Nonlinear rigidity automatic adjustment vibration isolation device and control method

Abstract

The invention discloses a non-linear rigidity automatic adjusting vibration isolation device and a control method. The device comprises a base, a supporting seat, a positive rigidity mechanism, a negative rigidity mechanism and a dynamic adjusting assembly. The negative stiffness mechanism adopts the design of three layers of uniformly distributed'connecting rod-tension spring 'transmission units, generates negative stiffness by converting vertical displacement of a supporting seat into horizontal movement of a tension spring, and is connected with positive stiffness provided by the positive stiffness mechanism in parallel to form a quasi-zero stiffness core mechanics framework. The dynamic adjusting assembly can accurately adjust the working height of the positive stiffness mechanism, and in combination with a feedback control system with an angle sensor as the core, self-adaptive adjustment of the balance position of the system under different loads and maintenance of the quasi-zero stiffness state are achieved. The positive stiffness mechanism is integrated with a magneto-rheological damper, and the damping force of the magneto-rheological damper can be subjected to real-time and intelligent adjustment through a feedforward-feedback composite control strategy based on multi-sensor information fusion so as to suppress resonance, impact and broadband vibration. The problems that in the prior art, the vibration isolation frequency band is narrow, load self-adaption cannot be achieved, damping adjustment is not intelligent and the like are solved, and high bearing, strong vibration reduction and full-working-condition self-adaption vibration isolation are achieved.

Description

Technical Field

[0001] This invention relates to the field of vibration isolation technology, and in particular to a nonlinear stiffness automatic adjustment vibration isolation device and control method. Background Technology

[0002] A seat is a piece of seating that provides support to users, aiming to improve riding comfort and safety. In vibrating environments such as vehicles, construction machinery, and aerospace, seats must have vibration damping capabilities. The core reason for this is to isolate or attenuate harmful mechanical vibrations and impacts transmitted from the outside to the human body. This not only directly affects riding comfort but also effectively prevents health problems such as spinal injuries and systemic vibration-related diseases caused by long-term exposure to vibration environments for drivers and operators.

[0003] Existing vibration-damping seats still have several inherent limitations, making it difficult to simultaneously meet the requirements of high load-bearing capacity and strong vibration reduction. First, the vibration isolation frequency band is narrow, especially the low-frequency isolation effect is poor. The vibration isolation performance of existing vibration-damping seats is limited by their fixed stiffness parameters, resulting in a narrow effective vibration isolation frequency band. For example, Chinese patent CN220557708U discloses an automotive vibration-damping seat that uses a double-spring superimposed structure. Although it can improve the vibration damping effect to a certain extent, its stiffness is essentially still fixed. This type of linear vibration isolation system based on fixed stiffness has a difficult-to-lower natural frequency. According to vibration isolation theory, the system can only effectively isolate vibrations when the excitation frequency exceeds its natural frequency. It takes time for the system to enter the effective vibration isolation zone. This makes traditional seats very ineffective at isolating low-frequency vibrations commonly found in vehicles and machinery, and they are prone to resonance due to frequency mismatch, seriously endangering ride comfort and the health of passengers. This is the primary problem that needs to be solved in existing technologies. Second, they cannot adapt to load changes, causing vibration isolation performance to decrease with load changes. Existing vibration-damping seats lack the ability to automatically compensate for load changes, resulting in their optimal vibration isolation performance being designed only for specific loads, severely limiting their practicality. When the user's weight changes or the load changes, the system's equilibrium position will shift, causing it to fail to operate in the preset optimal vibration isolation state. A smart vibration-damping seat disclosed in Chinese Patent No. CN116552345A attempts to adjust the airbag pressure to adapt to the load through pressure sensors, but its adjustment mechanism does not fundamentally change the system's stiffness characteristics, and its load-bearing capacity and long-term stability are limited by the material strength and durability of the airbag itself, failing to ensure a consistently stable and high-performance vibration isolation effect under different loads. Therefore, developing a system that can adaptively compensate for load changes and maintain the optimal vibration isolation state is an urgent problem to be solved. Third, the performance limitations of negative stiffness mechanisms affect the accuracy and stability of achieving quasi-zero stiffness characteristics. In related technologies, quasi-zero stiffness can be achieved by connecting positive and negative stiffness mechanisms in parallel, thereby reducing the natural frequency and widening the low-frequency isolation bandwidth. However, existing mechanisms for achieving negative stiffness typically employ a single- or double-layer "link-spring" design, which offers limited adjustment range and accuracy for negative stiffness. Furthermore, the frictional damping in the kinematic pairs directly affects the precise generation and cancellation of negative stiffness, thus impacting the overall vibration isolation performance of the system. Designing a low-friction, high-precision negative stiffness mechanism is one of the key challenges in achieving high-performance quasi-zero stiffness vibration isolation. Fourth, fixed or unintelligent damping characteristics cannot simultaneously meet the requirements for broadband vibration suppression. The damping characteristics of existing vibration-damping seats are often fixed or have a limited adjustment range, making it impossible to effectively suppress resonance and broadband vibration simultaneously. Fixed damping makes it difficult to simultaneously address the amplitude suppression requirements in the resonance zone and the energy dissipation requirements in the isolation zone. When passing through the resonance zone, insufficient damping leads to excessive amplitude, threatening stability; while excessive damping weakens vibration isolation efficiency in the high-frequency region. Therefore, a mechanism is needed that can intelligently adjust the damping force in real time according to vibration conditions to achieve comprehensive suppression of resonance, impact, and broadband vibration. Fifth, the lack of a complete sensing and control system makes it difficult to achieve real-time and precise adjustment through multi-information fusion. Furthermore, existing technologies lack a complete sensing and control system capable of comprehensively sensing external excitation, system state, and load changes. Most solutions have relatively simple sensor configurations (such as only detecting displacement or only detecting acceleration), resulting in insufficient and incomplete system state information acquired by the controller, failing to provide accurate and comprehensive feedback for intelligent damping adjustment.Therefore, existing technologies lack a mechanism that can adjust the damping force in real time and accurately based on actual vibration conditions and the real-time state of the system through multi-sensor information fusion, making it impossible to achieve optimal vibration reduction across the entire operating frequency band. Sixth, most existing quasi-zero stiffness systems are passive and cannot maintain optimal performance under varying loads. Although the quasi-zero stiffness concept offers unique advantages for solving low-frequency vibration problems, the stiffness mechanisms of most existing quasi-zero stiffness isolators are passive and cannot be accurately adjusted. When dealing with varying loads, their vibration isolation performance drops significantly, even falling below that of linear systems. Furthermore, the dynamic model of the quasi-zero stiffness seat suspension system exhibits strong nonlinear characteristics, and the magnetorheological damper, as the core actuator, also exhibits model nonlinearity. This presents significant challenges for controller design, making it difficult for existing technologies to achieve accurate and robust control of such strongly nonlinear systems.

[0004] Traditional vibration isolation systems often employ a structure consisting of a linear helical spring or air spring connected in parallel with a damper. According to vibration isolation theory, the isolation effect of a linear vibration isolator is limited only when the excitation frequency is higher than the system's natural frequency. It is only effective when the frequency is increased, and the vibration isolation efficiency increases with increasing frequency. To isolate low-frequency vibrations, the natural frequency of the vibration isolation system must be reduced, which usually means reducing the spring stiffness or increasing the load mass. However, an overly soft spring will result in excessive static deformation, poor static stability of the system, and difficulty in withstanding changing loads; while increasing the mass is often impractical on a moving platform.

[0005] In summary, existing technologies suffer from problems such as narrow vibration isolation bandwidth, inability to adapt to load changes, limited performance of negative stiffness mechanisms, lack of intelligent adjustment of damping performance, imperfect sensing and control systems, and performance degradation of quasi-zero stiffness systems under variable loads, which severely restrict further improvement of vibration-damping seat performance. Therefore, this invention proposes a nonlinear stiffness automatic adjustment vibration isolation device and control method, aiming to systematically solve the above-mentioned problems. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a nonlinear stiffness automatic adjustment vibration isolation device and control method.

[0007] The nonlinear stiffness automatic adjustment vibration isolation device provided by this invention includes a base, a support base, a positive stiffness mechanism, a negative stiffness mechanism, and a dynamic adjustment component. The base provides the installation foundation for the device; the support base is located at the top of the base cavity and is used to support the seat and occupants; the positive stiffness mechanism is installed inside the base and mainly provides positive stiffness in the vertical direction; the negative stiffness mechanism is also installed inside the base and is arranged in parallel with the positive stiffness mechanism to generate negative stiffness opposite to the positive stiffness effect; the dynamic adjustment component is fixed to the bottom wall of the base and acts on the positive stiffness mechanism. By precisely adjusting the vertical working height of the positive stiffness mechanism, the positive stiffness value it provides at the system equilibrium position cancels out the negative stiffness value generated by the negative stiffness mechanism, thereby causing the entire system to exhibit quasi-zero stiffness characteristics near the equilibrium point.

[0008] To achieve the aforementioned near-zero stiffness characteristic, the negative stiffness mechanism of this invention employs a three-layer, evenly distributed "link-spring" transmission unit design. Each transmission unit includes a horizontal slider sliding on a horizontal guide rail, a rotating shaft rotatably connected to the slider, a diagonal rod fixed to the rotating shaft, and a central shaft rotatably connecting the other end of the diagonal rod to the bottom support of the support base. Negative stiffness springs are connected between the horizontal sliders of different transmission units. When the support base is subjected to load and undergoes vertical displacement, the vertical motion is converted into the horizontal motion of the horizontal slider through the diagonal rod transmission, thereby stretching or compressing the negative stiffness springs and stably generating negative stiffness. The three-layer symmetrical layout effectively distributes the load, significantly reduces frictional resistance in the kinematic pairs, and improves the accuracy of negative stiffness generation and the dynamic performance of the system.

[0009] The positive stiffness mechanism comprises a positive stiffness spring and an intelligent damper arranged in parallel. The intelligent damper is preferably a magnetorheological damper, whose damping coefficient can be continuously and rapidly adjusted via the input current. The positive stiffness spring is coaxially sleeved around the magnetorheological damper, with its two ends connected to the piston rod end and cylinder end of the damper, respectively, forming a compact integrated structure that provides both static support force and adjustable damping force.

[0010] The dynamic adjustment component includes a stepper motor-driven scissor telescopic mechanism. The scissor telescopic mechanism achieves smooth and precise lifting movements via a lead screw and nut drive, with its top support platform fixedly connected to the bottom of the positive stiffness mechanism. By controlling the stepper motor, the working height of the positive stiffness mechanism can be dynamically adjusted, thereby changing the geometric configuration parameters of the negative stiffness mechanism (especially the initial tilt angle of the diagonal bar), achieving active control over the system's equilibrium position.

[0011] Multiple sensors are installed at key locations of the device: an angle sensor is installed at the connection between the inclined bar and the horizontal slider of the negative stiffness mechanism to monitor the rotation angle of the inclined bar in real time. This angle directly reflects the deviation between the actual equilibrium position of the system and the rated equilibrium position (θ=0); acceleration sensors are installed on the base and support respectively to monitor the external foundation excitation and the absolute acceleration response of the system.

[0012] Based on the above-mentioned device, the control method of the present invention achieves adaptive optimization of vibration isolation performance through multi-sensor information fusion and a feedforward-feedback composite control strategy, mainly including the following steps: S1: System State Awareness and Signal Processing: Real-time acquisition of acceleration signals from the base and support, as well as angle signals from the negative stiffness mechanism, which are then processed to obtain key state information such as external excitation, system relative displacement, and velocity.

[0013] S2: Feedforward-based Disturbance and Nonlinear Force Pre-compensation: Utilizing measurable base acceleration and the system's nonlinear stiffness model, a feedforward control force is calculated to actively counteract major external disturbances and internal nonlinear restoring forces, simplifying the system's dynamic characteristics. The output of this feedforward force follows a semi-active constraint principle to ensure its physical realizability.

[0014] S3: System Optimization Control Based on State Feedback: Based on the current model state, design a linear quadratic optimal controller. By establishing a system state-space model and optimizing the controller weight parameters for specific sensitive frequency bands (such as the frequency of human motion sickness), calculate the optimal state feedback control force to suppress residual disturbances, model errors, and unmodeled dynamics, ensuring system stability and robustness.

[0015] S4: Multi-objective adaptive tuning of controller parameters: A multi-objective optimization algorithm is adopted to weigh conflicting performance indicators (such as vibration isolation efficiency, dynamic travel, etc.) and automatically find the best combination of controller parameters to adapt to different working conditions and performance preferences.

[0016] S5: Synthesis and Physical Constraint Verification of Desired Control Force: The feedforward control force and feedback control force are synthesized to obtain the total desired control force. This force is then amplitude-limited, and its direction is verified based on the energy dissipation characteristics of the magnetorheological damper to ensure that the final output control command remains within the physically realizable range of the actuator.

[0017] S6: Mapping of control commands to actuators: Based on the pre-calibrated inverse model of the magnetorheological damper, the verified physically realizable desired control force is mapped to the corresponding input current signal.

[0018] S7: Drive execution and damping force output: The current signal is amplified and then used to drive the magnetorheological damper, which generates a corresponding controllable damping force, which is applied to the vibration isolation system to achieve real-time suppression of vibration.

[0019] S8: Adaptive stiffness adjustment based on load change (parallel or triggered execution): Continuously monitor the angle signal of the negative stiffness mechanism. When the system equilibrium position deviates from the preset optimal state due to load changes, the adjustment mechanism is triggered. The working height of the positive stiffness mechanism is adjusted through dynamic adjustment components to restore the system to quasi-zero stiffness characteristics and ensure that the vibration isolation performance remains optimal under different loads.

[0020] S9: Closed-loop operation and continuous optimization: After the damping force is applied to the system, its state changes. The sensor continuously collects a new round of data and repeats the above steps S1 to S8 to form a complete closed-loop control loop, realizing the continuous and adaptive optimization operation of the vibration isolation system.

[0021] The beneficial technical effects of this invention are: 1. A quasi-zero stiffness characteristic based on the parallel cancellation of positive and negative stiffness was achieved, significantly broadening the effective vibration isolation bandwidth and improving vibration isolation performance. This invention constructs the core mechanical framework of a system by arranging a positive stiffness mechanism and a negative stiffness mechanism in parallel. The positive stiffness mechanism primarily provides positive stiffness in the vertical direction, ensuring the system has high static load-bearing capacity. The negative stiffness mechanism, through its unique "link-tension spring" transmission mechanism, converts the vertical displacement of the support base into the horizontal movement of the moving end of the negative stiffness spring, thereby stably generating negative stiffness opposite to the positive stiffness effect. Crucially, by precisely adjusting the working height of the positive stiffness mechanism through a dynamic adjustment component, the system's equilibrium position can be adjusted to a specific rated equilibrium position (i.e., the inclined rod is parallel to the horizontal guide rail, and the angle sensor reading is zero) under different static load conditions. At this rated equilibrium position, the positive stiffness value provided by the positive stiffness mechanism and the negative stiffness value generated by the negative stiffness mechanism can precisely cancel each other out, causing the system's equivalent dynamic stiffness near the equilibrium point to approach zero, exhibiting a "quasi-zero stiffness" characteristic. The direct beneficial effect of this quasi-zero stiffness characteristic is that it significantly reduces the system's equivalent natural frequency. According to vibration isolation theory, vibration isolation systems only function when the excitation frequency exceeds its natural frequency. Only after this process is complete can the system enter the effective vibration isolation zone. This invention achieves near-zero stiffness, significantly reducing the system's natural frequency and thus drastically lowering the vibration isolation initiation frequency, extending the effective vibration isolation range to even lower frequency bands. This is particularly crucial for isolating harmful low-frequency and even ultra-low-frequency vibrations commonly found in vehicles and construction machinery, fundamentally improving vibration isolation performance and effectively preventing the harm caused by low-frequency resonance to human health and operational precision.

[0022] 2. It possesses adaptive adjustment capabilities based on angle feedback, solving the problem of vibration isolation performance degradation caused by load changes and ensuring performance consistency and stability. This invention introduces a closed-loop control system with an angle sensor as the core detection element, enabling proactive sensing and adaptive compensation of load changes. Specifically, the angle sensor monitors the rotation angle of the inclined rod in the negative stiffness mechanism in real time. This angle signal directly reflects the deviation between the system's current actual equilibrium position and its rated equilibrium position (θ=0). When the user sits down, stands up, or adjusts their posture, causing a load change, the displacement of the support seat will lead to a change in the angle of the inclined rod. After receiving the signal from the angle sensor and determining that it deviates from zero, the controller immediately outputs a command to drive the stepper motor. The stepper motor, through a lead screw and nut mechanism, precisely controls the extension or retraction of the scissor telescopic mechanism, thereby adjusting the vertical working height of the positive stiffness mechanism. This adjustment process changes the geometric configuration parameters of the negative stiffness mechanism (especially the initial tilt angle of the inclined rod), thereby adjusting its negative stiffness value until the system is pulled back to the rated equilibrium position, restoring the quasi-zero stiffness state. This makes the system's superior vibration isolation performance no longer dependent on fixed load conditions. Regardless of the user's weight, the system can automatically and quickly maintain the operating point at the optimal quasi-zero stiffness state through the above feedback adjustment mechanism. This completely overcomes the inherent defect of traditional fixed stiffness vibration reduction systems that deviate from the optimal design conditions due to load changes, resulting in a significant decrease in vibration isolation performance. It ensures that the seat can provide consistent, stable and high-performance vibration isolation in various actual use scenarios, greatly improving the practicality of the product and the user experience.

[0023] 3. By integrating a continuously adjustable intelligent damper and combining it with the coordinated feedback from acceleration and angle sensors, effective suppression of resonance and transient impacts is achieved, ensuring the system's wideband comprehensive vibration reduction performance. This invention integrates a continuously adjustable intelligent damper, preferably a magnetorheological damper, into a positive stiffness mechanism, connected in parallel with a positive stiffness spring. This magnetorheological damper can adjust its output damping force in real time and steplessly according to the control current. The system includes a base acceleration sensor and a support acceleration sensor that monitor external vibration input and system response in real time, while an angle sensor detects the angle of the inclined rod in the negative stiffness mechanism in real time, thereby deriving the relative displacement of the support. The controller comprehensively processes the vibration signals from the acceleration sensors and the displacement information from the angle sensors, dynamically outputting a control current to the magnetorheological damper. When the system passes through the resonance region near its extremely low natural frequency, the acceleration sensors can detect resonance signs in a timely manner. The controller increases the damping force to quickly dissipate the resonance energy, ensuring the stability and safety of the system under start-up, shutdown, or speed change conditions, thus mitigating potential stability issues in the resonance region of a quasi-zero stiffness system. Meanwhile, for transient vibrations caused by road impacts and bumps, the accelerometer provides rapid vibration information, and combined with displacement feedback from the angle sensor, the controller adaptively adjusts the damping force to efficiently dissipate impact energy, significantly improving ride stability and comfort. Ultimately, this multi-sensor collaborative intelligent damping adjustment mechanism works perfectly with the quasi-zero stiffness main structure, enabling the invention to simultaneously achieve effective control of resonance zones and mid-to-high frequency vibrations without sacrificing low-frequency vibration isolation performance. This achieves efficient, reliable, and adaptive vibration reduction across the entire operating frequency band, comprehensively improving the ride comfort and reliability of the vibration-damping seat.

[0024] 4. A three-layer "link-tension spring" negative stiffness mechanism is adopted, which reduces the impact of friction and expands the optimization space for low-frequency vibration isolation performance. This invention innovatively employs a three-layer, evenly distributed "link-tension spring" design for its negative stiffness mechanism. Compared to traditional single-layer or double-layer designs, this structure evenly distributes the load across three symmetrical transmission units, significantly reducing the positive pressure and corresponding frictional resistance borne by individual kinematic pairs (such as between the horizontal slider and the guide rail). This fundamentally weakens the adverse effects of additional damping introduced by friction on the precise generation of negative stiffness and the overall vibration isolation performance of the system. Simultaneously, the three transmission units provide the system with more adjustable geometric parameters, giving the suspension system superior dynamic performance and greater freedom in parameter design. Designers can optimize the initial layout of the three links to further broaden the system's low-frequency vibration isolation bandwidth while ensuring high load-bearing capacity, and finely adjust the shape of the negative stiffness curve to achieve more perfect cancellation with positive stiffness near the equilibrium position, thereby obtaining superior quasi-zero stiffness characteristics and vibration isolation effects compared to traditional single-layer or double-layer structures.

[0025] 5. By using a combined feedforward and feedback control mechanism, the control accuracy and robustness of nonlinear systems are significantly improved, and wideband adaptive vibration isolation is achieved.

[0026] This invention creatively employs a composite control strategy combining feedforward compensation and linear quadratic optimal (LQR) feedback control. First, a feedforward controller is designed based on the principle of structural invariance. Utilizing a real-time measurable fundamental acceleration signal and a nonlinear stiffness model of the system, it actively pre-compensates and cancels major external inertial disturbances and internal nonlinear stiffness forces. This effectively reduces the system's dynamic deviation and significantly reduces its dependence on the accuracy of the system model. Building upon this, an LQR feedback controller is designed for the simplified system after feedforward linearization. By establishing a system state-space model and solving the algebraic Riccati equations, the globally optimal state feedback gain is obtained, thereby systematically optimizing the system state and suppressing residual disturbances, model errors, and unmodeled dynamics that the feedforward could not completely cancel. The magnetorheological (MR) damper, as the core actuator, strictly adheres to semi-active constraint rules in generating control commands, ensuring that the theoretically calculated control force can be accurately mapped to a physically realizable input current without energy injection. The beneficial effects of this composite control mechanism are that it balances response speed and control accuracy, achieves high-precision vibration isolation force tracking under wide-band disturbances, and ensures that the control system has strong stability and robustness when facing parameter changes and unmodeled dynamics, thus providing a reliable control guarantee for the high-performance operation of the vibration isolation system in the entire operating frequency band.

[0027] 6. Based on the adaptive mechanism of vertical position and angle feedback, the vibration isolator achieves quasi-zero stiffness intelligent matching for different loads, ensuring the universality of the best low-frequency vibration isolation effect.

[0028] This invention equips the positive stiffness mechanism with a vertical position adaptive mechanism driven by a stepper motor and a lead screw and nut mechanism. This mechanism works in conjunction with an angle feedback system centered on an angle sensor to form a complete load adaptive adjustment loop. When users of different weights sit down, causing changes in load, the displacement of the support seat will cause the inclined bar in the negative stiffness mechanism to rotate. The angle sensor detects this angular deviation in real time. Based on this, the controller determines that the system has deviated from the preset rated static balance working point (inclined bar horizontal, angle zero), and then drives the stepper motor to operate. The lead screw and nut mechanism precisely controls the lifting and lowering of the scissor telescopic mechanism, thereby dynamically adjusting the vertical working height of the positive stiffness mechanism. This adjustment directly changes the geometric configuration parameters of the negative stiffness mechanism (especially the initial tilt angle of the inclined bar), thereby adjusting its negative stiffness value until the system is re-stabilized at the rated balance position and restores the quasi-zero stiffness state. The direct beneficial effect of this closed-loop adjustment process is that it completely solves the problem that the performance of traditional quasi-zero stiffness vibration isolators is sensitive to load and is only optimal under the design load. Regardless of changes in driver weight, the system can automatically and quickly adjust its operating point to the optimal near-zero stiffness state, achieving intelligent matching of near-zero stiffness under different loads. This not only ensures that every user receives consistent and optimal low-frequency vibration isolation, but also greatly improves the product's practicality and user satisfaction, making high-performance vibration isolation no longer limited to specific load conditions. Attached Figure Description

[0029] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a three-dimensional structural schematic diagram of the positive stiffness mechanism of the present invention; Figure 3 This is a three-dimensional structural schematic diagram of the negative stiffness mechanism of the present invention; Figure 4 This is a three-dimensional structural schematic diagram of the support of the present invention; Figure 5 This is a three-dimensional structural diagram of the dynamic adjustment component of the present invention; Figure 6 This is a front view structural schematic diagram of the present invention in the unloaded state (with the seat in a high position); Figure 7 This is a front view structural schematic diagram of the present invention under load (with the seat in a low position); Figure 8 This is a schematic diagram of the nonlinear stiffness compensation quasi-zero stiffness vibration isolation design method of the present invention; Figure 9 This is a flowchart of the control method for the nonlinear stiffness automatic adjustment vibration isolation device of the present invention; Figure 10 These are the acceleration curves for controlled and uncontrolled acceleration according to the present invention. Detailed Implementation

[0030] Example 1 like Figure 1-7 As shown, a nonlinear stiffness automatic adjustment vibration isolation device includes: a base 1, providing a stable installation foundation for the entire system; a support seat 2 disposed at the top of the inner cavity of the base 1 and used for connection with the seat; a positive stiffness mechanism 3 disposed inside the base 1, used to provide positive stiffness of the main support in the vertical direction; a negative stiffness mechanism 4 disposed inside the base 1 and arranged in parallel with the positive stiffness mechanism 3, used to generate negative stiffness opposite to that of the positive stiffness mechanism 3; and a dynamic adjustment component 5, fixedly connected to the inner bottom wall of the base 1 and acting on the positive stiffness mechanism 3, adjusting the working height of the positive stiffness mechanism 3 so that the positive stiffness value provided by it cancels out the negative stiffness value of the negative stiffness mechanism 4 at the system equilibrium position, thereby making the system exhibit quasi-zero stiffness characteristics.

[0031] Specifically, by setting up support base 2 as a load-bearing and transmission component, positive stiffness mechanism 3 provides the main static support capacity, negative stiffness mechanism 4 generates a mechanical effect opposite to positive stiffness, and by setting positive stiffness mechanism 3 and negative stiffness mechanism 4 in parallel, and cooperating with dynamic adjustment component 5 to adjust the working height of positive stiffness mechanism 3, the positive and negative stiffness are precisely canceled at the system equilibrium position, so that the system exhibits quasi-zero stiffness characteristics, thereby obtaining extremely low dynamic stiffness and excellent vibration isolation performance, achieving the dual advantages of "high load-bearing capacity and strong vibration reduction".

[0032] The base 1 has a support 6 inside, which is fixedly connected to the bottom of the support 2. One end of the negative stiffness mechanism 4 is fixedly connected to the end of the transmission unit on the support 6 away from the support 6, serving as a connecting transition component between the negative stiffness mechanism 4 and the support 2, ensuring effective force transmission and precise motion guidance.

[0033] The negative stiffness mechanism 4 includes six horizontal guide rails 41 fixedly connected to the inner wall of the base 1, providing precise horizontal motion guidance. The six horizontal guide rails 41 are divided into three groups: upper, middle, and lower. Each group contains two horizontal guide rails 41. A transmission unit is slidably mounted on each horizontal guide rail 41. One end of the transmission unit is rotatably connected to the support 6 to realize the conversion of motion mode. It also includes a negative stiffness elastic unit. The negative stiffness elastic unit has at least one movable end. The movable end of the negative stiffness elastic unit is connected to the end of the transmission unit away from the support 6. The transmission unit converts the vertical displacement of the support 2 into the horizontal movement of the movable end of the negative stiffness elastic unit, thereby generating a negative stiffness effect.

[0034] Each transmission unit includes a horizontal slider 401 slidably connected to two horizontal guide rails 41 in a set, so as to slide and transmit horizontal force on the guide rails. A rotating shaft 402 is rotatably connected to the surface of the horizontal slider 401, and a diagonal rod 403 is fixedly connected to the surface of the rotating shaft 402. A central shaft 404 is integrally provided at the other end of the diagonal rod 403. The central shaft 404 is rotatably connected to the end of the support 6. Through the combined structure of the horizontal slider 401, rotating shaft 402, diagonal rod 403 and central shaft 404, the precise conversion of vertical displacement to horizontal motion is realized, ensuring the stable generation of negative stiffness effect. The horizontal slider 401, diagonal rod 403 and support 2 are made of high-strength metal materials.

[0035] The negative stiffness elastic unit is a negative stiffness spring 42, which provides an adjustable negative stiffness force. In this embodiment, the negative stiffness spring 42 has two movable ends, and the two movable ends of the negative stiffness spring 42 are respectively connected to the horizontal sliders 401 of the two sets of transmission units. By connecting the horizontal sliders 401 of the two sets of transmission units through a negative stiffness spring 42, a symmetrical negative stiffness generation mechanism is formed to ensure the balance and stability of the system force. In other embodiments, the negative stiffness spring 42 may also have a movable end and a fixed end, and the movable end is connected to the corresponding horizontal slider 401.

[0036] The positive stiffness mechanism 3 includes a positive stiffness spring 31 and a damper 32 arranged in parallel. The positive stiffness spring 31 is used to provide static support force, and the damper 32 is used to provide dynamic damping force to dissipate vibration energy. By arranging the positive stiffness spring 31 and the damper 32 in parallel, the functions of static support and dynamic vibration reduction are realized at the same time, thereby improving the overall performance of the system.

[0037] Damper 32 is an intelligent damper with continuously adjustable damping coefficient, which enables adaptive adjustment to different vibration conditions and improves the intelligent level of vibration reduction effect.

[0038] The intelligent damper is a magnetorheological damper, providing controllable damping with fast response. The positive stiffness spring 31 is coaxially sleeved on the outside of the magnetorheological damper, and its two ends are respectively connected to the piston rod end and the cylinder end of the magnetorheological damper, achieving a compact layout. The piston rod end of the magnetorheological damper is fixedly connected to the bottom of the support base 2, and the cylinder end of the magnetorheological damper is fixedly connected to the top of the dynamic adjustment component 5. By coaxially sleeved on the outside of the magnetorheological damper, a compact integrated structure is formed, which simultaneously realizes the dual functions of providing positive stiffness and intelligent damping adjustment, improving space utilization and system integration.

[0039] An angle sensor 7 is mounted on the connection between the horizontal slider 401 and the inclined rod 403 via a bracket. This sensor is used to collect the rotation angle signal of the inclined rod 403 in real time and transmit it to the controller. The real-time collection of the rotation angle signal of the inclined rod 403 provides feedback information for the precise adjustment of the control system, thereby realizing closed-loop control. Preferably, in this embodiment, there are three sets of horizontal guide rails, and the angle sensor 7 is installed between the horizontal slider and the inclined rod of one set of horizontal guide rails.

[0040] The dynamic adjustment component 5 includes a drive component 51. The movable end of the drive component 51 is fixedly connected to the bottom of the positive stiffness mechanism 3, and is used to drive it to adjust its height in the vertical direction, thereby changing the geometric configuration parameters of the negative stiffness mechanism 4. A stepper motor 52 is fixedly connected to the inner bottom wall of the base 1, and the output end of the stepper motor 52 is fixedly connected to the input end of the drive component 51. The drive component 51 is a scissor telescopic mechanism, which includes a base 511 and a support platform 512. The base 511 is fixedly connected to the inner bottom wall of the base 1, and the support platform 512 is fixedly connected to the bottom of the positive stiffness mechanism 3. A cross link is provided between the base 511 and the support platform 512. The cross link is formed by hinged connection of a first link 513 and a second link 514 through a hinge shaft 515. One end of the first link 513 is rotatably connected to the inner wall of the base 511, and the other end of the first link 513 is rotatably connected to a first movable shaft 516. The first movable shaft 516 is connected to the inner wall of the support platform 512. The system features a sliding connection. One end of the second connecting rod 514 is rotatably connected to a second movable shaft 517, which is slidably connected to the inner wall of the base 511. The other end of the second connecting rod 514 is rotatably connected to the inner wall of the support platform 512. A nut block 518 is fixedly connected to the surface of the second movable shaft 517, and a lead screw 519 is threadedly connected to the inner wall of the nut block 518. The output end of the stepper motor 52 is fixedly connected to one end of the lead screw 519. The stepper motor 52 drives the lead screw 519 nut mechanism, thereby driving the scissor telescopic mechanism to achieve smooth and precise height adjustment. This changes the geometric configuration parameters of the negative stiffness mechanism 4, enabling the system to adapt to different load conditions and always maintain a near-zero stiffness state. The hinged arrangement of the first connecting rod 513 and the second connecting rod 514, along with the sliding connection of the movable shaft, ensures the smoothness and reliability of the lifting process. The lead screw 519 is a trapezoidal lead screw, providing high-efficiency transmission and allowing for long-term use without significant performance degradation.

[0041] A base acceleration sensor 8 is installed on the upper surface of the base 1, and a support acceleration sensor 9 is installed on the lower surface of the support base 2.

[0042] Working principle: The working principle of this quasi-zero stiffness adaptive vibration damping seat consists of the following processes: initial state, load response, angle detection and judgment, stiffness adjustment, dynamic vibration damping, and reverse adaptation. Specifically: 1. Initial State: When the seat is unloaded, the negative stiffness spring 42 is in a free state, the scissor telescopic mechanism is in the neutral position, and the magnetorheological damper height is the initial height. At this time, the angle sensor 7 detects the initial angle of the inclined rod 403 as θ0, and the system is in the initial state (e.g., Figure 6 When the inclined rod 403 is parallel to the horizontal guide rail 41, the angle sensor 7 has an angle of 0°. This state is the quasi-zero stiffness rated equilibrium state of the system. Figure 7 As shown; 2. Load Response: After the person is seated, the support 2 is subjected to a vertical load F, which causes the diagonal rod 403 to rotate around the central axis 404 of the support 6, resulting in an angle change Δθ. The diagonal rod 403 drives the horizontal slider 401 to slide along the horizontal guide rail 41 through a linkage mechanism, causing the negative stiffness spring 42 to stretch or relax, generating an elastic restoring force F_elastic. Where k is the spring stiffness, This represents the slider displacement; 3. Angle detection and judgment: Angle sensor 7 detects the θ value in real time and transmits it to the controller; The controller has a built-in quasi-zero stiffness angle threshold (θ=0). If θ≠0, it is determined that the system has not reached the quasi-zero stiffness rated balance state, and a control signal is output to the stepper motor 52. 4. Stiffness Adjustment: Stepper motor 52 drives the lead screw 519 of the scissor telescopic mechanism to rotate according to the control signal, causing the scissor telescopic mechanism to expand / contract, adjusting the working height H of the positive stiffness mechanism; the change of H changes the force state of the support 2, thereby adjusting the angle θ of the inclined bar 403 until θ=0. At this time, the equivalent negative stiffness value (Kneg) generated by the negative stiffness mechanism is equal to the stiffness value (Kpositive) of the positive stiffness mechanism, that is, |Kneg| = |Kpositive|, and the overall dynamic stiffness of the system approaches zero, which is the quasi-zero stiffness state; 5. Dynamic vibration reduction: In a vibrating environment (such as vehicle bumps), the support 2 generates vertical vibration, causing the angle of the diagonal rod 403 to fluctuate. The angle sensor 7 detects the angle fluctuation signal in real time and calculates the displacement change of the support 2 relative to the base 1 through a geometric model. At the same time, based on the acceleration obtained by the support acceleration sensor 9 and the base acceleration obtained by the base acceleration sensor 8, the controller dynamically adjusts the current of the magnetorheological damper, thereby adjusting the damping coefficient to dissipate vibration energy and achieve efficient vibration reduction. 6. Reverse Adaptability: When a person stands up or adjusts their posture, the load decreases, the negative stiffness spring 42 resets and pushes the horizontal slider 401 to move in the opposite direction, and the angle of the inclined rod 403 changes in the opposite direction; after the angle sensor 7 detects, the controller controls the stepper motor 52 to drive the scissor telescopic mechanism in the opposite direction, so that the system returns to the rated balance state.

[0043] Example 2 The present invention also provides a control method for the automatic stiffness adjustment vibration isolation device as described above, comprising the following steps: Step S1: Obtain key system parameters and calibrate the damper model First, key system parameters, including load mass, linear stiffness coefficient, and nonlinear stiffness coefficient, are obtained offline through static load experiments and frequency sweep tests. At the same time, the magnetorheological damper is experimentally calibrated to establish a model relating its output force to input current and motion speed. A current-force inverse mapping lookup table is also constructed to provide an accurate model basis for real-time control. Step S2: Real-time acquisition and processing of system status signals The base accelerometer measures the foundation vibration acceleration to reflect external disturbances, and the relative displacement and velocity of the vibration isolation system are obtained through angle sensor 7, base accelerometer 8 and support accelerometer 9. All signals are sampled and filtered at high frequency to ensure that the data is accurate and reliable, and to provide input for feedforward and feedback control. Step S3: Counteracting main disturbances and nonlinear forces based on feedforward compensation Based on the principle of structural invariance, a front feedback compensator and an LQR feedback controller (not shown in the figure) are set at the bottom of the support base. The goal is to generate corresponding control forces to cancel out the vibration isolation effect before the measurable disturbance and the nonlinear stiffness force of the system have an adverse effect on the vibration isolation effect, thereby significantly reducing the dynamic deviation of the controlled variable. The core task of the compensator is to calculate the feedforward control force. f ff ：

[0044] In the formula, Used to counteract the base acceleration The resulting external inertial disturbance, Used to counteract the system's nonlinear restoring force The cubic nonlinear stiffness force in the system is compensated in this way, which significantly simplifies the dynamic characteristics of the system near the equilibrium point and makes it more conducive to the subsequent optimization design of the feedback controller. Since the magnetorheological damper of the actuator can only consume energy and cannot inject energy, the calculated feedforward force must be... A physical feasibility assessment is performed. This assessment is based on real-time measurements of the system's relative velocity.

[0045] This constraint ensures that the control force will only be output when the direction of the desired feedforward force is opposite to the direction of piston movement; otherwise, the command will be set to zero, fundamentally avoiding the energy injection problem of the physical system. The feedforward controller is used to counteract measurable basic disturbances and nonlinear stiffness forces of the system. The calculated feedforward control force needs to be subject to semi-active constraint judgment: the control force is only effective when its direction and the direction of system motion meet the energy dissipation condition; otherwise, it is set to zero to ensure that the magnetorheological damper always works in an energy-dissipating state and avoids physically unrealizable energy injection. Step S4: Design an LQR feedback controller to optimize system state Establish a state-space model suitable for LQR design; let the system's state vector be... ,in u This represents the vertical displacement of the seat. For the vertical velocity, the linearized state equation of the system can be expressed as:

[0046] in, A For the system matrix, B For the input matrix, The output force of the LQR feedback controller; To achieve targeted suppression of the 0.1-0.5Hz frequency band sensitive to human motion sickness, a hybrid band-stop filter is innovatively introduced. The band-stop filter is used to extract the vibration components in the 0.1-0.5Hz frequency band from the acceleration response of the seat base in real time. z band； The extracted frequency band signal energy is used as the state weight matrix in the LQR cost function. Q Based on this, increase the matrix Q The weight elements in the cost function correspond to the absolute acceleration state. J The system imposes a higher penalty on vibrations in this frequency band:

[0047] This design allows the controller to prioritize minimizing the energy in the sensitive frequency band during optimization, thereby achieving precise suppression of vibrations at specific frequencies. (Weight matrix) R This is used to constrain and control energy, preventing excessive actuator demand; To solve for the optimal control force, it is necessary to solve the continuous-time algebraic Riccati equation to obtain the symmetric positive definite matrix. P Then, the optimal state feedback gain matrix is ​​calculated. The LQR feedback control law is:

[0048] The LQR feedback controller works in conjunction with the feedforward compensator. The feedforward compensator is responsible for quickly canceling known and measurable major disturbances and nonlinear forces. The LQR feedback is responsible for optimizing the system state and suppressing residual disturbances, model errors, and unmodeled dynamics that the feedforward could not completely cancel. Step S5: Tune the controller parameters using a multi-objective optimization algorithm. Using a multi-objective butterfly optimization algorithm, the optimal combination of LQR weight matrices Q and R is automatically found. A conflicting objective is defined to control for inherent performance contradictions. The objective function is as follows:

[0049] Among them, human body vibration frequency (HBVF), suspension working space (SWS), and human body acceleration (HA) are key performance indicators that fundamentally determine the comfort of the vehicle. The algorithm can weigh the above multiple conflicting objectives and find a set of Pareto optimal solutions, rather than a single optimal solution. From the set of Pareto optimal solutions, a set of parameters that satisfy all engineering constraints are selected to obtain an LQR controller with balanced performance and excellent suppression of motion sickness frequency band. Step S6: Synthesize the total desired control force and perform physical feasibility verification. The outputs of the feedforward controller and the LQR feedback controller are integrated to transform the theoretically calculated control commands into physical control signals that the magnetorheological damper can execute safely and effectively. The feedforward control force and the LQR feedback control force are algebraically superimposed to obtain the total desired control force. f des ; The feedforward control force and the LQR feedback control force are algebraically superimposed to obtain the total desired control force. f des To ensure the physical feasibility of the actuator, it is dynamically limited to ensure that its absolute value does not exceed the maximum output force of the magnetorheological damper. The desired control force after synthesis and limiting is... f des It can only consume energy, not inject energy; therefore, the system monitors the relative velocity of the vibration isolation mass in real time. Only when desired control f des Direction and speed of motion The opposite direction, that is At this time, the control force is in the damper's "energy dissipation quadrant," and the command is considered physically feasible and output. Conversely, if... This means that the command requires the damper to provide "negative damping" or inject energy, at which point the control command will be set to zero. This mechanism fundamentally guarantees the physical feasibility of the control scheme; Step S7: Map the desired control force to the damper input current Based on the physical characteristics of the magnetorheological damper, the desired control force is mapped to the corresponding input current. The mapping process strictly follows the semi-active constraint principle, that is, the corresponding current is only output when the damper is in the energy-consuming condition, otherwise the current is zero. The mapping relationship is obtained based on calibration experiments and is supplemented by current limiting protection. Establish a model relating its output force to its input current and velocity:

[0050] Where F(t) is the output force of the magnetorheological damper. i It is the input current, z def These are the damper displacements; a0, a1, a2, and a3 are model parameters determined through experimental calibration. V 0 / X 0 is the ratio of the lag critical velocity to the critical displacement; Step S8: Output current signal to drive the actuator The calculated current signal is output to the damper coil through a power amplifier, so that it generates a corresponding damping force to act on the vibration isolation system, thereby achieving real-time suppression of vibration. Step S9: Closed-loop feedback and system status update After the damping force is applied to the system, its dynamic response state is updated, and the system displacement, velocity and foundation acceleration signals are continuously collected by the sensors to form a closed-loop control loop, thereby realizing the continuous adaptive adjustment of the vibration isolation system.

[0051] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A nonlinear stiffness automatic adjustment vibration isolation device, comprising a base (1) and a support (2), characterized in that, Also includes: A positive stiffness mechanism (3) is disposed inside the base (1) to provide positive stiffness of the main support in the vertical direction; A negative stiffness mechanism (4) is disposed inside the base (1) and connected in parallel with the positive stiffness mechanism (3) to generate a negative stiffness opposite to that of the positive stiffness mechanism (3); The dynamic adjustment component (5) is fixed to the inner bottom wall of the base (1) and acts on the positive stiffness mechanism (3). By adjusting the working height of the positive stiffness mechanism (3), the system exhibits quasi-zero stiffness characteristics at the equilibrium position.

2. A control method for the nonlinear stiffness automatic adjustment vibration isolation device as claimed in the claim, characterized in that, Includes the following steps: S1: Real-time acquisition and processing of signals from base acceleration, support acceleration, and angle sensors to obtain system status information; S2: Based on the measurable basic acceleration and the system nonlinear model, calculate the feedforward control force to counteract the main disturbances and nonlinear forces, and verify the physical realizability according to the semi-active constraint principle; S3: Based on the linear quadratic optimal (LQR) controller, design a forward feedback controller and calculate the optimal state feedback control force; S4: Adaptive tuning of the LQR controller parameters is performed using a multi-objective optimization algorithm; S5: Synthesize the feedforward control force and the feedback control force, and perform amplitude limiting and direction verification to obtain the physically realizable desired control force; S6: Based on the calibrated inverse model of the magnetorheological damper, the desired control force is mapped into an input current signal; S7: Output current signal drives magnetorheological damper to generate damping force; S8: Continuously monitor load changes. When the angle sensor detects that the system deviates from the rated balance position, adjust the working height of the positive stiffness mechanism (3) through the dynamic adjustment component (5) to restore the system to the near-zero stiffness state. S9: Update the system status and return to step S1 to form closed-loop control.

Images