Haptic feedback aircraft flight trim control system

Abstract

This aircraft flight trim control system comprises a motor (3) and a variable friction actuator (6) coupled to the motor and to an output shaft (8). The variable friction actuator comprises a variable friction torque magnetic clutch linked to the output shaft. Figure for abstract: Fig 1

Description

Title of the invention: Haptic feedback aircraft flight trim control system

[0001] The present invention relates to flight control systems for aircraft and relates more particularly to the control of a flight compensator for an aircraft, in particular for a helicopter.

[0002] The compensators or TRIMs, have the function in particular of compensating for various disturbances likely to have an influence on the flight parameters of the aircraft, without the pilot having to act on the flight controls.

[0003] TRIM actuators conventionally return to the pilot a resistive force on the flight controls in the form of haptic feedback. This force is generally generated by a spring, a short-circuited electric motor, mechanical friction and is therefore essentially passive.

[0004] The haptic feedback applied to the flight controls by the TRIM actuators is therefore constant and corresponds to a resistive torque level fixed at the design time.

[0005] It is notably constant, whatever the position of the flight control.

[0006] In particular, spring TRIM actuators require a specific architecture for each flight control, in particular specific to roll, yaw, pitch, etc.

[0007] When one wishes to modify the haptic feedback, for example to propose a resistive force or damping, for example after testing a first prototype on an aircraft, it is necessary to reconfigure the entire force feedback chain.

[0008] It has been proposed to replace conventional TRIM actuators with active actuators comprising a powered and driven electric motor connected directly to the actuator output shaft and acting on the flight controls.

[0009] TRIM actuators of this type firstly require high capacity electric motors, which generate high electrical consumption and have a very high mass.

[0010] The control electronics must also be very efficient.

[0011] It has also been proposed to use an electric motor directly connected to the flight control and having a high and continuous rotation speed, and to use an actuator comprising a magnetorheological brake which provides controlled haptic feedback.

[0012] This type of actuator also has a number of major drawbacks relating to the high electrical consumption of the motor, operating noise, significant wear of the actuator and the use of control electronics. complex and therefore expensive.

[0013] The aim of the invention is therefore to overcome these various drawbacks and to propose a flight trim control system which is capable of providing haptic feedback which is variable.

[0014] The invention therefore relates to an aircraft flight trim control system comprising a motor and a variable friction actuator coupled to the motor and to an output shaft.

[0015] The actuator includes a variable friction torque magnetic clutch linked to the output shaft.

[0016] This control system further comprises a reducer placed between the motor and the actuator. Thanks to the reducer, it is possible to use a motor having a lower power, in particular a relatively low torque, and requiring less complex control electronics.

[0017] In addition, the variable friction torque clutch makes it possible to modify the haptic feedback provided to the pilot, for example by modifying the stiffness of the control or by creating virtual stops.

[0018] For example, the variable friction torque clutch comprises two discs, one connected to the engine and the other to the output shaft, a magnetorheological fluid in contact with the discs and a magnetic field source acting on the magnetorheological fluid to vary the friction torque between the discs.

[0019] According to another characteristic, the control system comprises an angular position sensor of the output shaft.

[0020] It may further comprise means for detecting a direction of the force applied to the output shaft.

[0021] For example, the detection means comprise a relative position sensor between two shaft portions connected with play.

[0022] In one embodiment, the reducer is an irreversible reducer.

[0023] In another embodiment, the control system further comprises a magnetorheological brake interposed between the magnetic clutch and the motor, the reducer being a reversible reducer.

[0024] The invention also relates to a helicopter comprising a trim control system as defined above.

[0025] 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:

[0026] [Fig.l] schematically illustrates the general structure of a flight control trim control system according to the invention; and

[0027] [Fig.2] schematically illustrates the structure of a control system of a com- flight thinker according to another embodiment.

[0028] In [Fig. 1], the general architecture of a TRIM control system for a helicopter according to the invention is shown, designated by the general numerical reference 1.

[0029] This control system is intended to provide haptic feedback to the pilot which can be modified under the effect of a command applied to it, in particular during the flight of the machine, and which has relatively low consumption and mass.

[0030] This control system comprises a geared motor 2 comprising a motor 3 associated with a motor position sensor 4 to enable the motor to be controlled and a reducer 5.

[0031] The motor 3 is a low torque, high rotation speed motor, for example of the order of 5 degrees per second, the reducer being a reducer with a high reduction ratio, for example of the order of 50.

[0032] The control system 1 further comprises a variable friction actuator 6 coupled to a motor shaft 7, at the output of the reducer, and linked to the output shaft 8 of the control system which acts on a flight control instrument, such as a stick or a rudder bar, via a steering wheel 9.

[0033] Furthermore, the control system comprises a first angular position sensor 10 ensuring the measurement of the angular position of the output shaft 8 relative to a fixed point, constituted for example by the frame of the control system.

[0034] Furthermore, in one embodiment, the shaft line of the output shaft comprises two shaft portions connected together with play allowing an angular movement for example of the order of 0.1° and with a low actuation stiffness. As illustrated, the control system then comprises a second angular position sensor 12 ensuring the measurement of the relative angular position between the two shaft portions in the play zone 13 to detect changes in the direction of the force applied by the pilot to the flight control instrument.

[0035] The control system is completed by an electronic card (not shown), receiving the angular position measurements delivered by the first position sensor 10 and by the second position sensor 12 and receiving the position measurement from the motor position sensor 4 to control the motor as well as the variable friction actuator 6.

[0036] The variable friction actuator 6 is constituted, in the illustrated embodiment example in [Fig.l], by a magnetic clutch with variable friction torque which is interposed between the output shaft of the reducer 5 and the output shaft of the control system linked to the flywheel 9. For example, this clutch comprises two discs 14 and 15 linked one to the drive shaft 7 and the other to the output shaft 8 and a magnetorheological fluid 16 locally filling the space between the two discs 14 and 15 of so as to be in contact with these discs, a source of magnetic field, for example a coil powered under the control of the electronic card, delivering a magnetic field acting on the magnetorheological fluid in the area located between the two discs so as to vary its viscosity and consequently the friction torque between the two discs.

[0037] Thus, depending on the command applied to it, the control system which has just been written can modify the force or damping applied to the flight control instrument in particular by acting on the rotation speed of the engine and on the friction torque supplied by the clutch, in particular according to the flight phases of the helicopter.

[0038] It also makes it possible to provide virtual stops making it possible to virtually increase the force required to reach certain positions of the control instrument according to the flight phases, for example to avoid critical positions likely to cause malfunctions.

[0039] This control system also makes it possible to provide piloting assistance by providing an active effort allowing the control instrument to be repositioned in its initial position.

[0040] In addition, the magnetic clutch is placed as close as possible to the output and therefore allows all the effects of the drive to be smoothed and erased. The control system benefits from a safety effect in the event of the geared motor 2 jamming, due to the possible slippage of the clutch to give control back to the pilot.

[0041] For example, the control system just described operates as follows.

[0042] First, the control system can be used to deliver a variable force according to an increasing force law.

[0043] In this case, the electric motor rotates in a direction opposite to that of the output shaft 8 linked to the control instrument. It is driven at a low rotational speed and the clutch provides a force feedback F according to a law F=f(position, speed) which increases as a function of the position and speed of the output shaft 8.

[0044] This operating mode ensures responsiveness and secures on-board equipment in the event of a breakdown.

[0045] When the pilot releases the control instrument, for example the stick, the electric motor, which was rotating in the opposite direction to that of the output shaft 8, returns the stick to its initial position.

[0046] If the pilot returns the stick to zero at low speed, that is to say at a speed lower than the rotation speed of the engine during the first phase, the second position sensor 12 detects that no change in the direction of the force supplied by the pilot has occurred. The clutch 6 provides a force feedback F=f(position, speed) to bring the stick back to low speed.

[0047] The electric motor then returns the handle to zero.

[0048] On the contrary, if the pilot brings the stick back to zero at high speed, that is to say at a speed higher than the speed of the electric motor of the first phase, the second position sensor 12 detects the change in direction of the force supplied by the pilot and the electric motor is accelerated until the position sensor again detects a change in direction of the force, the rotation speed of the motor, higher than the actuation speed of the control instrument, making it possible to take up the play which initially existed. Then, the electric motor returns the stick to zero.

[0049] It will be noted that between these various phases, the electric motor is stopped.

[0050] In the embodiment described with reference to [Fig. 1], the reducer 5 is an irreversible reducer, so that the forces applied to the control instrument are not transmitted by the reducer to the motor.

[0051] In another embodiment illustrated in [Fig. 2], in which the geared motor 2, the first and second position sensors 10 and 12 and the clearance zone 13 as well as the flywheel 9 are recognized, the friction actuator 6 comprises a magnetic clutch 17, similar to the magnetic clutch described previously with reference to [Fig. 1] and a magnetorheological brake 18 comprising for example a disk in contact with a rheological fluid whose viscosity and therefore the friction force is modified under the effect of a magnetic field. In this case, the reducer is not necessarily irreversible, the friction torque applied to the flywheel 9 being constituted by the sum of the effects of the friction provided by the clutch 17 and by the brake 18.

Claims

Claims

1. An aircraft flight trim control system, comprising a motor (3), and a variable friction actuator (6) coupled to the motor and to an output shaft (8), characterized in that the variable friction actuator comprises a magnetic clutch with variable friction torque linked to the output shaft, the aircraft flight trim control system comprising means for detecting a direction of force applied to the output shaft.

2. Control system according to claim 1, comprising a reducer (5) placed between the motor (3) and the actuator (6).

3. Control system according to one of claims 1 and 2, in which the magnetic clutch comprises two discs (14, 15) linked one to the motor and the other to the output shaft (8), a magnetorheological fluid (16) in contact with the discs and a source of magnetic field acting on the magnetorheological fluid to vary the friction torque between the discs.

4. System according to any one of claims 1 to 3, comprising an angular position sensor (10) of the output shaft (8).

5. System according to any one of claims 1 to 4, in which the detection means comprise a sensor (12) of relative position between two portions of the output shaft connected with play.

6. A system according to any one of claims 1 to 5 wherein the reducer is an irreversible reducer.

7. System according to any one of claims 1 to 5, further comprising a magnetorheological brake (18) interposed between the magnetic clutch and the motor, the reducer being a reversible reducer.

8. A helicopter comprising a trim control system according to any one of claims 1 to 7.

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