Aeronautics and astronautics – Aircraft control
Reexamination Certificate
1999-04-28
2001-06-05
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft control
C244S078200, C244S227000, C244S228000
Reexamination Certificate
active
06241182
ABSTRACT:
The present invention relates to a system for controlling an aerodynamic surface of an aircraft, such as a control surface, flap, aileron, etc.
It is known that, particularly on commercial airplanes, the system for controlling such an aerodynamic surface comprises, for reasons of redundancy, two hydraulic servocontrols in parallel. Thus, one of said servocontrols may be active, that is to say used for actuating said aerodynamic surface while the other is passive and used to damp the diverging vibrations which are due to the aerodynamic effects (flutter) and to which said aerodynamic surface is subjected. For this latter purpose, said servocontrols incorporate a damping system (shut-off valves, fluid reservoir, dashpot between the chambers of the servocontrols, etc.). Furthermore, when the active servocontrol breaks down, the passive servocontrol is activated to substitute for the latter one. Thus, continuity of the control of said aerodynamic surface is obtained.
However, such a known control system for aerodynamic surfaces has drawbacks, the main one of which is that the probability of the simultaneous loss of both servocontrols is of the order of 10
−7
/h, that is to say that such a loss is not improbable. There is therefore the need to provide, onboard the aircraft, an additional hydraulic fluid source to be used as a backup to pressurize at least one of the two servocontrols. Such an additional hydraulic fluid source therefore increases the mass and cost of said aircraft, while at the same time raising difficulties of installation and of performing functional tests onboard said aircraft.
Furthermore, the servocontrol damping systems also increase the cost and mass of these controls and require lengthy and difficult functional-test procedures.
The object of the present invention is to overcome these drawbacks.
To this end, according to the invention, the system for controlling an aerodynamic surface of an aircraft comprising a deliberate-actuation member available to a pilot and a hydraulic servocontrol controlled by said deliberate-actuation member, is noteworthy in that it additionally comprises:
an electric machine which can operate either as a motor or as a generator, the output of which is connected mechanically to said aerodynamic surface;
an electrical power supply, which can power said electric machine under the dependency of said deliberate-actuation member;
a resistive load into which said electric machine can output;
a switching device intended to electrically connect said electric machine either to said electrical power supply or to said resistive load;
a device for controlling the supply of hydraulic fluid to said servocontrol; and
a logic device receiving information about the operating status of said electrical power supply and of said hydraulic servocontrol and controlling the status of said switching device and of said device for controlling the hydraulic supply.
It can be seen that, by virtue of the present invention, it is possible to dispense with one of the hydraulic servocontrols of the known system described above, and this therefore lowers the costs and mass and dispenses with the damping effectiveness tests associated with said dispensed with hydraulic servocontrol. This control is replaced by the electric actuator formed by said electric machine and the mechanical connection connecting it to said aerodynamic surface. Such a mechanical connection may comprise a screw which rotates as one with the shaft of said electric machine and is engaged in a nut that is prevented from turning.
It will be readily understood that when said electric machine is operating as a motor it can actuate said aerodynamic surface via said mechanical connection. By contrast, when said aerodynamic surface is actuated by the hydraulic servocontrol, said mechanical connection transmits the movements of said aerodynamic surface to said electric machine so that said electric machine can operate as a generator and output current into said resistive load. It therefore damps the aerodynamic vibrations of said surface.
It will be noted that when said electric machine is operating as a generator, the current it outputs into the resistive load can be measured and the measured value of said current can be associated with the rate at which the control surface is moved (on commercial aircraft, there is at least one position sensor on the aerodynamic surface), so that it is possible to check that damping is occurring and even measure its performance. Such monitoring, which is simple, may be continuous.
Thus, the electric actuator formed by said electric machine, associated with said mechanical connection, can exert either the function of controlling or the function of damping said aerodynamic surface. For the same to be true of the hydraulic servocontrol, all that is required is for the latter to comprise, in the known way, a damping system such as those described above.
According to a first embodiment of the control system according to the present invention, this control system is noteworthy in that:
in normal operation, said hydraulic servocontrol takes priority for controlling said aerodynamic surface, the aerodynamic vibrations thereof being damped by said electric machine operating as a generator outputting into said resistive load; and
in back-up operation, when the hydraulic servocontrol has broken down, said electric machine operates as a motor to control said aerodynamic surface, said aerodynamic vibrations of said surface being damped by said hydraulic servocontrol.
In this case, said logic device may comprise:
a first input receiving information about the operating status of said electrical power supply;
a second input receiving information about the operating status of said hydraulic servocontrol;
a first output controlling the status of said switching device;
a second output controlling the status of said device for controlling the hydraulic supply;
a logic gate of the two-input AND type, of which one of the inputs is connected directly to said first input and the other is connected to said second input via an inverter, the output of said logic gate being connected to said first output; and
a direct connection between said second input and said second output.
By contrast, in an alternative form, the control system according to the present invention is noteworthy in that:
in normal operation, said electric machine operating as a motor takes priority for controlling said aerodynamic surface, the aerodynamic vibrations thereof being damped by said hydraulic servocontrol; and
in back-up operation, when said electric machine cannot operate as a motor, control of said aerodynamic surface is provided by said hydraulic servocontrol, the aerodynamic vibrations of said aerodynamic surface being damped by said electric machine operating as a generator outputting into said resistive load.
In this alternative form, the logic device may then comprise:
a first input receiving information about the operating status of said electrical power supply;
a second input receiving information about the operating status of said hydraulic servocontrol;
a first output controlling the status of said switching device;
a second output controlling the status of said device for controlling the hydraulic supply;
a logic gate of the two-input AND type, of which one of the inputs is connected directly to said second input and the other is connected to said first input via an inverter, the output of said logic gate being connected to said second output; and
a direct connection between said first input and said first output.
In a third embodiment, the control system according to the present invention is noteworthy:
in that it comprises:
an additional hydraulic servocontrol controlled by said deliberate-actuation member and capable of controlling said aerodynamic surface;
an additional device for controlling the supply of hydraulic fluid to said additional hydraulic servocontrol; and
in that, in normal operation, said hydraulic servocontrol and said additional hydraulic servocontrol take priority in controll
Durandeau Michel
Foch Etienne
Aerospatiale - Societe Nationale Industrielle
Barefoot Galen L.
Stevens Davis Miller & Mosher LLP
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