Damping-adjustable composite helicopter vibration isolation system and control method thereof

Abstract

The invention discloses a damping-adjustable composite helicopter vibration isolation system and a control method thereof, and belongs to the technical field of vibration control. The system comprises a supporting frame, a Halbach permanent magnet array negative stiffness unit, a positive stiffness structural unit, a magnetorheological damper and an electric control module. The Halbach permanent magnet array provides a negative stiffness effect and reduces the inherent frequency of the system; the positive stiffness unit adopts a cylindrical spiral spring to provide basic supporting stiffness; the magnetorheological damper realizes stepless adjustment of damping force by adjusting excitation current; the electric control module comprises a speed sensor, a power amplifier and a controller, monitors the vibration state of the seat in real time and dynamically adjusts the damping force of the magnetorheological damper; seat vibration signals are collected, expected control force is calculated, partial active control force compensation is provided in combination with a Halbach permanent magnet array, and the vibration isolation effect is optimized; the low-frequency vibration isolation performance is improved, the vibration isolation frequency band is widened, different working conditions can still be adapted under low energy consumption, and the system performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration control, and particularly relates to a compound helicopter vibration isolation system with adjustable damping and its control method. Background Art

[0002] During flight, the helicopter pilot's seat is affected by the periodic excitation force of the rotor blades, generating obvious low-frequency vibrations. According to the ISO 2631 standard, the human body is most sensitive to vertical vibrations in the range of 4 - 8 Hz, and the fundamental frequency (Ω) of the helicopter rotor and its harmonic frequencies (nΩ, 2nΩ, 3nΩ...) significantly excite the seat system. Among them, the fundamental frequency is usually in the range of 4 - 5 Hz, which is close to the natural frequency of the helicopter seat system and is extremely likely to cause resonance. The vibration of the helicopter will make the pilot less concentrated and reduce the reaction ability to emergencies, which will lead to wrong judgments by the pilot during mission execution, thus triggering serious flight accidents. Therefore, improving the vibration isolation performance of the helicopter seat, especially the suppression of low-frequency vibrations, has become an urgent technical problem to be solved.

[0003] Currently, the vibration isolation systems of helicopter seats mainly use linear spring-damper passive structures and semi-active devices such as magnetorheological dampers for vibration isolation, but these solutions still have many deficiencies. The traditional linear spring system is limited by the space displacement of the helicopter cockpit, with a relatively high natural frequency (above 4 Hz), resulting in limited vibration isolation performance and difficulty in effectively reducing the transmission of low-frequency vibrations. Although reducing the spring stiffness can improve the low-frequency vibration isolation ability, too low stiffness will increase the static displacement of the pilot's seat, affecting the seat height adjustment and the stability of the line of sight, and may even interfere with surrounding components. In addition, although the magnetorheological damper can provide adjustable damping, it cannot fundamentally reduce the natural frequency of the system, and its damping characteristics are difficult to achieve the optimal match with the support stiffness of the helicopter seat, resulting in limited vibration reduction effect.

[0004] In recent years, the negative stiffness vibration isolation technology has gradually attracted attention. This technology can reduce the equivalent dynamic stiffness of the system in a passive state, thereby reducing the natural frequency without reducing the static stiffness. However, the existing negative stiffness vibration isolators still have the following problems:

[0005] (1) The arrangement method of traditional negative stiffness elements (such as the arrangement of ordinary permanent magnets) generates limited negative stiffness under the same volume, making it difficult to fully exert its vibration isolation advantages;

[0006] (2) It is difficult for the existing negative stiffness vibration isolators to be well matched with the helicopter seat, and it is difficult to meet the requirements of high load capacity and low natural frequency at the same time;

[0007] (3) The design of the negative stiffness vibration isolator is complex, with high manufacturing costs, and its stability under dynamic conditions still needs to be optimized.

[0008] In summary, the existing helicopter seat vibration isolation systems are difficult to achieve ideal vibration suppression effects in the low-frequency range. There is an urgent need for a new vibration isolation technology solution with high environmental adaptability, high load-bearing capacity, and excellent low-frequency vibration isolation performance to meet the comfort requirements of helicopter pilots. Summary of the Invention

[0009] The purpose of the present invention is to overcome the defects in the above-mentioned background technology. The present invention discloses a damping-adjustable composite helicopter vibration isolation system and its control method, aiming to solve the problem that the existing helicopter seat vibration isolation system has poor vibration suppression effects in the human-sensitive frequency range; through the combination of the Halbach permanent magnet array negative stiffness unit and the magnetorheological damper, high-efficiency vibration isolation ability is provided in the low-frequency band, and the dynamic response performance of the system is further optimized through adjustable damping control.

[0010] The present invention adopts the following technical solutions to solve the above technical problems:

[0011] A damping-adjustable composite helicopter vibration isolation system, characterized in that the system includes:

[0012] A Halbach permanent magnet array negative stiffness unit, where the negative stiffness unit is formed by splicing radially magnetized magnetic tiles and axially magnetized magnetic tiles into an annular array. The inner and outer magnets are coaxially nested through linear bearings, and the axial movement accuracy is ensured through the outer magnet outer guide sleeve and the inner magnet outer guide sleeve to provide non-linear negative stiffness characteristics;

[0013] A positive stiffness structure unit, where the positive stiffness structure unit includes a cylindrical helical spring. The cylindrical helical spring is pre-compressed and installed inside the spring guide sleeve to provide basic support stiffness;

[0014] A magnetorheological damper, where the magnetorheological damper includes a piston rod, an excitation coil, and a cylinder block. The excitation coil is used to adjust the input current to change the magnetic field strength, thereby dynamically adjusting the damping characteristics;

[0015] An electronic control module, where the electronic control module includes a speed sensor, a power amplifier, and a controller. The controller is used to monitor the vibration state of the seat in real time and adjust the damping parameters of the magnetorheological damper based on the damping optimization strategy to optimize the vibration isolation performance.

[0016] Furthermore, the outer magnet and the inner magnet of the Halbach permanent magnet array negative stiffness unit are coaxially nested through linear bearings to ensure the free sliding of the magnet assembly in the axial direction, and the lateral displacement is restricted through the guide sleeve to improve the movement accuracy.

[0017] Further, the upper end of the cylindrical helical spring of the positive stiffness structural unit is connected to the adjustment boss, and the lower end is fixed on the support frame through the lower support end cover to provide stable support stiffness.

[0018] Further, the piston of the magnetorheological damper is arranged inside the damper cylinder body, forming two independent chambers in the inner cavity of the cylinder body. The electromagnetic coil is wound around the outer wall of the piston. When energized, a magnetic field is generated around the piston to change the rheological characteristics of the magnetorheological fluid, thereby adjusting the damping force.

[0019] Further, the speed sensor of the electronic control module is installed on the seat structure to collect the seat vibration speed signal. The controller includes a system controller and a damper controller, which are respectively used to calculate the desired control force and adjust the input current of the magnetorheological damper. The power amplifier is used to amplify the control signal and drive the excitation coil of the magnetorheological damper.

[0020] Further, the Halbach permanent magnet array negative stiffness unit and the magnetorheological damper act together to reduce the natural frequency of the system, effectively suppress vibration in the human sensitive frequency range, and improve the low-frequency vibration isolation ability of the seat.

[0021] Further, the electronic control module calculates the damping optimization strategy based on the real-time vibration signal and determines the desired damping force through the force limiter to optimize the dynamic response performance of the system.

[0022] Further, the magnet arrangement angle, magnet thickness, and remanence characteristics of the Halbach permanent magnet array negative stiffness unit can be adjusted to meet the stiffness requirements of different application scenarios.

[0023] Further, the magnetorheological damper can operate as a passive vibration isolator under zero current to ensure efficient vibration suppression under low power consumption conditions.

[0024] A control method for a damping-adjustable composite helicopter vibration isolation system, the control method specifically includes the following steps:

[0025] Step S1: Real-time collect the seat vibration signal through the speed sensor and transmit it to the controller; the system controller calculates the desired control force based on the seat dynamic response and determines the desired damping force through the force limiter. Further, the force limiter equation of the magnetorheological damper is as follows:

[0026]

[0027] Step S2: According to the desired damping force and the helicopter seat response, the inverse model of the magnetorheological damper calculates the desired control current and inputs it to the power amplifier; the power amplifier outputs the current to the electromagnetic coil, thereby adjusting the magnetic field strength of the magnetorheological fluid to achieve real-time regulation of the damping force; finally, the magnetorheological damper and the negative stiffness unit work together to effectively attenuate the helicopter seat vibration.

[0028] Compared with the prior art, the present invention adopts the above technical solutions and has the following beneficial effects:

[0029] (1) Through the optimized arrangement of the Halbach permanent magnet array, the negative stiffness unit provides a stronger negative stiffness effect under the same volume, significantly reducing the natural frequency of the system, thereby improving the low-frequency vibration isolation ability and enhancing the stability and comfort of the seat.

[0030] (2) By adjusting the magnet arrangement angle, magnet thickness and remanence characteristics of the Halbach permanent magnet array, the negative stiffness characteristics can be flexibly adjusted; at the same time, the magnetorheological damper can dynamically adjust the damping parameters according to the real-time vibration signal, enabling the system to adapt to different working conditions and improving the adaptability and control accuracy of the vibration isolation system.

[0031] (3) The negative stiffness unit and the magnetorheological damper work together, enabling the seat vibration isolation system to effectively suppress vibration transmission within the frequency range of the human sensitive area (4 - 8 Hz), dynamically optimizing the vibration isolation effect according to different flight conditions, reducing the vibration transmission rate, improving the vibration isolation effect of the seat, and enhancing the riding comfort.

[0032] (4) The negative stiffness unit can generate driving force by itself, improving the vibration damping performance while reducing the system energy consumption; in addition, the magnetorheological damper can work as a passive vibration isolator in the zero-current state, ensuring that the system can still achieve efficient vibration suppression under low-power conditions.

[0033] (5) The negative stiffness unit adopting the Halbach permanent magnet array has a compact structure, occupies less space than the traditional negative stiffness structure, and is convenient to be integrated into the existing seat vibration isolation system. This vibration isolation system can be directly applied to high-performance vibration control scenarios such as aerospace, rail transit and special vehicles, improving the overall vibration damping effect and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the overall structural schematic diagram of the damping-adjustable composite helicopter vibration isolation system of the present invention;

[0035] Figure 2 is the top view sectional view at the permanent magnet array structure of the present invention;

[0036] Figure 3 is the structural schematic diagram of the Halbach permanent magnet array of the present invention;

[0037] Figure 4 are the characteristic curves of magnetic force and magnetic stiffness under axial magnetization arrangement and Halbach arrangement;

[0038] Figure 5 is the working flow chart of a damping-adjustable composite helicopter vibration isolation system;

[0039] Figure 6 is the schematic diagram of the seat response characteristics under different control strategies in the random vibration environment of a helicopter.

[0040] In the figure: 1 - upper base plate, 2 - central guiding shaft, 3 - axial positioning notch, 4 - linear bearing, 5 - upper fixing cover, 6 - upper end plate of outer magnet, 7 - outer guiding sleeve of outer magnet, 8 - outer magnet, 9 - inner guiding sleeve of outer magnet, 10 - lower end plate of outer magnet, 11 - inner magnet limiting ring, 12 - inner magnet, 13 - inner guiding sleeve of inner magnet, 14 - lower end plate of inner magnet, 15 - locking nut, 16 - adjusting boss, 17 - cylindrical helical spring, 18 - threaded section of central shaft, 19 - spring guiding sleeve, 20 - spring guiding block, 21 - lower supporting end cover, 22 - lower base plate, 23 - upper piston rod, 24 - upper sealing end cover, 25 - damper cylinder body, 26 - damper piston, 27 - damper electromagnetic coil, 28 - lower piston rod, 29 - lower sealing end cover, 30 - connecting sleeve, 31 - first bolt, 32 - second bolt, 33 - third bolt, 34 - fourth bolt, 35 - outer permanent magnet positioning boss, 36 - inner permanent magnet positioning boss. Detailed implementation manners

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners. It should be understood that the following embodiments are only used to illustrate a part of the present invention, rather than all embodiments. Equivalent replacements or adjustments made by those of ordinary skill in the art without creative efforts according to the content described in the present invention all fall within the protection scope of the present invention.

[0042] As Figure 1 shown, the present invention provides a damping-adjustable composite helicopter vibration isolation system, and the vibration isolation system includes: a support frame, a high-static low-dynamic nonlinear spring, a magnetorheological damper, and an electronic control module connected to the magnetorheological damper.

[0043] The support frame includes an upper base plate (1) and a lower base plate (22), which are made of 304 stainless steel. Among them: the upper base plate (1) is used to carry the load and is provided with mounting holes for connecting to the high-static low-dynamic nonlinear spring and the magnetorheological damper through bolts; the lower base plate (22) is used to transmit vibration and is provided with mounting holes for installing vibration isolation components to ensure the stability and fixity of the system.

[0044] The high-static and low-dynamic non-linear spring includes a Halbach permanent magnet array negative stiffness unit and a positive stiffness structure unit, where: the Halbach permanent magnet array negative stiffness unit includes an outer magnet (8), an inner magnet (12), an outer magnet outer guiding sleeve (7), an outer magnet inner guiding sleeve (9), an outer permanent magnet positioning boss (35), an inner magnet guiding sleeve (13), an inner permanent magnet positioning boss (36), an outer magnet upper end plate (6), an outer magnet lower end plate (10), an inner magnet limiting ring (11), an inner magnet lower end plate (14), and a linear bearing (4); the positive stiffness structure unit includes a cylindrical helical spring (17), a spring guiding sleeve (19), a spring guiding block (20), an adjusting boss (16), a central guiding shaft (2), a central shaft threaded section (18), a locking nut (15), and a lower supporting end cover (21).

[0045] Further, the outer magnet (8) and the inner magnet (12) are coaxially nested through the linear bearing (4) to ensure the free sliding of the magnet assembly in the axial direction and guarantee the motion accuracy. As Figure 2 shown, the outer magnet is restricted from lateral displacement by the outer magnet outer guiding sleeve (7) and the outer magnet inner guiding sleeve (9); the inner magnet is restricted from lateral displacement by the inner magnet guiding sleeve (13) and the inner magnet limiting ring (11). As Figure 3 shown, the Halbach permanent magnet array negative stiffness unit is formed by splicing radially magnetized magnetic tiles and axially magnetized magnetic tiles into an annular array. Each magnetic tile is made of neodymium iron boron (NdFeB) material, and the overall magnet structure exhibits an alternating magnetization characteristic to enhance the stability and intensity of the magnetic field. The negative stiffness unit realizes the negative stiffness effect by using non-contact electromagnetic force, and has the advantages of no wear, no fatigue, and compact structure compared with mechanical negative stiffness mechanisms. As Figure 4 shown, it can be seen from the finite element simulation that the negative stiffness effect of this Halbach array negative stiffness mechanism is nearly twice that of the traditional repulsive negative stiffness structure.

[0046] The positive stiffness unit described above includes a cylindrical helical spring (17). This spring is installed inside the spring guiding sleeve (19) and is limited by the spring guiding block (20). The upper end of the cylindrical helical spring (17) is connected to the adjusting boss (16), and the lower end is fixed on the supporting frame through the lower supporting end cover (21) to provide the necessary supporting stiffness.

[0047] The magnetorheological damper adopts a shear valve type double-rod structure, and includes a damper piston (26), an upper piston rod (23), a lower piston rod (28), a damper cylinder block (25), a damper electromagnetic coil (27), an upper sealing end cover (24), a lower sealing end cover (29), and a connecting sleeve (30). Among them, the upper piston rod (23) and the lower piston rod (28) are connected to the damper piston (26), and the damper piston (26) is arranged inside the damper cylinder block (25) and divides the inner cavity of the damper cylinder block (25) into two independent chambers. When the damper piston (26) reciprocates relative to the damper cylinder block (25), the magnetorheological fluid exchanges and flows between the two chambers through the annular gap between the damper cylinder block (25) and the damper piston (26). When the magnetorheological fluid flows from the high-pressure chamber to the low-pressure chamber through the damping gap due to the pressure effect, the damping gap shears the "magnetic chain" formed by the magnetorheological fluid due to the magnetic field effect, generating a damping force. By passing currents of different magnitudes through the damper electromagnetic coil (27), the shear yield stress of the magnetorheological fluid at the annular gap is different, thereby achieving the purpose of controlling the magnitude of the damping force.

[0048] Further, as Figure 5 shown, the electronic control module includes a speed sensor, a power amplifier, and a controller, and is used to monitor the vibration state of the seat in real time and control the magnetorheological damper to optimize the vibration isolation performance. Further, the speed sensor is installed on the seat structure and is used to collect the seat vibration speed signal; the controller includes a system controller and a damper controller, which are respectively used to calculate the desired control force and adjust the control current of the magnetorheological damper; the power amplifier is used to amplify the control signal and drive the electromagnetic coil in the magnetorheological damper to dynamically adjust the damping force.

[0049] A control method for a damping adjustable composite helicopter vibration isolation system includes the following steps:

[0050] Step S1: Collect the seat vibration signal in real time through the speed sensor and transmit it to the controller; the system controller calculates the desired control force based on the seat dynamic response and determines the desired damping force through the force limiter. Further, the force limiter equation of the magnetorheological damper is as follows:

[0051]

[0052] Step S2: According to the desired damping force and the helicopter seat response, the inverse model of the magnetorheological damper calculates the desired control current and inputs it to the power amplifier. The power amplifier outputs the current to the electromagnetic coil, thereby adjusting the magnetic field strength of the magnetorheological fluid and realizing the real-time regulation of the damping force. Finally, the magnetorheological damper and the negative stiffness unit cooperate to effectively attenuate the helicopter seat vibration, and the vibration reduction effect is as Figure 6 shown.

[0053] In another embodiment, an aluminum alloy support frame can be adopted to reduce the system weight while ensuring the structural strength. In addition, the magnitude of the negative stiffness can be optimized by adjusting the magnet angle, magnet thickness, and remanence characteristics of the negative stiffness unit to meet the requirements of different application scenarios.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite helicopter vibration isolation system with adjustable damping, characterized in that, The system includes: A Halbach permanent magnet array negative stiffness unit, where the negative stiffness unit is formed by splicing radially magnetized magnetic tiles and axially magnetized magnetic tiles into an annular array. The inner and outer magnets are coaxially nested through linear bearings, and the axial movement accuracy is ensured through the outer magnet outer guiding sleeve and the inner magnet outer guiding sleeve to provide a non-linear negative stiffness characteristic; A positive stiffness structure unit, where the positive stiffness structure unit includes a cylindrical helical spring. The cylindrical helical spring is pre-compressed and installed inside the spring guiding sleeve to provide a basic support stiffness; A magnetorheological damper, where the magnetorheological damper includes a piston rod, an excitation coil, and a cylinder block. The excitation coil is used to adjust the input current to change the magnetic field strength, thereby dynamically adjusting the damping characteristic; An electronic control module, where the electronic control module includes a velocity sensor, a power amplifier, and a controller. The controller is used to monitor the seat vibration state in real time and adjust the damping parameters of the magnetorheological damper based on a damping optimization strategy to optimize the vibration isolation performance.

2. The damped adjustable composite helicopter vibration isolation system according to claim 1, wherein The outer and inner magnets of the Halbach permanent magnet array negative stiffness unit are coaxially nested through linear bearings to ensure the free sliding of the magnet assembly in the axial direction, and the lateral displacement is restricted through the guiding sleeve to improve the movement accuracy.

3. A damping-adjustable composite helicopter vibration isolation system according to claim 1, characterized in that, The upper end of the cylindrical helical spring of the positive stiffness structure unit is connected to the adjustment boss, and the lower end is fixed on the support frame through the lower support end cover to provide a stable support stiffness.

4. A damping-adjustable composite helicopter vibration isolation system according to claim 1, characterized in that, The piston of the magnetorheological damper is arranged inside the damper cylinder block, forming two independent chambers in the inner cavity of the cylinder. The electromagnetic coil is wound around the outer wall of the piston. When energized, a magnetic field is generated around the piston to change the rheological characteristics of the magnetorheological fluid, thereby adjusting the damping force.

5. A damping-adjustable composite helicopter vibration isolation system according to claim 1, characterized in that, The velocity sensor of the electronic control module is installed on the seat structure to collect the seat vibration velocity signal. The controller includes a system controller and a damper controller, which are respectively used to calculate the desired control force and adjust the input current of the magnetorheological damper. The power amplifier is used to amplify the control signal and drive the excitation coil of the magnetorheological damper.

6. A damping adjustable composite helicopter vibration isolation system according to claim 1, wherein, The Halbach permanent magnet array negative stiffness unit and the magnetorheological damper work together to reduce the natural frequency of the system and effectively suppress vibration within the human sensitive frequency range, improving the low-frequency vibration isolation ability of the seat.

7. A damping adjustable composite helicopter vibration isolation system according to claim 1, characterized in that, The electronic control module calculates a damping optimization strategy based on the real-time vibration signal and determines the desired damping force through a force limiter to optimize the dynamic response performance of the system.

8. A damped adjustable composite helicopter vibration isolation system according to claim 1, characterized in that The magnet arrangement angle, magnet thickness, and remanence characteristics of the Halbach permanent magnet array negative stiffness unit are adjustable to adapt to the stiffness requirements of different application scenarios.

9. A damping-adjustable composite helicopter vibration isolation system according to claim 1, characterized in that, The magnetorheological damper can operate as a passive vibration isolator under zero current to ensure efficient vibration suppression under low power consumption conditions.

10. A control method for a damping adjustable composite helicopter vibration isolation system, where the control method is applied to a damping adjustable composite helicopter vibration isolation system as described in any one of claims 1-9, and specifically includes the following steps: Step S1: The seat vibration signal is collected in real time by a speed sensor and transmitted to the controller. Based on the dynamic response of the seat, the system controller calculates the desired control force and determines the desired damping force through a force limiter. Further, the force limiter equation of the magnetorheological damper is as follows: Step S2: According to the desired damping force and the helicopter seat response, the inverse model of the magnetorheological damper calculates the desired control current and inputs it to the power amplifier. The power amplifier outputs current to the electromagnetic coil, thereby adjusting the magnetic field strength of the magnetorheological fluid to achieve real-time regulation of the damping force. Finally, the magnetorheological damper and the negative stiffness unit work together to effectively attenuate the helicopter seat vibration.

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