Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
1998-10-05
2001-02-27
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C277S377000
Reexamination Certificate
active
06195599
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and a device for decoupling of the behavior of an aircraft, particularly a helicopter.
In the context of the present invention, coupling of the behavior is understood to mean the interaction which exists between various controls and/or attitudes of an aircraft, such that a change to a control (for example the actuation of the pitch control column of a helicopter with a view to altering the pitch trim) or of an attitude entails not only an associated corresponding alteration of the behavior of the aircraft (representative of the said change), but also moreover an interfering action generated on other attitudes.
Hence, a method or a device for decoupling of the behavior of an aircraft, in the context of the present invention, represents a method or a device intended, upon a change to a particular attitude or to a control, to eliminate the interfering action arising from the coupling of the aircraft.
It is known that, on a helicopter, the couplings of the behavior thereof are many and are essentially of two different origins, namely control couplings and axis couplings.
In a known way, the control couplings exhibit very clear-cut and instantaneous effects after action on the controls. A characteristic example is the collective-pitch/yaw coupling. The lift of the main rotor keeps the helicopter in the air. The drag of the rotor blades creates, by reaction, a torque which tends to make the helicopter turn in yaw. In the equilibrium state, this torque is compensated for by that generated by the rear rotor. Hence, if the position of the collective pitch is altered, the drag of the main rotor blades is also altered, and an interfering torque is created, generating the onset of yaw.
Moreover, in a known way, the axis couplings are of very varied origins and exhibit a significant effect appearing after the alteration to the flight configuration, for example a change of speed, incidence or sideslip. A characteristic example is the rotor/empennage interaction. It is known that, between about 50 km/h and 150 km/h, an empennage in the low position lies within the downwash from the rotor. This results in an increase in the pitch-up moment (and of the roll if the empennage is asymmetric).
These couplings of the behavior of the aircraft are consequently very troublesome.
Various methods intended to limit these couplings are known, particularly:
the control coupling can be combated by flat-rate control decoupling. In the case of the “collective-pitch/yaw” decoupling, the movement of the collective lever causes a proportional movement of the yaw control, which is added to the yaw control generated by the pilot of the aircraft; and
the axis decoupling can be performed by a flat-rate feedback to the controls of parameters measured in flight, such as the lateral and vertical load factors, for example.
However, in practice, by reason of the complexity of the phenomena at play, these methods at best make it possible to attenuate the effect of a limited number of couplings. None of the preceding solutions is therefore totally satisfactory for overall decoupling.
SUMMARY OF THE INVENTION
The object of the present invention is to remedy these drawbacks. It relates to a method and a device making it possible to decouple the behavior of an aircraft, particularly of a helicopter, in a robust way, that is to say being capable of being adapted to all the types of couplings likely to exist, throughout the entire flight envelope of the aircraft, while observing the situations relating to the perception of control margins (replication, via the position of the controls, of the position of the control surfaces in the medium term).
According to the invention, the method for decoupling of the behavior of an aircraft, particularly of a helicopter, is noteworthy in that:
a) a first control demand is determined, representative of the actuation of a control member;
b) a transfer function is determined, representative of the behavior of the aircraft upon actuation of the control member;
c) at least on the basis of a partial inversion of the said transfer function and of that part of the transfer function not taken into account by the partial inversion, a second control demand is determined, capable of generating the decoupling;
d) an overall demand is calculated from the sum of the first and second control demands; and
e) the overall demand thus calculated is applied to the aircraft.
Hence, since by virtue of the invention the second control demand intended to achieve the decoupling is calculated from the transfer function representative of the behavior of the aircraft, an overall decoupling is achieved, and not a decoupling limited to a limited number of couplings, as is the case for the above-mentioned known solutions.
Moreover, by virtue of the invention, the method is not dependent on or exclusive of the type of coupling or of the particular flight configuration, so that its use is not limited to specific instances of application.
Furthermore, the device in accordance with the invention for decoupling of the behavior of an aircraft, particularly a helicopter, the aircraft including at least:
a control member capable of being actuated by a pilot of the aircraft;
means for determining first control demands as a function of the actuation of the control member; and
means for actuating a member controlled as a function of control demands received,
is noteworthy in that it includes:
a calculating unit which, by means of a transfer function representative of the behavior of the aircraft upon the actuation of the control member, determines a second control demand capable of generating the decoupling, at least on the basis of a partial inversion of the transfer function and of that part of the transfer function not taken into account by the partial inversion; and
a calculating means calculating, from the sum of the first and second control demands, an overall demand which is conveyed to the means of actuating the controlled member as a control demand.
Moreover, according to the invention, in order to calculate the second control demand, the result obtained by the partial inversion and by taking into account the non-inverted part of the transfer function is advantageously filtered and/or multiplied by a weighting factor and/or a correction factor. In addition, advantageously, a limitation is applied at least to the value of the result.
Furthermore, advantageously, in order to achieve a replication of the control margins, the control member is brought into a position representative of the overall demand.
REFERENCES:
patent: 5001646 (1991-03-01), Caldwell et al.
patent: 5678786 (1997-10-01), Osder
patent: 2073114A (1981-10-01), None
Liceaga-Castro et al., “Helicopter Flight Control Using Individual Channel Design”, IEEE Proceedings: Control Theory and Applications, vol. 142, No. 1, Jan. 1995, pp. 58-72.
Spurgeon, S. K. et al., “An Assessment of Rubustness of Variable Structure Control Systems for Advanced Aircraft Manoeuvres” IEEE Proceedings: Conference on Decision and Control, Dec. 5-7, 1990, vol. 6, pp. 3588-3593.
Jones et al., “Fuzzy Control of a Three Fin Torpedo”, IEEE Proceedings: American Control Conference, May 1990, vol. 2, pp. 1474-1478.
French Search Report dated May 22, 1998, 3 pages.
Eurocopter
Gibson Eric M
Marshall O'Toole Gerstein Murray & Borun
Zanelli Michael J.
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