Semi-active Isolation Research Articles

Performance evaluation of a novel semi-active absorption and isolation co-control strategy with magnetorheological seat suspension for commercial vehicle

Abstract Vibration isolation performance of seat suspension plays a critical role in protection of drive’s physical health as the last barrier. In this paper, the integrated magnetorheological (MR) dynamic tuned mass damper (TMD) is firstly designed and utilized into seat suspension. A semi-active co-control algorithm with MR damper and MR TMD is designed, analyzed and validated by comparative experiments. The dynamic models of two MR devices have been tested and fitted. Comparing with simulation and experimental results under various excitations and control conditions, this co-control algorithm with MR TMD is validated to be highly effective. The transmissibility at resonance frequency reaches to 0.81 which is less than 1. This phenomenon has hardly been investigated in seat suspension. It illustrates that resonance has been suppressed and improved significantly. The peak acceleration decreases to 1.19 m s−2 with a reduction of 57.2%, in contrast to passive condition with MR damper. The comfort index is increased by 45.6% under random excitation than passive condition. According to these comparisons, the vibration isolation property and comfort of seat suspension can be further improved by the proposed co-control algorithm with two MR devices.

Advanced seismic control strategies for smart base isolation buildings utilizing active tendon and MR dampers

This paper investigates the seismic behaviour of a five-storey shear building that incorporates a base isolation system. Initially, the study considers passive base isolation and employs a multi-objective archived-based whale optimization algorithm called MAWOA to optimize the parameters of base isolation. Subsequently, a novel model is proposed, which incorporates an interval type-2 Takagi-Sugeno fuzzy logic controller (IT2TSFLC) utilizing clustering techniques. The building includes Magneto-rheological (MR) dampers installed at the base isolation level and two active tendons positioned on the first and second storeys of the structure. The semi-active control force of the base isolation with MR dampers is determined by the fuzzy system, while the active control force for the active tendons is computed using the linear quadratic regulator (LQR) algorithm, enabling control force provision during seismic events. The primary objective of this model is to enhance the seismic control of the building. Therefore, it is classified as a proposed model. The structural system is subjected to seismic analyses, considering three different structural configurations: uncontrolled, equipped with passive base isolation, and equipped with semi-active base isolation combining MR dampers and active tendons. The findings of the research demonstrate that by considering the optimization of parameters of the passive base isolation based on the white noise scenario and using these parameters as design parameters, during seismic analysis of the structure in some earthquakes, increased structural responses were observed when compared to uncontrolled structure, highlighting a potential risk. Nevertheless, the proposed system effectively addresses this drawback of passive control systems by markedly reducing structural responses, as compared to both passive base isolation and uncontrolled structure. These results suggest that the proposed system is an effective solution for mitigating seismic risks in structural seismic control.

Modelling and simulation of MR damper characterization and uncertainty assessment in marine engine vibration isolation with FLPID control

ABSTRACT This paper meticulously examines the magneto-rheological (MR) damper to exploring its application in a semi-active isolator system. The MR damper’s distinctive capability to regulate damping force through an externally applied magnetic field is investigated via extensive experimental testing. Sinusoidal displacement inputs with varying electromagnet currents reveal a direct correlation between higher current levels and augmented MR damper forces. Validation of the experimental results is achieved through the Viscous Plus Dahl Model, showcasing its accuracy in capturing the damper’s hysteresis behavior. The study extends its scope to practical implementation by integrating the MR damper into a marine diesel engine system. A fuzzy logic-based self-tuning PID controller collaborates with the MR damper to establish a semi-active vibration isolator. The integrated model, encompassing primary and secondary masses, the engine, and the isolator with passive and semi-active systems, is rigorously analyzed. Experimental validation and theoretical simulations, aligned with data gathered from experiments, affirm the model’s fidelity in representing the MR damper. Simulation outcomes underscore the significant enhancement in vibration reduction characteristics of the semi-active isolator system compared to its passive counterpart, particularly evident in the improved performance of the 1200 kg engine under diverse operating conditions.

Improvement of ride quality for a wheel loader with semi-active cab isolation system via fuzzy self tuning of PID controller

Improving driver ride comfort of a wheel loader is important to avoid potential health hazards from the whole-body vibration. A fuzzy self-tuning of PID controller is designed to control the damping coefficient of Semi-active cab isolation system (SCIS) for a wheel loader. A dynamic model of a wheel loader is establish under survey conditions for analysis and evaluation. The r.m.s acceleration responses of the vertical driver's seat and pitch angle of vehicle body according to ISO2631-1 (1997-E) are chosen as objective functions. The effectiveness of the proposed control strategy is analyzed through simulations involving excitations for a random road profile in time domain. The proposed SCIS is simulated and analyzed by Matlab/Simulink software in comparison with a passive cab isolation system (PCIS) under survey conditions. The achieved results indicate that ride comfort effectiveness of a wheel loader with SCIS is better than PCIS under survey conditions. In addition, the study results are the initial basis for optimizing controller parameters.

A Hybrid Vibration Isolator Based on Elastomeric and Electromagnetic Restoring Force

The protection of structures and machines from ground vibrations is a deeply felt and widely studied problem. These vibrations are typically generated by the operation of machines, vehicular traffic, seismic events, shocks, explosions, etc., and are generally characterized by frequencies that are not known a priori, making the use of passive isolation systems problematic. Just away from the source, ground vibrations have a predominantly horizontal component. To meet the conflicting requirements of passive isolation systems, which should have higher stiffness when the structure is at rest and lower stiffness when the ground forces it to vibrate, active or semi-active isolation systems can be adopted. In the following article, the possibility of adopting a hybrid isolator is evaluated; it consists of shear-stressed elastomeric pads coupled with an electromagnetic actuator; the latter consists of three coils, two of which are connected to the ground and the other one to the body to be isolated. This kind of isolator has the same flexibility and adaptability as the active ones, with the advantage of ensuring its functioning even in the absence of an external energy source. Its flexibility is due to the presence of a smart element that allows one to tune the characteristics of the isolator to consider the instantaneous isolation requirements. The proposed solution allows one to modify the isolation system’s characteristics in a sufficiently wide range of displacements equal to that defined by the maximum allowed deformation of the elastomeric pads. This paper reports the description of the isolation system and an analytical model to describe its restoring force; then, an experimental setup is adopted to identify the parameters of the analytic model; finally, several simulations are reported to compare the analytical and the experimental trends of the restoring force and to characterize the isolator.

AN INTELLIGENT ISOLATION SYSTEM BASED-ON LONG SHORT-TERM MEMORY MODULE MODEL FOR GROUND MOTION CHARACTERISTICS PREDICTION

An intelligent control system based on a semi-active variable stiffness isolation system and the Long Short-Term Memory (LSTM) is proposed in this study. In the field of semi-active control, the design of control laws relies on the measurement and feedback of the structural response when an earthquake occurs. The optimal control parameters should be determined in real time to achieve the performance-oriented control target by identifying the ground motion characteristics, which have a great influence on the control performance in the early stage. To deploy the optimal control parameters, a LSTM-based module for predicting ground motion characteristics is first proposed. In addition, a sensitivity analysis using the world-wide ground motion database is also conducted, and the representative cases are selected to optimize the fuzzy inference surface for the Leverage-type Stiffness Controllable Isolation System (LSCIS). Numerical simulation indicates, by using the proposed GA-LSTM control system, prominent effect of suppressing the isolation displacement and superstructure acceleration for near-fault and far-field ground motions can be achieved respectively. Series of shaking table tests was also conducted to verify the actual control performance of the proposed system. Both numerical and experimental results have demonstrated that the proposed intelligent control system has high efficiency and reliability to protect the structures from earthquakes of all types of ground motion characteristics.

Dynamic behavior modelling of a hybrid magnetorheological elastomer with encapsulated fluid for base vibration isolation

Magnetorheological elastomers (MRE) based semi-active isolators utilize MREs whose mechanical properties, such as stiffness and damping, change in response to an external magnetic field. MREs implementation in semi-active isolation remains challenging due to their slow response time caused by the suspension of the magnetic particles inside the elastomeric matrix and limited damping capabilities. Hybrid MREs, a combination of MREs and MRFs, have been developed to improve semi-active isolation's material properties and performance. However, modelling the nonlinear and hysteretic behavior of hybrid MRE-based isolators remains a challenge and needs to be adequately addressed. To bridge the gap, this study presents a parametric model for a hybrid semi-active isolator's nonlinear and hysteretic behavior that utilizes a hybrid MRE (H-MRE). The behavior of conventional and hybrid MRE-based isolators are experimentally tested under varying loading conditions of excitation frequency and input current. Simulation models are created using combinations of three different phenomenological models, Bouc-Wen, Modified-Dahl and LuGre friction. The experimental data are used to optimize and fit the simulated response of each model, and hence optimal values of the MRE and MRF hysteresis parameters are determined. The parameter estimation results indicate that a combination of LuGre friction for the MRE and Bouc-Wen for the MRF improves the accuracy of predicting the dynamic behaviour of the hybrid isolator. The relationship between the model parameters and loading conditions is also investigated and described through polynomial equations of the third order. These findings could provide valuable insights for the system identification and control of hybrid semi-active isolators and pave the way for developing smart base isolation systems utilizing hybrid MREs in future research.

Development and Experimental Verification of an Intelligent Isolation System Based on Long Short-Term Memory Module Model for Ground Motion Characteristics Prediction

Semiactive seismic control requires appropriate control laws that dictate the behavior of seismic suppression devices based on measurements and feedback during an earthquake. Optimal control parameters should be determined in real time to achieve high performance. The initial ground motion characteristics of an earthquake substantially affect control performance. In this study, a genetic algorithm (GA)-optimized long short-term memory (LSTM)-based intelligent control system (hereafter denoted GA-LSTM system) for obtaining optimal control parameters for a semiactive variable-stiffness isolation system was proposed. First, the LSTM module classifies earthquakes as near-fault or far-field events to determine the optimal control strategy. Second, earthquakes from a global database are analyzed to determine a fuzzy inference surface for the optimal parameters of the earthquake suppression system. Both numerical simulations and shaking table experimental results indicated that the proposed GA-LSTM system exhibited superior isolation displacement and superstructure acceleration suppression for both near-fault and far-field earthquakes when compared with other control techniques. The proposed intelligent control system is highly efficient and could reliably protect structures from earthquakes with any ground motion characteristics.

Numerical realization of a semi-active virtual acoustic black hole effect

Noise mitigation by means of the acoustic black hole (ABH) effect is a well-known engineering solution. However, the conventional method of applying ABH effect which requires modification of the structure geometry has various limitations which encourage the research of virtual ABH concept. In this study, the effect of ABH was applied through introducing virtual stiffness by a shunt circuit. According to the force-voltage electric analogy, stiffness has an inverse relationship with capacitance. So that the ABH effect can be virtually realized by following a power law profile using an array of independent capacitive shunts. The concept is studied through finite element simulation developing a macro code in ANSYS Parametric Design Language (APDL). To evaluate the influence of capacitance profile on the acoustic radiated power, parametric studies are conducted. Based on the results of the parametric studies, the capacitance profile is tuned for minimum radiated power. It is revealed that the virtual acoustic black hole (ABH) effect can offer 10.29%, 6.37%, and 7.47% reduction in the radiated power from the first to the last targeted mode, respectively. The virtual ABH effect introduced in this study can be used for semi-active structural noise isolation without any weight or manufacturing penalty.

Development of a Control Algorithm for a Semi-Active Mid-Story Isolation System Using Reinforcement Learning

The semi-active control system is widely used to reduce the seismic response of building structures. Its control performance mainly depends on the applied control algorithms. Various semi-active control algorithms have been developed to date. Recently, machine learning has been applied to various engineering fields and provided successful results. Because reinforcement learning (RL) has shown good performance for real-time decision-making problems, structural control engineers have become interested in RL. In this study, RL was applied to the development of a semi-active control algorithm. Among various RL methods, a Deep Q-network (DQN) was selected because of its successful application to many control problems. A sample building structure was constructed by using a semi-active mid-story isolation system (SMIS) with a magnetorheological damper. Artificial ground motions were generated for numerical simulation. In this study, the sample building structure and seismic excitation were used to make the RL environment. The reward of RL was designed to reduce the peak story drift and the isolation story drift. Skyhook and groundhook control algorithms were applied for comparative study. Based on numerical results, this paper shows that the proposed control algorithm can effectively reduce the seismic responses of building structures with a SMIS.

A semi-active quasi-zero stiffness vibration isolator based on magnetorheological elastomer with a fast convergence switch control

Quasi-zero stiffness (QZS) isolators have attracted extensive attention due to their high-static–low-dynamic stiffness. The effectiveness of the traditional QZS (T-QZS) isolators to attenuate low-frequency vibration has been extensively studied. The T-QZS isolator, however, cannot usually provide satisfactory vibration mitigation performance under ultra-low frequency excitation. To tackle this challenge, we propose a semi-active QZS isolator featuring magnetorheological elastomer (SAQZS-MRE isolator). The prominent merit of the proposed design is that the applied MRE material can provide varying stiffness and damping to the proposed SAQZS-MRE isolator, making the isolator suitable for vibration isolation under wide-band low-frequency range. The dynamic viscoelasticity properties of the MRE are experimentally characterized, to formulate the dynamic modeling of the SAQZS-MRE isolator. The open-loop vibration isolation characteristics of the SAQZS-MRE isolator are assessed using the harmonic balance method (HBM). Subsequently, two semi-active control strategies including skyhook and fast convergence switch (FCS) are effectively utilized in the proposed SAQZS-MRE isolator to evaluate their closed-loop performance. The results demonstrate that the SAQZS-MRE isolator with FCS control can eliminate the resonance peak and reduce the initial isolation frequency. In the higher frequency range, it can also improve the vibration isolation performance compared with the SAQZS-MRE isolator with passive control.

Seismic Fragility Assessment of RC Building Using HAZUS Methodology and Incremental Dynamic Analysis

The technique of coupled building strategy is more viable to protect the adjacent buildings of dissimilar in characteristics against seismic hazards. The philosophy of coupled building control in which adjacent buildings are allowed to exerts counter-acting forces one upon another. This study includes the seismic performance of various Coupled Buildings with respect to Uncoupled Buildings for which two models of Coupled Building are considered that is, first one is the two-shear type adjacent buildings connected in-line with MR dampers and second one is same as first with taller building is isolated by Resilient-Friction Base Isolator at its foundation. The seismic response analysis of RC coupled buildings are studied in terms of peak responses subjected to unidirectional excitation due to Kobe 1995 earthquake. The governing equation of motion of various coupled buildings is solved numerically by Newmark’s step-by-step method. The dynamic behaviour of semiactive MR damper and R-FBI base isolation system has been predicted by modified Bouc-Wen model and Wen’s model respectively. This study employed the Lyapunov direct approach as a control algorithm for the stability analysis and design of semiactive MR controller. The responses of various coupled buildings and uncoupled buildings are simulated through MATLABâ computing software. This study outlined that model of Coupled Building-2 performs more effective in controlling the seismic responses whereas model of Coupled Building-1 performs well not only in reducing the responses but also avoid pounding from the adjacent buildings. Further, there is significant reduction in responses of taller building isolated by base isolation system whereas marginal reduction takes place in shorter building which is not isolated.

Uncertainty in the seismic performance of semi-active base isolation systems

In a conventional base isolation system, minimizing the seismic responses of the superstructure is always at the cost of increasing the isolator's response. The semi-active control of the isolator has been considered an effective solution to such a dilemma. It tunes the real-time properties of the isolator according to preset rules to further reduce the superstructure's seismic responses without increasing that of the isolator or vice versa. However, the number of ground motion records used to design and validate the controller, i.e., the preset rules, in existing studies is usually very small and therefore is suspectable if it is adequate to address the significant uncertainty in the shaking of future earthquakes. This paper critically reviews the performance of the proportional-integral-derivative (PID), linear-quadratic regulator (LQR), and fuzzy controllers in semi-active base isolation systems with magnetorheological (MR) dampers subjected to highly uncertain ground motion inputs through numerical simulations. The results show that the control performance of the controllers varies significantly with the increasing number of input records, suggesting the necessity of using at least 50 ground motion records to appropriately assess the performance uncertainty of semi-active base isolation systems. More importantly, the superior performance of the optimized controllers is not guaranteed if the system is subjected to ground motions that are new to the controller, even if the controller has been optimized for thousands of existing ground motions. It highlights the need of improving the adaptability of the semi-active systems for uncertain ground motion inputs.

Structural optimization and experiment of a semi-active hourglass-type electromagnetic isolator with negative resistance shunt circuit

The present work proposed a semi-active electromagnetic isolator with negative resistance shunt circuit to improve isolation performance on micro-vibration. By an innovative combination of an hourglass-type displacement amplifier and electromagnetic mechanism with negative resistance shunt circuit, the proposed isolator can not only solve the difficulty for electromagnetic isolators to isolation micro-amplitude vibration but also achieve a significant electromechanical coupling effect to obtain excellent vibration isolation performance by a self-sensing method. First, the design of the isolator and motion relationship are presented. Then, the electromechanical coupling dynamic model of the isolator is established. Moreover, the angle of the hourglass-type displacement amplifier is optimized, and the influence of the negative resistance on the additional damping ratio and system stability is explored. Finally, the isolator was manufactured and several experiments were carried on. The experiment results demonstrated that the isolator has an excellent isolation performance. And meanwhile, the comparison between experiment and simulation also indicated the correctness of the model.

Investigation of a new metamaterial magnetorheological elastomer isolator with tunable vibration bandgaps

Semi-active isolators with laminated magnetorheological elastomer (MRE) structures draw increasing attentions for vibration control because of their resonance-frequency-shift property. Their vibration attenuation capacity can be further improved by integrating the acoustic metamaterial characteristics with tunable vibration bandgaps at designed frequencies. On this basis, a novel metamaterial MRE isolator with controllable vibration bandgaps was designed and prototyped. The mechanism of the formation of vibration bandgaps was analysed theoretically using the method of mass-spring model. Both infinite and finite periodic structures were discussed respectively. The equivalent negative stiffness of the metamaterial MRE isolator was studied. The evaluation experiments were conducted to study bandgaps of the metamaterial MRE isolator and its vibration isolation capacity. Results demonstrate that the new metamaterial MRE isolator possesses controllable bandgaps and can provide improved vibration isolation performance.

Optimal Design of Semi-Active Mid-Story Isolation System using Supervised Learning and Reinforcement Learning

Optimal Design of Semi-Active Mid-Story Isolation System using Supervised Learning and Reinforcement Learning

Study on bandgap vibration isolation of super-cell phononic crystals based on magnetorheological elastomers

A two-dimensional super-cell phononic crystal semi-active isolator based on magnetorheological elastomers is designed, which can be used for vibration isolation of mechanical devices at medium and high frequencies. The plane wave expansion method of the super-cell is introduced to model the dynamic characteristics of the proposed phononic crystal isolator. The influence of the constituent materials, dimension parameter of the super-cell, and magnetic field intensity on the band structure is investigated by the plane wave expansion method. The results show that the change of material will affect the bandgap frequency of the super-cell and the dimension parameter of the super-cell will affect the bandgap formation mechanism. It is worth pointing out that the bandgap frequency and width of the isolator can be adjusted by controlling the applied current of the magnetorheological elastomer. Therefore, this method offers a broad range of possibilities for phononic crystal vibration isolation design.

Verification of a Stiffness-Variable Control System with Feed-Forward Predictive Earthquake Energy Analysis.

Semi-active isolation systems with controllable stiffness have been widely developed in the field of seismic mitigation. Most systems with controllable stiffness perform more robustly and effectively for far-field earthquakes than for near-fault earthquakes. Consequently, a comprehensive system that provides comparable reductions in seismic responses to both near-fault and far-field excitations is required. In this regard, a new algorithm called Feed-Forward Predictive Earthquake Energy Analysis (FPEEA) is proposed to identify the ground motion characteristics of and reduce the structural responses to earthquakes. The energy distribution of the seismic velocity spectrum is considered, and the balance between the kinetic energy and potential energy is optimized to reduce the seismic energy. To demonstrate the performance of the FPEEA algorithm, a two-degree-of-freedom structure was used as the benchmark in the numerical simulation. The peak structural responses under two near-fault and far-field earthquakes of different earthquake intensities were simulated. The isolation layer displacement was suppressed most by the FPEEA, which outperformed the other three control methods. Moreover, superior control on superstructure acceleration was also supported by the FPEEA. Experimental verification was then conducted with shaking table test, and the satisfactory performance of the FPEEA on both isolation layer displacement and superstructure acceleration was demonstrated again. In summary, the proposed FPEEA has potential for practical application to unexpected near-fault and far-field earthquakes.

Seismic Analysis of Multi-storied RCC Building Involving Semiactive VF Damper and Base Isolators

Seismic Analysis of Multi-storied RCC Building Involving Semiactive VF Damper and Base Isolators

Design and Research of Semiactive Quasi-Zero Stiffness Vibration Isolation System for Vehicles

The vehicle-mounted equipment is easy to be disturbed by external vibration excitations during transportation, which is harmful to the measurement accuracy and performance of the equipment. Aiming at the vibration isolation of the vehicle-mounted equipment, a semiactively controlled quasi-zero stiffness (QZS) vibration isolator with positive and negative stiffness is proposed. The vertical spring is paralleled with a magnetorheological (MR) damper, and the semiactive on-off control scheme is adopted to control the vibration. The analytical expression of the isolator’s displacement transmissibility is derived via the averaging method. Then, the vibration isolation performance under different road excitations and different driving speeds is simulated and compared with the uncontrolled passive QZS vibration isolator. In addition, the mechanical structure of the semiactive QZS isolator is designed and manufactured, and the test system is built by LabVIEW software and PXI embedded system. The isolation effect of the semiactive QZS isolator is verified through test data. It is found that the proposed semiactive QZS isolator shows excellent vibration isolation performance under various road excitations, while the passive QZS isolator is effective only under harmonic excitations. The vertical acceleration of vehicle-mounted device can be decreased over 70% after isolation, and the vibration isolation effect is remarkable. The design idea and research results of the semiactive QZS isolator may provide theoretical guidance and engineering reference for vibration isolation.