An active pitch control rod for helicopter rotors

Abstract

This invention discloses an active pitch control rod for helicopter rotors, relating to the field of active vibration reduction technology for helicopter rotors. While meeting both support and vibration reduction requirements, it achieves coaxial arrangement of the vibration reduction direction with the center of the piezoelectric actuator, effectively avoiding the adverse effects of unbalanced centrifugal force. The active pitch control rod, from top to bottom, includes an upper lug, an upper cover, an outer sleeve, a wedge-shaped structure, a spring, and a lower lug. The wedge-shaped structure is connected to the piezoelectric actuator and below the outer sleeve. The spring also contains an inner spindle fixedly connected to the lower lug. The top end of the inner spindle extends into the wedge-shaped structure, and the piezoelectric actuator presses against the wedge-shaped structure, thereby changing the clamping force applied to the top end of the inner spindle. Through integrated design, vibration reduction is achieved under different flight conditions in the application of helicopter pitch control rods, resulting in good vibration reduction performance and a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of active vibration reduction technology for helicopter rotors. Background Technology

[0002] Currently, helicopters generate excessive noise and vibration during flight, which is harmful to passenger health, the surrounding environment, and the aircraft itself. This noise and vibration primarily originate from the aerodynamic loads experienced by the helicopter rotor blades, and are most pronounced during forward flight and descent.

[0003] There are basically three types of active control vibration reduction technology based on helicopter rotors: 1) active trailing edge flap control, 2) active rotor torsion control, and 3) active pitch control struts. The first two vibration reduction methods are based on blade vibration reduction research. Active pitch control struts use active control strut devices to replace traditional pitch control struts to reduce vibration in helicopter rotors. This vibration reduction method does not involve blade adjustment and preserves the integrity of the blades.

[0004] On April 25, 2023, the applicant filed a Chinese invention patent application entitled "A Pitch Variable Rod for Helicopter Rotor with Active Vibration Damping Mechanism," with publication number CN116443247A. This application describes a pitch variable rod powered by a piezoelectric actuator. However, this type of alternative to the pitch variable rod suffers from the piezoelectric actuator being placed perpendicular to the axial direction, causing the overall structure to be subjected to significant unbalanced centrifugal forces during dynamic load tests or practical applications. Furthermore, in this type of structure, critical components such as the piezoelectric actuator are exposed. Considering the complex, harsh, and severe flight environment faced by helicopters in actual operation, this can easily lead to the failure or damage of critical components such as the piezoelectric actuator. Summary of the Invention

[0005] To address the above problems, this invention proposes an active pitch control rod for helicopter rotors. While meeting both support and vibration reduction requirements, it achieves a coaxial arrangement between the vibration reduction direction and the center of the piezoelectric actuator, effectively avoiding the various adverse effects caused by unbalanced centrifugal force.

[0006] The technical solution of the present invention is as follows: the active variable pitch tie rod includes, from top to bottom, an upper hanging lug 111, an upper cover 110, an outer sleeve 103, a wedge-shaped structure part 2, a spring 104, and a lower hanging lug 112;

[0007] The upper hanging ear 111, upper cover 110, and outer sleeve 103 are fixedly connected. Inside the outer sleeve 103, a piezoelectric actuator 102 is arranged coaxially with the spring 104. The top end of the piezoelectric actuator 102 is fixedly connected to the outer sleeve 103. The wedge-shaped structure 2 is connected to the piezoelectric actuator 102 and the outer sleeve 103. The bottom end of the spring 104 is fixedly connected to the lower hanging ear 112. Inside the spring 104, an inner spindle 115 is fixedly connected to the lower hanging ear 112. The top end of the inner spindle 115 extends into the wedge-shaped structure 2. The piezoelectric actuator 102 presses the wedge-shaped structure 2, thereby changing the clamping force applied to the top end of the inner spindle 115.

[0008] The wedge-shaped structure 2 includes a wedge-shaped movable retaining ring 105 and a wedge ring block 107;

[0009] The wedge-shaped movable retaining ring 105 is installed at the bottom opening of the outer sleeve 103 by circumferentially distributed pre-tightening bolts 108 and pre-tightening nuts 109, and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring 113 is also fitted on the pre-tightening bolts 108. The disc spring 113 abuts between the bottom surface of the wedge-shaped movable retaining ring 105 and the pre-tightening nut 109, and the disc spring 113 keeps the wedge-shaped movable retaining ring 105 in contact with the bottom opening of the outer sleeve 103. After the piezoelectric actuator 102 extends, it contacts the wedge-shaped movable retaining ring 105 and drives the wedge-shaped movable retaining ring 105 to move downward against the force of the disc spring 113.

[0010] The wedge-shaped movable retaining ring 105 has a tapered through hole at the center, which is larger at the top and smaller at the bottom;

[0011] The outer wall of the wedge ring block 107 is a conical surface that is larger at the top and smaller at the bottom, and a wedge ring block groove 301 is provided on the wedge ring block 107 from top to bottom; the lower part of the wedge ring block 107 extends into the conical through hole, and the wedge ring block 107 is fixedly connected to the outer sleeve 103 through a fixed shaft 101 passing through the center of the piezoelectric actuator 102. A mandrel receiving hole is also provided in the center of the wedge ring block 107, and the top end of the inner mandrel 115 extends into the mandrel receiving hole.

[0012] When the piezoelectric actuator 102 is not in contact with the wedge-shaped movable retaining ring 105, the wedge ring block 107 tightens the wedge ring block groove 301 under the action of the conical surface due to the compression of the disc spring 113, thereby maintaining the clamping of the top end of the inner spindle 115. When the piezoelectric actuator 102 extends and drives the wedge-shaped movable retaining ring 105 to move downward against the force of the disc spring 113, the wedge-shaped movable retaining ring 105 will gradually reduce the compression of the wedge ring block 107, thereby allowing the wedge ring block 107 to gradually and naturally reset, and then gradually weaken the clamping force on the top end of the inner spindle 115 until there is no clamping force, thereby changing the friction force applied to the top end of the inner spindle 115, and thus achieving the purpose of adjusting the overall stiffness of the variable pitch tie rod.

[0013] The top end of the inner mandrel 115 has a stepped axial side plane 802, and the inner wall of the mandrel receiving hole has a wedge ring block inner wall friction plane 303. The wedge ring block inner wall friction plane 303 and the stepped axial side plane 802 of the inner mandrel are arranged opposite to each other. On the one hand, this can effectively prevent rotation; on the other hand, the two opposing planes can also ensure that different degrees of clamping force, i.e., different degrees of friction force, can be stably applied to the top end of the inner mandrel 115 during the gradual natural reset of the wedge ring block 107.

[0014] To accommodate the length of the outer sleeve 103, there are several piezoelectric actuators 102. All piezoelectric actuators 102 are mounted on the fixed shaft 101 and are connected end to end. The piezoelectric actuator 102 located at the bottom is also loosely fitted with the wedge ring block 107.

[0015] Regarding the sensors required for data acquisition:

[0016] An acceleration sensor is fixedly installed on the upper cover 110 to obtain the acceleration of the active pitch control rod;

[0017] A displacement sensor and an acceleration sensor are fixedly installed on the inner mandrel 115. The displacement sensor detects the spring deformation, and the acceleration sensor detects the vibration of the mechanism. Specifically, a fixed magnet is connected to the lower platform 803 of the inner mandrel, and a Hall sensor is connected to the lower end face 704 of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field to the Hall sensor, thereby obtaining the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner mandrel through the Hall sensor.

[0018] A force sensor is also provided between the piezoelectric actuator 102 and the wedge-shaped movable retaining ring 105 to detect the magnitude of the piezoelectric actuator's output force.

[0019] Regarding the specific mounting structure used in helicopter pitch control booms:

[0020] The upper lug is connected to the rotor, and the lower lug is connected to the rotating ring of the automatic swashplate.

[0021] Before operation, the wedge-shaped structure 2 is pre-tightened by adjusting the pre-tightening bolt 108. Due to the pre-tightening force, the inner wall of the wedge ring block 107 and the inner core shaft 115 are not prone to relative movement due to the presence of friction. At this time, the variable pitch rod is equivalent to a rigid rod. When the accelerometer detects a large vibration, the control system outputs a control voltage. Under the excitation of the control voltage, the piezoelectric actuator 602 generates a micro-displacement. Driven by the piezoelectric actuator 602, the distance between the wedge-shaped movable retaining ring 105 and the wedge ring block 107 increases. At this time, relative movement can occur between the inner spindle 115 and the inner wall of the wedge ring block 107. Since the preload between the inner spindle 115 and the inner wall of the wedge ring block still exists, friction still exists to hinder the relative movement between the inner spindle 115 and the outer sleeve 103 and the spring 114, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the variable pitch rod is between that of a rigid rod and a spring. As the output displacement of the piezoelectric actuator 602 continues to increase, the force between the wedge-shaped movable retaining ring 105 and the wedge ring block 107 continuously decreases. When the preload between the inner spindle 115 and the inner wall of the wedge ring block 107 disappears, the variable pitch rod is equivalent to a spring, further enhancing the vibration reduction effect.

[0022] This invention effectively overcomes the problem that the stiffness and damping of traditional variable pitch rods cannot be adjusted in real time and can only handle noise or vibration under specific flight conditions. It also solves the problem that the variable pitch rod structure bears a large unbalanced centrifugal force and key components are exposed when in use. Through integrated design, it achieves vibration reduction under different flight conditions in the field of helicopter variable pitch rod applications, with good vibration reduction effect and wide applicability. Attached Figure Description

[0023] Figure 1a This is a schematic diagram of the exterior structure of this case;

[0024] Figure 1b This is a schematic diagram of the internal structure of this case;

[0025] Figure 2 Connection diagram for the functional implementation of the wedge-shaped structure;

[0026] Figure 3 Here is a detailed diagram of the wedge ring block structure;

[0027] Figure 4 a is a top view of the wedge-shaped movable retaining ring. Figure 4 b is a side view of the wedge-shaped movable retaining ring;

[0028] Figure 5 a is an oblique view of the outer sleeve. Figure 5 b is a bottom view of the outer sleeve;

[0029] Figure 6 a is a side view of the piezoelectric actuator. Figure 6 b is a bottom view of the piezoelectric actuator;

[0030] Figure 7 This is a schematic diagram of the spring connection structure;

[0031] Figure 8 This is a schematic diagram of the inner mandrel structure;

[0032] Figure 9 This is a schematic diagram of a spring structure;

[0033] Figure 10 This is a schematic diagram of the invention applied to a helicopter rotor.

[0034] In the diagram: 101, fixed shaft; 102, piezoelectric actuator; 103, outer sleeve; 104, spring; 105, wedge-shaped movable retaining ring; 107, wedge ring block; 108, preload bolt; 109, preload nut; 110, upper cover; 111, upper hanging ear; 112, lower hanging ear; 113, disc spring; 114, bolt; 115, inner spindle; 116, fixing bolt; 301, wedge ring block groove; 302, upper end face of wedge ring block; 303, inner wall friction plane of wedge ring block; 401, through hole of wedge-shaped movable retaining ring; 402, downward concave stepped platform of wedge-shaped movable retaining ring; 403, upper end face of wedge-shaped movable retaining ring; 404, lower end face of wedge-shaped movable retaining ring. 501. Threaded end; 502. Through hole on the flange side of the lower end of the outer sleeve; 503. Through hole for fixing the shaft at the upper end of the outer sleeve; 504. Bolt through hole at the upper end of the outer sleeve; 601. Lower end face of the flange side of the lower end of the outer sleeve; 602. Piezoelectric actuator head; 701. Threaded hole at the bottom end of the piezoelectric actuator; 702. Nut; 703. Stepped shaft surface of the inner mandrel; 704. Lower end face of the wedge-shaped movable retaining ring; 801. Through hole at the bottom of the inner mandrel; 802. Stepped shaft side plane at the upper end of the inner mandrel; 803. Platform surface at the lower end of the inner mandrel; 901. Threaded end of the upper end of the spring; 902. Stepped shaft hole at the upper end of the spring; 903. Through hole plane at the lower end of the spring;

[0035] 2 is the wedge-shaped structure, 1001 is the active pitch control rod, and 1002 is the helicopter rotor. Detailed Implementation

[0036] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0037] As shown in Figure 1 to Figure 10 As shown, the active pitch control rod has two effective stiffness states and one transition stiffness state. The active pitch control rod includes, from top to bottom, an upper lug 111, an upper cover 110, an outer sleeve 103, a wedge-shaped structure 2, a spring 104, and a lower lug 112.

[0038] The upper hanging ear 111, upper cover 110, and outer sleeve 103 are fixedly connected. Inside the outer sleeve 103, a piezoelectric actuator 102 is arranged coaxially with the spring 104. The top end of the piezoelectric actuator 102 is fixedly connected to the outer sleeve 103. The wedge-shaped structure 2 is connected to the piezoelectric actuator 102 and the outer sleeve 103. The bottom end of the spring 104 is fixedly connected to the lower hanging ear 112. Inside the spring 104, an inner spindle 115 is fixedly connected to the lower hanging ear 112. The top end of the inner spindle 115 extends into the wedge-shaped structure 2. The piezoelectric actuator 102 presses the wedge-shaped structure 2, thereby changing the clamping force applied to the top end of the inner spindle 115.

[0039] The wedge-shaped structure 2 includes a wedge-shaped movable retaining ring 105 and a wedge ring block 107;

[0040] The wedge-shaped movable retaining ring 105 is installed at the bottom opening of the outer sleeve 103 by circumferentially distributed pre-tightening bolts 108 and pre-tightening nuts 109, and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring 113 is also fitted on the pre-tightening bolts 108. The disc spring 113 abuts between the bottom surface of the wedge-shaped movable retaining ring 105 and the pre-tightening nut 109, and the disc spring 113 keeps the wedge-shaped movable retaining ring 105 in contact with the bottom opening of the outer sleeve 103. After the piezoelectric actuator 102 extends, it contacts the wedge-shaped movable retaining ring 105 and drives the wedge-shaped movable retaining ring 105 to move downward against the force of the disc spring 113.

[0041] The wedge-shaped movable retaining ring 105 has a tapered through hole at the center, which is larger at the top and smaller at the bottom;

[0042] The outer wall of the wedge ring block 107 is a conical surface that is larger at the top and smaller at the bottom, and a wedge ring block groove 301 is provided on the wedge ring block 107 from top to bottom; the lower part of the wedge ring block 107 extends into the conical through hole, and the wedge ring block 107 is fixedly connected to the outer sleeve 103 through a fixed shaft 101 passing through the center of the piezoelectric actuator 102. A mandrel receiving hole is also provided in the center of the wedge ring block 107, and the top end of the inner mandrel 115 extends into the mandrel receiving hole.

[0043] When the piezoelectric actuator 102 is not in contact with the wedge-shaped movable retaining ring 105, the wedge ring block 107 tightens the wedge ring block groove 301 under the action of the conical surface due to the compression of the disc spring 113, thereby maintaining the clamping of the top end of the inner spindle 115. When the piezoelectric actuator 102 extends and drives the wedge-shaped movable retaining ring 105 to move downward against the force of the disc spring 113, the wedge-shaped movable retaining ring 105 will gradually reduce the compression of the wedge ring block 107, thereby allowing the wedge ring block 107 to gradually and naturally reset, and then gradually weaken the clamping force on the top end of the inner spindle 115 until there is no clamping force, thereby changing the friction force applied to the top end of the inner spindle 115, and thus achieving the purpose of adjusting the overall stiffness of the variable pitch tie rod.

[0044] The top end of the inner mandrel 115 has a stepped axial side plane 802, and the inner wall of the mandrel receiving hole has a wedge ring block inner wall friction plane 303. The wedge ring block inner wall friction plane 303 and the stepped axial side plane 802 of the inner mandrel are arranged opposite to each other. On the one hand, this can effectively prevent rotation; on the other hand, the two opposing planes can also ensure that different degrees of clamping force, i.e., different degrees of friction force, can be stably applied to the top end of the inner mandrel 115 during the gradual natural reset of the wedge ring block 107.

[0045] To accommodate the length of the outer sleeve 103, there are several piezoelectric actuators 102. All piezoelectric actuators 102 are mounted on the fixed shaft 101 and are connected end to end. The piezoelectric actuator 102 located at the bottom is also loosely fitted with the wedge ring block 107.

[0046] Regarding the sensors required for data acquisition:

[0047] An acceleration sensor is fixedly installed on the upper cover 110 to obtain the acceleration of the active pitch control rod;

[0048] A displacement sensor and an acceleration sensor are fixedly installed on the inner mandrel 115. The displacement sensor detects the spring deformation, and the acceleration sensor detects the vibration of the mechanism. Specifically, a fixed magnet is connected to the lower platform 803 of the inner mandrel, and a Hall sensor is connected to the lower end face 704 of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field to the Hall sensor, thereby obtaining the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner mandrel through the Hall sensor.

[0049] A force sensor is also provided between the piezoelectric actuator 102 and the wedge-shaped movable retaining ring 105 to detect the magnitude of the piezoelectric actuator's output force.

[0050] Regarding the specific mounting structure used in helicopter pitch control booms:

[0051] The upper lug is connected to the rotor, and the lower lug is connected to the rotating ring of the automatic swashplate.

[0052] Installation process of variable pitch tie rod device:

[0053] Using the outer sleeve 103 as a reference, insert the piezoelectric actuator 102 and fix the bottom end of the piezoelectric actuator to the inner side of the upper end of the outer sleeve with bolts. Then insert the second piezoelectric actuator, and then insert the fixed shaft 101. The bottom end of the fixed shaft has a threaded hole. The fixing bolt 116 can be threaded with a washer to fix the fixed shaft 101 to the upper end of the outer sleeve. Then, the upper end face 302 of the wedge ring block 107 abuts against the lower end face of the fixed shaft, and the wedge-shaped movable retaining ring 105 is covered. Then, connect the spring 104 and the inner spindle 115. After inserting the inner spindle into the spring, use the nut 70. 2. Bolt 114 is used to fix the two together. After the two are fixed together, the whole is inserted into the wedge ring block 107. The spring and the wedge-shaped movable retaining ring 105 are connected by internal and external threads. At this time, the fixing bolt 116 can be finely adjusted so that the gap between the lower end face of the outer sleeve flange and the wedge-shaped movable retaining ring is appropriate when the wedge-shaped movable retaining ring is pressed against the wedge ring block. Then, the disc spring 113 is threaded on the pre-tightening bolt 108 and pre-tightened and connected with the pre-tightening nut 109. At this time, the whole device is in a rigid rod state. Finally, the upper cover 110, the upper hanging ear 111 and the lower hanging ear 112 are installed.

[0054] like Figures 2 to 5 As shown, the wedge-shaped movable retaining ring 105 has four or more through holes 401 on its flange edge. The lower flange edge of the outer sleeve has through holes 501 with the same number and size as the holes on the wedge-shaped movable retaining ring. Several pre-tightening bolts 108 are fitted with disc springs 113 and pass through the through holes 501 on the lower flange edge of the outer sleeve and the through holes 401 of the wedge-shaped movable retaining ring. The pre-tightening nut 109 is screwed onto the pre-tightening bolts 108 and contacts the disc springs 113. When the pre-tightening nut 109 is tightened, the bolt pre-tightening force compresses the disc springs 113, causing deformation and simultaneously driving the wedge-shaped movable retaining ring 105 to move relative to the fixed wedge ring block 107. The groove 301 on the surface of the wedge ring block 107 deforms, providing the initial pre-tightening force of the wedge-shaped structure 2. The pre-tightening nut 109 adjusts the initial compression of the disc springs 113.

[0055] By adjusting the output force / displacement of the piezoelectric actuator head on the lower end of the wedge-shaped movable ring, the initial bolt preload is changed, thereby changing the magnitude of the frictional force between the adjusting wedge-shaped structure 2 and the inner core 115.

[0056] As shown in 3 and 4, the wedge ring block 107 of the wedge-shaped structure 2 and the wedge-shaped movable retaining ring 105 are tightly fitted together. Both the lower end 504 of the outer sleeve 103 and the upper end face 403 of the wedge-shaped movable retaining ring are provided with flange edges. The preload bolt 108 passes through the flange edge hole 501 at the lower end of the outer sleeve 103 and the flange edge hole 401 at the upper end of the wedge-shaped movable retaining ring 105. A disc spring 113 is provided between the preload nut 109 and the lower end face of the flange edge hole of the wedge-shaped movable retaining ring 105. A gap exists between the upper end face 403 of the wedge-shaped movable retaining ring and the lower end face 504 of the outer sleeve flange. When a bolt preload is applied to the wedge-shaped structure 2, the wedge-shaped movable retaining ring 105 undergoes a slight displacement, which can press the wedge ring block 107 fitted inside it. Under the pressing action of the fixed shaft 101, the wedge ring block 107 will not undergo axial displacement. Furthermore, the wedge-shaped movable retaining ring deforms by squeezing the groove 301 of the wedge ring block during the slight displacement, thereby gripping the inner mandrel 115. The downwardly recessed stepped platform 402 of the wedge-shaped movable retaining ring is used to receive the output of the piezoelectric actuator 102.

[0057] like Figure 5 As shown, the fixing bolts secure the fixing shaft to the outer sleeve through the fixing through hole 502. The through hole 501 on the flange side of the lower end of the outer sleeve is used to connect the outer sleeve to the wedge-shaped movable retaining ring and the disc spring. The bolt through hole 503 at the upper end of the outer sleeve is used to securely connect the piezoelectric actuator 102 after the bolts are installed.

[0058] like Figure 6 As shown, the piezoelectric actuator 102 is composed of a stack of piezoelectric ceramics and a piezoelectric actuator head 601. The bottom end of the piezoelectric actuator 102, which is close to the bottom of the inner end of the outer sleeve, is bolted to the upper end of the outer sleeve 103. The piezoelectric actuator head 601, which is close to the upper end of the wedge-shaped movable retaining ring, abuts against the upper end face 403 of the wedge-shaped movable retaining ring.

[0059] like Figure 7 , 8 As shown in Figures 9 and 1, the bottom end of the inner spindle 115 is provided with a through hole 801, which is fixedly connected to the bottom opening 701 of the spring by a nut 702 and a bolt 114.

[0060] The lower end of the wedge-shaped movable retaining ring is screwed into the upper end of the spring with an external thread 404 for connection. A stepped hole 902 is opened at the upper end of the spring 104, corresponding to the stepped shaft 703 designed at the upper end of the inner core shaft 115, so as to provide a limiting function for the movement of the spring and the variable pitch tie rod structure in the transition and elastic states.

[0061] A flat surface 903 is machined at the lower end of the spring to allow the bolt head face to contact the nut face.

[0062] A fixed magnet is connected to the lower platform 803 of the inner mandrel, and a Hall sensor is connected to the lower end face 704 of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field to the Hall sensor, thereby obtaining the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner mandrel through the Hall sensor.

[0063] like Figure 10 As shown, the active pitch control rod 1001 of the present invention replaces the traditional pitch control rod in the application of helicopter rotor 1002. When in use, the upper mounting lug is connected to the rotor and the lower mounting lug is connected to the automatic swashplate. Without changing the shape of the blade, the vibration of the blade and the vibration transmitted from the blade to the helicopter fuselage are reduced by changing the stiffness of the support rod itself.

[0064] Before operation, the wedge-shaped structure in the strut structure used in the helicopter rotor pitch control rod is pre-tightened by adjusting the pre-tightening bolts and nuts. Due to the applied pre-tightening force, when the outer sleeve is subjected to external pressure transmitted from the upper cover to the wedge-shaped movable retaining ring, the inner wall of the wedge ring block and the inner spindle are not prone to relative movement due to the friction between the friction surface and the friction plate. At this time, the strut device is equivalent to a rigid rod. When the acceleration sensor detects a large vibration, the control system outputs a control voltage. Under the excitation of the control voltage, the piezoelectric actuator produces a micro-displacement. Since the pre-tightened disc spring is not fully compressed, the wedge ring block can be displaced. Therefore, under the push of the piezoelectric actuator, the distance between the wedge ring block and the wedge-shaped movable retaining ring increases, and the force between the inner spindle and the wedge ring block increases. As the force decreases, relative movement can occur between the inner mandrel and the outer sleeve. Since the preload between the inner mandrel and the wedge ring block still exists, frictional force still exists between the friction surface and the friction plate during the relative movement of the inner mandrel and the outer sleeve, hindering the relative movement between the inner mandrel and the wedge ring block, thus achieving the purpose of vibration reduction. At this time, the stiffness of the strut device is between that of a rigid rod and a spring. As the output force / displacement of the piezoelectric actuator continues to increase, due to the relative movement between the wedge-shaped structural parts, the force between the upper surface of the inner mandrel and the wedge ring block continuously decreases. When the groove of the wedge ring block recovers its deformation, that is, when the wedge ring block no longer holds the inner mandrel, the strut device is equivalent to a spring, further enhancing the vibration reduction effect. Its stiffness is determined by the spring stiffness.

[0065] An acceleration sensor can be fixed to the top cover to obtain the overall acceleration of the active pitch control rod; a platform is opened at the bottom of the inner spindle to place displacement sensors, acceleration sensors, etc.

[0066] A fixed magnet is connected to the lower platform of the inner mandrel, and a Hall sensor is connected to the lower end face of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field to the Hall sensor, thereby obtaining the relative displacement between the bottom end of the wedge-shaped movable retaining ring and the bottom end of the inner mandrel through the Hall sensor.

[0067] During helicopter operation, the vibration of the strut assembly is detected by acceleration and displacement sensors, and the collected signals are transmitted to the control system. The control system analyzes the rotor vibration state based on the signals detected by the sensors and adjusts the control voltage of the piezoelectric actuator. Since the output displacement of the piezoelectric actuator is different under different control voltages, the preload between the inner mandrel and the inner wall of the wedge ring block can be adjusted by adjusting the control voltage of the piezoelectric actuator, thereby adjusting the stiffness of the pitch rod to achieve vibration reduction of the helicopter rotor under different flight conditions.

[0068] Considering the safety of the active vibration damping strut mechanism applied to the pitch control rod of the helicopter rotor, when the piezoelectric actuator is suddenly de-energized, the piezoelectric actuator has no displacement output at this time, the initial preload of the wedge structure is restored, and the pitch control rod at this time is equivalent to a rigid strut, so the vibration of the rotor will not change abruptly.

[0069] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. An active pitch control rod for a helicopter rotor, characterized in that, The active pitch control rod includes, from top to bottom, an upper lug (111), an upper cover (110), an outer sleeve (103), a wedge-shaped structure (2), a spring (104), and a lower lug (112). The upper hanging ear (111), the upper cover (110) and the outer sleeve (103) are fixedly connected, and a piezoelectric actuator (102) is provided inside the outer sleeve (103) and arranged coaxially with the spring (104). The top end of the piezoelectric actuator (102) is fixedly connected to the outer sleeve (103). The wedge-shaped structure (2) is connected below the piezoelectric actuator (102) and the outer sleeve (103). The bottom end of the spring (104) is fixedly connected to the lower hanging ear (112), and an inner spindle (115) is also provided inside the spring (104) and fixedly connected to the lower hanging ear (112). The top end of the inner spindle (115) extends into the wedge-shaped structure (2). The wedge-shaped structure (2) is pressed by the piezoelectric actuator (102), thereby changing the clamping force applied to the top end of the inner spindle (115). The wedge-shaped structure (2) includes a wedge-shaped movable retaining ring (105) and a wedge ring block (107). The wedge-shaped movable retaining ring (105) is installed at the bottom of the outer sleeve (103) by circumferentially distributed pre-tightening bolts (108) and pre-tightening nuts (109), and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring (113) is also fitted on the pre-tightening bolts (108). The disc spring (113) abuts between the bottom surface of the wedge-shaped movable retaining ring (105) and the pre-tightening nut (109). The disc spring (113) keeps the wedge-shaped movable retaining ring (105) in contact with the bottom of the outer sleeve (103). After the piezoelectric actuator (102) extends, it contacts the wedge-shaped movable retaining ring (105) and drives the wedge-shaped movable retaining ring (105) to move downward against the force of the disc spring (113). The wedge-shaped movable retaining ring (105) has a tapered through hole that is larger at the top and smaller at the bottom in the center; The outer wall of the wedge ring block (107) is a conical surface with a larger upper part and a smaller lower part. A wedge ring block groove (301) is provided on the wedge ring block (107) from top to bottom. The lower part of the wedge ring block (107) extends into the conical through hole. The wedge ring block (107) is fixedly connected to the outer sleeve (103) through a fixed shaft (101) passing through the center of the piezoelectric actuator (102). A mandrel receiving hole is also provided in the center of the wedge ring block (107). The top end of the inner mandrel (115) extends into the mandrel receiving hole.

2. The active pitch control rod for a helicopter rotor according to claim 1, characterized in that, The top end of the inner mandrel (115) is provided with a stepped axial side plane (802) at the upper end of the inner mandrel, and the inner wall of the mandrel receiving hole is provided with a wedge ring block inner wall friction plane (303). The wedge ring block inner wall friction plane (303) and the stepped axial side plane (802) at the upper end of the inner mandrel are arranged opposite to each other.

3. The active pitch control rod for a helicopter rotor according to claim 1, characterized in that, The piezoelectric actuator (102) has several units, and the several piezoelectric actuators (102) are all mounted on the fixed shaft (101), and the several piezoelectric actuators (102) are connected end to end. The piezoelectric actuator (102) located at the bottom is also loosely fitted with the wedge ring block (107).

4. An active pitch control rod for a helicopter rotor according to any one of claims 1-3, characterized in that, An acceleration sensor is fixedly installed on the upper cover (110) to obtain the acceleration of the active pitch lever; A displacement sensor and an acceleration sensor are fixedly installed on the inner mandrel (115). The displacement sensor detects the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism. A force sensor is also provided between the piezoelectric actuator (102) and the wedge-shaped movable retaining ring (105) to detect the magnitude of the piezoelectric actuator output force.

5. An active pitch control rod for a helicopter rotor according to any one of claims 1-3, characterized in that, The upper lug is connected to the rotor, and the lower lug is connected to the rotating ring of the automatic swashplate.

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