Variable impedance helicopter pull rod vibration reduction device and method

Abstract

The present invention provides a variable impedance helicopter tie rod vibration reduction device and method. The device comprises a rigid rod, with a friction block I disposed on its upper portion. The inner side of the friction block I abuts against a T-shaped frame, and the outer side abuts against a friction block II. Friction block I also has a through hole. The T-shaped frame, friction block I, and friction block II are connected by bolts passing through the through hole. The bolts pass through friction block II and are connected to torque nuts, thereby locking the T-shaped frame, friction block I, and friction block II together. Piezoelectric stack actuators are disposed on both sides of the T-shaped frame, with one end of the piezoelectric stack actuator fixed to the T-shaped frame and the other end abutting against friction block II. A vibration damping spring is sleeved between the friction block I and the lower end of the rigid rod. A sliding gap exists between the through hole and the bolt along the axial direction of the rigid rod. The present invention can change the tie rod impedance characteristics, achieve significant vibration isolation effects, and provide high safety.

Description

Technical Field

[0001] The present invention relates to the field of vibration control technology, and in particular to a variable impedance helicopter pull rod vibration reduction device and method. Background Art

[0002] High vibration levels in helicopters can lead to reduced flight performance, reduced fatigue life of structural components due to vibration, and reduced precision of onboard electronic equipment. Furthermore, they can cause decreased central nervous system function and increase physiological stress for passengers. Currently, vibration reduction primarily relies on transfer path vibration control. While this can reduce vibration transmitted from the source to other components, it is indirect vibration reduction and has no effect on suppressing the vibration of the source. Furthermore, it requires the addition of devices to the transfer path, potentially compromising its integrity.

[0003] Technical content

[0004] The purpose of the present invention is to provide a variable impedance helicopter tie rod vibration reduction device and method. The present invention can change the tie rod impedance characteristics, has a significant vibration isolation effect, and is highly safe.

[0005] The technical solution of the present invention is a variable impedance helicopter pull rod vibration reduction device, comprising a rigid rod, with a friction block I disposed on the upper portion of the rigid rod. The inner side of the friction block I abuts against a T-shaped frame, and the outer side abuts against a friction block II. The friction block I is also provided with a through hole. The T-shaped frame, friction block I, and friction block II are connected by bolts passing through the through hole. The bolts pass through the friction block II and are connected to a constant torque nut, thereby locking the T-shaped frame, friction block I, and friction block II together. Piezoelectric stack actuators are disposed on both sides of the T-shaped frame, with one end of the piezoelectric stack actuator fixed to the T-shaped frame and the other end abutting against the friction block II. A vibration reduction spring is sleeved between the friction block I and the lower end of the rigid rod. A sliding gap exists between the through hole and the bolt along the axial direction of the rigid rod.

[0006] In the aforementioned variable impedance helicopter tie rod vibration reduction device, when the excitation frequency is 15-25 Hz and the positive pressure between friction blocks I and II is 2500 N, the force generated by the expansion of the piezoelectric stack actuator is 1500-2400 N.

[0007] In the aforementioned variable impedance helicopter tie rod vibration reduction device, more than one pair of piezoelectric stack actuators are provided on both sides of the T-shaped frame.

[0008] In the aforementioned variable impedance helicopter tie rod vibration reduction device, the model of the piezoelectric stack actuator is Pst150 / 10 / 140.

[0009] In the aforementioned variable impedance helicopter pull rod vibration reduction device, the single-side travel of the bolt sliding along the axial direction of the rigid rod in the through hole does not exceed 1 mm.

[0010] In the aforementioned variable impedance helicopter tie rod vibration reduction device, the expansion stroke of the piezoelectric stack actuator does not exceed 500 μm.

[0011] In the aforementioned variable impedance helicopter pull rod vibration reduction device, the friction block I is made of epoxy resin-based friction material, and its friction coefficient is 0.3-0.4.

[0012] The working method of the aforementioned variable impedance helicopter tie rod vibration reduction device includes a variable impedance mode: applying voltage to the piezoelectric stack actuator 3 to cause it to expand, applying force along the axis of the bolt 7 to the friction block II, reducing the positive pressure of the fixed torque nut on the T-frame 9, the friction block I and the friction block II. Under the action of external excitation, the friction block I and the friction block II and the T-frame 4 slide relative to each other, generating friction impedance to consume the blade root load excitation energy; adjusting the voltage applied by the piezoelectric stack actuator to change the positive pressure of the fixed torque nut, thereby adjusting the friction impedance characteristics.

[0013] The working method of the aforementioned variable impedance helicopter pull rod vibration reduction device also includes a rigid mode. In this mode, the T-frame 4, friction block I and friction block II are fixed by positive pressure, and the blade root load is only transmitted to the automatic tilt device through the rigid rod. At this time, the variable impedance pull rod acts as an ordinary variable pitch pull rod. When the piezoelectric stack actuator is not applied with voltage, the circuit is broken, or the piezoelectric stack actuator fails, the variable impedance pull rod is in the rigid mode.

[0014] Beneficial effects

[0015] Compared to the prior art, the variable-impedance helicopter rod vibration damping device of the present invention can directly act on the rotor system's pitch lever, directly acting on the vibration source. While the rotor is rotating, the pitch lever's impedance characteristics can be altered via an actuator, thereby dissipating the vibration energy generated by the rotor and achieving a vibration reduction effect. While reducing vibration transmitted to the rotor's automatic tilt mechanism, the device effectively increases the vibration isolation frequency bandwidth of the vibration damping device by varying the rod's impedance characteristics, enabling vibration control under varying frequency conditions. The device is suitable for both conventional fixed-speed helicopters and new variable-speed helicopters, and can be used in components such as the main rotor pitch lever and tail rotor pitch lever, thus achieving a wide range of applications.

[0016] The variable impedance helicopter pull rod vibration reduction device of the present invention primarily consists of a rigid rod, a vibration-damping spring, and a friction system. The friction system includes a piezoelectric stack actuator, a T-shaped frame, a friction block, a bolt, and a matching torque-fixed nut. During installation and use, the structure is mounted on the rotor blade root and the automatic tilting mechanism via universal joints above and below the rigid rod (variable impedance pull rod), achieving vibration isolation. Based on vibration isolation design requirements, the variable impedance pull rod vibration reduction device can simultaneously utilize friction damping and spring vibration absorption functions, thus providing a fail-safe mode, high safety, a lightweight structure, significant vibration reduction effects, and adaptability to different vibration isolation frequencies.

[0017] The present invention adopts a piezoelectric stack actuator as the impedance adjustment structure of the helicopter pull rod. Under the premise of having a failure protection mode, the piezoelectric stack actuator is used to adjust the positive pressure of the friction block and the rigid rod according to the excitation frequency of the rotor, thereby changing the impedance characteristics of the pull rod to achieve the purpose of vibration reduction. The structure is simple and the adjustment is flexible.

[0018] The variable impedance helicopter tie rod vibration reduction device of the present invention achieves an ideal vibration reduction effect by adjusting the torque of the fixed torque nut and the voltage of the piezoelectric stack, consuming the excitation energy through impedance at different frequency points or frequency ranges, and absorbing the excitation energy through the vibration reduction spring. At the same time, the piezoelectric stack actuator installed on the T-shaped frame can be expanded or reduced in pairs, which increases the maximum load that the tie rod can bear and broadens the scope of application of the tie rod. Since the present invention has a failure protection mode, compared to the vibration reduction device on the transmission path that will cause greater damage once the vibration reduction device fails, the present invention can still be used as an ordinary variable pitch tie rod when the vibration reduction device fails due to an emergency situation, without affecting the normal flight of the helicopter, effectively avoiding greater damage to the helicopter due to the failure of the variable impedance mode, and has high safety.

[0019] Specifically, the load transmitted downward using the traditional pull rod is 1 relative to the excitation load, while the load transmitted downward using the pull rod of the present invention is about 0.5 relative to the excitation load, with a vibration reduction effect of about 50%. Details are shown in Table 1 below.

[0020] Table 1 Vibration reduction effect at different excitation frequencies

[0021]

[0022]

[0023] It can be seen from the above table that the present invention achieves good vibration isolation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Structural diagram of variable impedance helicopter pull rod vibration reduction device;

[0025] Figure 2 Schematic diagram of the variable impedance helicopter pull rod vibration reduction device.

[0026] Figure numerals: 1-rigid rod; 2-damping spring; 3-piezoelectric stack actuator; 4-T-shaped frame; 5-friction block; 6-constant torque nut; 7-bolt; 8-friction block I; 9-through hole. DETAILED DESCRIPTION

[0027] Example 1. A variable impedance pull rod vibration reduction device installed between the propeller root and the automatic tilting device, comprising: Figure 1 and 2As shown, it is mainly composed of a rigid rod 1, a damping spring 2, and a friction system; the friction system includes a pair of piezoelectric stack actuators 3, a T-shaped frame 4, a friction block I8, a friction block II5, a bolt 7 and a matching constant torque nut 6.

[0028] The assembly relationship of the variable-impedance helicopter tie rod vibration damping device is as follows: the lower end of the vibration damping spring 2 is fixed to the rigid rod 1, and the upper end of the vibration damping spring 2 is fixed to the T-shaped frame 4. At this time, the T-shaped frame 4 is fixed to the rigid rod 1 through the vibration damping spring 2. One end of the piezoelectric stack actuator 3 is fixed to the edge of the T-shaped frame 4, and the other end is free to rest against the friction block II5. The bolt 7 passes through the through hole 9 of the T-shaped frame 4, the friction block I8, and the friction block II5 in sequence. The above three are tightened by a constant torque nut with positive pressure. At this time, the T-shaped frame 4 is fixed to the rigid rod through the friction block I8. Specifically, the structural relationship of the variable-impedance helicopter tie rod vibration damping device is as follows:

[0029] It includes a rigid rod 1, a friction block I8 is provided on the upper part of the rigid rod 1, the inner side of the friction block I8 abuts against the T-shaped frame 4, and the outer side abuts against the friction block II5, and a through hole 9 is also provided on the friction block I8; the T-shaped frame 4, the friction block I8 and the friction block II5 are connected by a bolt 7 passing through the through hole 9, and the bolt 7 passes through the friction block II5 and is connected with the fixed torque nut 6, thereby locking the T-shaped frame 4, the friction block I8 and the friction block II5 together; piezoelectric stack actuators 3 are provided on both sides of the T-shaped frame 4, one end of the piezoelectric stack actuator 3 is fixed on the T-shaped frame 4, and the other end abuts against the friction block II5; a damping spring 2 is sleeved between the friction block I8 and the lower end of the rigid rod 1; there is a sliding gap between the through hole 9 and the bolt 7 along the axial direction of the rigid rod 1.

[0030] When the excitation frequency is 15-25 Hz and the positive pressure between the friction blocks I and II is 2500 N, the force generated by the expansion of the piezoelectric stack actuator 3 is 1500-2400 N.

[0031] At least one pair of piezoelectric stack actuators 3 are provided on both sides of the aforementioned T-shaped frame 4 .

[0032] The model of the aforementioned piezoelectric stack actuator 3 is Pst150 / 10 / 140.

[0033] The single-side travel of the aforementioned bolt 7 sliding axially along the rigid rod 1 in the through hole 9 does not exceed 1 mm.

[0034] The expansion stroke of the aforementioned piezoelectric stack actuator 3 does not exceed 500 μm.

[0035] The aforementioned friction block I8 is made of epoxy resin-based friction material, and its friction coefficient is 0.3-0.4.

[0036] The variable impedance helicopter pull rod vibration reduction device has two working modes:

[0037] Rigid mode, also known as fail-safe mode, holds the T-frame 4, friction blocks I8, and II5 in place through positive pressure. The propeller root load is transmitted to the automatic tilt mechanism solely through rigid rod 1. The entire variable impedance rod functions like a conventional variable pitch rod. This rigid mode occurs when the piezoelectric stack actuator is de-energized, the circuit is open, or the piezoelectric stack actuator fails.

[0038] In the variable impedance mode, when voltage is applied to the piezoelectric stack actuator 3, it expands, exerting a force along the bolt axis on friction block II5, reducing the positive pressure exerted by the torque nut on the T-frame 4, friction block I8, and friction block II5. Under external excitation, friction block I8 slides relative to friction block II5 and the T-frame 4, generating friction impedance that dissipates the excitation energy of the blade root load. Adjusting the applied voltage of the piezoelectric stack actuator changes the positive pressure of the torque nut, thereby adjusting the friction impedance characteristics. This mode is called the variable impedance mode. In this mode, part of the excitation energy of the blade root load is dissipated by the friction impedance, part is converted into the elastic potential energy of the damping spring, and only a small portion is transmitted through the lower end of the rigid rod 1 to the automatic tilt mechanism, achieving a vibration reduction effect. By adjusting the applied voltage of the piezoelectric stack actuator, the positive pressure of the torque nut can be changed, thereby adjusting the friction impedance characteristics, changing the ratio of the excitation energy dissipated by the impedance to the elastic potential energy converted into the damping spring, and achieving a better vibration reduction effect. When unexpected situations such as power supply circuit interruption or piezoelectric stack failure occur, the force exerted by the piezoelectric stack actuator on the friction block disappears, and the T-frame 4, friction block I8 and friction block II5 remain relatively stationary under the tightening force of the fixed torque nut. The variable impedance pull rod degenerates into an ordinary variable pitch pull rod, effectively avoiding greater damage to the helicopter due to pull rod failure.

Claims

1. A variable impedance helicopter pull rod vibration reduction device, characterized in that: The invention comprises a rigid rod (1), a friction block I (8) is provided on the upper part of the rigid rod (1), the inner side of the friction block I (8) abuts against the T-shaped frame (4), and the outer side abuts against the friction block II (5), and a through hole (9) is further provided on the friction block I (8); the T-shaped frame (4), the friction block I (8) and the friction block II (5) are connected by a bolt (7) passing through the through hole (9), and the bolt (7) passes through the friction block II (5) and is connected to the fixed torque nut (6), thereby The frame (4), the friction block I (8) and the friction block II (5) are locked together; piezoelectric stack actuators (3) are provided on both sides of the T-shaped frame (4), one end of the piezoelectric stack actuator (3) is fixed on the T-shaped frame (4), and the other end is against the friction block II (5); a damping spring (2) is sleeved between the friction block I (8) and the lower end of the rigid rod (1); a sliding gap exists between the through hole (9) and the bolt (7) along the axial direction of the rigid rod (1).

2. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: When the excitation frequency is 15-25 Hz and the positive pressure between the friction blocks I and II is 2500 N, the force generated by the expansion of the piezoelectric stack actuator (3) is 1500-2400 N.

3. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: More than one pair of piezoelectric stack actuators (3) are provided on both sides of the T-shaped frame (4).

4. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: The model of the piezoelectric stack actuator (3) is Pst150 / 10 / 140.

5. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: The single-side travel of the bolt (7) sliding axially along the rigid rod (1) in the through hole (9) does not exceed 1 mm.

6. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: The expansion stroke of the piezoelectric stack actuator (3) does not exceed 500 μm.

7. The variable impedance helicopter tie rod vibration reduction device according to claim 1, characterized in that: The friction block I (8) is made of epoxy resin-based friction material, and its friction coefficient is 0.3-0.

4.

8. A method for operating the variable impedance helicopter tie rod vibration reduction device according to any one of claims 1 to 7, characterized in that: The invention comprises a variable impedance mode: applying voltage to the piezoelectric stack actuator (3) to cause it to expand, applying force along the axis direction of the bolt (7) to the friction block II (5), reducing the positive pressure of the fixed torque nut on the T-shaped frame (4), the friction block I (8) and the friction block II (5), and under the action of external excitation, the friction block I (8) and the friction block II (5) and the T-shaped frame (4) slide relative to each other, generating friction impedance to consume the excitation energy of the blade root load; The voltage applied by the piezoelectric stack actuator is adjusted to change the positive pressure of the constant torque nut, thereby adjusting the friction impedance characteristics.

9. The operating method of the variable impedance helicopter tie rod vibration reduction device according to claim 8, characterized in that: It also includes a rigid mode, in which the T-frame (4), friction block I (8) and friction block II (5) are fixed by positive pressure, and the root load of the propeller is transmitted to the automatic tilt device only through the rigid rod. At this time, the variable impedance pull rod acts as an ordinary variable pitch pull rod. When the piezoelectric stack actuator is not applied with voltage, the circuit is broken or the piezoelectric stack actuator fails, the variable impedance pull rod is in the rigid mode.

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