GB2436258A

GB2436258A - Device for orientation of the rotor head for helicopters

Info

Publication number: GB2436258A
Application number: GB0712603A
Authority: GB
Inventors: Pierre Maillard
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-01-14
Filing date: 2006-01-12
Publication date: 2007-09-19
Anticipated expiration: 2026-01-12
Also published as: GB0712603D0; WO2006075096A1; GB2436258B; FR2880866B1; FR2880866A1; WO2006075096A8

Abstract

The invention relates to a device for orientation of the rotor head (12) of a helicopter, said head being mobile with relation to the fuselage (1), by means of a joint (16) the movements of which are controlled by at least three rams (17, 18 and 19). The device provides a large degree of redundancy in control and permits the detection of gusts of wind. The invention is of application to piloted and unpiloted helicopters.

Description

HELICOPTER ROTOR HEAD ORIENTATION DEVICE

This invention relates firstly to the manufacture of means for orientating the rotor head of a pendular piloted helicopter. In such a helicopter, the rotor head generally comprises two counter rotating rotors and is attached to the fuselage by means of a swivel joint that allows it to be orientated in pitch and roll with respect to said fuselage, by a pilot control with the aid of actuators for example. This invention also applies to classic helicopters whose rotor plane movements are controlled by cyclic variations of the pitch of the blades. It also applies to all vertical take-off aircraft, equipped with rotors whose orientation may be varied with respect to the structure.

The American patent n 5 791 592 describes a pendular piloted helicopter whose rotor head orientation is controlled by two hydraulic actuators. The French patent n 2 801 034 describes a pendular piloted helicopter whose rotor head is also controlled by two actuators but which is characterised by a displacement of said rotor head greater than +1-10% and by its automatic controls for the orientation of said head.

The rotor head orientation device of the invention provides a decisive advantage, as not only does it provide a very high level of redundancy of said control, it also guarantees great reactivity of the machine and permits gusts of wind to be measured. This last characteristic is particularly advantageous for facilitating the take off and landing on boats manoeuvres.

The invention consists of using at least three and preferably six actuators for controlling the orientation of the rotor head, to use a measurement of the force exerted by the actuators to calculate the horizontal wind and to introduce into the calculation of the actuator control a combination of.the angular speeds of the fuselage and the rotor head to increase the reactivity of the helicopter.

The invention applies to all aircraft for which the direction of the action of the propellers or rotors is modified with respect to the fuselage.

The invention applies to both unpiloted and piloted aircraft, with thermal or electric motors.

The invention thus concerns an orientation device for a rotor head of a pendular piloted helicopter of the type comprising: -a fuseiage, -a rotor head, that is mobile with respect to the fuselage by means of an articulation and equipped with two counter rotating rotors which rotate around a same axis, connected to the fuselage by a mobile connection, -means for orientating said rotor head with respect to the fuselage, characterised in that the comprise at least three actuators.

Embodiments of the invention will be described hereunder, provided by way of non-restrictive examples, in reference to the appended drawings in which: Figure 1 is a stripped perspective view of a pendular piloted helicopter

of the prior art.

Figure 2 is a perspective view of a first embodiment of the device of the invention.

Figure 3 is an enlarged view of the rotor head of figure 2.

Figure 4 is a block diagram of the actuator controls of the device of figure2.

Figure 5 is a diagrammatical representation of the rotation angles of the rotor head with respect to the fuselage.

Figure 6 is a variant of the block diagram of the actuator controls of the device of figure 2.

Figure 7 is a perspective view of a preferred embodiment of the device of the invention.

Figure 8 is an enlarged view of the rotor head of figure 6, and Figure 9 is a diagram of the actuator controls of the device of figure 7.

Figure 1 shows one unpiloted embodiment of a pendular piloted

helicopter of the prior art. It comprises:

-a fuselage 1, -a rotor head 2, connected to the fuselage I by a swivel joint 3, -two actuators, respectively 4 and 5, connecting the fuselage I to the rotor head 2, so as to control the orientation of said rotor head in pitch and roll, with respect to said fuselage 1, -at least one and preferably two directional fins, 6 and 7.

The fuselage, which is mounted on an undercarriage, 8, comprises: -a motor unit 9, -means 10 of transmitting the energy from the motor unit 9 to the rotor head 2, -means for controlling the actuators 11.

As shown in figures 2 and 3, the general composition of a helicopter equipped with the device of the invention is analogue to that of the helicopter

of the prior art.

This helicopter comprises: -a fuselage 1 with a reference trihedron, of which a first axis 29 is the roll of the machine, a second axis 30 is the pitch axis and a third axis 31 is the yaw, -a rotor head 12, which has an axis 28, equipped with two counter rotating rotors 13 and 14 and an orientation control plate 15, preferably circular and perpendicular to the axis 28 of the rotor head, -an articulation, of the shaft type, not shown in the figure, between said fuselage 1 and said rotor head 12, which has a centre or articulation point 16 preferably situated in the plane of the orientation control plate 15, -at least three actuators 17, 18, 19, preferably electric, but which may be hydraulic or pneumatic, attached to the fuselage for example by means of a plate 20 and acting, with the aid of three control rods 21, 22 and 23, articulated on at least three points of application of the forces, 24, 25 and 27, situated around the contour of the orientation control plate 15, wherein said points of application of the forces form a polygon that is preferably regular and substantially perpendicular to the axis 28 of said rotor head, wherein said point of articulation 16 is substantially at the barycentre of said polygon.

-means for generating orders to control the actuators.

-means to measure the external forces exerted on the rotor head 12.

In the case of three actuators, the three points of application of the forces 24, 25 and 27 of the control rods 21, 22 and 23 of the actuators are substantially situated at 1200 from one another around the contour of the orientation plate 15 of the rotor head 12.

The actuators are positioned on the plate 20 and therefore on the fuselage such that their control rods 21, 22 and 23 are substantially parallel to the axis 28 of the rotor head when the latter is in a mean position, which is to say when said axis 28 is substantially perpendicular to the roll axis 29 and the pitch axis 30 of the helicopter.

One of the actuators 17 is preferably positioned in the plane of symmetry of the fuselage and therefore acts directly on the pitch control of the rotor head. The two other actuators 18 and 19 act mainly on the roll but also on the pitch.

The actuators 17, 18 and 19 may be indifferently linear or rotary. They are preferably each equipped with a position sensor, respectively 32, 33 and 34, which supply information a, b and c based on which the values of three angles A, B and C may be deduced, which are those of the orientation plate with respect to the fuselage, at the three points of attachment 24, 25 and 27 of the control rods 21, 22 and 23.

In the case of linear actuators, th angles A, B and C are substantially equal to: A = Arcsinus (a/R), B = Arcsinus (b/R), C = Arcsinus (c/R), where R is the distance separating each point of attachment from the centre of the orientation plate and where a, b and c are the linear movements of the actuators.

In the case of rotary actuators, as shown in figures 2 and following, they are equipped with levers 35, 36 and 37, with a length r at the end of which are attached the control rods 21, 22 and 23. The angles A, B and C are substantially equal to: S A = Arcsinus (rIR.sin(a)), B = Arcsinus (r/R.sin(b)), C = Arcsinus (r/R.sin(c)), As shown in figure 4, the control means comprise: -a generator 38 of two angles uc and 13c to control the rotor head, -a generator 39 of two pitch 8 and roll 4) angles of the fuselage, -a generator 40 of the angular speeds 0' and 4)' of the pitch and roll of the fuselage, -a computer 41 to control the actuators, -servo electronics 42, 43 and 44 for each actuator, preferably equipped with a current measurement device, respectively 45, 46 and 47, consumed by said actuator and which provides the power required for the control of the actuator at one of the three angles A, B or C, -the three actuators 17, 18 and 19.

Thus controlled, the rotor head adopts the orientations a and 13 with respect to a reference trihedron 48 which has two horizontal axes 49 and 50 and a vertical axis 51. This trihedron is such that the roll axis 29 of the machine is contained in the plane formed by its axes 49 and 51. These orientations a and f3 determine the orientation of the lift of the rotors and enable the piloting, guiding and navigation of the helicopter.

The two pitch 0 and roll 4) angles of the fuselage are determined with respect to the reference trihedron 48.

The 0 and 4) angle generator 39 and the 0' and 4)' angular speed generator 40 may be composed by a central bearing unit or preferably by a central navigation inertial unit.

The computer 41 for controlling the actuators 17, 18 and 19 elaborates two angles c and öc to control the head with respect to the fuselage by: = dC -0 + f(0', 5') 6pc = 13c -4) + f(4', &p') where f(8', 8a') and f(4)', Sp') are terms designed to reduce the machine's response times.

S It then elaborates three angles Ac, Be and Dc to control, via the servo electronics 42, 43 and 44, and actuators 17, 18 and 19, the orientation control plate 15: -AC&aC BC 2/13.Bpc -Cc = -* 2//3. c -8c/2 Figure 5 shows the relationships between the angles A, B and C and the angles ö and ö which are identical to those between the controlled angles Ac, Bc and Dc and the controlled angles aC and öc. In this figure, an ellipse 52 shows the plane of the roll 29 and pitch 30 axes of the machine, an ellipse.53 shows the plane perpendicular to the axis 28 of the rotor head. The angle ö is the angle which the two ellipses form in the plane of the roll 29 and yaw 31 axes of the machine. The angle is the angle which the two ellipses form in the plane of the pitch 30 and yaw 31 axes of the machine.

The angle A measured by the sensor 32 of the actuator 17 is substantially equal to 8. The angles B and C are the angles formed by the two ellipses in the planes containing the yaw axis 31 of the machine and which respectively represent 1200 and 240 with the roll axis 29. The angles thus described and their mathematical relationships are easily deduced.

To avoid the actuators working against one another, the controlled angles must be corrected from any possible errors of non linearity induced by -the mechanism connecting each actuator and the orientation plate of the head.

Due to the fact that the position of the centre 16 of the orientation plate of the rotor head 12 is fixed with respect to the fuselage 1 and the plate 20, it is clear that its orientation is perfectly determined by just two of the three contro!s Ac, Bc and Cc. An actuator 17, 18 or 19 may therefore break down without this causing any loss of control of the machine.

As created, this device thus permits most of the electrical failures where an actuator no longer responds to be overcome. The devices for measuring the currents of the actuators 45, 46 and 47 supply the required information to identify this type of failure.

Examining the angles A, B and C effectively obtained and measured by the sensors 32, 33 and 34 of the actuators 17, 18 and 19 permits a check to be made that there are no other failures.

In fact, the tilt in pitch 8 and roll 6p of the rotor head 12 with respect to the fuselage 1 may be calculated as follows: öa=Awhere8a=B+C, = 13/4.(B -C), 6p = 13/2.(B + A/2) where 8p-'/3/2.(C A/2) The comparison between the controlled angles 6 and the angles 6 thus calculated establish if an actuator is operating correctly or not.

The failure of a position sensor of one of the actuators or a mechanical connection between one of these actuators and the orientation plate of the rotor head makes the calculated 8 values incoherent.

Processing the information available from the control computer of the actuators allows the majority of these failures to be identified and to decide how the mission is to be continued.

The means for measuring the external forces which are exerted on the rotor head 12 are, for example, made using force or torque sensors. They permit the detection of gusts of wind, to which the helicopter is subjected to.

Indeed, in a stabilised flight, whether stationary or not, the orientations of the head 12 and the fuselage 1 are such that the lift of the rotors balances all of the forces acting on the machine. When a gust of wind occurs, the. drag of the rotor head 12 and the fuselage 1 are modified and, due to the relatively low inertia of the rotor head 12 with respect to that of the fuselage 1, it tends to move quicker than said fuselage. A torque then occurs around the point of articulation 16, which tends to make the head spin.

One preferred method of the invention consists of.using as force sensors the current measuring devices 45, 46 and 47 in the actuators 17, 18 and 19. They provide in fact three different pieces of information which are the images of the torques developed by each actuator and thus the efforts that they must provide to maintain the rotor head 12 in the requested position and thus overcome the forces which try to move it. The sensors 32, 33 and 34 detect the rotation and the servo electronics 42, 43 and 44, in order to maintain the head in position, modify the control currents of the actuators in order to counter the rotation torque. The currents measured by the measuring devices 45, 46 and 47 thus contain the parameters of the gust of wind. The current measurements are then processed in the computer 41 to produce said gust parameters.

The diagram of figure 6 is a preferred embodiment to that of figure 4, where the position control of the rotor head 12 is no longer controlled by a servo control of each actuator by means of servo electronics 42, 43 and 44 specific to said actuators but by the computer 41 controlling the actuators itself.

The servo electronics 42, 43 and 44 are replaced by power amplifiers 53, 54 and 55 which are also equipped with current measuring devices 45, 46 and 47.

In this way, the actuators are no longer controlled independently from one another by the difference between the controlled angles, Ac, Bc and Cc and the measured angles A, B and C but simply by two independent differences öaC -öu and öc -8 between the angles that the head 12 must make with respect to the fuselage 1 and those that it makes in reality.

The control computer 41 of the actuators elaborates three control voltages for the actuator motors as follows: VA G. (6aC -a) VB = G. (Ki. (pc K2. (öaC -8)) VC = -G. (Ki. (8pc -öp). + K2. (öC -ö)) where G is a servo transfer function that may be accompanied by a frequency corrector and where the coefficients Ki and K2 are preferably taken respectively as equal to /3/2 and 0.5 so that, taking account of the lever effects due to the angles of 120 and 2400 of the position of the actuators 18 and 19, the torques exerted by the motors, on each of the roll and pitch axes, are equal to 1.5 times the torque exerted by a single motor.

This solution has the advantage of avoiding the corrections of non linearity required in the previous case without risking the possibility of having the motors working against one another.

The device described above may be made with 4 or 5 actuators applying the same principles. In the event of 5 actuators being used, it is thus possible to identif' with certainty, at least one and theoretically two failures of one of the actuator sensors or one of the mechanical connections between an actuator and the orientation plate of the rotor head.

The preferred solution of the invention consists, figures 7 and 8, of using six actuators 17, 18; 19, 56, 57 and 58, which transmit their efforts via control rods 21, 22, 23, 62, 63 and 64 and whose points of application of the forces 24, 25, 27, 65, 66 and 67 are also spaced out around the orientation plate 15 of the rotor head 12, substantially every 600, thus forming a hexagon that is preferentially regular. The six actuators are also each equipped with a position sensor respectively 32, 33, 34, 59, 60 and 61, which provide six pieces of information a I, b 1, ci, a2, b2 and c2 of which we deduce, as seen previously for linear or rotary actuators, six values Al, B 1, Cl, A2, B2 and C2 of angles of orientation of the control plate of the head at the point of attachment of the six control rods.

In the case of a control that is not shown of the type of that of the block diagram qf figure 4, the angles to control each actuator are: * 25 Aic = bc A2c = -8c Bc = 2//3.8pc -Sac/2 82c = -(2/'/3.6pc -8aC/2) Cc = -2/113. &pc -6c/2 C2c = 2/I3. 8pc + &c/2) In the case of the preferred solution described for figure 6 and shown in figure 9, the computer 41 for controlling the actuators elaborates six control voltages as follows: VA1 = G. C 5c - VB1 = G. (13 /2. (&pc öp) -0, 5. (öc -VC1 = -G.('/3/2.(öpC -öp) + 0,5.(öaC -ö)) VA2 = -G. (5cc -öa) VB2 = -G.('13/2.(6pC -8) -0,5.(öaC VC2 = G. (13/2. (6c -öp) +0,5. C -8)) These voltages are sent to the motors of the actuators 17, 18, 19, 56, 57 and 58 by six power amplifiers 53, 54, 55, 62, 63 and 64 preferably equipped with six current measuring devices 45, 46, 47, 65, 66 and 67.

The angle values Al, B!, Cl, A2, B2 and C2 deduced from the information provided by the actuator sensors are dependent on one another and may be combined in several ways to determine any possible failures of * one or more sensors or possible failures of mechanical connections between the actuators and the rotor head.

Wecanthus write: ö=A1 = -A2 = Bi +C1 = -(B2+ C2) = Bi -C2 =C1 -B2, and * = 13/4. (Bi -Cl) = -/3/4. (32 -C2) = 13/4.(B3. + C2) = -13/4.(C]. -32) = 13/2.(Bl + Al/2) = 13/2.(Bl -A2/2) = -13/2. (C]. -Al/2) = -13/2. (Cl + A2/2) = -/3/2.(B2 -Al/2) = -13/2.(B2 + A2/2) = 13/2.(c2 + Al/2) = 13/2.(C2 -A2/2) Processing these equations, among all those known to those skilled in the art, permits certain determination at least two failures and theoretically three of sensors or mechanical connections.

Processing of the same equations and current values in the actuators permits at least two and theoretically three of all of the electrical or mechanical failures of the rotor head orientation device of the invention and to * provide the parameters of any gusts of wind. -Il-

Claims

CLAIMS

1. Rotor head orientation device for a pendular piloted helicopter of the type comprising: -a fuselage (I), -a rotor head (12), that is mobile with respect to the fuselage by means of an articulation (16) and equipped with two counter rotating rotors (13, 14) which rotate around a same axis (28), connected to the fuselage (1) by a mobile connection, -means for orientating said rotor head (12) with respect to the fuselage (1), characterised in that the comprise at least three actuators (17, 18 and 19).

2. Rotor head orientation device for a pendular piloted helicopter of claim 1, characterised in that the points of application of the forces (24, 25, 27) of the actuators (17, 18 and 19) form a polygon that is preferably regular and substantially perpendicular to the axis (28) of said rotor head (12).

3. Rotor head orientation device for a pendular piloted helicopter of claim 2, characterised in that the centre (16) of rotation of the articulation of the rotor head (12) with respect to the fuselage (1) is substantially at the barycentre of the points of application of the forces (24, 25, 27) of the actuators (17, 18 and 19).

4. Rotor head orientation device for a pendular piloted helicopter of any of the previous claims, characterised in that it comprises six actuators (17, 18, 19, 56, 57 and 58) whose points of application of the forces (24, 25, 27, 65, 66 and 67) form a hexagon that is preferentially regular. -12-

5. Rotor head orientation device for a pendular piloted helicopter of any of the previous claims, characterised in that each actuator (17, 18, 19, 56, 57 and 58) is equipped with a position sensor (32, 33, 34, 59, 60 and 61) which provide information on the tilt angle of the axis (28) of the rotor head.

6. Rotor head orientation device for a pendular piloted helicopter of any of the previous claims, characterised in that it comprises force sensors capable of measuring external torques applied to the rotor head (12) especially by gusts of wind.

7. Rotor head orientation device for a pendular piloted helicopter of the previous claim, characterised in that the force sensors are composed of devices (45, 46, 47, 65, 66, 67) for measuring the current consumed by each actuator (17, 18, 19, 56, 57 and 58).

8. Rotor head orientation device for a pendular piloted helicopter of any of the previous claims, characterised in that the servo control of the rotor head (12) is achieved via two independent difference signals c -6 and 80c -representing the difference of the position of the head with respect to the position commanded, wherein the angles & and are respectively the angles between said rotor head (12) and the fuselage (1) respectively around the pitch (30) and roll (29) axes, wherein c and 8pc are the corresponding commanded angles, the commands sent to each of the actuators are of the form: VA = G.(8c -VB = G. (Ki. (6pc -&p) -K2. (&aC -8)) VC = -G.(K1.(6c -öp) + K2.(8C -where G is a servo transfer function that may be accompanied by a frequency corrector and where the coefficients KI and K2 are preferably taken respectively as equal to 13/2 and 0.5.

9. Rotor head orientation device for a pendular piloted helicopter of any of the claims 1 to 3 and 5 to.8, characterised in that it detects a possible failure of an actuator (17, 18, 19) by comparing the values of the rotor head tilt angles 6 and & calculated by' combining the measurements A, B and C of the sensors (32, 33, 34) of said three actuators as follows: 6=Aor8=B+C S = 13/4.(B -C), 6 = I3/2.(B + A/2) or = -13/2.(C + A12) 10. Rotor head orientation device for a pendular piloted helicopter of any of the claims 6 to 8, characterised in that it detects a possible failure of one of the six actuators (17, 18, 19, 56, 57, 58) by comparing the values of the rotor head tilt angles D6 and &, calculated by combining the measurements Al, DI, Cl, A2, B2 and C2 of the sensors (32, 33, 34, 59, 60 and 61) of said six actuators as follows: = Al = -A2 = Bi + Cl = -(B2 + C2) = Bi -C2 = Cl B2, and = I3/4. (Bi -Cl) = -13/4. (B2 -C2) = 13/4.(Bl + C2)= -13/4. (Cl -B2) : Al/2) = J3/2.(Bl -A2/2) = -1312.(Cl -Al/2) = -13/2.(C1 + A2/2) = -13/2.(B2 -Al/2) = -13/2.(B2 + A2/2) = 13/2.(c2 + Al/2) = 13/2.(C2 -A2/2) 11. Rotor head orientation device for a pendular piloted helicopter of any of the previous claims, characterised in that a computer 41 uses a combination of pitch 0 and roll 4) angles of the fuselage (1), the angular speeds 8 and 4) of said fuselage and angular speeds öa' and ö' of the rotor head (12) with respect to said fuselage, to elaborate two orders &a'C and 61'c to controL the orientation of said rotor head (12).