to said aerodynamic surfaces (2A to 2N):
• initially, solely the individual control commands which have been deduced from individual piloting commands obtained on the basis of positive gains Ki;
• and
• after a predetermined duration, all said individual control commands.