System for reducing vibrations or stresses in a rotor blade system

Abstract

System for reducing vibrations or stresses in a rotor blade system, which has at least three rotor blades (11, 12, 13, 14, 15, 16) rotatable about a main rotor axis, each of which is adjustable by an electrically adjustable control rod (21, 22, 23, 24, 25, 26), - wherein a first number of control rods (21, 22, 23, 24, 25, 26) forms a first group of control rods, a second number of control rods (21, 22, 23, 24, 25, 26) forms a second group of control rods, and a third number of control rods (21, 22, 23, 24, 25, 26) forms a third group of control rods, - wherein at least a first circuit (41) is provided for activating or deactivating the first group of control rods, at least a second circuit (42) is provided for activating or deactivating the second group of control rods and at least a third circuit (43) is provided for activating or deactivating the third group of control rods, - wherein the control rods (21, 22, 23, 24, 25, 26) can be connected to a distributor (40) via the respective circuit (41, 42, 43) by means of an associated switch (35, 36, 37), - wherein an even number of rotor blades (11, 12, 13, 14, 15, 16) is provided, wherein the control rods (21, 22, 23, 24, 25, 26) assigned to the first group and the control rods (21, 22, 23, 24, 25, 26) assigned to the second group are arranged successively in the circumferential direction of the main rotor axis, - wherein the group assignment of the control rods (21, 22, 23, 24, 25, 26) is such that opposite control rods (21, 22, 23, 24, 25, 26) are not assigned to the same group.

Description

The invention relates to a system for reducing vibrations or stresses in a rotor blade system, which has at least three rotor blades which can be rotated about an axis and which can each be electrically adjusted by means of a control rod which can be electrically adjusted in its longitudinal direction.DE 10 2009 001 393 A1 discloses a control rod arrangement for adjusting rotor blades of a helicopter, in which each control rod is adjustable in the longitudinal direction within predetermined stops for reducing vibrations, wherein the stops of each control rod are adjustable jointly for changing the adjustment range in the longitudinal direction of the control rod. The rotor blades with the actuators assigned to them are divided among a plurality of power supplies, so that the actuators of a part of the entire rotor blades are supplied by a first common power supply and the actuators of another part of the rotors are supplied by a further power supply.DE 10 2008 022 895 A1 discloses an active helicopter rotor with distributed redundancies.DE 601 01 928 T2 shows a rotary wing vehicle with electrical pitch angle adjustment control.DE 101 25 178 A1 shows an individual rotor blade control device for a helicopter main rotor having a rotor mast which can be driven in rotation by a main transmission.U.S. Pat. No. 5,511,944 A shows a control rod for adjusting the angle of incidence of rotor blades of a rotorcraft and an adjusting device.It is known to influence the vibration level in a helicopter as a function of flight status by means of in-flight tuning (IFT) and thus to reduce it. Vibrations impair the structural integrity of the helicopter, reduce the service life of various assemblies, adversely affect the function of some instruments, and increase the physical and mental loading of crew and passengers. The effects of the 1 / rev and n / rev vibrations caused by the main rotor can range, depending on the vibration amplitude, from low loss of comfort to catastrophic errors. It is characteristic of the IFT to represent the connection between the rotating part of the swashplate and the rotor blade articulation with a linear actuator, for example a smart pitch rod (SPR). By means of such an actuator, each rotor blade can be controlled individually, and in addition to the adjustment by the swashplate, with a small travel amplitude. The adjustment is carried out automatically on the basis of permanently detected and processed vibration signals which are evaluated by a computer unit and which deliver corresponding calculations an optimum adjustment of the SPR as output variable, as is described, for example, in the two articles by Uwe Arnold et al., "In-Flight Tuning: Wind Tunnel Test Results and Flight Test Preparation", 67th American Helicopter Society, Virginia Beach, 3-5. May, 2011, and "Flight Testing of an In-Flight Tuning System on a CH-53G Helicopter", 70th American Helicopter Society, Montrai, 20-22. May, 2014.It is also known to classify risk or risk potentials. For example, errors can occur in the control or regulation of the length adjustment of a control rod. The adjustable length, which is also referred to as authority, is directly proportional to the possible change in the vibration amplitude (delta vibrations). The classification is dependent on an overall authority of the rotor blade system with a plurality of electrically length-adjustable control rods.In order to be able to realize software and electronic hardware for adjusting the length of the control rods as simply and economically as possible, it is necessary that possible failures represent a low risk or risk potential. However, this aim is in contradiction to the requirement for the greatest possible overall authority in order to be able to reduce the vibrations over the widest possible operating range.It is an object of the present invention to provide an improved and less expensive system for reducing vibrations or stresses in a rotor blade system. In particular, it is an object of the present invention to provide a system for reducing vibrations or stresses in a rotor blade system, which system can be controlled and regulated by means of cost-effective soft and electronic hardware.The object is achieved by the subject matter of claim 1.A first number of control rods forms a first group of control rods, a second number of control rods forms a second group of control rods, an at least first circuit is provided for activating or deactivating the first group of control rods, and an at least second circuit is provided for activating or deactivating the second group of control rods.The electrically adjustable control rods arranged in the rotating system of the helicopter can be supplied with a voltage source arranged in the cell of the helicopter, the non-rotating system of the helicopter, via at least two switchable circuits.The at least three rotor blades are arranged uniformly about a rotor axis. The control rods each have an adjustment mechanism with self-locking, which acts in a self-locking manner when the length is adjusted to be electrically inactive. The control rods could also be provided with a brake or lock which prevents, i.e. blocks, the length adjustment when no electric voltage is applied.The invention allows a great overall authority of the system with simultaneously low demands on the safety level of soft and hardware for adjusting the length of the control rods.The overall authority describes the totality of the length adjustment of the electrically adjustable control rods. The greater the overall authority of the system, the less effective is an error which occurs, for example an error in the control or regulation of the control rod adjustment.The lower requirements can be realized by combining the control rods in groups and feeding each group from a separately switchable circuit.A group of control rods may include multiple control rods as well as only a single control rod. For example, a three-blade rotor has two groups of control rods, a first group comprising two control rods and a second group of control rods comprising a single control rod. In this sense, the term "number of control rods" is also to be understood.In a first preferred embodiment, provision is made for an even number of rotor blades to be provided and for the control rods to be assigned in groups in such a way that opposite control rods are not assigned to the same group. Opposite means that two rotor blades lying in a rotor blade plane span an angle of 180°. This allows an even further optimized reduction of the vibrations, because it can be ruled out that control rods arranged on the same line of action cancel each other out in terms of their action.An even number of rotor blades are provided, and the control rods associated with the first group and the control rods associated with the second group are arranged one after the other in the circumferential direction of the axle.An even number of rotor blades are provided and circumferentially adjacent control rods are associated with different groups.Furthermore, it is preferred that the number of electrically adjustable control rods with linearly independent adjustment directions is equal to the number of rotor blades.It is furthermore preferred that the two circuits can be connected independently of one another. This can be done, for example, manually.A third number of control rods form a third group of control rods and a third circuit for activating or deactivating the third group is provided.The figures, the description of the figures and the claims contain numerous features in combination. The skilled person will advantageously also consider the features individually and summarize them to form further meaningful combinations.They show FIG. 1 : control rod according to the prior art; FIGS. 2 a- 2 d : displacement(s) of helicopter vibrations by adjusting one or more SPRs; FIG. 3 : a first preferred embodiment of the system according to the invention in a schematic view; FIGS. 4a-4d show further preferred embodiments with three, four and five rotor blades; and FIGS. 5a-5c show still further preferred embodiments with 6 rotor blades.FIG. 1 shows an electrically adjustable control rod (SPR) 1 according to the prior art. The electrically adjustable control rod 1 for adjusting a rotor blade of a helicopter has, in a manner known per se, a bearing receptacle on the rotor blade side at one end and a long receptacle on the motor side at the other end. The control rod 1 is designed to be adjustable in the longitudinal direction within a predetermined adjustment range. For adjusting the control rod, the control rod 1 has at least one actuator 2 which comprises a spindle drive which is driven by an electric motor 4 via a planetary gear 3. The spindle drive comprises a spindle nut 5 connected to the control rod 1, which is moved axially by a spindle 6. The spindle 6 is driven via a gear wheel or spur gear stage 7, which is driven by the electric motor 4 via the planetary gear 3.The term authority is to be described in more detail with reference to FIGS. 2a to 2d: the mechanical change in length of a SPR causes a displacement of helicopter vibrations from A along a straight line in a complex plane to Al, as is illustrated in FIG. 2a. The adjustable length of an individual SPR is directly proportional to the possible change in the vibration amplitude and is thus a measure of authority. The length of the displacement of the vibrations is thus dependent on the mechanical adjustment travel of an SPR. The direction of displacement is dependent on which rotor blade the SPR is mounted on.In FIG. 2 b, this is illustrated using the example of a four-blade rotor. The displacement of a first SPR 21 on a first main rotor blade 11 displaces the vibrations from A to Al. The movement of a second SPR 22 on a second main rotor blade 12 displaces the vibrations from A to A2. The displacement of a third SPR 23 on a third main rotor blade 13 displaces the vibrations from A0 to A3. The displacement of a fourth SPR 24 on a fourth main rotor blade 14 displaces the vibrations of the resulting displacement vectors in the complex plane is 90°.FIG. 2 cshows a simultaneous adjustment of two SPRs which are not located on an active axis, i.e. are not opposite. In such an adjustment, the individual adjustments add up together vectorially, i.e. a displacement plane is defined. Only by adjusting two SPRs can all points on the adjustment plane be reached. The result of the vectorial addition yields the overall authority. In FIG. 2 c, the resulting displacement of the vibrations from A to A 41 is shown by way of example when the SPR 21 and the SPR 24 are adjusted.By using the remaining SPR on the two remaining rotor blades, the overall authority of the system can be further increased. In FIG. 2d, the resulting displacement of the vibrations from A to A41-2-3 is shown when the length of SPR 21 and 24 is adjusted in the positive direction and SPR 22 and 23 is adjusted in the negative direction.FIG. 3 shows a schematic diagram of an in-flight tuning system for a helicopter main rotor system having four rotor blades arranged uniformly around a main rotor axis.In a helicopter non-rotating system 80, sensors 52 are provided for detecting 1 / rev vibrations and sensors 51 for detecting further vibrations. The sensors 51, 52 transmit the detected signals 55 to a computing unit 50. the computing unit 50 evaluates the transmitted signals 55 and transmits control signals 45 to a distributor 40 on the basis of this evaluation. the distributor 40 has conventional elements, not shown, such as safety and switching elements for distributing electrical energy and uses 28 volts direct current 44, which is generated by means of a generator, not shown.In a helicopter rotating system 90, four rotor blades 11, 12, 13 and 14 are arranged with their respective SPRs 21, 22, 23 and 24. The SPR 21 can adjust the rotor blade 11, SPR 22 the rotor blade 12, SPR 23 the rotor blade 13 and SPR 24 the rotor blade 14. The SPRs 21 and 22 of the rotor blades 11 and 12 can be connected to the distributor 40 by means of a first switch 35 via a first circuit 41. The SPRs 23 and 24 of the rotor blades 13 and 14 can be connected to the distributor 40 by means of a second switch 36 via a second circuit 42. By means of a slip ring 30, the electrical power and signal transmission takes place from the non-rotating system 80 into the rotating system 90 and vice versa. The switches 35 and 36 can be selectively closed or opened. In the present embodiment, they may be manually switched by, for example, a pilot. FIG. 3 shows the open state of both switches 35, 36, i.e. the SPRs 21 to 24 are switched off.Figures 4a-5c show preferred embodiments of the system of the present invention for different helicopter main rotor systems, with only a portion of the rotating system 90 shown.FIG. 4 ashows a preferred embodiment for a helicopter main rotor system with three rotor blades 11, 12 and 13 arranged uniformly around a main rotor axis. The rotor blade 11 is adjustable with an SPR 21, wherein the SPR 21 is assigned to a first circuit 41. The rotor blades 12, 13 are adjustable by means of SPR 22 and 23, respectively, wherein the SPR 22 and 23 are assigned to a second circuit 42. The first circuit can be switched with a first switch 35, not shown, and the second circuit 42 with a second switch 36, not shown. In this embodiment, the SPR 21 forms a first group of control rods. The SPRs 22, 23 form a second group of control rods.Figure 4b shows the preferred embodiment of Figure 3.The SPRs 21, 22 of the rotor blades 11, 12 form a first group of control rods and the SPRs 23, 24 of the rotor blades 13, 14 form a second group of control rods. The rotor blade 11 is adjustable with the SPR 21, the rotor blade 12 is adjustable with the SPR 22, the rotor blade 13 is adjustable with the SPR 23 and the rotor blade 14 is adjustable with the SPR 24. The first group of control rods is associated with a first circuit 41 and the second group of control rods is associated with a second circuit. The first circuit can be switched with a first switch 35, not shown, and the second circuit 42 with a second switch 36, not shown. In a rotor system with four rotor blades, it is obligatory that only those SPRs are assigned to the same group which are adjacent in the circumferential direction to the main rotor axis, so that rotor blades are assigned to one of the same group, not opposite one another. This means at the same time that in a four-blade rotor, two SPRs must always be assigned to a respective group.FIG. 4 cshows a preferred embodiment for a helicopter main rotor system with five rotor blades 11, 12, 13, 14 and 15 arranged uniformly around the main rotor axis. SPR 21, 22 of the rotor blades 11, 12 form a first group of control rods and SPR 23, 24, 25 of the rotor blades 13, 14 and 15 form a second group of control rods. The rotor blade 11 is adjustable with the SPR 21, the rotor blade 12 is adjustable with the SPR 22, the rotor blade 13 is adjustable with the SPR 23, the rotor blade 14 is adjustable with the SPR 24 and the rotor blade 15 is adjustable with the SPR 25. The first group of control rods is associated with a first circuit 41 and the second group of control rods is associated with a second circuit. The first circuit can be switched with a first switch 35, not shown, and the second circuit 42 with a second switch 36, not shown. Thus, in Figure 4c, in the circumferential direction of the main rotor axis, two consecutive SPRs 21, 22 form the first group and circumferentially three consecutive SPRs 23, 24 and 25 form the second group of control rods. Of course, all 2:3 combinations are conceivable.FIG. 4 d shows a further preferred embodiment for a helicopter main rotor system with five rotor blades 11, 12, 13, 14 and 15 arranged uniformly around a main rotor axis. The SPRs 21 and 24 of the rotor blades 11 and 14, respectively, form a first group of control rods and the SPRs 22, 23 and 25 of the rotor blades 12, 13 and 15 form a second group of control rods. The first group of control rods is associated with a first circuit 41 and the second group of control rods is associated with a second circuit. The first circuit can be switched with a first switch 35, not shown, and the second circuit 42 with a second switch 36, not shown. In contrast to FIG. 4 c, the SPR group members are therefore not arranged successively in the circumferential direction in the respective group.In a rotor system with five rotor blades, it is also conceivable to assign only a single rotor blade or a single SPR to one group of control rods and to assign the remaining four SPR to the other group of control rods. It is also conceivable to assign the five SPRs to three groups of control rods and to assign a respective circuit to each group. For example, SPR 21 could be associated with a group and a first circuit 41, SPR 22, 23 could be associated with a second group and a second circuit 42, and SPR 24, 25 could be associated with a third group and a third circuit 43. Here too, all 1:2:2 combinations are conceivable.FIG. 5 ashows a preferred embodiment for a helicopter main rotor system with six rotor blades 11, 12, 13, 14, 15 and 16 arranged uniformly around a main rotor axis. The SPRs 24, 25, 26 form a second group and are associated with a second circuit 42. The first circuit can be switched with a first switch 35, not shown, and the second circuit 42 with a second switch 36, not shown.FIG. 5 bshows a further preferred embodiment for a helicopter main rotor system with six rotor blades 11, 12, 13, 14, 15 and 16 arranged uniformly around a main rotor axis. The SPRs 22, 24, 26 form a second group of control rods and are associated with a second circuit 42. Thus, in Figure 5b, an SPR always has an SPR of the other group to the neighbor.FIG. 5 cshows a further preferred embodiment for a helicopter main rotor system with six rotor blades 11, 12, 13, 14, 15 and 16 arranged uniformly around a main rotor axis. The SPRs 21 and 22 form the first group and are associated with the first circuit 41. The SPRs 23 and 24 form the second group and are associated with the second circuit 42. The SPRs 25 and 26 form the third group and are associated with the third circuit 43. The circuit 41 can be switched manually by means of a first switch 35, not shown. The circuit 42 can be switched manually by means of a second switch 36, not shown. The circuit 43 can be switched manually by means of a third switch 37, not shown.In the case of a six-blade rotor, several possibilities are also conceivable with regard to the group assignment. It is thus also conceivable to assign one SPR to a first group, two SPR to a second group and three SPR to a third group.Reference numerals denote reference numerals1 Control rod, SPR, generally 2 actuator 3 planetary gear 4 electric motor 5 spindle nut 6 spindle 7 gear wheel or spur gear stage 11 first rotor blade 12 second rotor blade 13 third rotor blade 14 fourth rotor blade 15 fifth rotor blade 16 sixth rotor blade 21 first SPR 22 second SPR 23 third SPR 24 fourth SPR 25 fifth SPR 26 sixth SPR 30 slip ring 35 first switch 36 second switch 37 third switch 40 distributor 41 first circuit 42 second circuit 43 third circuit 44 28 volt direct current 45 control signals 50 computing unit 51 vibration sensor 52 1 / rev vibration sensor 55 vibration signals 80 non-rotating system 90 rotating system 100 system for reducing vibrations or stresses A, Al,... A4 Vibrations

Claims

A system for reducing vibrations or stresses in a rotor blade system, which comprises at least three rotor blades (11, 12, 13, 14, 15, 16) rotatable about a main rotor axis, which are each adjustable with an electrically adjustable control rod (21, 22, 23, 24, 25, 26), - wherein a first number of control rods (21, 22, 23, 24, 25, 26) forms a first group of control rods, a second number of control rods (21, 22, 23, 24, 25, 26) forms a second group of control rods and a third number of control rods (21, 22, 23, 24, 25, 26) forms a third group of control rods, - wherein an at least first circuit (41) is provided for activating or deactivating the first group of control rods, an at least second circuit (42) for activating or deactivating the second group of control rods and an at least third circuit (43) for activating or deactivating the third group of control rods is provided, - wherein the control rods (21, 22, 23, 24, 25, 26) can be connected to a distributor (40) via the respective circuit (41, 42, 43) by means of an associated switch (35, 36, 37), - wherein an even number of rotor blades (11, 12, 13, 14, 15, 16) is provided, wherein the control rods (21, 22, 23, 24, 25, 26) associated with the first group and the control rods (21, 22, 23, 24, 25, 26) associated with the second group are each arranged successively in the circumferential direction of the main rotor axis, - wherein the group-by-group assignment of the control rods (21, 22, 23, 24, 25, 26) takes place in such a way that opposite control rods (21, 22, 23, 24, 25, 26) are not associated with the same group.System according to claim 1, characterised in that the at least two circuits (41, 42) can be connected independently of one another.

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