A combined stiffness-adjustable liquid spring vibration isolator and a stiffness adjusting method thereof

Abstract

The application provides a combined stiffness-adjustable liquid spring vibration isolator and a stiffness adjusting method thereof, and relates to the technical field of liquid spring vibration isolators.The application combines a rubber and an air spring to provide required elastic stiffness.The application collects and processes signals from an inner cylinder displacement sensor, an outer cylinder displacement sensor and a pressure sensor by using an electronic controller (ECU controller), compares and analyzes the signals with preset target displacement difference signals of the inner and outer cylinders, dynamically adjusts a duty cycle of an output pulse width modulation signal based on a comparison result, controls opening and closing of a solenoid valve in an air spring assembly, adjusts stiffness of the air spring, and compensates stiffness reduction caused by aging of a rubber material.The control scheme effectively maintains stability of a vibration isolation frequency of the liquid spring vibration isolator, and ensures performance reliability of a vibration isolation system in a long-term operation process.

Description

Technical Field

[0001] This invention relates to the field of liquid spring vibration isolators, specifically to a combined stiffness-adjustable liquid spring vibration isolator and its stiffness adjustment method. Background Technology

[0002] In helicopter dynamics research, inherent vibration excitation is identified as a significant factor affecting aircraft performance and structural integrity. In particular, the rotor system, as a key vibration source in helicopters, experiences alternating aerodynamic loads that generate hub excitation forces. These excitation forces possess specific frequency characteristics and influence the fuselage structure through the transmission path connecting the main gearbox and the fuselage. Liquid-jet isolators, as a highly efficient and compact primary vibration damping device for helicopters, feature high static stiffness and low dynamic stiffness near the isolation frequency, and are widely used in new helicopters abroad.

[0003] The liquid-elastic vibration isolator employs the principle of dynamic anti-resonance. Its working principle involves the shearing action of the inner and outer cylinders on the rubber layer, providing the necessary elastic stiffness. Simultaneously, the reciprocating motion of the liquid in the inertial channel causes pressure changes in the upper and lower liquid chambers, effectively counteracting external excitation forces. At the designed target isolation frequency, the system achieves significant vibration isolation. However, during continuous operation of the liquid-elastic vibration isolator, the rubber layer gradually heats up due to prolonged shear force. Furthermore, the time-dependent nature of the rubber material leads to creep behavior. Under the combined effect of these factors, the stiffness of the rubber layer degrades, resulting in a decrease in the isolator's isolation frequency and an inability to accurately isolate all vibrations transmitted to the fuselage from the rotor hub and main gearbox. Therefore, the effectiveness of the liquid-elastic vibration isolator in isolating helicopter rotor hub vibrations is weakened, failing to meet the stringent vibration reduction requirements of helicopters. Summary of the Invention

[0004] To address the problem mentioned in the background art where the stiffness of the rubber layer degrades, leading to a decrease in the isolation frequency of the isolator and an inability to accurately isolate all vibrations transmitted from the propeller hub and main reducer to the fuselage, this invention proposes a combined, stiffness-adjustable hydraulic spring isolator and its stiffness adjustment method. This scheme uses a base to fix multiple hydraulic spring isolators to the main damping support rod. Furthermore, a composite elastic system combining rubber and air springs is employed to provide the required elastic stiffness. By utilizing the reciprocating motion of the liquid in the inertial channel, pressure fluctuations are induced in the upper and lower liquid chambers, thereby counteracting external excitation forces and ensuring efficient vibration isolation performance within a predetermined isolation frequency range, thus achieving the goal of isolating the main reducer from transmitting vibrations to the fuselage.

[0005] Furthermore, this invention introduces a PID control system to adjust the duty cycle of the pulse width modulation signal output by the electronic controller (ECU), thereby controlling the opening and closing state of the solenoid valve and adjusting the stiffness of the air spring to compensate for the decrease in stiffness caused by the aging of the rubber material. This control method effectively maintains the stability of the vibration isolation frequency of the liquid spring isolator and ensures the performance reliability of the vibration isolation system during long-term operation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a combined stiffness adjustable liquid spring vibration isolator, comprising: a liquid spring vibration isolator body and an air spring assembly, wherein the liquid spring vibration isolator body includes an inner cylinder assembly, a rubber assembly and an outer cylinder assembly;

[0008] The outer cylinder assembly includes an upper outer cylinder assembly and a lower outer cylinder assembly. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder assembly through a rubber vulcanization process. The lower end of the inner cylinder assembly is connected to the lower outer cylinder assembly and extends to the bottom of the lower outer cylinder assembly.

[0009] The inner cylinder assembly has an inertial channel for sealing liquid at its center, and the inertial channel is equipped with an upper liquid replenishment chamber and a lower liquid replenishment chamber.

[0010] The air spring assembly is disposed inside the lower outer cylinder assembly and distributed on the lower outer periphery of the inner cylinder assembly. The air spring assembly has an air chamber. The air chamber is filled and released by a semi-active control system to achieve pressure regulation within the air chamber, thereby continuously controlling the stiffness of the air spring assembly and thus realizing continuous dynamic adjustment of the vibration isolator stiffness.

[0011] As a further illustration of the present invention, the air spring assembly includes a solenoid valve and an air bladder;

[0012] The solenoid valve is mounted on the inflation / deflation port of the airbag, and the inflation / deflation port is connected to an air storage tank through an air guide tube, so that the solenoid valve can control the inflation and deflation of the airbag.

[0013] As a further explanation of the present invention, the semi-active control system includes an electronic controller, an inner cylinder displacement sensor, an outer cylinder displacement sensor, and a pressure sensor.

[0014] The pressure sensor is used to collect pressure change signals in the air chamber in real time, the inner cylinder displacement sensor is used to collect displacement signals of the inner cylinder assembly in real time, and the outer cylinder displacement sensor is used to collect displacement signals of the outer cylinder assembly in real time.

[0015] The electronic controller is used to collect and process signals from the inner cylinder displacement sensor, the outer cylinder displacement sensor and the pressure sensor, and compare and analyze them with the preset target displacement difference signal between the inner and outer cylinders. Then, based on the comparison result, the duty cycle of the output pulse width modulation signal is dynamically adjusted to control the opening and closing of the solenoid valve in the air spring assembly, thereby realizing continuous dynamic adjustment of the stiffness of the vibration isolator.

[0016] As a further explanation of the present invention, the inner cylinder assembly includes an inner cylinder and a first flange disposed on the outer periphery of the inner cylinder. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder through a rubber vulcanization process. The upper end of the lower outer cylinder assembly is fixedly connected to the first flange, thereby forming a receiving cavity for holding the air spring assembly.

[0017] As a further explanation of the present invention, the pressure sensor is disposed on the airbag, the inner cylinder displacement sensor is located at the lower part of the first flange of the inner cylinder, and the outer cylinder displacement sensor is located at the lower end of the lower outer cylinder assembly.

[0018] As a further explanation of the present invention, the waist of the airbag is provided with a rubber waist ring, the upper end of the airbag is connected to the first mounting groove at the lower part of the first flange through an elastic coupling, and the lower end of the airbag is connected to the second mounting groove in the lower outer cylinder assembly.

[0019] As a further explanation of the present invention, the upper outer cylinder assembly includes an integrally formed upper outer cylinder cap and an upper outer cylinder, and the lower outer cylinder assembly includes an integrally formed lower outer cylinder cap and a lower outer cylinder, with the upper end of the lower outer cylinder fixedly connected to the first flange.

[0020] The upper end cap and the lower end cap of the outer cylinder are used to connect to the helicopter fuselage and fix it to the helicopter fuselage.

[0021] The outer wall of the inner cylinder assembly is fixedly connected to the base by a clamp, thereby achieving effective coupling between the liquid bullet vibration isolator and the helicopter main gearbox.

[0022] A second aspect of the present invention provides a method for adjusting the stiffness of the above-mentioned combined stiffness adjustable hydraulic isolator, comprising the following steps:

[0023] Determine the target isolation frequency of the combined adjustable stiffness hydraulic isolator.

[0024] The sum of the initial stiffnesses of the air spring assembly and the rubber is calculated based on the target vibration isolation frequency and denoted as the target stiffness of the vibration isolator.

[0025] Based on the target stiffness of the vibration isolator, the target displacement difference between the outer cylinder assembly and the inner cylinder assembly is calculated.

[0026] During the use of the vibration isolator, the real-time displacement difference between the outer cylinder assembly and the inner cylinder assembly is monitored. When the real-time displacement difference is less than the target displacement difference, the air spring assembly is inflated by a semi-active control system until the real-time displacement difference equals the target displacement difference.

[0027] As a further explanation of the present invention, the vibration isolation frequency of the combined stiffness adjustable hydraulic spring isolator is related to the sum of the stiffnesses of the air spring assembly and the rubber as follows:

[0028] ;

[0029] in, This indicates the isolation frequency of the combined adjustable stiffness hydraulic isolator. This indicates the stiffness of the rubber in the vibration isolator. This indicates the stiffness of the air spring assembly. This indicates the mass of the liquid within the inertial channel of the liquid-elastic vibration isolator. This indicates the amplification ratio of the combined hydraulic spring isolator.

[0030] As a further explanation of the present invention, the relationship between the target displacement difference and the sum of the initial stiffness of the air spring assembly and the rubber is as follows:

[0031] ;

[0032] in, For the target displacement difference, This represents the maximum static load on the combined adjustable stiffness hydraulic isolator. and These represent the displacements of the inner cylinder assembly and the outer cylinder assembly when the rubber is not aged. and These represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly, respectively.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] This invention utilizes a PID control strategy and employs an elastic stiffness element composed of a rubber material and an air spring assembly to continuously and in real-time adjust the stiffness of the combined adjustable-stiffness liquid spring vibration isolator. This ensures that the combined liquid spring vibration isolator can maintain the stability of its vibration isolation frequency even under the aging conditions of the rubber material, thereby improving the long-term reliability and effectiveness of the vibration isolation system.

[0035] Other features and advantages of this technical solution will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the technical solution. The objectives and other advantages of this technical solution can be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0036] The technical solution of this invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] The accompanying drawings are provided to further understand the present technical solution and form part of the specification. They are used together with the embodiments of the present technical solution to explain the present technical solution and do not constitute a limitation on the present technical solution.

[0038] Figure 1 This is a schematic diagram of the overall structure of the combined stiffness adjustable hydraulic spring vibration isolator provided by the present invention.

[0039] Figure 2 This is a schematic diagram showing the disassembled composite stiffness adjustable hydraulic spring vibration isolator provided by the present invention.

[0040] Figure 3 This is a front sectional view of the combined stiffness adjustable hydraulic spring vibration isolator provided by the present invention.

[0041] Figure 4 This is a left sectional view of the combined stiffness adjustable hydraulic spring vibration isolator provided by the present invention.

[0042] Figure 5 This is a schematic diagram of the air spring assembly provided by the present invention.

[0043] Figure 6 This is a force diagram of the combined stiffness adjustable hydraulic spring vibration isolator provided by the present invention.

[0044] Figure 7 This is a schematic diagram illustrating the principle of the semi-active control air spring provided by the present invention.

[0045] In the attached diagram:

[0046] 1-Liquid-elastic vibration isolator body; 101-Upper fluid replenishment chamber; 102-Inner cylinder; 103-Inertial channel; 104-First flange; 105-Bolt; 106-Lower fluid replenishment chamber; 107-Outer wall of inner cylinder; 108-First mounting groove; 109-Rubber; 110-Inner cylinder displacement sensor; 111-First mounting hole;

[0047] 2-Air spring assembly; 201-Flexible coupling; 202-Waist ring; 203-Airbag; 204-Solenoid valve; 205-Air chamber; 206-Pressure sensor;

[0048] 3-Outer cylinder; 301-Upper end cap of outer cylinder; 302-Second mounting groove; 303-Second mounting hole; 304-Upper outer cylinder; 305-Lower end cap of outer cylinder; 306-Lower outer cylinder; 307-Third mounting hole; 308-Electronic controller (ECU controller); 309-Outer cylinder displacement sensor; 310-Fourth mounting hole;

[0049] 401 - Gas storage tank; 402 - Gas delivery pipe. Detailed Implementation

[0050] The preferred embodiments of this technical solution are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for illustration and explanation of this technical solution and are not intended to limit this technical solution.

[0051] like Figure 1-5 As shown, the present invention first provides a combined stiffness adjustable liquid spring vibration isolator, including: a liquid spring vibration isolator body 1 and an air spring assembly 2. The liquid spring vibration isolator body 1 includes an inner cylinder assembly, rubber 109 and an outer cylinder assembly 3; the outer cylinder assembly 3 includes an upper outer cylinder assembly and a lower outer cylinder assembly. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder assembly through a rubber 109 vulcanization process. The lower end of the inner cylinder assembly is connected to the lower outer cylinder assembly and extends to the bottom of the lower outer cylinder assembly. An inertial channel 103 for sealing liquid is provided in the center of the inner cylinder assembly. The inertial channel 103 is equipped with an upper liquid replenishment chamber 101 and a lower liquid replenishment chamber 106. The air spring assembly 2 is disposed in the lower outer cylinder assembly and distributed on the lower outer periphery of the inner cylinder assembly. An air chamber 205 is provided in the air spring assembly 2. The air chamber 205 is filled and released by a semi-active control system to realize the pressure regulation in the air chamber 205, thereby continuously controlling the stiffness of the air spring assembly 2, and thus realizing continuous dynamic adjustment of the stiffness of the vibration isolator.

[0052] In one feasible embodiment, the air spring assembly 2 includes a solenoid valve 204 and an air bladder 203. The solenoid valve 204 is mounted on the inflation / deflation port of the air bladder 203, which is connected to an air tank 401 via an air guide pipe 402, enabling the solenoid valve 204 to control the inflation and deflation of the air bladder 203. The air guide pipe 402 is designed to connect the air tank 402 to the solenoid valve 204 of the air spring assembly 2, thereby enabling continuous inflation and deflation of the air spring assembly 2. The solenoid valve 204, connected to the air guide pipe 402, enables the regulation of the air chamber pressure to adapt to different working requirements.

[0053] In one feasible manner, the semi-active control system includes an electronic controller 308, an inner cylinder displacement sensor 110, an outer cylinder displacement sensor 309, and a pressure sensor 206. The pressure sensor 206 is used to acquire pressure change signals in the air chamber 205 in real time, the inner cylinder displacement sensor 110 is used to acquire displacement signals of the inner cylinder assembly in real time, and the outer cylinder displacement sensor 309 is used to acquire displacement signals of the outer cylinder assembly 3 in real time. The electronic controller 308 is used to collect and process signals from the inner cylinder displacement sensor 110, the outer cylinder displacement sensor 309, and the pressure sensor 206, and simultaneously outputs pulse width modulation signals to control the opening and closing of the solenoid valve 204 in the air spring assembly 2, thereby realizing continuous dynamic adjustment of the vibration isolator stiffness.

[0054] In one possible embodiment, the inner cylinder assembly includes an inner cylinder 102 and a first flange 104 disposed on the outer periphery of the inner cylinder 102. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder 102 by a rubber vulcanization process 109. The upper end of the lower outer cylinder assembly is fixedly connected to the first flange 104, thereby forming a receiving cavity for holding the air spring assembly 2.

[0055] In one possible configuration, pressure sensor 206 is mounted on airbag 203, inner cylinder displacement sensor 110 is located below the first flange 104 of inner cylinder 102, outer cylinder displacement sensor 309 is located at the lower end of the lower outer cylinder assembly, and air spring assembly 2, air tank 401, air guide pipe 402 and electronic controller 308 are all located in the receiving cavity of the outer cylinder below the first flange 104 of inner cylinder 102.

[0056] In one feasible configuration, the airbag 203 has a rubber waist ring 202 around its waist. The upper end of the airbag 203 is connected to the first mounting groove 108 at the lower part of the first flange 104 via a flexible coupling 201, and the lower end of the airbag 203 is connected to the second mounting groove 302 inside the lower outer cylinder assembly. The waist ring 202 serves as a limiting element; the cooperation between the flexible coupling 201 and the first mounting groove 108 ensures connection stability and transmission efficiency.

[0057] In one feasible configuration, the upper outer cylinder assembly includes an integrally formed upper outer cylinder cap 301 and an upper outer cylinder 304, and the lower outer cylinder assembly includes an integrally formed lower outer cylinder cap 305 and a lower outer cylinder 306. The upper end of the lower outer cylinder 306 is bolted to the first flange 104 via a fourth mounting hole 310. The upper outer cylinder cap 301 and the lower outer cylinder cap 305 are used to connect to and fix the outer cylinder to the helicopter fuselage. Specifically, the upper outer cylinder cap 301 and the lower outer cylinder cap 305 are connected to and fixed to the helicopter fuselage via a second mounting hole 303 and a third mounting hole 307. The outer wall 107 of the inner cylinder is fixedly connected to the base via a clamp, achieving effective coupling between the liquid-jet vibration isolator and the helicopter main gearbox. The inner cylinder outer wall of the combined stiffness adjustable liquid spring vibration isolator of the present invention is fixedly connected to the base through a special clamp, thereby realizing the coupling with the helicopter main gearbox; its outer cylinder upper end cover and outer cylinder lower end cover are connected to the helicopter fuselage through the second mounting hole and the third mounting hole to fix it to the helicopter fuselage. This installation method is used to transmit the excitation force generated by the vibration of the main gearbox.

[0058] In one feasible manner, rubber sealing rings are provided between the upper liquid replenishment chamber 101 and the upper end cap 301 of the outer cylinder, and between the lower liquid replenishment chamber 106 and the lower end cap 305 of the outer cylinder, to ensure sealing performance and prevent liquid leakage.

[0059] The working principle of the combined stiffness adjustable hydraulic isolator provided by this invention is as follows:

[0060] In the initial stage of use of the liquid-elastic vibration isolator, when the rubber material does not show obvious signs of aging, the liquid-elastic vibration isolator performs vibration isolation operation based on the principle of dynamic anti-resonance. At this time, the rubber layer and the air spring work together to provide the required elastic stiffness. When the combined liquid-elastic vibration isolator is subjected to the excitation force from the main reducer, the rubber layer and the air spring will generate an action force. At the same time, the liquid in the inertial channel is squeezed and flows up and down in the inertial channel to generate inertial force, which cancels out the action force generated by the elastic element and plays the role of vibration isolation.

[0061] As the rubber material ages, the relative displacement between the inner and outer cylinders of the vibration isolator gradually increases. To maintain the performance of the vibration isolation system, a proportional-integral-derivative (PID) closed-loop control strategy is adopted. This strategy involves comparing the displacement signals collected by displacement sensors installed on the inner and outer cylinders with a preset target displacement signal. Based on this comparison result, the electronic controller dynamically adjusts the duty cycle of the output pulse width modulation (PWM) signal to control the opening and closing state of the solenoid valve in the air spring assembly, thereby achieving real-time dynamic adjustment of the vibration isolator stiffness.

[0062] The present invention also provides a method for adjusting the stiffness of the above-mentioned combined stiffness adjustable hydraulic isolator, comprising the following steps:

[0063] Step 1: Determine the target isolation frequency of the combined stiffness adjustable hydraulic spring isolator.

[0064] The theoretical model of this invention can be equivalent to: Figure 6 As shown. In this model, This indicates the mass of the vibration-isolated components, including the helicopter rotor and main gearbox, as well as the inner cylinder. This indicates the mass of the fuselage and outer cylinder base. This indicates the mass of the liquid within the inertial channel of the liquid-elastic vibration isolator. This represents the cross-sectional radius of the upper and lower liquid chambers of the hydraulic spring isolator. Indicates the cross-sectional radius of the inertial channel. This indicates the stiffness of the rubber in the vibration isolator. Indicates the stiffness of the air spring. This is the length of the inertial channel. This represents the periodic excitation force acting on the inner cylinder of the liquid-elastic vibration isolator. These represent the displacements of the inner and outer cylinders under the action of external excitation force, respectively. This indicates the displacement of the inertial fluid within the inertial channel of the vibration isolator. Let be the pressures in the upper and lower liquid chambers, respectively. Let the damping of the vibration isolator be... Let be the cross-sectional area of ​​the upper and lower liquid cavities. This represents the cross-sectional area of ​​the inertial channel.

[0065] In the theoretical analysis of the liquid-elastic vibration isolator, the following basic assumptions are proposed to simplify the model:

[0066] (1) Ignore the liquid density and physical state of the rubber during the operation of the liquid spring vibration isolator.

[0067] The impact of changes on work status;

[0068] (2) The change in rubber stiffness is a linear process;

[0069] (3) The liquid spring isolator always maintains axial motion.

[0070] Based on the theoretical analysis of the above hydraulic spring isolator, the isolation frequency of the combined stiffness-adjustable hydraulic spring isolator is determined as follows:

[0071] The dynamic equations of the combined hydraulic-elastic vibration isolator system are as follows:

[0072]

[0073] Define the ratio of the cross-sectional area of ​​the upper and lower liquid chambers to the cross-sectional area of ​​the inertial channel in a combined hydroelastic vibration isolator. The amplification ratio of the combined hydraulic-elastic vibration isolator can be obtained from the continuity equation of the liquid mass in the inertial channel:

[0074]

[0075] Combining the above equations, the dynamic equation of the combined hydraulic-elastic vibration isolator can be simplified to:

[0076]

[0077] Depend on The resonant frequency of this combined hydraulic-elastic vibration isolator can be obtained as follows:

[0078]

[0079] Therefore, the force transmission rate of the combined hydraulic-elastic vibration isolator can be defined as the ratio of the force transmitted to the fuselage through the isolator to the amplitude of the external excitation force:

[0080] ;

[0081] in:

[0082] ;

[0083] ;

[0084] ;

[0085] Increase the force transmission rate of the combined hydraulic vibration isolator The relationship between the isolation frequency of the combined stiffness adjustable hydraulic spring isolator and the sum of the stiffnesses of the air spring assembly and the rubber is as follows:

[0086] ;

[0087] in, This indicates the isolation frequency of the combined adjustable stiffness hydraulic isolator. This indicates the stiffness of the rubber in the vibration isolator. This indicates the stiffness of the air spring assembly. This indicates the mass of the liquid within the inertial channel of the liquid-elastic vibration isolator. This indicates the amplification ratio of the combined hydraulic spring isolator.

[0088] Step 2: Calculate the sum of the initial stiffness of the air spring assembly and the rubber based on the target vibration isolation frequency, and record it as the target stiffness of the vibration isolator.

[0089] Based on the relationship between the isolation frequency of the combined adjustable stiffness liquid spring isolator and the sum of the stiffnesses of the air spring assembly and the rubber, it can be known that when the mass of the liquid in the inertial channel of the liquid spring isolator and the amplification ratio of the combined liquid spring isolator are both known constants, the sum of the initial stiffnesses of the air spring assembly and the rubber can be calculated based on the known target isolation frequency.

[0090] Step 3: Calculate the target displacement difference between the outer cylinder assembly and the inner cylinder assembly based on the target stiffness of the vibration isolator.

[0091] Since the vibration isolation frequency is fixed (the target vibration isolation frequency is known), and the rubber ages during use, leading to a decrease in stiffness, the air spring needs to be inflated to replenish the stiffness lost by the rubber. In this application, displacement sensors are used to detect the displacement of the inner and outer cylinders and compare it with the target displacement to determine whether the stiffness will change.

[0092] The relationship between the target displacement difference and the sum of the initial stiffness of the air spring assembly and the rubber is as follows:

[0093] ;

[0094] in, For the target displacement difference, This represents the maximum static load on the combined adjustable stiffness hydraulic isolator. and These represent the displacements of the inner cylinder assembly and the outer cylinder assembly when the rubber is not aged. and These represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly, respectively. The target displacement difference of the system is determined by the maximum static load and the initial overall stiffness of the system.

[0095] Step 4: During the use of the vibration isolator, monitor the real-time displacement difference between the outer cylinder assembly and the inner cylinder assembly. When the real-time displacement difference is less than the target displacement difference, control the air spring assembly to be filled with air through the semi-active control system until the real-time displacement difference equals the target displacement difference.

[0096] The theoretical formula for calculating the stiffness of an air spring is:

[0097] ;

[0098] in, The pressure in the air chamber. Atmospheric pressure, Let V be the volume of the air spring. The effective area of ​​the air spring. The polytropic index of a gas is generally taken as... . This refers to the vertical deformation of the air spring. The effective area change rate depends on the structure of the air spring and is constant in this system.

[0099] From the theoretical formula for calculating the stiffness of an air spring, it can be seen that the stiffness of an air spring changes with the pressure in its air chamber; that is, by changing the pressure in its air chamber... This allows for control over the stiffness of the air spring.

[0100] In the application of the combined stiffness-adjustable hydraulic-elastic vibration isolator, the real-time displacement difference calculation expression in the ECU controller is as follows:

[0101] ;

[0102] in, For real-time displacement, and This is for real-time detection of the displacement signals of the inner and outer cylinders.

[0103] During use, rubber ages, leading to a decrease in stiffness. To maintain a constant vibration isolation frequency, the stiffness of the air springs needs to be increased. In this application, the system stiffness is adjusted by means of changes in the displacement signal. When the displacement signal input to the ECU controller... At this time, the ECU controller outputs a control signal to drive the solenoid valve to open, and the air spring inflates to adjust the stiffness increase. When When the system reaches the specified vibration isolation frequency, the solenoid valve closes.

[0104] In addition, to ensure the safety of this combined stiffness-adjustable hydraulic spring isolator system, the maximum pressure threshold of the air spring assembly is used. As a safety constraint within this PID control framework, given that the volume of the air spring in this system remains constant, a pressure sensor located on the air spring assembly is responsible for monitoring and maintaining the internal pressure of the air spring below a preset maximum threshold to ensure safe system operation. Determine the maximum threshold pressure inside the air spring's air chamber. As shown in the following formula.

[0105] ;

[0106] In this PID control framework, the maximum pressure threshold The introduction of this element serves as a key security constraint, and its function is as follows:

[0107] (1) Limit the internal pressure of the air spring to prevent structural damage or system failure due to overpressure.

[0108] (2) Provide feedback signals to the PID controller to ensure that the control action is performed within the safe operating range.

[0109] (3) By adjusting the PID control parameters, the stiffness of the air spring can be optimized while ensuring that the system stability is not affected.

[0110] Obviously, those skilled in the art can make various modifications and variations to this technical solution without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this technical solution and their equivalents, this technical solution also intends to include these modifications and variations.

Claims

1. A combined stiffness-adjustable liquid spring vibration isolator, characterized in that, The application relates to a liquid-air spring vibration isolator, which comprises a liquid-air spring vibration isolator body (1) and an air spring assembly (2), wherein the liquid-air spring vibration isolator body (1) comprises an inner cylinder assembly, rubber (109) and an outer cylinder assembly (3); the air spring assembly (2) comprises an electromagnetic valve (204) and an air bag (203); the outer cylinder assembly (3) comprises an upper outer cylinder assembly and a lower outer cylinder assembly, the inner wall of the upper outer cylinder assembly is firmly connected with the upper part of the inner cylinder assembly through a rubber (109) vulcanization process, the lower end of the inner cylinder assembly is connected with the lower outer cylinder assembly and extends to the inner bottom end of the lower outer cylinder assembly; the upper outer cylinder assembly comprises an integrally-formed outer cylinder upper end cover (301) and an upper outer cylinder (304), and the lower outer cylinder assembly comprises an integrally-formed outer cylinder lower end cover (305) and a lower outer cylinder (306); the outer cylinder upper end cover (301) and the outer cylinder lower end cover (305) are used for being connected with a helicopter body to be fixed on the helicopter body; the outer wall (107) of the inner cylinder assembly is fixedly connected with a base through a clamp to realize effective coupling between the liquid-air spring vibration isolator and a helicopter main speed reducer; the inner cylinder assembly comprises an inner cylinder (102) and a first flange (104) arranged on the outer periphery of the inner cylinder (102), the inner wall of the upper outer cylinder assembly is firmly connected with the upper part of the inner cylinder (102) through a rubber (109) vulcanization process, the upper end of the lower outer cylinder assembly is fixedly connected with the first flange (104), thereby forming a containing cavity for containing the air spring assembly (2), and the upper end of the lower outer cylinder (306) is fixedly connected with the first flange (104); an inertial passage (103) filled with sealing liquid is arranged in the center of the inner cylinder assembly, and the inertial passage (103) is attached with an upper liquid supplementing cavity (101) and a lower liquid supplementing cavity (106); the air spring assembly (2) is arranged in the lower outer cylinder assembly and is distributed on the outer periphery of the lower part of the inner cylinder assembly, the air spring assembly (2) is internally provided with an air cavity (205), the air cavity (205) is controlled to charge and discharge through a semi-active control system, the pressure in the air cavity (205) is regulated, thereby continuously controlling the rigidity of the air spring assembly (2) and realizing continuous dynamic regulation of the rigidity of the vibration isolator. The electromagnetic valve (204) is assembled on the charging and discharging port of the air bag (203), the charging and discharging port is connected with a gas storage tank (401) through a gas guide pipe (402), and the electromagnetic valve (204) can control the charging and discharging of the air bag (203). The semi-active control system comprises an electronic controller (308), an inner cylinder displacement sensor (110), an outer cylinder displacement sensor (309) and a pressure sensor (206); the pressure sensor (206) is used for collecting pressure change signals in the air cavity (205) in real time, the inner cylinder displacement sensor (110) is used for collecting inner cylinder assembly displacement signals in real time, and the outer cylinder displacement sensor (309) is used for collecting outer cylinder assembly (3) displacement signals in real time. ​ ​ ​ ​ ​ ​ ​ 2. The combined stiffness-adjustable liquid spring vibration isolator according to claim 1, wherein, ​ 3. The combined stiffness-adjustable liquid spring vibration isolator according to claim 1, wherein, ​ ​ The electronic controller (308) is used to collect and process signals from the inner cylinder displacement sensor (110), the outer cylinder displacement sensor (309) and the pressure sensor (206), and compare them with the preset target displacement difference signal of the inner and outer cylinders, and then dynamically adjust the duty cycle of the output pulse width modulation signal based on the comparison result, so as to control the opening and closing of the electromagnetic valve (204) in the air spring assembly (2), thereby realizing continuous dynamic adjustment of the stiffness of the vibration isolator.

4. The combined stiffness-adjustable liquid spring vibration isolator according to claim 3, wherein, The pressure sensor (206) is arranged on the air bag (203), the inner cylinder displacement sensor (110) is arranged at the lower part of the first flange (104) of the inner cylinder (102), and the outer cylinder displacement sensor (309) is arranged at the lower end of the lower outer cylinder assembly.

5. The combined stiffness-adjustable liquid spring vibration isolator according to claim 1, wherein, The waist of the air bag (203) is provided with a waist ring (202) made of rubber, the upper end of the air bag (203) is connected with the lower part of the first flange (104) through the elastic coupling (201) and the first mounting groove (108), and the lower end of the air bag (203) is connected with the second mounting groove (302) in the lower outer cylinder assembly.

6. A method of adjusting the stiffness of the combined stiffness-adjustable liquid spring vibration isolator according to any one of claims 1-5, characterized in that, The method comprises the following steps: determining the target isolation frequency of the combined stiffness adjustable liquid spring vibration isolator; calculating the sum of the initial stiffness of the air spring assembly and the rubber according to the target isolation frequency, and recording it as the target stiffness of the vibration isolator; calculating the target displacement difference of the outer cylinder assembly and the inner cylinder assembly according to the target stiffness of the vibration isolator; monitoring the real-time displacement difference of the outer cylinder assembly and the inner cylinder assembly during the use of the vibration isolator, and when the real-time displacement difference is less than the target displacement difference, controlling the inflation of the air cavity of the air spring assembly through the semi-active control system until the real-time displacement difference is equal to the target displacement difference.

7. The method of adjusting the stiffness of a combined stiffness-adjustable liquid spring vibration isolator according to claim 6, wherein, The relationship between the isolation frequency of the combined stiffness adjustable liquid spring vibration isolator and the sum of the stiffness of the air spring assembly and the rubber is: ； wherein, represents the isolation frequency of the combined stiffness-adjustable hydro-elastic isolator, represents the stiffness of the isolator rubber, represents the stiffness of the air spring assembly, represents the mass of the liquid in the inertia passage of the hydro-elastic isolator, represents the amplification ratio of the combined hydro-elastic isolator.

8. The method of adjusting the stiffness of a combined stiffness-adjustable liquid spring vibration isolator according to claim 6, wherein, The relationship between the target displacement difference and the sum of the initial stiffness of the air spring assembly and the rubber is: ； wherein, is the target displacement difference, is the maximum static load received by the combined stiffness-adjustable liquid spring isolator, and respectively represent the inner cylinder assembly displacement and the outer cylinder assembly displacement when the rubber is not aged, and respectively represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly.

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