A rotor strut with actively adjustable stiffness and damping

Abstract

The present invention discloses a rotor strut with actively adjustable stiffness and damping, which relates to the technical field of active vibration reduction of helicopter rotors. While meeting the requirements of both support and vibration reduction, the coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator is achieved, which can effectively avoid various adverse effects caused by unbalanced centrifugal force. The rotor strut comprises an upper hanging ear, an upper cover, a wedge-shaped structure, an outer sleeve, a lower cover, a spring and a lower pull rod from top to bottom; an inner core shaft fixedly connected to the lower hanging ear is also provided inside the spring, and the inner core shaft passes through the lower cover, the outer sleeve and the piezoelectric actuator from bottom to top, and then extends into the wedge-shaped structure; the wedge-shaped structure is pressed by the piezoelectric actuator, thereby changing the clamping force applied to the top end of the inner core shaft. Vibration reduction under different flight conditions is achieved in the application field of helicopter pitch rod through an integrated and integrated design, with good vibration reduction effect and a wide range of applications.

Description

Technical Field

[0001] The invention relates to the technical field of active vibration reduction of helicopter rotors. Background Art

[0002] Currently, helicopters generate excessive noise and vibration during flight, which is harmful to passenger health, the surrounding environment, and the aircraft itself. The source of this noise and vibration is mainly due to the aerodynamic loads experienced by the helicopter rotor blades, and is most prominent during forward flight and descent.

[0003] There are three basic types of active control vibration reduction technologies for helicopter rotors: 1) active trailing-edge flap control, 2) active rotor torsion control, and 3) active pitch control. The first two methods focus on blade-based vibration reduction. Active pitch control utilizes an active control strut device to replace the traditional pitch control rod. This method eliminates blade adjustment and preserves blade integrity.

[0004] On April 25, 2023, the applicant applied for a Chinese invention patent application entitled: A helicopter rotor pitch rod with an active vibration reduction mechanism, with publication number: CN116443247A. The application describes a pitch rod with a piezoelectric driver as the power source. However, this type of structure that replaces the pitch rod has a device that places the piezoelectric actuator perpendicular to the axial direction for its active vibration reduction function, which may cause the overall structure to be subjected to large unbalanced centrifugal forces during dynamic load tests or actual applications. In addition, in this type of structure, key function implementation parts such as piezoelectric actuators are exposed. Considering that helicopters face complex, harsh and adverse flight environments in actual operation, it is also very easy to cause failure or damage to key components such as piezoelectric actuators. Summary of the Invention

[0005] In response to the above problems, the present invention proposes a rotor strut with actively adjustable stiffness and damping, which not only meets the requirements of both support and vibration reduction, but also achieves a coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator, which can effectively avoid the various adverse effects caused by unbalanced centrifugal force.

[0006] The technical solution of the present invention is as follows: the rotor strut comprises, from top to bottom, an upper hanging ear 111, an upper cover 105, a wedge-shaped structure 2, an outer sleeve 103, a lower cover, a spring 104 and a lower pull rod 112;

[0007] The upper hanging ear 111, the upper cover 105, the outer sleeve 103 and the lower cover are fixedly connected in sequence from top to bottom, and a piezoelectric actuator 102 coaxially arranged with the spring 104 is provided inside the outer sleeve 103, the bottom end of the piezoelectric actuator 102 is fixedly connected to the outer sleeve 103, and the wedge-shaped structure part 2 is installed between the upper cover 105 and the outer sleeve 103 and is above the piezoelectric actuator 102; the spring 104 is fixedly connected between the lower hanging ear and the lower cover, and an inner core shaft 101 fixedly connected to the lower hanging ear 112 is further provided inside the spring 104, and the inner core shaft 101 passes through the lower cover, the outer sleeve 103 and the piezoelectric actuator 102 from bottom to top, and then extends into the wedge-shaped structure part 2; the wedge-shaped structure part 2 is pressed by the piezoelectric actuator 102, thereby changing the clamping force applied to the top end of the inner core shaft 101;

[0008] The wedge-shaped structure 2 includes a wedge-shaped movable ring 201 and a wedge-shaped retaining ring 106;

[0009] The wedge-shaped retaining ring 106 is fixedly installed between the upper cover 105 and the outer sleeve 103, and a tapered through hole with a larger upper portion and a smaller lower portion is opened in the center of the wedge-shaped retaining ring 106;

[0010] The lower portion of the wedge-shaped movable ring 201 is in the shape of a cone with a larger upper portion and a smaller lower portion, and a wedge-shaped movable ring groove 303 is provided on the lower portion of the wedge-shaped movable ring 201, which passes through from top to bottom. The outer edge of the wedge-shaped movable ring 201 is mounted on the wedge-shaped movable retaining ring 106 via circumferentially uniformly distributed pre-tightening bolts 203, and the lower portion of the wedge-shaped movable ring 201 is accommodated in the conical through-hole. A disc spring 202 is also mounted on the pre-tightening bolt 203, and the disc spring 202 is pressed between the head of the pre-tightening bolt 203 and the top surface of the wedge-shaped movable ring 201, so that the wedge-shaped movable ring 201 maintains a downward movement trend through the disc spring 202.

[0011] The bottom surface of the wedge-shaped movable ring 201 is lower than the wedge-shaped retaining ring 106 , and the lower end surface 304 of the wedge-shaped movable ring is above the piezoelectric actuator 102 for contacting the piezoelectric actuator 102 . The center of the wedge-shaped movable ring 201 is sleeved on the top of the inner core shaft 101 .

[0012] When the piezoelectric actuator 102 contacts the wedge-shaped movable ring 201 but does not extend to apply a force, the pressure of the disc spring 202 causes the lower part of the wedge-shaped movable ring 201 to tighten the wedge-shaped movable ring groove 303 under the action of the conical surface, thereby maintaining the clamping of the top of the inner core shaft 101; when the piezoelectric actuator 102 extends and drives the wedge-shaped movable ring 201 to overcome the force of the disc spring 202 and move upward, the wedge-shaped retaining ring 106 gradually reduces the pressure on the lower part of the wedge-shaped movable ring 201, thereby causing the lower part of the wedge-shaped movable ring 201 to gradually return to its original position naturally, and then gradually weaken the clamping force on the top of the inner core shaft 101, thereby achieving the purpose of changing the friction force applied to the top of the inner core shaft 101 until there is no clamping force, thereby achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0013] In order to facilitate the installation of the wedge-shaped movable ring, the upper part of the wedge-shaped movable ring 201 is disc-shaped, and a number of wedge-shaped movable ring waist-shaped through holes 301 are evenly distributed along the circumference of the upper part of the wedge-shaped movable ring 201. The pre-tightening bolt 203 passes through the wedge-shaped movable ring waist-shaped through holes 301 from top to bottom and is threadedly connected to the wedge-shaped retaining ring 106.

[0014] In order to adapt to the length of the outer sleeve 103, there are several piezoelectric actuators 102, and the several piezoelectric actuators 102 are all mounted on the inner core shaft 101, and the several piezoelectric actuators 102 are connected end to end. The piezoelectric actuator 102 located at the bottom is fixedly connected to the outer sleeve 103, and the piezoelectric actuator 102 located at the top contacts the wedge-shaped movable ring 201 after extension.

[0015] Regarding the sensors required for data acquisition:

[0016] An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the entire support rod;

[0017] A displacement sensor and an acceleration sensor are fixedly mounted on the inner core shaft. The displacement sensor is used to detect the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism. Specifically, a fixed magnet is connected to the platform 702 at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface 505 of the outer sleeve. The magnet provides a magnetic field for the Hall sensor, thereby obtaining the relative displacement between the bottom end of the outer sleeve and the bottom end of the inner core shaft through the Hall sensor.

[0018] A force sensor is also provided between the piezoelectric actuator and the wedge-shaped movable ring for detecting the magnitude of the output force of the piezoelectric actuator.

[0019] Regarding the specific installation structure used in the helicopter pitch lever:

[0020] The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

[0021] The present invention pre-tightens the wedge-shaped structure by adjusting the pre-tightening bolts before operation. Due to the applied pre-tightening force, the inner wall of the wedge-shaped movable ring and the inner core shaft are not easily moved relative to each other due to the existence of friction. At this time, the rotor strut is equivalent to a rigid rod. When the acceleration sensor detects a large vibration, the control system outputs a control voltage, and the piezoelectric driver generates a micro-displacement under the excitation of the control voltage. Under the push of the piezoelectric actuator, the distance between the wedge-shaped movable ring and the wedge-shaped retaining ring increases. At this time, relative movement can occur between the inner core shaft and the inner wall of the wedge-shaped movable ring. Because the pre-tightening force between the inner core shaft and the inner wall of the wedge-shaped movable ring still exists, there is still friction to hinder the relative movement between the inner core shaft and the outer sleeve spring, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the rotor strut is between the stiffness of a rigid rod and a spring. As the output displacement of the piezoelectric driver continues to increase, the pre-tightening force between the wedge-shaped retaining ring and the wedge-shaped movable ring continues to decrease. When the pre-tightening force between the inner core shaft and the inner wall of the wedge-shaped movable ring disappears, the rotor strut is equivalent to a spring, further enhancing the vibration reduction effect.

[0022] The present invention effectively overcomes the problem that the stiffness and damping of traditional pitch rods cannot be adjusted in real time and can only handle noise or vibration under specific flight conditions. It solves the problem in previous inventions that the pitch rod structure is subjected to large unbalanced centrifugal forces when in use and key components are exposed. Through an integrated and integrated design, vibration reduction under different flight conditions is achieved in the application field of helicopter pitch rods, with good vibration reduction effect and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0025] Figure 2 A connection diagram for the wedge-shaped structural function;

[0026] Figure 3 This is a detailed diagram of the wedge-shaped movable ring structure;

[0027] Figure 4 This is a detailed diagram of the wedge-shaped retaining ring structure;

[0028] Figure 5 a is the side view of the outer sleeve, Figure 5 b is a bottom view of the outer sleeve;

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

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

[0031] Figure 8 a is a schematic diagram of the support structure installation. Figure 8 b is a schematic diagram of the support structure after installation;

[0032] Figure 9 This is a schematic diagram of the present invention being applied to and installed on a helicopter rotor;

[0033] In the figure: 101, inner core shaft; 102, piezoelectric actuator; 103, outer sleeve; 104, spring; 105, upper cover; 106, wedge-shaped retaining ring; 107, mounting nut; 108, bolt for piezoelectric actuator; 109, 110, bolt, nut; 111, upper hanging ear; 112, lower hanging ear; 201, wedge-shaped movable ring; 202, disc spring; 203, pre-tightening bolt; 204, upper end face of the wedge-shaped movable ring flange; 301, waist-shaped through hole of the wedge-shaped movable ring; 302, lower end of the flange edge of the wedge-shaped movable ring Surface; 303, wedge-shaped movable ring groove; 304, lower end surface of wedge-shaped movable ring; 401, wedge-shaped retaining ring threaded hole; 402, wedge-shaped retaining ring upper end surface; 403, wedge-shaped retaining ring external thread; 501, outer sleeve upper end internal thread; 502, outer sleeve lower end external thread; 503, outer sleeve lower end through hole; 504, outer sleeve lower end axial hole; 505, outer sleeve lower end surface; 601, piezoelectric actuator head; 602, piezoelectric actuator bottom end threaded hole; 701, spring through hole; 702, inner core shaft bottom open platform;

[0034] 2 is a wedge-shaped structural part, 901 is an active variable pitch pull rod, and 902 is a helicopter rotor. DETAILED DESCRIPTION

[0035] In order to clearly illustrate the technical features of this patent, this patent is described in detail below through specific implementation methods and in combination with its accompanying drawings.

[0036] like Figures 1 to 9 As shown, the rotor strut has two effective stiffness states and a transition stiffness state. The rotor strut includes, from top to bottom, an upper hanging ear 111, an upper cover 105, a wedge-shaped structure 2, an outer sleeve 103, a lower cover, a spring 104, and a lower hanging ear 112;

[0037] The upper hanging ear 111, the upper cover 105, the outer sleeve 103 and the lower cover are fixedly connected in sequence from top to bottom, and a piezoelectric actuator 102 coaxially arranged with the spring 104 is provided inside the outer sleeve 103, the bottom end of the piezoelectric actuator 102 is fixedly connected to the outer sleeve 103, and the wedge-shaped structure part 2 is installed between the upper cover 105 and the outer sleeve 103 and is above the piezoelectric actuator 102; the spring 104 is fixedly connected between the lower hanging ear and the lower cover, and an inner core shaft 101 fixedly connected to the lower hanging ear 112 is further provided inside the spring 104, and the inner core shaft 101 passes through the lower cover, the outer sleeve 103 and the piezoelectric actuator 102 from bottom to top, and then extends into the wedge-shaped structure part 2; the wedge-shaped structure part 2 is pressed by the piezoelectric actuator 102, thereby changing the clamping force applied to the top end of the inner core shaft 101;

[0038] The wedge-shaped structure 2 includes a wedge-shaped movable ring 201 and a wedge-shaped retaining ring 106;

[0039] The wedge-shaped retaining ring 106 is fixedly installed between the upper cover 105 and the outer sleeve 103, and a tapered through hole with a larger upper portion and a smaller lower portion is opened in the center of the wedge-shaped retaining ring 106;

[0040] The lower portion of the wedge-shaped movable ring 201 is in the shape of a cone with a larger upper portion and a smaller lower portion, and a wedge-shaped movable ring groove 303 is provided in the lower portion of the wedge-shaped movable ring 201, which passes through from top to bottom. The outer edge of the wedge-shaped movable ring 201 is mounted on the wedge-shaped retaining ring 106 via circumferentially evenly distributed pre-tightening bolts 203, and the lower portion of the wedge-shaped movable ring 201 is accommodated in the conical through-hole. A disc spring 202 is also mounted on the pre-tightening bolt 203, and the disc spring 202 is pressed between the head of the pre-tightening bolt 203 and the top surface of the wedge-shaped movable ring 201, so that the wedge-shaped movable ring 201 maintains a downward movement trend through the disc spring 202.

[0041] The bottom surface of the wedge-shaped movable ring 201 is lower than the wedge-shaped retaining ring 106 , and the lower end surface 304 of the wedge-shaped movable ring is above the piezoelectric actuator 102 for contacting the piezoelectric actuator 102 . The center of the wedge-shaped movable ring 201 is sleeved on the top of the inner core shaft 101 .

[0042] When the piezoelectric actuator 102 contacts the wedge-shaped movable ring 201 but does not extend to apply a force, the pressure of the disc spring 202 causes the lower part of the wedge-shaped movable ring 201 to tighten the wedge-shaped movable ring groove 303 under the action of the conical surface, thereby maintaining the clamping of the top of the inner core shaft 101; when the piezoelectric actuator 102 extends and drives the wedge-shaped movable ring 201 to overcome the force of the disc spring 202 and move upward, the wedge-shaped retaining ring 106 gradually reduces the pressure on the lower part of the wedge-shaped movable ring 201, thereby causing the lower part of the wedge-shaped movable ring 201 to gradually return to its original position naturally, and then gradually weaken the clamping force on the top of the inner core shaft 101, thereby achieving the purpose of changing the friction force applied to the top of the inner core shaft 101 until there is no clamping force, thereby achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0043] In order to facilitate the installation of the wedge-shaped movable ring, the upper part of the wedge-shaped movable ring 201 is disc-shaped, and a number of wedge-shaped movable ring waist-shaped through holes 301 are evenly distributed along the circumference of the upper part of the wedge-shaped movable ring 201. The pre-tightening bolt 203 passes through the wedge-shaped movable ring waist-shaped through holes 301 from top to bottom and is threadedly connected to the wedge-shaped retaining ring 106.

[0044] In order to adapt to the length of the outer sleeve 103, there are several piezoelectric actuators 102, and the several piezoelectric actuators 102 are all mounted on the inner core shaft 101, and the several piezoelectric actuators 102 are connected end to end. The piezoelectric actuator 102 located at the bottom is fixedly connected to the outer sleeve 103, and the piezoelectric actuator 102 located at the top contacts the wedge-shaped movable ring 201 after extension.

[0045] Regarding the sensors required for data acquisition:

[0046] An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the entire support rod;

[0047] A displacement sensor and an acceleration sensor are fixedly mounted on the inner core shaft. The displacement sensor is used to detect the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism. Specifically, a fixed magnet is connected to the platform 702 at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface 505 of the outer sleeve. The magnet provides a magnetic field for the Hall sensor, thereby obtaining the relative displacement between the bottom end of the outer sleeve and the bottom end of the inner core shaft through the Hall sensor.

[0048] A force sensor is also provided between the piezoelectric actuator and the wedge-shaped movable ring for detecting the magnitude of the output force of the piezoelectric actuator.

[0049] Regarding the specific installation structure used in the helicopter pitch lever:

[0050] The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

[0051] About the installation process of the variable pitch pull rod device:

[0052] Taking the outer sleeve 103 as a reference, after inserting the piezoelectric actuator 102 from the opening at the upper end of the outer sleeve, the bottom end of the piezoelectric actuator is fixedly connected to the bottom opening 503 of the outer sleeve by the bolt 108, and then the second piezoelectric actuator is placed. The spring thread is screwed into the threaded part 502 at the bottom end of the outer sleeve. After inserting the inner core shaft 101, the bottom end 701 of the spring is fixed to the end of the inner core shaft. Then the wedge-shaped movable ring 201 is inserted into the wedge-shaped retaining ring 106 and the mounting nut 107 is screwed on to tighten it. The wedge-shaped retaining ring is screwed down until the bottom end face 304 of the wedge-shaped movable ring is against the head end 601 of the piezoelectric actuator without gap, and the mounting nut 107 is tightened. Then the wedge-shaped retaining ring 106 is screwed up until it is clamped, the pre-tightening bolt 203 is tightened, and the mounting nut is removed. Finally, the upper cover 105 and the upper and lower hanging ears 111 and 112 are installed.

[0053] like Figure 2 、 3 As shown in Figure 4, the wedge-shaped movable ring 201 of the wedge-shaped structural part 2 and the wedge-shaped retaining ring 106 are tightly fitted and contacted with each other, and a number of pre-tightening bolts 203 are provided between the wedge-shaped movable ring 201 and the wedge-shaped retaining ring 106. A disc spring 202 is provided between the pre-tightening bolts and the upper end face 204 of the wedge-shaped movable ring flange. There is a gap between the upper end face 402 of the wedge-shaped retaining ring and the lower end face 302 of the flange of the wedge-shaped movable ring. A groove 303 is provided on the wedge-shaped movable ring, so that when the wedge-shaped structural part 2 is subjected to a pre-tightening force, the wedge-shaped movable ring 201 produces a micro-displacement. Due to the conical sleeve structure, it can be pressed by the fixed wedge-shaped retaining ring 106, thereby squeezing the groove 303 of the wedge-shaped movable ring to produce deformation, thereby clamping the inner core shaft.

[0054] The flange position of the wedge-shaped movable ring 201 is provided with four or more waist-shaped through holes 301, and the wedge-shaped retaining ring is provided with threaded holes 401 with the same number and size as the holes on the wedge-shaped movable ring. A plurality of pre-tightening bolts 203 are sleeved on the disc springs 202 and pass through the waist-shaped through holes 201 of the wedge-shaped movable ring and are screwed into the threaded holes 401 of the wedge-shaped retaining ring. When tightened, the pre-tightening force of the bolts squeezes the disc springs 202 to cause deformation and drives the wedge-shaped movable ring 201 and the wedge-shaped retaining ring 106 to cause relative displacement, thereby providing the initial pre-tightening force of the wedge-shaped structure part 2. The pre-tightening bolts 203 adjust the initial compression amount of the disc springs 202.

[0055] The assembly relationship between the inner core shaft 101 and the inner hole of the piezoelectric actuator 102, the outer sleeve shaft hole 504, and the inner hole of the spring 104 is overfitting, which makes the overall structural assembly more stable and reduces shaking.

[0056] Furthermore, at the contact surface between the inner hole wall of the wedge-shaped movable ring 201 of the wedge-shaped structural part 2 and the outer surface of the inner core shaft 101, a friction surface is provided on the outer surface of the inner core shaft, and a friction plate facing the friction surface is fixedly connected to the inner hole wall of the wedge-shaped movable ring.

[0057] When the outer thread 403 of the wedge-shaped retaining ring is screwed into the inner thread 501 of the outer sleeve, in addition to the processing accuracy, the waist-shaped through hole 301 on the wedge-shaped movable ring provides assembly margin for the corresponding positioning connection between the threaded holes of the wedge-shaped retaining ring and the waist-shaped through hole of the wedge-shaped movable ring.

[0058] 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 force is changed, thereby changing the friction force between the wedge-shaped structure part 2 and the inner core shaft 101.

[0059] like Figure 6 As shown, the bottom opening 602 of the piezoelectric actuator is fixedly connected to the opening 503 at the lower end of the inner portion of the outer sleeve by means of bolts.

[0060] The piezoelectric actuator 102 is composed of a piezoelectric ceramic stack and a piezoelectric actuator head 601. The bottom end of the piezoelectric actuator 102 near the bottom end of the outer sleeve is fixedly connected to the bottom end bolt of the outer sleeve 103, and the piezoelectric actuator head near the lower end of the wedge-shaped movable ring is against the lower end surface 304 of the wedge-shaped movable ring.

[0061] like Figure 7 As shown, the bottom end of the inner core shaft 101 is fixedly connected to the bottom end opening 701 of the spring by a bolt 109 and a nut 110.

[0062] like Figure 8 As shown, the structure of the present invention involves a specific installation process, and a mounting nut 107 is used to assist in the assembly of the entire device. After the piezoelectric actuator 102 is placed in the opening at the upper end of the outer sleeve, the bottom end of the piezoelectric actuator is fixedly connected to the bottom opening 503 of the outer sleeve by means of bolts 108, and then the second piezoelectric actuator is placed. The spring thread is then screwed into the threaded portion 502 at the bottom end of the outer sleeve for connection. After inserting the inner core shaft 101, the bottom end 701 of the spring is fixedly connected to the end of the inner core shaft. The wedge-shaped movable ring 201 is then inserted into the wedge-shaped retaining ring 106 and the mounting nut 107 is screwed on to tighten it. The wedge-shaped retaining ring is screwed down until the bottom end surface 304 of the wedge-shaped movable ring is against the head end 601 of the piezoelectric actuator without a gap. The mounting nut 107 is tightened, and the wedge-shaped retaining ring 106 is screwed up until it is clamped. The pre-tightening bolts 203 are tightened, and the mounting nut is then removed. Finally, the upper cover 105 and the upper and lower hanging ears 111 and 112 are installed. The mounting nuts are not included in the assembly table of the final structural device.

[0063] like Figure 9 As shown, the strut device 901 of the present invention replaces the traditional pitch rod in the application of the helicopter rotor 902. When used, the upper ear bearing is connected to the rotor, and the lower ear bearing is connected to the automatic tilt mechanism dynamic ring. 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 strut itself.

[0064] Before work, the wedge-shaped structure part in the strut structure used for the helicopter rotor pitch rod is pre-tightened by adjusting the pre-tightening bolts. Due to the application of pre-tightening force, when the outer sleeve is subjected to external pressure transmitted from the upper cover to the wedge-shaped retaining ring, the inner wall of the wedge-shaped movable ring and the inner core shaft are not easy to move relative to each other 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, and the piezoelectric actuator generates a micro-displacement under the excitation of the control voltage. Since the pre-tightening disc spring is not fully compressed, the wedge-shaped movable ring can be displaced. Therefore, under the push of the piezoelectric actuator, the distance between the wedge-shaped movable ring and the wedge-shaped retaining ring increases, and the pre-tightening force between the inner core shaft and the wedge-shaped movable ring is reduced. Small, at this time relative movement can be generated between the inner core shaft and the outer sleeve, because the pre-tightening force between the inner core shaft and the wedge-shaped movable ring still exists, so in the process of relative movement of the inner core shaft and the outer sleeve, there is still friction between the friction surface and the friction plate to hinder the relative movement between the inner core shaft and the wedge-shaped movable ring, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the strut device is between the stiffness of the rigid rod and the 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 pre-tightening force between the inner wall of the inner core shaft and the wedge-shaped movable ring continues to decrease. When the wedge-shaped movable ring groove recovers its deformation and the wedge-shaped movable ring no longer holds the inner core shaft, the strut device is equivalent to a spring, which further enhances the vibration reduction effect. Its stiffness is determined by the spring stiffness.

[0065] An acceleration sensor may be fixed on the upper cover to obtain the acceleration of the entire support rod; a platform is provided at the bottom end of the inner core shaft to place a displacement sensor, an acceleration sensor, etc.;

[0066] A fixed magnet is connected to the open platform at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface 502 of the outer sleeve. The magnet provides a magnetic field to the Hall sensor, so that the relative displacement between the bottom end of the outer sleeve and the bottom end of the inner core shaft is obtained through the Hall sensor.

[0067] During the operation of the helicopter, the vibration of the strut device is detected by acceleration sensors and displacement sensors, and the collected signals are transmitted to the control system. The control system analyzes the vibration state of the rotor according to 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 force between the inner walls of the wedge-shaped movable ring groove of the inner core shaft can be adjusted by adjusting the control voltage of the piezoelectric actuator, thereby adjusting the stiffness of the pitch rod to achieve vibration reduction under different flight conditions of the helicopter rotor.

[0068] Considering the safety of the active vibration damping strut mechanism used in the helicopter rotor pitch rod, when the piezoelectric actuator suddenly loses power, the piezoelectric actuator has no displacement output, the preload force of the wedge-shaped structure is restored, and the pitch rod is now equivalent to a rigid strut, so the vibration of the rotor will not change suddenly.

[0069] There are many specific implementation ways of the present invention. The above is only the preferred implementation method of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principles of the present invention. These improvements should also be considered as the scope of protection of the present invention.

Claims

1. A rotor strut with actively adjustable stiffness and damping, characterized in that: The rotor strut comprises, from top to bottom, an upper hanging ear (111), an upper cover (105), a wedge-shaped structure (2), an outer sleeve (103), a lower cover, a spring (104), and a lower pull rod (112); The upper hanging ear (111), the upper cover (105), the outer sleeve (103) and the lower cover are fixedly connected in sequence from top to bottom, and a piezoelectric actuator (102) coaxially arranged with the spring (104) is provided inside the outer sleeve (103), the bottom end of the piezoelectric actuator (102) is fixedly connected to the outer sleeve (103), and the wedge-shaped structure (2) is installed between the upper cover (105) and the outer sleeve (103) and is located above the piezoelectric actuator (102); The spring (104) is fixedly connected between the lower hanging ear and the lower cover, and an inner core shaft (101) fixedly connected to the lower hanging ear (112) is also provided inside the spring (104). The inner core shaft (101) passes through the lower cover, the outer sleeve (103) and the piezoelectric actuator (102) from bottom to top, and then 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 core shaft (101). The wedge-shaped structural portion (2) comprises a wedge-shaped movable ring (201) and a wedge-shaped retaining ring (106); The wedge-shaped retaining ring (106) is fixedly installed between the upper cover (105) and the outer sleeve (103), and a tapered through hole with a larger upper portion and a smaller lower portion is provided in the center of the wedge-shaped retaining ring (106); The lower portion of the wedge-shaped movable ring (201) is in the shape of a cone with a larger upper portion and a smaller lower portion, and a wedge-shaped movable ring groove (303) is provided on the lower portion of the wedge-shaped movable ring (201) and passes through from top to bottom; the outer edge of the wedge-shaped movable ring (201) is mounted on the wedge-shaped retaining ring (106) through circumferentially uniformly distributed pre-tightening bolts (203), and the lower portion of the wedge-shaped movable ring (201) is accommodated in the conical through hole; a disc spring (202) is also mounted on the pre-tightening bolt (203), and the disc spring (202) is pressed between the head of the pre-tightening bolt (203) and the top surface of the wedge-shaped movable ring (201), so that the wedge-shaped movable ring (201) maintains a downward movement trend through the disc spring (202); The bottom surface of the wedge-shaped movable ring (201) is lower than the wedge-shaped retaining ring (106), and the lower end surface (304) of the wedge-shaped movable ring is located above the piezoelectric actuator (102) and is used to contact the piezoelectric actuator (102). The center of the wedge-shaped movable ring (201) is sleeved on the top end of the inner core shaft (101).

2. The rotor strut with active adjustable stiffness and damping according to claim 1, characterized in that: The upper portion of the wedge-shaped movable ring (201) is disc-shaped, and a plurality of wedge-shaped movable ring waist-shaped through holes (301) are evenly distributed along the circumference of the upper portion of the wedge-shaped movable ring (201). The pre-tightening bolts (203) penetrate the wedge-shaped movable ring waist-shaped through holes (301) from top to bottom and are then threadedly connected to the wedge-shaped retaining ring (106).

3. The rotor strut with active adjustable stiffness and damping according to claim 1, characterized in that: There are a plurality of piezoelectric actuators (102), all of which are mounted on the inner core shaft (101), and the piezoelectric actuators (102) are connected end to end. The piezoelectric actuator (102) at the bottom is fixedly connected to the outer sleeve (103), and the piezoelectric actuator (102) at the top contacts the wedge-shaped movable ring (201) after being extended.

4. A rotor strut with active adjustable stiffness and damping according to any one of claims 1 to 3, characterized in that: An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the entire support rod; A displacement sensor and an acceleration sensor are fixedly mounted on the inner core shaft, the displacement sensor is used to detect 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 and the wedge-shaped movable ring for detecting the magnitude of the output force of the piezoelectric actuator.

5. A rotor strut with active adjustable stiffness and damping according to any one of claims 1 to 3, characterized in that: The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

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