首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper, a novel semi-active variable admittance (VA) concept is proposed, and a seat suspension prototype with a magnetorheological fluid damper based rotary VA device is designed, manufactured, and experimentally validated. The conventional inerter with a single flywheel has a constant inertance, which can effectively improve the suspension performance by being integrated into a mechanical network with springs and dampers. The proposed rotary VA device comprises a gear reducer, two flywheels and a variable damping (VD) device which is used to connect the two flywheels. With carefully designing, the rotary VA device is compacted and is similar with a VD device in size. The rotary VA device is installed in the centre of a seat suspension's scissors structure to form a VA seat suspension. According to the test results, the equivalent inertance of the seat suspension can vary from 11.3 Kg–76.6 Kg with a 3 Hz frequency and 5 mm amplitude sinusoidal movement by changing the current from 0 A–1 A. By analysing the system characteristics, a hybrid controller with two acceleration feedbacks is proposed. Thereafter, the seat suspension and controller are validated in experiments by comparing the performance with a conventional passive seat suspension. The random vibration test shows the excellent performance of the proposed seat suspension; the frequency weighted root mean square acceleration of the seat is reduced by 43.6%, which indicates a great improvement of the ride comfort. The VA device shows great prospect in the suspension application.  相似文献   

2.
The paper presents an explicit two-step calibration procedure for tuned inerter based vibration absorbers on flexible structures. It makes use of a local approximate representation of the structural response to the device force, in which the contribution of the non-resonant modes is represented approximately around the resonance frequency by a background flexibility and a background inertia term. The calibration procedure then consists of two steps. The first step calibrates an equivalent vibration absorber including the background terms, and the second step subsequently evaluates the parameters of the actual device by extracting the background flexibility and inertia parameters. The first step represents the classic idealized single degree of freedom representation of the structure, whereas the second step leads to an increase of stiffness, inertia and damping parameters of the actual device due to background flexibility of the structure. The procedure is illustrated in detail for three inerter based vibration absorbers: parallel coupling of damper and stiffness, parallel coupling of damper and inerter, and finally a device with two dampers in parallel with stiffness and inerter elements, respectively. Explicit expressions for the calibration are obtained for each device, and it is demonstrated that the procedure leads to a balanced plateau of amplification around the resonance frequency of the magnitude assumed as the basis for the device parameter calibration.  相似文献   

3.
This study introduces a novel particle inerter system (PIS) designed for vibration mitigation of structures. The new system comprises an inerter subsystem, a spring, and a tuned particle element, where the spring is used for tuning the particle element and the inerter subsystem is set for energy absorption and dissipation. The structural performance and the vibration mitigation effect of the PIS are assessed in terms of displacement and acceleration responses. An optimal design method is developed for a PIS under a performance-oriented design framework. Following the criterion of lightweight control, the added mass of the PIS is minimized under the constraints of target displacement and acceleration responses. A parametric analysis is performed and the robustness of the PIS for seismic response mitigation is verified. Design cases are carried out for the illustration of the proposed design method. The results show that the structural displacement and acceleration responses can be reduced significantly with the help of a PIS. Compared with the particle tuned mass damper with the same parameters, both the energy absorption and dissipation effects of the PIS are increased and the relative displacement response of the container in the PIS is reduced by the inerter subsystem. Under the same performance target, the required physical mass of the container and particles in the PIS is minimized and is significantly smaller than that of the conventional particle tuned mass damper.  相似文献   

4.
In this paper a novel type of frictionless mechanical inerter device is presented, where instead of gears, motion of the flywheel is achieved using living-hinges. The design is a type of pivoted flywheel inerter inspired in part by the Dynamic Anti-resonant Vibration Isolator (DAVI) concept, which was first developed in the 1960s. Unlike the DAVI, it will be shown that the pivoted flywheel inerter has the advantage of producing balanced forces. Furthermore the use of living-hinges eliminates the need for gears or other frictional elements in the inerter mechanism. To demonstrate the utility of the new concept, a bench-top experiment was performed using a small-scale living-hinge inerter manufactured using polypropylene hinges. By estimating the experimental system parameters, the transmissibility results from the experiment could be compared to a mathematical model. These results showed that the living-hinge inerter provided an isolation effect of at least three orders of magnitude in terms of the maximum amplitude reduction from the uncontrolled system compared to that with the inerter added. Although friction was eliminated, the living-hinges did introduce additional damping, and this was found to correspond to an increase in the equivalent damping ratio for the uncontrolled system of 1.2%. It is shown that the living-hinge inerter developed in this paper fits all of the essential conditions required to be a practical inerter device. Furthermore, as it operates without mechanical friction, or fluid flow, it represents a new paradigm in experimental inerter technology.  相似文献   

5.
Vibration suppression capabilities of linear passive vibration absorbers, such as traditional tuned mass damper (TMD), and recently proposed inerter-based vibration absorbers, have been studied for multiple mechanical systems. In particular, significant performance advantages have been obtained with a specific device making use of both inerter and mass elements, namely the tuned mass damper inerter (TMDI). However, there are still countless mass-included inerter-based configurations that have not been studied, which can potentially provide more preferred dynamic properties. In this paper, an immittance-function-layout (IFL) is introduced, which can cover a large range of topological connection possibilities with both mass and inerter elements. With the recently proposed structural immittance format, a systematic approach is established to identify the most beneficial IFL type mass-included inerter-based configurations with pre-determined number of each element type. Vibration suppression performance with single-IFL type device and two parallel-connected IFLs (i.e. dual-IFL) type devices are investigated in this paper. Three optimal configurations are identified for mitigating the maximum inter-storey drift of an example 3-storey building model subjected to base excitation. With this 3-storey building model, results show that, for the optimum single-IFL configuration, the performance improvement is 7.3% compared with the optimum TMDI, and with identified beneficial dual-IFL configurations, up to 34.9% performance advantages are obtained. Furthermore, consistent performance gains are shown under real-life earthquake inputs and with a 10-storey building model using identified absorber configurations.  相似文献   

6.
In recent years different inerter-based vibration absorbers (IVAs) emerged for the earthquake protection of building structures coupling viscous and tuned-mass dampers with an inerter device. In the three most popular IVAs the inerter is functioning either as a motion amplifier [tuned-viscous-mass-damper (TVMD) configuration], mass amplifier [tuned-mass-damper-inerter (TMDI) configuration], or mass substitute [tuned-inerter-damper (TID) configuration]. Previous work has shown that through proper tuning, IVAs achieve enhanced earthquake-induced vibration suppression and/or weight reduction compared to conventional dampers/absorbers, but at the expense of increased control forces exerted from the IVA to the host building structure. These potentially large forces are typically not accounted for by current IVA tuning approaches. In this regard, a multi-objective IVA design approach is herein developed to identify the compromise between the competing objectives of (i) suppressing earthquake-induced vibrations in buildings, and (ii) avoiding development of excessive IVA (control) forces, while, simultaneously, assessing the appropriateness of different modeling assumptions for practical design of IVAs for earthquake engineering applications. The potential of the approach to pinpoint Pareto optimal IVA designs against the above objectives is illustrated for different IVA placements along the height of a benchmark 9-storey steel frame structure. Objective (i) is quantified according to current performance-based seismic design trends using first-passage reliability criteria associated with the probability of exceeding pre-specified thresholds of storey drifts and/or floor accelerations being the engineering demand parameters (EDPs) of interest. A variant, simpler, formulation is also considered using as performance quantification the sum of EDP variances in accordance to traditional tuning methods for dynamic vibration absorbers. Objective (ii) is quantified through the variance of the IVA force. It is found that reduction of IVA control force of up to 3 times can be achieved with insignificant deterioration of building performance compared to the extreme Pareto optimal IVA design targeting maximum vibration suppression, while TID and TMDI achieve practically the same building performance and significantly outperform the TVMD. Moreover, it is shown that the simpler variant formulation may provide significantly suboptimal reliability performance. Lastly, it is verified that the efficacy of optimal IVA designs for stationary conditions is maintained for non-stationary stochastic excitation model capturing typical evolutionary features of earthquake excitations.  相似文献   

7.
Since being postulated more than a decade ago, inerters have been successfully employed to enhance the dynamic performance of mechanical systems in several applications. Their ability to lend a high dynamic mass presence to systems that employ them with only a relatively small static device mass makes them unique among mechanical elements. This study explores the mechanical wave manipulation characteristics of nonlinear inertant acoustic metamaterial (NLIAM) configurations using analysis and simulations for their one-dimensional discrete element lattice representations. Firstly, based on notional concepts for nonlinear inertant devices, potential frequency-dependent and acceleration-dependent nonlinear inertant models are identified. Using an effective mass model for the NLIAM with frequency-dependent inertance in the local resonator attachment, the dispersion characteristics of inverse square law and power law inertance models are examined and contrasted with those for an acoustic metamaterial with frequency invariant inertance. While a tuned inverse square law inertance model ensures the existence of a band gap over almost the entire frequency bandwidth of interest even encompassing the extremely low frequency regime, the low and high frequency limits for this inertance law would not be realizable in practice. A potentially more practical power law approximation is proposed and shown to deliver a widening of the band gap by more than 100% towards frequencies below the lower bound of the band gap for the acoustic metamaterial with frequency invariant inertance. Further, drawing inspiration from the Duffing-type stiffness, an acceleration-dependent cubically nonlinear inertance model is proposed. First order corrections to the dispersion characteristics are obtained for an NLIAM with acceleration-dependent inertance using a perturbation approach. For weakly nonlinear cases, excitation amplitude-activated shifts in the dispersion curves are found to enable this NLIAM to act as a passive adaptive filter for mechanical waves based solely on their excitation amplitude. Practical manifestations of such NLIAM could therefore provide a means to realize extraordinary wave manipulation capabilities especially suitable for low frequency structural dynamic applications.  相似文献   

8.
Novel nonlinear damping control is proposed for the second-order systems. The proportional output feedback is combined with the damping term which is quadratic to the output derivative and inverse to the set-point distance. The global asymptotic stability, passivity property, and convergence time and accuracy are demonstrated. Also the control saturation case is explicitly analyzed. The suggested nonlinear damping is denoted as optimal since requiring no additional design parameters and ensuring a fast convergence, without transient overshoots for a non-saturated and one transient overshoot for a saturated control configuration.  相似文献   

9.
In this paper we investigate an inerter equipped with a prototype continuously variable transmission (CVT) designed for the novel tuned mass damper. Inerter enables stepless changes of inertance via varying transmission ratio of the CVT. The main difference from classical inerter is addition of CVT, hence we present its design and properties in details. Motion of the proposed CVT is oscillatory and we test it for the actual working conditions. We derive the mathematical model of the system that include dissipation via dry friction. We analyse the actual transmission ratio, internal motion resistances and identify the inertia of CVT components using energy conservation method and validate further. Finally, we apply actual working conditions and compare the experimental and numerical exciting torques of the CVT. We obtain good agreement between them, hence the proposed model is robust and gives reliable results.  相似文献   

10.
This paper investigates the benefits of the inerter in improving vibration suppression of milling machine tools. The traditional method for repressing the cutting vibration of milling machines includes applying passive mechanical networks that consist of masses, dampers, and springs. However, because the mass element is not a genuine two-terminal network element, the achievable performance of the passive mechanical networks might be restricted. The inerter was invented to substitute the mass element and has been successfully applied to many mechanical systems, such as vehicles and buildings. This paper extends the application of the inerter to a milling machine and discusses the resulting vibration suppression improvements. We first built a model of the milling machine via experiments, followed by applying three basic suspension layouts to the model and illustrating how the inerter can help reduce system vibration. Lastly, we conducted experiments to verify the effectiveness of the inerter in improving the manufacturing performance of the milling machine.  相似文献   

11.
Recently, a lot of attention has been given to a mechanical device known as the inerter. It is a mechanical component that can be compared to a capacitor with two ungrounded terminals in the mechanical-electrical systems analogy. In this paper, it is shown that although the concept of an inerter as a separate mechanical element is relatively new, there are several well-established vibration isolation systems that exhibit similar behavior to a simple lumped parameter system containing an inerter. Through a review of the literature, a link is established between the old and new ideas. Furthermore, a comparison between the systems is carried out using the quantities of mechanical impedance and displacement transmissibility. The advantages and disadvantages of using the inerter in vibration isolation are discussed, and a simple way of improving the high-frequency performance without severely degrading the low-frequency performance is described.  相似文献   

12.
流阻和摩擦对流体流动作功装置性能的影响   总被引：1，自引：0，他引：1  
严宁榕 《科技通报》2000,16(1):61-64
研究非线性流阻和作功机械内部摩擦对流体流动作功装置性能的影响,导出输出功率与机械效率以及功率损耗与机械效率间的关系,又由此导出最大输出功率及其相应的一些重要性能参数,并作些有意义的讨论。所得结论可为流体流动作功装置的优化设计提供些新理论依据。  相似文献   

13.
汶川地震建筑结构震害概述及分析   总被引：1，自引：0，他引：1  
2008年5月12日四川省汶川县发生里氏8.0级地震,汶川地震是我国建国以来最为严重的地震,造成了震区房屋大量垮塌和破坏.文章对收集到的建筑震害进行概述,针对各种建筑结构的典型震害进行了详细分析,总结了房屋震害特点,思考了此次地震带给我们的经验和教训.  相似文献   

14.
The optimal location of a static synchronous compensator (STATCOM) and its coordinated design with power system stabilizers (PSSs) for power system stability improvement are presented in this paper. First, the location of STATCOM to improve transient stability is formulated as an optimization problem and particle swarm optimization (PSO) is employed to search for its optimal location. Then, coordinated design problem of STATCOM-based controller with multiple PSS is formulated as an optimization problem and optimal controller parameters are obtained using PSO. A two-area test system is used to show the effectiveness of the proposed approach for determining the optimal location and controller parameters for power system stability improvement. The nonlinear simulation results show that optimally located STATCOM improves the transient stability and coordinated design of STATCOM-based controller and PSSs improve greatly the system damping. Finally, the coordinated design problem is extended to a four-machine two-area system and the results show that the inter-area and local modes of oscillations are well damped with the proposed PSO-optimized controllers.  相似文献   

15.
Bugholes are surface imperfections that appear as small pits and craters on concrete surface after the casting process. Bugholes are cosmetic surface imperfections and do not affect the structural integrity of the concrete structure. However, existences of these imperfections increase cost since bugholes require additional surface preparations before painting or finishing the concrete surface. Additionally, these surface imperfections cause secondary problems by decreasing the cover on RC making incretion of salts into the reinforcement bars inside RC. In this paper, authors discuss development of a new device to measure “bughole” rating of concrete surface. The innovative technique used in design enables us to manufacture a compact instrument, which is physically small, lightweight and practical. The paper explains the design principles of the device and the procedure used for optimization of design parameters for the best performance. Last section of the paper gives simulation results to compare the performance of the device to current state of the art methods used for bughole rating in industry.  相似文献   

16.
The space debris removal system (SDRS) of tethered space tug is modelled as a cable dragged flexible spacecraft. The main goal of this paper is to develop a dynamic modeling approach for mode characteristics analysis and forced vibration analysis of the planar motion of a cable dragged flexible spacecraft. Solar arrays of the spacecraft are modelled as multi-beams connected by joints with additional rotating spring where the nonlinear stiffness, damping and friction are considered. Using the Global mode method (GMM), a novel analytical and low-dimensional nonlinear dynamic model is developed for vibration analysis of SDRS to enhance the design capacity for better fulfillment of space tasks. The linear and nonlinear partial differential equations that governing transverse vibration of solar arrays, transverse and longitudinal vibrations of cable are derived, along with the matching and boundary conditions. The natural frequencies and analytical global mode shapes of SDRS are determined, and orthogonality relations of the global mode shapes are established. Dynamical equations of the system are truncated to a set of ordinary differential equations with multiple-DOF. The validity of the method is verified by comparing the natural frequencies obtained from the characteristic equation with those obtained from FEM. Interesting mode localization and mode shift phenomena are observed in mode analysis. Dynamic responses of the system excitated by fluctuation of attitude control torque and short-time attitude control torque are worked out, respectively. Nonlinear behaviors are observed such as hardening, jump and super-harmonic resonances. Residual vibration of the overall system with considering the varous values of nonlinear stiffness, damping coefficient and friction coefficient has shown that the nonlinearity of joints has a great influence on the vibration of the overall system.  相似文献   

17.
The inerter has garnered much attention in the past two decades owing to its unique mechanical characteristics. As a substitution of the capacitance element based on the electrical-mechanical analogy, the inerter has outstanding advantages. Extensive investigations have been conducted for the development of inerter-based vibration isolation system. This paper provides a retrospective perspective and an update on the inerter's progress for vibration isolation in different fields. The advantages of inerter compared with mass element are analyzed and revealed. Some existing reviews and highly-cited papers are summarized to outline the inerter development progress. Thereafter, the inerter is reviewed in detail from the perspective of network analogy and synthesis, mechanical domain, and power flow transmission. The devices improvement and control approach are summarized. Finally, the significance of inerter research, the challenge in current studies, and promising inerter application fields are presented and discussed. This paper is closed by conclusions, which highlight the necessity of inerter research, current challenges, and future research directions.  相似文献   

18.
The flow focusing is a fundamental prior step in order to sort, analyze, and detect particles or cells. The standard hydrodynamic approach requires two fluids to be injected into the microfluidic device: one containing the sample and the other one, called the sheath fluid, allows squeezing the sample fluid into a narrow stream. The major drawback of this approach is the high complexity of the layout for microfluidic devices when parallel streams are required. In this work, we present a novel parallelized microfluidic device that enables hydrodynamic focusing in each microchannel using a single feed flow. At each of the parallel channels, a cross-filter region is present that allows removing fluid from the sample fluid. This fluid is used to create local sheath fluids that hydrodynamically pinch the sample fluid. The great advantage of the proposed device is that, since only one inlet is needed, multiple parallel micro-channels can be easily introduced into the design. In the paper, the design method is described and the numerical simulations performed to define the optimal design are summarized. Moreover, the operational functionality of devices tested by using both polystyrene beads and Acute Lymphoid Leukemia cells are shown.  相似文献   

19.
基于流体力学理论,研究发动机液力悬置惯性通道内阻尼力,建立一种液力悬置力学模型和数学模型,进行动特性仿真,从流体力学的角度分析了液力悬置的结构参数对其动态特性的影响。  相似文献   

20.
This paper investigates the finite-time stability (FTS) and finite-time stabilization for a class of nonlinear singular time-delay Hamiltonian systems, and proposes a number of new results on these issues. Firstly, an equivalent form is obtained for the nonlinear singular time-delay Hamiltonian systems by the singular matrix decomposition method, based on which some delay-independent and delay-dependent conditions on the FTS are derived for the systems by constructing a kind of novel Lyapunov function. Secondly, we use the equivalent form as well as the energy shaping plus damping injection technique to investigate the finite-time stabilization problem for a class of nonlinear singular port-controlled Hamiltonian (PCH) systems with time delay, and present a specific control design procedure for the systems. Finally, we give several illustrative examples to show the effectiveness of the results obtained in this paper.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号