Flight control system for an aircraft's active, hybrid, friction-based flight trim

Abstract

This flight control system (1) for the collective pitch of an aircraft flight trimmer comprises a control element (3) pivoting about at least one axis of rotation (5), at least one mechanical force feedback means (9) linked to the control element, said mechanical means (9) comprising a variable friction module (11) and an electric motor (15), the friction module (11) on the one hand and the motor (15) on the other hand being connected to the control element (3) by a multi-way gearbox (17), the flight control system (1) comprising a digital haptic controller (29) controlling the friction module (11) and the motor (15) so as to generate active force feedback to the control element (3). Figure for the abbreviation: Fig. 3

Description

Description Title of the invention: Flight control system for a com- friction-driven, active, hybrid aircraft flight engineer Technical field

[0001] — The present invention relates, in general, to control systems for aircraft flight and more particularly relates to a flight trim for aircraft, especially for helicopters. Previous techniques

[0002] = Flight compensators, or trim, have the function of compensating for the drifts linked to disturbances likely to exert an influence on the parameters of the aircraft's flight, without the pilot having to act on the flight controls.

[0003] — In addition, the flight compensators conventionally restore to the pilot the aircraft a resistive force on the flight controls in the form of a return effort. This effort is generally passive, either linear (spring trimmers) or constant (friction trims), and can also be active. Resistant effort is also called restoring force, or force return.

[0004] — With regard to flight compensators providing a passive force of the type friction or spring, these are configured to provide a linear force or even constant once a de-anchoring force is applied to the flight controls, by example on a control organ such as a control stick. These compensators flight have a setting specific to each flight control axis, especially for collective pitch control.

[0005] — When we wish to modify the restoring force, in other words the force law of the control system, it is necessary to reconfigure the equipment settings for example by changing components. Indeed, passive force feedback does not are not configurable.

[0006] — [Fig.1] shows schematically the law of force of a restoring force of a flight compensator providing a passive torsion spring force. In par- In particular, the force feedback is illustrated by a torque C in Newton meters and given in function of the angle A of rotation of a shaft connected to the flight controls, for example to a control organ. In particular, the force law includes an angular position P anchoring of the flight controls, the flight controls being able to move away from the anchoring position P when the pilot provides an effort greater than a torque called unanchoring force F. For an angle A allowing exit from the anchoring position P, the force law is linear according to a gradient G depending on the spring used. We call gradient the stiffness of the spring, once a force greater than the unanchoring force applied. The unanchoring force corresponds to the force to be applied before the spring begins to move, i.e. the preload of the spring. [Fig.2] also shows schematically the force law of a return force of a flight compensator providing a passive friction force. In this case, the force is constant once the angle A is beyond the anchoring position P. Flight compensators providing active force comprise controllable equipment such as a motor and / or a brake that provides variable force feedback adapted to flight conditions. The term controllable for equipment means that its operating state, whether binary or having several levels of discretization, can be modified by means of associated electronics. A hybrid architecture in which a flight compensator implements a mechanical force law assisted by electrical assistance is also configurable. It allows, for example, to modify the de-anchoring force and the force feedback gradient in a more precise and complex manner than passive systems. However, a friction-type force law is generally used at the collective axis of an aircraft, while a more widely parameterizable spring-type force law is generally used on the other axes. In addition, the electric assistance of existing hybrid architectures is generally controlled by electronics external to the trim, of the analog type, typically the flight control computer. Thus, the electric assistance, although variable, has little flexibility in the use of this hybrid architecture. Presentation of the invention The present invention therefore aims to overcome the aforementioned drawbacks and to provide a trim control system capable of generating a more widely configurable force law for the collective axis of an aircraft. The present invention relates to a flight control system for collective pitch of a flight trim tab of an aircraft, said system comprising a piloting member pivoting about at least one axis of rotation, at least one mechanical force feedback means linked to the piloting member, said mechanical means comprising a variable friction module and an electric motor, the friction module on the one hand and the motor on the other hand being connected to the piloting member by a multi-way reducer, the flight control system comprising a digital haptic controller controlling the friction module and the motor so as to generate active force feedback to the piloting member. Thus, the multi-way reducer makes it possible to promote the multitude of force laws achievable for the mechanical means of force feedback. The haptic controller digital also allows for better precision and centralization of the control instruction from a single haptic controller for all the modules and motors of an aircraft that can generate force feedback, and unlike current trims, which operate separately. Advantageously, the motor simulates the elastic return in position of a spring force law. In a particular embodiment, the motor simulates a variable anchoring point of a spring and / or a variable stiffness of a spring and / or a variable unanchoring force of a spring. Alternatively, the simulation of a variable stiffness of a spring is carried out by the friction module or by a collaboration of the friction module and the motor. In one embodiment, the friction module generates friction proportional to the setpoint current sent by the haptic controller. Advantageously, the flight control system comprises a means for controlling and supplying power to the motor, the haptic controller controlling the motor by current via the control and supply means. According to one embodiment, the mechanical force feedback means comprises a main shaft connecting the multi-way reducer and the control member, and at least one angular position sensor of the main shaft and / or of the multi-way reducer, said angular position sensor communicating with the haptic controller so that said haptic controller controls the motor and the friction module according to information communicated by the angular position sensor. Advantageously, the haptic controller controls the friction module and the motor as a function of the angular position of the control member, angular positions of the multi-way reducer, and the supply currents of the motor and the friction module. Advantageously, the haptic controller comprises a parameter table comprising all the singular points of a force law profile of the mechanical force feedback means that can be produced. In one embodiment, the motor is a three-phase synchronous motor with permanent magnets and / or a brushed motor, and / or piezoelectric, rotationally connected to the multi-way reducer via an irreversible reducer. The invention also relates to a helicopter comprising a flight control system as defined above, and at least one flight control system for cyclic pitch of a swashplate piloted with a haptic controller, the haptic controller being unique for all the flight control systems. Brief description of the drawings Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which: [Fig.1] which has already been mentioned is a graph schematically representing the force law of a restoring force of a torsion spring flight compensator; [Fig.2] which has already been mentioned is a graph schematically representing the force law of a restoring force of a friction flight compensator; and [Fig.3] is a schematic representation of a flight control system according to the invention. Detailed description of at least one embodiment [Fig.3] schematically shows a flight control system 1 for an aircraft according to the invention. The aircraft is for example a helicopter comprising said flight control system 1 controlling a collective pitch of said helicopter. The flight control system 1 comprises a frame (not shown) and a control member 3 mounted to pivot relative to the frame around at least one axis of rotation 5. The control member 3 is for example a control stick 3 and makes it possible for example to control the cyclic pitch of the aircraft. The frame includes mechanical stops 7 against which the control member 3 abuts to limit its angular travel. The flight control system 1 comprises at least one mechanical force feedback means 9 linked to the piloting member 3, the return force being directed in the opposite direction to an external force applied by the pilot of the aircraft to the piloting member 3. The mechanical means 9 comprises a variable friction module 11, a main shaft 13 and an electric motor 15 arranged so that the friction module 11 on the one hand and the motor 15 on the other hand are connected to the control member by a multi-way reducer 17. The multi-way reducer 17 is, for example, a differential reducer or an epicyclic reducer. The motor 15 is for example a three-phase synchronous motor with permanent magnets, and / or a brushed motor, and / or piezoelectric, optionally equipped with a position sensor. In particular, a first end 19 of the multi-way reducer 17 is constrained to move in rotation under the action of the motor 15, a second end 21 of the multi-way reducer 17 is connected to the friction module 11, and a third end 23 of the multi-way reducer 17 is connected to the control member via the main shaft 13. The mechanical force feedback means 9 also comprises a control and power supply means 25 for the motor 15. The control means 25 is for example an electronic control unit. The mechanical force feedback means 9 also comprises an irreversible reducer 27, such as a worm screw and a toothed wheel, positioned integral in rotation with the motor 15 and the position of which defines an anchoring point of the mechanical force feedback means 9. More precisely, the irreversible reducer 27 is arranged between the motor 15 and the multi-way reducer 17. The flight control system 1 further comprises a digital haptic controller 29 controlling the motor 15 as well as the friction module 11 so as to generate active force feedback to the control member. In particular, the friction module 11 makes it possible to generate a variable friction torque, in particular a passive friction-type force law, and the motor 15 makes it possible to return the control member 3 to the position, for example by generating a variable active force law and being able, for example, to simulate the shape of a force law of a spring, for example a torsion spring. More precisely, the motor 15 and / or the friction module 11 can then simulate a variable stiffness of a spring and / or a variable unanchoring force of a spring and / or a variable anchoring point of a spring. The anchoring point is in particular obtained jointly with the irreversible reducer 27, towards which the motor can create a resistive force.One of the advantages of using controllable equipment, here the combination between the motor 15 and the friction module 11, is that the latter can be used to independently modify the apparent stiffness and the preload, in other words the apparent unanchoring force of the spring simulated by said motor 15 and / or said friction module. The combination of the motor 15 and the friction module 11 therefore makes it possible to produce an elaborate and hybrid force feedback behavior, comprising both an active and passive component. The force law obtained is thus freely configurable and can in particular include changes in gradients and changes in de-anchoring force, said changes being able to be carried out in real time and making it possible to create complex force laws, more advanced than a purely passive or active system, or comprising an analog controller. The haptic controller 29 for example directly controls the friction module 11 in current, the friction module generating a friction proportional to the setpoint current sent by the haptic controller 29, the control being carried out in current as a function of the position of the main shaft 13 and allowing to recreate a variable spring type law in combination with the motor 15. At 0 Ampere, the friction module is disengaged while when the current is maximum, the friction module is engaged and generates maximum force feedback. The wide range available between a minimum and a maximum friction makes the system 1 all the more easily configurable. The haptic controller 29 also controls the motor 15 with current but via the control and power supply means 25 of the motor 15. The mechanical force feedback means 9 may optionally comprise a safety pin 31 between the multi-way reducer 17 and the control member 3 so as to disconnect said mechanical means 9, for example in the event of a breakdown. Furthermore, the mechanical means 9 comprises at least one sensor 33, for example of the rotary variable differential transformer type also called RVDT sensor, or of the resolver type, Hall effect sensor, potentiometer or any other type of sensor, to measure the angular position of the main shaft 13, said sensor 33 communicating with the haptic controller 29 so that said haptic controller 29 controls the motor 15 and the friction module 11 according to information communicated by the sensor 33, the sensor 33 being able to be connected to the main shaft 13 via a safety pin 35 so as to be able to disconnect it, for example in the event of a breakdown. Optionally, and so as to have a redundant measurement, the mechanical means 9 comprises several sensors 33 connected to the main shaft 13. The mechanical means 9 optionally comprises at least one RVDT and / or Hall effect and / or resolver type, potentiometer or any other type of sensor 37, configured to measure the deformation and / or position of the ends of the multi-way reducer 17. Advantageously, at least one of the sensors 37 communicates with the haptic controller 29 so that said haptic controller 29 controls the motor 15 and the friction module 11 according to information communicated by the sensor 37. Optionally, and so as to have a redundant measurement, the mechanical means 9 comprises several sensors 37. The haptic controller 29 controls the motor 15 and the friction module 11 as a function of all the parameters that may be deemed relevant by the aircraft's on-board computer. For example, the haptic controller 29 takes into account the angular position of the control member 3, the potential angular position measurements of the multi-channel reducer 17, as well as the supply currents of the motor 15 and / or the friction module 11 for their control, these currents being indicators of the force applied by the pilot to the control member 3 and the speed of movement of said control member 3. The haptic controller 29 controls the motor 15 and the friction module 11 in a closed loop and without a force sensor, the force measurement being proportional to the measurement of the supply currents, in particular the supply currents of the friction module 11, giving an image of the force applied. The haptic controller 29 controls the friction module 11 and the motor 15 as a function of the angular position of the main shaft 13 given by the position sensors 33, in order to modulate the force felt by the pilot when moving the control member, and to achieve a return to the anchoring characteristic of a spring-type force law. The haptic controller 29 implements a first servo loop in the position of the control member 3. The haptic controller 29 integrates into this first loop a current servo loop, used for controlling the motor 15 and / or the friction module 11. The force law of a restoring force of a flight control system 1 according to the invention may be configurable in real time on request, for example from an operator or the on-board computer, the latter sending an instruction to the haptic controller 29. This function will be achieved by providing access to a parameter table included in the haptic controller 29, which contains all the singular points of the force law profile that can be achieved. Therefore, it will be possible to freely modify the force law of system 1 within the limits of the validity domain. The haptic controller 29 also implements protection to provide a gradual torque transition between a current setpoint and a new setpoint when a setpoint is changed by a driver or the onboard computer. An alert will be raised by the haptic controller 29 if a risk of inappropriate configuration is detected, for example near the mechanical stops, in order to guarantee the mechanical integrity of the system 1. The invention also relates to a helicopter comprising the system 1. The helicopter also comprises other control systems, in particular for cyclic pitch, for example for the pitch axis and the roll axis. The helicopter then comprises a single haptic controller 29 for all the cyclic and collective pitches of the helicopter.

Claims

Claims

1. Flight control system (1) for collective pitch of a trim tab of flight of an aircraft, said system (1) comprising a piloting member (3) pivoting about at least one axis of rotation (5), at least one mechanical means (9) of force feedback linked to the control member, said mechanical means (9) comprising a variable friction module (11) and an electric motor (15), characterized in that the friction module (11) on the one hand and the motor (15) on the other hand are connected to the organ of control (3) by a multi-way reducer (17), the system (1) of flight control comprising a digital haptic controller (29) controlling the friction module (11) and the motor (15) so as to generate active force feedback to the control unit (3).

2. A flight control system (1) according to claim 1, wherein the motor (15) simulates the elastic return in position of a force law of a spring.

3. System (1) according to claim 2, wherein the engine (15) simulates a variable anchor point of a spring and / or a variable stiffness of a spring and / or a variable unanchoring force of a spring.

4. System (1) according to any one of claims 1 to 3, in which the friction module (11) generates a friction proportional to the setpoint current sent by the haptic controller (29).

5. System (1) according to any one of claims 1 to 4, comprising a means (25) for controlling and supplying the motor (15), the haptic controller (29) driving the motor (15) by current by via the control and power supply means (25).

6. Flight control system (1) according to any one of the claims- indications 1 to 5, in which the mechanical force feedback means (9) comprises a main shaft (13) connecting the multi-way reducer (17) and the control member (3), and at least one position sensor (33; 37) angular of the main shaft (13) and / or the multi-way reducer (17), said angular position sensor (33; 37) communicating with the haptic controller (29) such that said haptic controller (29) controls the motor (15) and the friction module (11) in function information communicated by the position sensor (33; 37) angular.

7. Flight control system (1) according to any one of the claims- indications 1 to 6, in which the haptic controller (29) controls the module friction (11) and the motor (15) depending on the angular position of the control member (3), of angular positions of the multi-way reducer {17), and the supply currents of the motor (15) and the module of friction (11).

8. Flight control system (1) according to any one of the claims- indications 1 to 7, wherein the haptic controller (29) comprises a parameter table including all the singular points of a profile of force law of the mechanical means {9) of force feedback which can be accomplished.

9. Flight control system (1) according to one of claims | to 8, wherein the motor (15) is a three-phase synchronous magnet motor permanent and / or a brushed motor, and / or piezoelectric, integral in rotation with the multi-way reducer (17) via a irreversible reducer (27).

10. | Helicopter characterized in that it comprises a system (1) of flight control according to any one of claims 1 to 9, and less a flight control system for cyclic pitch of a plateau cyclic controlled with a haptic controller, the haptic controller (29) being unique for all flight control systems.

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