A large-stroke dual-working-condition self-adaptive quasi-zero stiffness vibration isolator and a semi-active control method thereof

Abstract

The application discloses a large-stroke double-working-condition self-adaptive quasi-zero stiffness vibration isolator and a semi-active control method thereof, and belongs to the technical field of vibration control. In order to solve the problem that the existing vibration isolator is difficult to adapt to different load weights and simultaneously maintain the vibration isolation performance under a large stroke because of fixed parameters, the application provides a vibration isolator which comprises a base unit, a bearing unit, and a negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism which are arranged in parallel between the base unit and the bearing unit. The adjustable nonlinear positive stiffness mechanism is configured to be capable of being semi-actively adjusted, so as to compensate for the nonlinear distortion of the negative stiffness mechanism under a large displacement in a semi-active manner, so that the system can dynamically maintain a quasi-zero stiffness state under different load working conditions, and simultaneously meet the large-stroke vibration isolation demand. The application is suitable for occasions such as precision instruments and optical platforms which have high requirements for low-frequency and large-amplitude vibration isolation, and especially has the capability of adapting to single load change or two specific load working conditions.

Description

Technical Field

[0001] This application belongs to the field of vibration control technology, specifically relating to a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator and its semi-active control method. Background Technology

[0002] Vibration isolation is a key technology for ensuring the stability and reliability of high-precision equipment. Traditional linear vibration isolation systems, limited by their natural frequency, struggle to effectively isolate low-frequency (especially below their natural frequency) vibrations while bearing static loads. To overcome this bottleneck, quasi-zero stiffness vibration isolation technology has emerged. This type of isolator connects a negative stiffness mechanism in parallel with a linear positive stiffness mechanism, making its total dynamic stiffness near the equilibrium position approach zero, thus theoretically achieving extremely high low-frequency vibration isolation performance and high static load-bearing capacity.

[0003] Existing quasi-zero stiffness vibration isolators typically consist of a fixed negative stiffness element (such as a tilted spring, magnetic reed structure, or buckling beam) connected in parallel with a linear spring. While this design has theoretical advantages, it has limitations in practical applications: First, its ideal quasi-zero stiffness characteristics are usually only effective within a very narrow displacement amplitude range. When the external excitation amplitude is large and the system operating point deviates from the designed equilibrium position, the nonlinear force-displacement characteristics rapidly deviate from the ideal curve, leading to stiffness hardening or softening and a sharp decline in vibration isolation performance, i.e., poor stability of vibration isolation performance under large excitation. Second, the parameters of most quasi-zero stiffness vibration isolators (such as negative stiffness value and equilibrium position) are fixed and difficult to adjust once manufactured. This means that the same isolator cannot adaptively serve loads with different weights or changing operating conditions. To achieve optimal vibration isolation for different operating loads (e.g., weight changes after replacing a component in a device, or the need to place two objects of different weights on the same platform), it is often necessary to redesign or replace the entire vibration isolation device, resulting in poor versatility and adaptability, and high costs. Summary of the Invention

[0004] This application aims to address the problem that existing vibration isolators cannot effectively serve loads that simultaneously require varying loads and large strokes, and provides a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator and its semi-active control method.

[0005] A large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator is disclosed. The isolator includes a base unit for fixing the isolator to a load-bearing structure or vibration source platform. The base unit contains a load-bearing unit for supporting the vibration isolator. The base unit and the load-bearing unit are connected by a stiffness generating unit for vibration isolation. The stiffness generating unit includes a negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism, which are arranged in parallel. The nonlinear distortion of the negative stiffness mechanism of the isolator under large displacement is offset by the active compensation of the adjustable nonlinear positive stiffness mechanism.

[0006] Furthermore, the base unit includes a base body, which is a "U"-shaped frame. The base body is provided with a follower limiting block for limiting the adjustable nonlinear positive stiffness mechanism. The follower limiting block is arranged parallel to the bottom of the base body, and both ends of the follower limiting block are fixedly connected to a vertical part in the base body.

[0007] Furthermore, the follower limiting block has an X-shaped structure, and a guide hole for cooperating with the adjustable nonlinear positive stiffness mechanism is machined at the center of the follower limiting block.

[0008] Furthermore, mounting holes for connecting to the load-bearing structure or vibration source platform are machined at the four corners of the bottom of the base body. A connecting arm for installing a negative stiffness mechanism is fixed to the upper part of the inner side of each vertical part in the base body. A pin mounting hole is machined on the connection end of each connecting arm and the negative stiffness mechanism.

[0009] Furthermore, the bearing unit includes a bearing platform, which is installed in the base body through a negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism. The bearing platform integrates a displacement sensor and a processor. A connecting rod for connecting to the negative stiffness mechanism is fixed to each side of the bearing platform. The connecting end of the connecting rod and the negative stiffness mechanism is machined with a pin mounting hole.

[0010] Furthermore, the negative stiffness mechanism includes two horizontal linear springs, which are arranged opposite each other on both sides of the bearing platform. One end of each horizontal linear spring is hinged to the corresponding connecting arm via a pin, and the other end of each horizontal linear spring is hinged to the corresponding connecting rod via a pin.

[0011] Furthermore, the adjustable nonlinear positive stiffness mechanism includes a longitudinal support assembly, a cam adjustment assembly, and a quick-release mounting assembly. The cam adjustment assembly is installed on the inner bottom of the base body via the quick-release mounting assembly. The longitudinal support assembly is located between the bearing platform and the cam adjustment assembly. The top end of the longitudinal support assembly is fixedly connected to the bottom of the bearing platform, and the bottom end of the longitudinal support assembly passes through the guide hole of the follower limiting block and contacts the cam adjustment assembly.

[0012] Furthermore, the quick-release mounting assembly includes two detachable limiting blocks, which are installed opposite each other on the inner bottom of the base body, and an installation gap is provided between the two detachable limiting blocks. Each detachable limiting block has a mounting through hole for mounting the cam adjustment assembly machined on the upper part of one side.

[0013] Furthermore, the cam adjustment assembly includes a cam and a motor for driving the cam to rotate. The motor is located outside the two removable limit blocks, and the motor housing is detachably connected to an adjacent removable limit block. The motor's power output shaft passes through one removable limit block in sequence and is inserted into the other removable limit block. The motor's power output shaft is detachably connected to both removable limit blocks via bearings. The cam is located in the installation gap between the two removable limit blocks, and the cam is fitted on the motor's power output shaft and rotates synchronously with the motor's power output shaft.

[0014] Furthermore, the longitudinal support assembly includes a follower guide rod and a linear spring. The follower guide rod is vertically positioned directly below the bearing platform and guided and limited by a follower limiting block. The linear spring is positioned between the follower guide rod and the bearing platform, with the axes of the follower guide rod, the bearing platform, and the linear spring being collinear. The top end of the linear spring is fixedly connected to the bottom of the bearing platform, and the bottom end of the linear spring is fixedly connected to the top end of the follower guide rod. A roller follower is provided at the bottom end of the follower guide rod, which contacts the cam profile and is rotatably connected to the follower guide rod via a pin.

[0015] A semi-active control method for a long-stroke dual-condition adaptive quasi-zero stiffness vibration isolator is implemented through the following steps:

[0016] Step 1: Displacement signal acquisition: The processor receives the vertical displacement y of the bearing platform measured by the displacement sensor in real time;

[0017] Step 2: Target Cam Angle Calculation: Based on the displacement y, the processor calculates the target cam angle θ of the servo motor according to the preset displacement-angle mapping relationship θ = f(y). target (y);

[0018] Step 3: Servo motor follow-up control: The processor controls the target cam rotation angle θ. target (y) is sent as a position command to the servo motor driver, which drives the servo motor to rotate, so that the actual rotation angle of the cam follows the target rotation angle θ. target (y);

[0019] Step 4: Cyclic execution: Steps 1 to 3 above are repeated in each control cycle. The control cycle is preferably 1ms to 10ms, so that the cam rotation angle can follow the change of the load-bearing platform displacement in real time, thereby dynamically maintaining the near-zero stiffness state of the system.

[0020] Furthermore, in step 2, the displacement-rotation mapping relationship θ = f(y) is a monotonic nonlinear function, which can be expressed as follows:

[0021]

[0022] Introduce a geometric reference point P, let the distance between the cam shaft and point P be |OP1|=|OP0|=ρ, the distance between the platform and point P be |L1|=|L0|= L, and the vertical distance between the platform's equilibrium position and the cam shaft be H0=H, where H1=Hy;

[0023] Furthermore, step 3 also includes a closed-loop position servo circuit based on the rotation angle deviation, whereby the processor receives the current actual rotation angle θ fed back by an encoder mounted on the servo motor or cam shaft. current (y), calculate the rotational deviation e =θ target (y)-θ current (y), and generates motor drive commands through a proportional-integral-derivative (PID) control algorithm to ensure fast and accurate tracking of the cam rotation angle;

[0024] Furthermore, the semi-active control method also includes step 5: adaptive correction of the equilibrium position. Since load changes may cause the static equilibrium position to drift, the processor records the average value y of the current displacement signal when the system is in a quasi-static or low-disturbance state. bias And correct the displacement used in step 2, that is, use y' = y - y bias As input query mapping relationship

[0025] The beneficial effects of this application compared to the prior art are:

[0026] 1. This application provides a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator, which uses a servo motor to drive the cam to rotate in real time to actively compensate for nonlinear positive stiffness. This can counteract the nonlinear distortion of the negative stiffness mechanism under large displacement, enabling the system to maintain near-zero dynamic stiffness over a wider range of vibration amplitudes. This significantly broadens the effective vibration isolation frequency band and improves the system's isolation performance against large low-frequency excitations.

[0027] 2. This application provides a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator, which can design or select a cam with a specific profile according to the mass of the load and the expected excitation level. After installing the corresponding cam, the system can automatically optimize its force-displacement curve to provide the best large-amplitude low-frequency vibration isolation effect for the specific load.

[0028] 3. This application provides a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator. When two objects of different weights need to be placed on the load-bearing platform, a special cam can be designed so that the vibration isolator does not need to replace the cam component. The static force balance of the system can be achieved according to different loads, and the dynamic stiffness at that position can be made close to zero. Thus, it can provide effective low-frequency vibration isolation for two different loads at the same time, solving the problem of performance degradation of traditional vibration isolators under multi-level loads and asymmetrical loads.

[0029] 4. The adjustment function of the core of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator provided in this application is achieved by replacing the standardized cam component without modifying the main structure of the vibration isolator. This mode of fixed main body and replaceable key components greatly reduces the cost of customizing vibration isolation systems for different application scenarios, and also makes on-site commissioning and maintenance quick and easy. Attached Figure Description

[0030] Figure 1 This is an isometric drawing of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0031] Figure 2 This is a front view of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0032] Figure 3 This is a top view of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0033] Figure 4 This is an isometric drawing of the base unit in the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0034] Figure 5 This is an isometric drawing of the horizontal linear spring in the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0035] Figure 6 This is an isometric drawing of the adjustable nonlinear positive stiffness mechanism in the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0036] Figure 7 This is a flowchart illustrating the operation of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator described in this application.

[0037] Figure 8 This is a comparison diagram of the vibration transmissibility of this application under a single-stage load with that of a conventional three-spring vibration isolator and a linear vibration isolation device.

[0038] Figure 9 Force-displacement curves of the two-stage load of this application under different mass ratios are shown.

[0039] Figure 10This is a force transmissibility curve of the two-level load adaptive vibration isolation in this application.

[0040] Figure 11 This is a schematic diagram of the state when the two-level load adaptive vibration isolation of this application is working.

[0041] Figure 12 This is a schematic diagram illustrating the selection of reference points in the fourth specific implementation method of this application.

[0042] In the diagram: 1. Base body, 2. Bearing platform, 3. Cam, 4. Horizontal linear spring, 5. Follower guide rod, 6. Roller follower, 7. Detachable limit block, 8. Motor, 9. Pin, 10. Linear spring, 11. Base mounting hole, 12. Limit block mounting hole, 13. Follower limit block, 14. Mounting through hole, and 15. Connecting arm. Detailed Implementation

[0043] Specific implementation method one: Combining Figures 1 to 10 This embodiment describes a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator, which includes a base unit for fixing the isolator to a load-bearing structure or vibration source platform. The base unit contains a load-bearing unit for supporting the vibration isolator. The base unit and the load-bearing unit are connected by a stiffness generating unit for vibration isolation. The stiffness generating unit includes a negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism, which are arranged in parallel. The nonlinear distortion of the negative stiffness mechanism under large displacement is offset by the active compensation of the adjustable nonlinear positive stiffness mechanism.

[0044] The base unit includes a base body 1, which is a "U"-shaped frame. The base body 1 has a follower limiting block 13 for limiting the adjustable nonlinear positive stiffness mechanism. The follower limiting block 13 is set parallel to the bottom of the base body 1. The two ends of the follower limiting block 13 are fixedly connected to a vertical part of the base body 1. The follower limiting block 13 has an X-shaped structure. The anti-torsion and anti-lateral pressure performance of the X-shaped structure is far superior to that of a single plate limiting structure. Under the complex working conditions of the vibration isolator being subjected to large low-frequency vibration, the limiting constraint effect can be maintained for a long time without decay, ensuring the stability of the stiffness adjustment of the vibration isolation system. A guide hole for cooperating with the adjustable nonlinear positive stiffness mechanism is machined at the center of the follower limiting block 13.

[0045] The four corners of the base body 1 are machined with base mounting holes 11 for connecting with the load-bearing structure or vibration source platform. The base body 1 is fixedly connected to the load-bearing structure or vibration source platform with bolts or pins to ensure the stability of the vibration isolator during operation. The upper part of the inner side of each vertical part of the base body 1 is fixedly connected with a connecting arm 15 for installing a negative stiffness mechanism. Each connecting arm 15 has a pin mounting hole machined on the connection end with the negative stiffness mechanism.

[0046] The bearing unit includes a bearing platform 2, which is installed in the base body 1 via a negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism. The bearing platform 2 integrates a displacement sensor and a processor. A connecting rod for connecting to the negative stiffness mechanism is fixed to each side of the bearing platform 2. The connecting rods have pin mounting holes machined on their connecting ends to the negative stiffness mechanism. The displacement sensor and processor in the bearing platform 2 are signal-connected to the adjustable nonlinear positive stiffness mechanism. The processor is configured to: receive the displacement signal from the displacement sensor, process it according to a preset control algorithm, and output control commands to the adjustable nonlinear positive stiffness mechanism. The adjustable nonlinear positive stiffness mechanism performs active compensation according to the received commands.

[0047] The negative stiffness mechanism includes two horizontal linear springs 4, which are arranged opposite to each other on both sides of the bearing platform 2. One end of each horizontal linear spring 4 is hinged to the corresponding connecting arm 15 through a pin 9, and the other end of each horizontal linear spring 4 is hinged to the corresponding connecting rod through a pin 9. The two horizontal linear springs 4 together constitute the negative stiffness mechanism of the vibration isolator. The negative stiffness mechanism is used to provide negative stiffness in the vertical direction to the bearing unit.

[0048] The adjustable nonlinear positive stiffness mechanism includes a longitudinal support assembly, a cam adjustment assembly, and a quick-release mounting assembly. The cam adjustment assembly is installed at the inner bottom of the base body 1 via the quick-release mounting assembly. The longitudinal support assembly is positioned between the bearing platform 2 and the cam adjustment assembly. The top end of the longitudinal support assembly is fixedly connected to the bottom of the bearing platform 2, and the bottom end of the longitudinal support assembly passes through the guide hole of the follower limiting block 13 and contacts the cam adjustment assembly. Considering the slight lateral vibration interference that may occur in the actual working environment of the vibration isolator, the follower limiting block 13 can effectively isolate the influence of lateral vibration on the movement of the guide rod and firmly lock the longitudinal support assembly. The vertical motion trajectory avoids lateral interference that could cause the contact position between the roller and the cam profile to shift, thus preventing unexpected deviations in the linear spring compression. This ensures that the overall dynamic stiffness of the vibration isolation system remains close to zero, guaranteeing the stability of low-frequency large-amplitude vibration isolation performance and preventing performance degradation due to structural guidance deviations. The adjustable nonlinear positive stiffness mechanism is the core component of this application. It adopts a modular design, with the cam adjustment assembly mounted on the base unit via quick-release components. Vibration isolation parameters can be flexibly adjusted by replacing cam adjustment assemblies with different profiles, eliminating the need to redesign and re-process the main structure of the vibration isolator. Standardized cam components can be mass-produced, significantly reducing the R&D and manufacturing costs of customized vibration isolation systems for different application scenarios. Furthermore, on-site commissioning, operating condition switching, and equipment maintenance only require quick cam replacement, simplifying operation and reducing time consumption, greatly improving the deployment and maintenance efficiency of precision equipment vibration isolation systems.

[0049] Specific Implementation Method Two: Combining Figures 1 to 10This embodiment is a further definition of the adjustable nonlinear positive stiffness mechanism in the first specific embodiment. In this embodiment, the quick-release mounting assembly includes two detachable limiting blocks 7, which are installed opposite each other on the inner bottom of the base body 1, and there is an installation gap between the two detachable limiting blocks 7. Each detachable limiting block 7 has a mounting through hole for mounting the cam adjustment assembly on its upper side.

[0050] The cam adjustment assembly includes a cam 3 and a motor 8 for driving the cam 3 to rotate. The motor 8 is located outside the two removable limit blocks 7, and the housing of the motor 8 is detachably connected to an adjacent removable limit block 7. The power output shaft of the motor 8 passes through one removable limit block 7 in sequence and is inserted into the other removable limit block 7. The power output shaft of the motor 8 is detachably connected to both removable limit blocks 7 via bearings. The cam 3 is located in the installation gap between the two removable limit blocks 7, and the cam 3 is mounted on the power output shaft of the motor 8 and rotates synchronously with the power output shaft of the motor 8.

[0051] The longitudinal support assembly includes a follower guide rod 5 and a linear spring 10. The follower guide rod 5 is vertically positioned directly below the bearing platform 2 and guided and limited by the follower limiting block 13. The linear spring 10 is positioned between the follower guide rod 5 and the bearing platform 2, and the axes of the follower guide rod 5, the bearing platform 2, and the linear spring 10 are collinear. The top end of the linear spring 10 is fixedly connected to the bottom of the bearing platform 2, and the bottom end of the linear spring 10 is fixedly connected to the top end of the follower guide rod 5. A roller follower 6 is provided on the bottom end of the follower guide rod 5, which contacts the surface of the cam 3, and the roller follower 6 is rotatably connected to the follower guide rod 5 by a pin.

[0052] In this embodiment, the detachable limiting block 7 is connected to the base body 1 by insertion. This ensures the stability of the cam adjustment component when the vibration isolator is working, and also facilitates the replacement of the cam adjustment component when the load changes. The cam adjustment component has an active adjustment function. The motor 8 is a servo motor. The processor integrated in the bearing platform 2 is connected to the motor 8 by signal. The vertical displacement signal of the bearing platform is collected in real time by the displacement sensor. After the processor calculates the signal, it drives the servo motor to drive the cam to rotate precisely and adjusts the compression of the linear spring in real time. This actively compensates for the nonlinear stiffness distortion of the negative stiffness mechanism under large displacement, so that the system can maintain the ideal quasi-zero stiffness characteristic with the total dynamic stiffness approaching zero in a wider range of vibration displacement amplitude. This completely solves the defects of traditional quasi-zero stiffness vibration isolators, which are only effective in a very narrow displacement range and are prone to stiffness hardening / softening and a sharp drop in vibration isolation performance under large excitation. Simultaneously, it significantly reduces the system's initial vibration isolation frequency, effectively broadening the low-frequency and ultra-low-frequency vibration isolation band. For scenarios such as precision instruments, optical platforms, and aerospace payloads, its large-amplitude low-frequency vibration isolation effect is far superior to traditional three-spring quasi-zero stiffness vibration isolators and conventional linear vibration isolation devices. For single loads with different weights and external excitation levels, standardized cams with corresponding surface profiles can be designed or selected to quickly match load characteristics and operating conditions. After installing the matching cam, the system can automatically optimize the force-displacement characteristic curve, achieving optimal static force balance and quasi-zero stiffness output at the load's equilibrium position. Without modifying the main structure of the vibration isolator, it can provide a dedicated large-amplitude low-frequency vibration isolation effect for a single load, solving the problems of fixed parameters, inability to adapt to load weight changes, and extremely poor versatility of traditional quasi-zero stiffness vibration isolators.

[0053] The vibration isolator system provided in this application constructs a semi-active closed-loop control loop integrating displacement monitoring, processor calculation, motor drive, and cam adjustment. It can respond in real-time to external vibration excitation and load disturbances, dynamically correcting the positive stiffness compensation amount to ensure the system remains stable within the ideal quasi-zero stiffness range under complex vibration environments and fluctuating load conditions. Compared to purely passive quasi-zero stiffness isolators, it possesses stronger environmental adaptability and operational robustness, continuously ensuring the performance stability and operational reliability of high-end precision equipment under harsh vibration environments. Based on this, it features a unique dual-load adaptation mechanism. Through the geometrical nonlinear adjustment of a dedicated cam, it achieves adaptive static force balance for two different weight loads without replacing any components. Furthermore, at the equilibrium positions of both loads, the system's dynamic stiffness approaches zero, simultaneously providing stable and efficient low-frequency vibration isolation for both loads. This design completely solves the industry pain point of traditional vibration isolators being unable to adapt to multi-level loads and asymmetrical loads, resulting in a sharp deterioration in vibration isolation performance. It can meet the vibration isolation requirements of complex operating conditions such as mounting precision equipment of different weights on the same platform or mounting dual loads in aerospace applications.

[0054] This vibration isolator adopts a core configuration of parallel negative stiffness mechanism and adjustable nonlinear positive stiffness mechanism, combined with semi-active closed-loop control and cam quick-change adapter structure. Through real-time active compensation for stiffness distortion and adaptive matching of load weight, it achieves stable quasi-zero stiffness vibration isolation under wide amplitude, ultra-low frequency, and dual load conditions. The specific working principle is as follows:

[0055] The vibration isolator uses a base unit as the installation foundation and a load-bearing platform as the load-bearing end. A negative stiffness mechanism and an adjustable nonlinear positive stiffness mechanism are arranged in parallel between the two. The negative stiffness mechanism consists of horizontal linear springs symmetrically arranged on both sides. When the load-bearing platform undergoes vertical displacement, the horizontal linear springs generate a negative stiffness effect in the vertical direction. The adjustable nonlinear positive stiffness mechanism and the negative stiffness mechanism have their stiffness superimposed. Through precise adjustment, the total dynamic stiffness of the system approaches zero at the equilibrium position, forming a quasi-zero stiffness vibration isolation foundation.

[0056] The adjustable nonlinear positive stiffness mechanism consists of a longitudinal support assembly, a cam adjustment assembly, and a quick-release mounting assembly. The follower guide rod is constrained by an X-shaped follower limit block, allowing movement only in the vertical direction. Its bottom roller follower remains in contact with the cam profile, and its top is connected to the load-bearing platform via a linear spring. A servo motor drives the cam to rotate, and the change in the cam profile profile pushes the roller follower and follower guide rod to vertical displacement, altering the linear spring compression and adjusting the nonlinear characteristics of the system's positive stiffness in real time. This actively counteracts the stiffness hardening or softening distortion of the negative stiffness mechanism under large displacements.

[0057] The support platform integrates displacement sensors and a processor, forming a closed-loop control circuit for displacement monitoring, computation, motor drive, and cam adjustment. The displacement sensor collects the vertical displacement signal of the support platform in real time, the processor calculates the compensation amount according to a preset algorithm and outputs control commands, the servo motor drives the cam to precisely rotate the angle, and continuously corrects the system's normal stiffness, so that the vibration isolator can stably maintain a near-zero stiffness state over a wide vibration amplitude range.

[0058] Under single-load conditions, by replacing the cam profile with one that matches the load mass and excitation level, the system automatically optimizes the force-displacement curve, achieving static force balance and optimal near-zero stiffness vibration isolation at the equilibrium position. Under dual-load conditions, a dedicated dual-balance point cam is used, eliminating the need to replace any parts. The system can adapt to two different load weights, achieving static force balance at the corresponding equilibrium positions, while maintaining dynamic stiffness close to zero at both points, simultaneously meeting the high-efficiency low-frequency vibration isolation requirements of dual loads.

[0059] Based on the above working principle, a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator was designed. Comparisons were obtained of the force transmissibility curves of the traditional three-spring structure, linear vibration isolator, and the present invention under a single-stage load with the same negative stiffness structure. The force transmissibility curve of the present invention under two-stage load is also shown in the attached figures. It can be seen that under a single-stage load, if the negative stiffness structure is kept the same, the initial isolation frequency and peak transmissibility of the transmissibility curve obtained by the present invention are superior to those of the traditional three-spring vibration isolator and linear vibration isolator. Under two-stage load, the present invention achieves adaptive static balance under different designable mass ratios, providing effective low-frequency vibration isolation for both different loads, and has broad application prospects.

[0060] Specific implementation method three: Combining Figures 1 to 12 This embodiment describes a semi-active control method for a large-stroke dual-condition adaptive quasi-zero stiffness isolator. Existing semi-active control schemes for quasi-zero stiffness isolators typically require online solving of a system of nonlinear equations, including negative stiffness force, positive stiffness force, and cam profile, within each control cycle to obtain the target control quantity. This method has a heavy computational burden, demands high real-time processing power from the processor, and is prone to decreased control accuracy due to model parameter perturbations in engineering implementation.

[0061] In fact, in the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator mechanical structure proposed in this application, the output force of the nonlinear positive stiffness mechanism is determined by the linear spring compression, which in turn uniquely depends on the displacement y of the bearing platform and the cam radius (i.e., the distance from the center of the cam shaft to the contact point of the roller follower). Therefore, if the desired stiffness matching characteristics have been solidified through the cam profile during the mechanism design stage, the system has a definite geometric constraint relationship in an ideal state: for each displacement y of the bearing platform, there is a unique corresponding cam rotation angle θ, making the total stiffness of the system at that position approach zero. Based on this geometric characteristic, this application proposes a simple, efficient, and semi-active control method that does not require complex online calculations; the control method includes the following steps:

[0062] Step 1: Displacement Signal Acquisition: The processor receives the vertical physical displacement of the load-bearing platform measured by the displacement sensor in real time. After the system is powered on and bears the load, it first determines the current static equilibrium position through an initial adaptive process and marks this position as the zero displacement point y=0 used by the control algorithm. Subsequent real-time displacement y is based on this, with upward displacement being positive and downward displacement being negative.

[0063] Step 2, Target Cam Angle Calculation: Based on the displacement y, the processor calculates the target cam angle θ of the servo motor according to the preset displacement-angle mapping relationship θ = f(y). target (y).

[0064] Step 3, Servo motor follow-up control: The processor controls the target cam rotation angle θ. target (y) is sent as a position command to the servo motor driver. The servo motor driver drives the servo motor to rotate, causing the actual rotation angle of the cam to follow the target rotation angle θ. target (y).

[0065] Step 4, Execute repeatedly: Steps 1 to 3 above are executed repeatedly in each control cycle. The control cycle is preferably 1ms to 10ms, so that the cam rotation angle can follow the change of the load-bearing platform displacement in real time, thereby dynamically maintaining the quasi-zero stiffness state of the system.

[0066] In this embodiment, the displacement-rotation mapping relationship θ = f(y) is determined by the geometric constraints and mechanical design objectives of the vibration isolator. The specific derivation logic is as follows: For any given displacement y of the bearing platform, in order to ensure that the total stiffness of the system at that location satisfies the quasi-zero stiffness condition (i.e., the output force of the positive stiffness mechanism exactly cancels out the restoring force of the negative stiffness mechanism and compensates for the small linear residual stiffness), a linear spring (with a stiffness of K) is used. v A specific target compression value δ is required. target (y) makes the system's normal stiffness force F p =K v *δ(y), and the compression amount δ should satisfy the following relationship:

[0067] δ(y) = y + r w -r wb In this formula, r w r wb These are the radial vector magnitudes at any point on the working segment contour and the initial position radial vector magnitude, respectively. By changing r... wb It allows control over the overall dimensions of the outline.

[0068] From the above geometric relationship, it can be seen that for a given y, there exists a unique θ such that the compression δ(y) reaches the target compression value δ. target Therefore, the mapping function θ = f(y) can be obtained by offline traversal calculation or analysis of the inverse function.

[0069] Specific implementation method four: Combination Figures 1 to 12 This embodiment further defines step 2 in specific embodiment three. In this embodiment, the displacement-rotation mapping relationship θ = f(y) in step 2 is a monotonic nonlinear function, which can be expressed as follows:

[0070]

[0071] Introducing a geometric reference point P, let the distance between the cam shaft and point P be |OP1|=|OP0|=ρ, the distance between the platform and point P be |L1|=|L0|=L, and the vertical distance between the platform's equilibrium position and the cam shaft be H0=H, where H1=Hy. Furthermore, to improve real-time control efficiency, the processor pre-stores a one-dimensional displacement-target rotation angle lookup table generated based on the above mapping relationship. During step 2, the processor uses the current displacement y to look up the table and perform linear interpolation to directly obtain the target cam rotation angle θ. target (y).

[0072] Specific Implementation Method Five: Combining Figures 1 to 12 This embodiment further defines step 3 in specific embodiment three. In this embodiment, step 3 also includes a closed-loop position servo circuit based on the rotation angle deviation. The processor receives the current actual rotation angle θ fed back by the encoder mounted on the servo motor or cam shaft. current (y), calculate the rotational deviation e=θ target (y)-θ current (y), and generates motor drive commands through a proportional-integral-derivative (PID) control algorithm to ensure fast and accurate tracking of the cam rotation angle.

[0073] Specific Implementation Method Six: Combination Figures 1 to 12 This embodiment further defines the semi-active control method in Specific Embodiment 3. The semi-active control method in this embodiment also includes an optional step 5: adaptive correction of the equilibrium position.

[0074] During long-term system operation or changes in operating conditions, a slow offset may occur between the control displacement zero point calibrated in step 1 and the actual static equilibrium position due to factors such as slight load shifts and temperature drift. To automatically compensate for this drift, the processor continuously monitors the system status:

[0075] When the processor detects that the fluctuation amplitude of the displacement signal y within a preset monitoring time window (e.g., 1 second) is consistently lower than a preset threshold, it determines that the system is currently in a quasi-static / low-disturbance state. At this time, the processor calculates the average value y of the displacement signal y within that time window. bias The average value y bias This represents the offset of the new equilibrium position relative to the original control zero point.

[0076] If the offset y bias If the value exceeds the allowable threshold, the processor automatically performs zero-point correction, generating a corrected effective displacement y' for all subsequent control calculations. The correction relationship is y' = y – y bias .

[0077] Subsequently, the control logic described in step 2 will use y' as a new input to query the mapping relationship θ= f(y') to obtain the target cam rotation angle, thereby enabling the system control reference to automatically follow the actual balance position and broaden the adaptability of the vibration isolator to drift under variable load conditions and long-term operating conditions.

[0078] This application has disclosed preferred embodiments above, but it is not intended to limit this application. Any person skilled in the art should be able to make some modifications or alterations to the structure and technical content disclosed above, without departing from the scope of the technical solution of this application, to form equivalent embodiments. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator, characterized in that: The vibration isolator includes a base unit for fixing the vibration isolator on a bearing structure or a vibration source platform. A bearing unit for bearing vibration isolation objects is arranged in the base unit. The base unit and the bearing unit are connected by a stiffness generation unit for vibration isolation. The stiffness generation unit includes a negative stiffness mechanism and an adjustable non-linear positive stiffness mechanism, and the negative stiffness mechanism and the adjustable non-linear positive stiffness mechanism are arranged in parallel. The active compensation of the adjustable non-linear positive stiffness mechanism is used to offset the non-linear distortion of the negative stiffness mechanism of the vibration isolator under large displacements.

2. The large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 1, characterized in that: The base unit includes a base body (1). The base body (1) is a "U"-shaped frame. A follower limiting block (13) for limiting the adjustable non-linear positive stiffness mechanism is arranged in the base body (1). The follower limiting block (13) is arranged parallel to the bottom of the base body (1), and both ends of the follower limiting block (13) are fixedly connected to one of the vertical parts in the base body (1).

3. The large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 2, characterized in that: Base mounting holes (11) for connecting with the bearing structure or the vibration source platform are processed at the four corners of the bottom of the base body (1). Connecting arms (15) for installing the negative stiffness mechanism are fixedly connected to the upper parts inside each vertical part of the base body (1). Pin mounting holes are processed at the connecting ends of each connecting arm (15) and the negative stiffness mechanism.

4. The large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 3, characterized in that: The bearing unit includes a bearing platform (2). A displacement sensor and a processor are integrated in the bearing platform (2). The bearing platform (2) is installed in the base body (1) through the negative stiffness mechanism and the adjustable non-linear positive stiffness mechanism. A displacement sensor and a processor are integrated in the bearing platform (2). Connecting rods for connecting with the negative stiffness mechanism are fixedly connected to both sides of the bearing platform (2). Pin mounting holes are processed at the connecting ends of the connecting rods and the negative stiffness mechanism.

5. A large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 4, characterized in that: The negative stiffness mechanism includes two horizontal linear springs (4). The two horizontal linear springs (4) are arranged oppositely on both sides of the bearing platform (2). One end of each horizontal linear spring (4) is hinged to the corresponding connecting arm (15) through a pin (9), and the other end of each horizontal linear spring (4) is hinged to the corresponding connecting rod through a pin (9).

6. A large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 5, characterized in that: The adjustable non-linear positive stiffness mechanism includes a longitudinal support component, a cam adjustment component and a quick-release mounting component. The cam adjustment component is installed on the inner bottom of the base body (1) through the quick-release mounting component. The longitudinal support component is arranged between the bearing platform (2) and the cam adjustment component. The top end of the longitudinal support component is fixedly connected to the bottom of the bearing platform (2). The bottom end of the longitudinal support component passes through the guiding hole of the follower limiting block (13) and contacts the cam adjustment component. The quick-release mounting component includes two detachable limiting blocks (7). The two detachable limiting blocks (7) are installed oppositely front and back on the inner bottom of the base body (1), and an installation gap is arranged between the two detachable limiting blocks (7). An installation through hole for installing the cam adjustment component is processed at the upper part of one side of each detachable limiting block (7). The cam adjustment assembly includes a cam (3) and a motor (8) for driving the cam (3) to rotate. The motor (8) is located outside the two removable limit blocks (7), and the housing of the motor (8) is detachably connected to one of the adjacent removable limit blocks (7). The power output shaft of the motor (8) passes through one removable limit block (7) in sequence and is inserted into the other removable limit block (7). The power output shaft of the motor (8) is detachably connected to both removable limit blocks (7) through bearings. The cam (3) is located in the installation gap between the two removable limit blocks (7), and the cam (3) is mounted on the power output shaft of the motor (8) and rotates synchronously with the power output shaft of the motor (8). The longitudinal support assembly includes a follower guide rod (5) and a linear spring (10). The follower guide rod (5) is set vertically below the bearing platform (2) and guided and limited by the follower limiting block (13). The linear spring (10) is set between the follower guide rod (5) and the bearing platform (2). The axis of the follower guide rod (5), the axis of the bearing platform (2) and the axis of the linear spring (10) are collinear. The top of the linear spring (10) is fixedly connected to the bottom of the bearing platform (2). The bottom of the linear spring (10) is fixedly connected to the top of the follower guide rod (5). The bottom of the follower guide rod (5) is provided with a roller follower (6) that contacts the cam (3) profile. The roller follower (6) is rotatably connected to the follower guide rod (5) by a pin.

7. A semi-active control method for any one of the large-stroke dual-condition adaptive quasi-zero stiffness vibration isolators according to claims 1 to 6, characterized in that: The method is implemented through the following steps: Step 1: Displacement signal acquisition: The processor receives the vertical displacement y of the bearing platform measured by the displacement sensor in real time; Step 2: Target Cam Angle Calculation: Based on the displacement y, the processor calculates the target cam angle θ of the servo motor according to the preset displacement-angle mapping relationship θ = f(y). target (y); Step 3: Servo motor follow-up control: The processor controls the target cam rotation angle θ. target (y) is sent as a position command to the servo motor driver, which drives the servo motor to rotate, so that the actual rotation angle of the cam follows the target rotation angle θ. target (y); Step 4: Cyclic execution: Steps 1 to 3 above are repeated in each control cycle. The control cycle is preferably 1ms to 10ms, so that the cam rotation angle can follow the change of the load-bearing platform displacement in real time, thereby dynamically maintaining the quasi-zero stiffness state of the system.

8. The semi-active control method for a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 7, characterized in that: In step 2, the displacement-rotation mapping relationship θ = f(y) is a monotonic nonlinear function, which can be expressed as: Introduce a geometric reference point P, let the distance between the cam shaft and point P be |OP1|=|OP0|=ρ, the distance between the platform and point P be |L1|=|L0|= L, and the vertical distance between the platform's equilibrium position and the cam shaft be H0=H, where H1=Hy.

9. The semi-active control method for a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 8, characterized in that: Step 3 also includes a closed-loop position servo circuit based on angular deviation, whereby the processor receives the current actual rotation angle θ fed back by an encoder mounted on the servo motor or cam shaft. current (y), calculate the rotational deviation e =θ target (y)-θ current (y), and generates motor drive commands through a proportional-integral-derivative (PID) control algorithm to ensure fast and accurate tracking of the cam rotation angle.

10. The semi-active control method for a large-stroke dual-condition adaptive quasi-zero stiffness vibration isolator according to claim 9, characterized in that: The semi-active control method further includes step 5: adaptive correction of the equilibrium position.

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