Semi-active Devices Research Articles

Optimal replicator dynamic controller for semi active control of long span cable stayed bridge with considering special variability of seismic excitations

Cable-stayed bridges are lifeline infrastructures. However, due to their design and structural characteristics, they are sensitive to the vibrations. Thus, vibration control in these structures is essential. Semi-active control systems have gained significant attention due to their high performance and adaptability. However, the implementation of these systems has always faced serious challenges particularly when it comes to developing appropriate control algorithms because semi active devices have complex and non-linear characteristics. Inspired by evolutionary game theory, the author utilizes the replicator dynamic controller concept to optimize the performance of MR dampers to improve the vibration reduction of cable-stayed bridges. Two key parameters in the proposed control methodologies using replicator dynamics are the total population (total available resources or the sum of actuator forces) and the growth rate. Instead of using the sensitivity analysis that has been done in previous studies for vibration reduction of highway bridges using a replicator controller, the author used an evolutionary algorithm named the nondominated sorting genetic algorithm (NSGA-II) to create an optimal replicator dynamic controller for more effective vibration reduction. The proposed methodology is evaluated through its numerical application to a second-generation benchmark example based on the Bill Emerson Memorial Bridge, which considers a more realistic behavior of the cable-stayed bridge by accounting for multiple support excitations. The study indicates that the optimal replicator dynamic controller improves the vibration reduction performance of MR dampers. Specifically, deck displacement is reduced by 46 % compared to passive control system and shear forces at the tower base are reduced by 33 % compared to active control systems for the El Centro earthquake. The results indicate that the proposed Replicator Dynamic Controller optimized through NSGA-II provides a robust and effective solution for improving seismic resilience of cable-stayed bridges.

Smart whole-body vibration attenuation, cushion for heavy equipment seating: Model and simulation

Off-road mobile machine operators are exposed to whole-body vibration (WBV) which can result in adverse health effects. Seat suspensions are used to reduce WBV exposure, but typical passive seats cannot attenuate frequencies below 1.13 Hz. The proposed device is designed to minimize transmissibility from 0 to 20 Hz because this bandwidth contains the dominant frequency for most off-road vehicles. The semi-active smart device uses bang-bang control and is designed to be installed in place of the seat-pan cushion in OEM passive seats. Modelled as a two degree of freedom system, simulations were performed using a lumped mass model (ωn = 3 Hz; sinusoidal base excitation 0-20 Hz). Using a hexapod robot, a prototype reduced transmissibility compared to a passive OEM seat. The device was up to 5 times more effective than a passive seat in reducing vibration transmissibility. Simulations revealed that operator mass and seat stiffness variations have little effect on device WBV attenuation performance.

Reconstructing Magnetic Hysteresis Behavior with Flux Model and Identifying Parameters for Dual-Coil MR Actuator

Magnetorheological (MR) actuators represent an important class of semi-active devices that have received extensive investigation and deployment in the field of vibration reduction systems. Their notable features include a significant reduction in energy consumption, along with an impressive tunable range of continuously controllable damping forces. The force output of these devices is a complex function that involves two hysteretic mechanisms: magnetic and mechanical (i.e. hydraulic). While the total hysteresis mechanism of these devices has been the subject of considerable study, comparatively little attention has been paid to their magnetic hysteretic behavior. In this study, the authors examine the behavior of the dual coil MR actuator’s control circuit and attempt to extract the magnetic flux information from the laboratory measurements of electrical signals applied to it. The study is further enhanced by the incorporation of the Bouc-Wen (B-W) hysteretic unit, which serves to replicate the flux-current (or magnetic) hysteretic relationship. The B-W model's parameters are identified through the use of a hybrid algorithm, namely the particle swarm optimization and fmincon hybrid optimizing strategy. It incorporates the advantages of both algorithms, resulting in an average improvement of 0.38% in standard deviation compared to fmincon, across 1A to 5A, when comparing the experimental and simulation data. This strategy is employed to fit the model predictions to the flux data, derived from the reconstructed flux and current in time histories. The findings of the study demonstrate that the B-W model is an effective tool for predicting the variation in magnetic flux in response to an exciting current. The results can be implemented for prototyping or validating a model-based controller for MR actuator systems.

Exploring the Structural Response of High-Rise Buildings using Fuzzy Logic and Genetic Algorithms

Exploring the dynamic behaviour of high-rise buildings presented a critical challenge. In this study, Fuzzy Logic and Genetic Algorithm (FLGA) were employed to comprehensively investigate the structural response of high-rise buildings (HRBs) for adaptive vibration control systems employing semiactive damper devices. The study integrated a fuzzy logic inference system with a Genetic Algorithm (GA) to create FLGA, which was then employed in a 3-story shear building under real earthquake conditions and multi-dimensional wind loads. The analytical model for a semi-active tuned mass damper (STMD) was examined and evaluated before integrating it into the proposed FLGA system. The results indicated that FLGA reduced story acceleration by an average of 20% and story drift by approximately 50% while efficiently controlling the structure within allowable movement limits and resident comfort criteria under multi-directional wind loads. The suggested optimal controller mitigated both displacement and acceleration responses by 15 to 20% without amplification. The study demonstrated FLGA's effectiveness as a model-free control strategy for managing structural response uncertainties.

Numerical investigations of seismic-resilient techniques for legged fluid storage tanks utilising magnetorheological dampers

Different energy-dissipating devices have been proposed in the literature to attenuate the destructive effects of base excitations over fluid storage tanks. These structures have numerous applications in strategic industries and their failure can result in environmental hazards and huge economic losses. Proposed techniques in the literature for seismic energy dissipation of fluid-contained tanks are mostly centred on passive and active control mechanisms. Semi-active control devices using materials with adjustable properties offer advantages of both active and passive systems while removing their drawbacks. In this paper, the performance of a Magnetorheological (MR) damper on the seismic response reduction of fluid storage tanks through the application of three different control strategies including H2/LQG, PID, FOPID, and two passive techniques, i.e. Passive On, and Passive Off has been investigated. Parameters of the semi-active controllers are optimally designed for each aspect ratio and the applied ground motion using the Hunger Game Search (HGS) technique and finally, the semi-active Clipping algorithm commands the voltage to the damper. The fluid-tank-MR damper system has been examined under three Far-Fault and three Near-Fault ground motions. Numerical simulations have demonstrated that depending on the aspect ratio, applied ground motion, and the control strategy, the MR damper can mitigate the peak relative displacements and absolute accelerations of the two major modes of the system, i.e the rigid and impulsive modes, up to 72% and 67%, respectively. This proves the efficacy of these dampers in reducing the maximum base shear and overturning moment, hence mitigating the damage risks in these structures.

Investigation of a newly developed shear built-in valve type MR damper with high damping: Theories and experiments

Magnetorheological (MR) dampers are widely used as semi-active energy-dissipation devices in structural vibration control. Traditional MR dampers, particularly their working mode, often struggle to achieve a high damping force output and sometimes fail to meet the needs of practical engineering. Therefore, it is necessary to study MR dampers that can provide a high damping force. This study proposes an MR damper that combines a built-in shear valve with various working modes of shear extrusion. The damper generates a higher damping force by applying a current to the coils at different positions and altering its working mode. First, the ANSYS Maxwell software simulates the internal magnetic circuit of the damper to assess whether the magnetic field intensity distribution and circuit direction meet the design requirements. Analysis revealed that the internal magnetic circuit distribution was reasonable and satisfied the operating requirements of the damper. Furthermore, the mechanical models of the two working modes were derived based on the Bingham and double-viscous models. Finally, the accuracies of the mechanical models were verified experimentally. The experimental results showed that the simulation values closely matched the experimental values under all the working conditions. Therefore, the proposed mechanical models are reasonable, and can provide significant reference values for practical engineering applications.

Material Characterisation of Deflated Structured Fabrics

AbstractStructured fabrics are made by interwoven rigid elements that form flexible garments such as chain mail armours. Traditionally, the mechanical properties of these materials were considered fixed. However, recent research has revealed their mechanical properties may be varied. Notably, studies have demonstrated that applying vacuum pressure between layers of 3D-printed chain mails enclosed in a bag induces particle and layer jamming of the elements, thereby affecting the material’s bending modulus. This arises from both compressive frictional forces and the complex geometrical interlocking of the rigid elements. This paper presents a comprehensive set of experimental tests for the characterisation of the stiffness and damping properties with respect to the type and number of fabrics and with respect to the vacuum pressure. More specifically, the study examines experimentally the changes in static properties in response to vacuum pressure changes evaluated on a four- and six-point bending setups. The outcome of this measurement campaign is then reported into the Ashby diagrams to compare the mechanical properties of the in-vacuum structured fabrics with those of classical materials. The potential applications of this research include the development of lightweight adaptive and semi-active vibration mitigation devices.

Development of a Prandtl-Ishlinskii hysteresis model for a large capacity magnetorheological fluid damper

Magnetorheological (MR) fluid (MRF) dampers, serving as fail-safe semi-active devices, exhibit nonlinear hysteresis characteristics, emphasizing the necessity for accurate modeling to formulate effective control strategies in smart systems. This paper introduces a novel stop operator-based Prandtl-Ishlinskii (PI) model, featuring a reduced parameter set (seven), designed to estimate the nonlinear hysteresis properties of a large-scale bypass MRF damper with variable stiffness capabilities under varying applied current. With only seven parameters, the model realizes current, displacement, and rate dependencies. The force-displacement and force-velocity responses of the designed MRF damper were experimentally characterized under broad ranges of applied current (0–2 A), excitation frequency (0.5–4 Hz), and displacement amplitude (1–2.5 mm). A training dataset was subsequently used to develop a novel field-dependent modified PI model, incorporating multiple hysteresis operators with and without a friction element. The proposed model accurately predicted the MRF damper behavior within the training dataset, and its validity was assessed against data from diverse experimental conditions. The PI model with friction element generally outperformed the model without friction when frequency exceeds 0.5 Hz, demonstrating its ability to characterize nonlinear hysteresis force-displacement and force-velocity properties of the MRF damper under the ranges of applied current and excitations considered with reasonable accuracy. Experimental data were also estimated by the Bouc–Wen model, and compared with those obtained via the formulated PI model, affirming the overall superiority of the proposed PI models considering the computational cost, and total number of parameters. Leveraging the simplicity, minimal parameter requirements, and analytic invertibility of PI models, the proposed PI model is considered a superior choice for modeling and subsequently controlling smart structures employing MRF dampers.

Experimental study on the double-skyhook controls of semi-active suspension with variable inertance and damping

As a conventional control approach, the skyhook damping control algorithm can respond to changes in road circumstances but not to those in load circumstances. The skyhook inertance control algorithm, a newly developed control approach, may adapt to changes in load circumstances rather than in road circumstances. The recent introduction of double-skyhook control algorithms has allowed vehicle suspension systems to accomplish both load and road adaptation. This paper presents an experimental investigation contrasting the performance of the double-skyhook configuration to that of the traditional skyhook damper configuration and the skyhook inerter configuration. By integrating the double-skyhook control strategy with semi-active devices with variable inertance and damping, the paper proposes two strategies for coordinating skyhook inertance and skyhook damping control. A controller using the double-skyhook control strategy is designed to employ the Development to Production rapid control prototyping platform. The controller mode is adjusted using MotoTune software to implement control methods. Three tests were conducted under various road conditions, load conditions, and impact conditions for semi-active suspension. Test results indicate that the double-skyhook configuration considerably enhances driving comfort compared to the single-skyhook configuration. Moreover, the greater the deterioration of road conditions and the decrease in load, the more pronounced the enhancement.

Feasibility Study of a Novel Modal Decomposition Method for Low-Frequency Structure with Nonproportionally Distributed Rate-Independent Linear Damping

Compared with conventional linear viscous damping (LVD), rate-independent linear damping (RILD) mitigates floor response acceleration in low-frequency structures more effectively without compromising the control performance of displacement responses during long-period or low-frequency earthquakes. Although theoretical and experimental attempts have been made to overcome the noncausality of RILD devices and realize RILD using passive or semiactive devices, only a few studies have highlighted the impulse-response precursor and modal analysis method of multistory structures incorporated into RILD devices. This study investigated the impulse-response precursor of a noncausal RILD system and proposed a novel modal decomposition method for the structures equipped with nonproportionally distributed RILD devices. Additionally, real-time hybrid simulation was conducted to validate the effectiveness of the proposed modal analysis method and the feasibility of realizing ideal RILD using mechanical devices. This study is the first to demonstrate the differences between RILD and LVD devices in terms of controlling the modal responses of low-frequency structures and how RILD can lower the floor response acceleration more effectively compared to LVD.

Intuitive and versatile bionic legs: a perspective on volitional control.

Active lower limb prostheses show large potential to offer energetic, balance, and versatility improvements to users when compared to passive and semi-active devices. Still, their control remains a major development challenge, with many different approaches existing. This perspective aims at illustrating a future leg prosthesis control approach to improve the everyday life of prosthesis users, while providing a research road map for getting there. Reviewing research on the needs and challenges faced by prosthesis users, we argue for the development of versatile control architectures for lower limb prosthetic devices that grant the wearer full volitional control at all times. To this end, existing control approaches for active lower limb prostheses are divided based on their consideration of volitional user input. The presented methods are discussed in regard to their suitability for universal everyday control involving user volition. Novel combinations of established methods are proposed. This involves the combination of feed-forward motor control signals with simulated feedback loops in prosthesis control, as well as online optimization techniques to individualize the system parameters. To provide more context, developments related to volitional control design are touched on.

A versatile semi-active magnetorheological inerter with energy harvesting and active control capabilities

Semi-active devices typically adjust the system’s damping coefficient to control vibration, offering advantages such as excellent performance and low power consumption. However, the output force of the traditional variable damping (VD) device can only be opposite to the relative motion direction of the device’s two terminals, which limits the vibration control performance. This paper introduces a versatile semi-active magnetorheological (MR) inerter with three operating modes, the VD, energy harvesting, and active control modes, to break through the performance bottleneck of traditional semi-active devices. The MR inerter combines two MR dampers and a flywheel, acting as the controllable units and energy sink. The built prototype is tested, and its parameters are identified. When the innovative semi-active inerter works with a corresponding control strategy to regulate the current in two MR dampers, it can achieve vibration energy storage and release. The harvested energy can help to reduce the high dependency of the semi-active output force on external inputs. The proposed semi-active inerter has excellent potential in the future applications.

Performance analysis of the damper with built-in magnetorheological valve

Commercial vehicles are usually equipped with suspension seats to improve ride comfort. As a semi-active intelligent device, magnetorheological damper can effectively improve seat comfort when applied to seat suspension. Firstly, a novel damper with built-in magnetorheological valve (MRVD) based on the squeeze mode of magnetorheological fluid (MRF) is designed, which integrates the magnetorheological valve (MRV) into the piston. This structure adopts a bidirectional controllable flow channel, double coil, and double squeeze chamber. Secondly, the mathematical model of the MRVD is derived based on the Bingham plastic model of the MRF. Then, the distribution of magnetic flux density in the effective damping gaps is simulated using finite element method. Finally, it is shown from a comparative work between the simulation results from the derived mathematical model and experimental test results of the MRVD that the established mathematical model can predict the field-dependent damping force well. The idea of integrating the MRV into the piston provides a new approach for the application of magnetorheological technology.

Low frequency noise control using coupled loudspeaker and negative impedance circuit

It remains a technical challenge for low-frequency duct noise control devices to combine compact and broadband features at same time. A semi-active noise control approach is introduced to solve this problem. The device consists of a main pipe and two loudspeakers connected by a circuit containing a negative impedance network. Due to the effect of the negative impedance circuit, the virtual bypass is composed of the coupled loudspeaker and the circuit has sound transmission characteristics close to a physical duct in a certain frequency range. The effect of the negative impedance network and circuit on the performance of the silencer is studied by using the transfer matrix method. Through the design of the circuit, the sound transmission process of the virtual bypass can be realized. If the proper circuit network and parameters are selected, the virtual bypass HQ tube can achieve compact broadband noise control at low frequencies. A semi-active noise control device has 10dB noise reduction in the range of 100-300Hz.

Multi-objective control optimization of isolated bridge using replicator controller and NSGA-II

Earthquakes can cause significant damage to constructed structures, leading engineers to design systems that effectively reduce damage and improve real-time vibration control. While base isolation is a commonly used passive method for seismic protection in highway structures, it has limitations such as a lack of immediate adaptation, constrained power dissipation capacity, and poor performance during earthquakes. To address the limitations of passive base isolation bearings, a hybrid control system that includes semi-active MR dampers is being introduced into isolated highway bridge structures. The aim is to enhance vibration reduction and improve overall performance. One of the major challenges in implementing this technology is developing appropriate control algorithms to handle the nonlinear behavior of semi-active devices. This paper proposes an adaptive data-driven control algorithm, informed by evolutionary game theory and a multi-objective optimization process, to optimize the distribution of voltage to semi-active MR dampers based on measurements of the damper's response to input signals. The algorithm is designed to provide optimal seismic protection. The performance of the replicator dynamics in the control system depends on three critical parameters: total population, which represents the total available resources or the sum of actuator forces; growth rate, which is the rate at which resources are distributed among control devices; and the fictitious fitness function, which regulates power consumption. Previous studies used sensitivity analysis to ascertain the best values for population size and growth rate, a time-consuming and unreliable process. This study aims to improve the performance of the system by solving a multi-objective problem. The proposed approach integrates a control algorithm with a multi-objective optimization algorithm, namely NSGA-II, to find Pareto optimal values for all parameters of the replicator dynamics. These parameters include total population, growth rate, and the fictitious function, with the aim of ensuring sustainability. By considering multiple objectives simultaneously, the proposed approach can provide a more comprehensive and effective solution for the bridge control problem. The effectiveness of this proposed approach is demonstrated through sample results Utilizing a case study centered around the Southern California Interstate 91/5 Overcrossing Highway Bridge, which is exposed to seismic activities.

Semi-active structural vibration control with magnetorheological damper based on hybrid fuzzy sliding mode controller

Recently, structural vibration control has proved its capacity to save lives and keep structures safe during earthquakes. Furthermore, there is a wealth of research in both numerical and experimental studies. As a result, due to its simplicity and performance in mitigating structural vibrations generated by ground motions, semi-active control played a significant role in the majority of these studies. Nonetheless, the magnetorheological damper is the most often used semi-active device. In particular, the rheological fluid properties have gained adequate attention in earthquake energy dissipation and structural vibrations management, particularly in the civil engineering field. The semi-active control of three scaled excited structures is addressed in this study. A magnetorheological damper operated by a hybrid fuzzy sliding mode controller ensures the proposed control. However, to provide the appropriate current for the damper to operate, this proposed intelligent controller is combined with a clipped optimum algorithm. Otherwise, the numerical simulation results of the seismic excited scaled structure demonstrate the resilience of the suggested controller. As a result, four time-scaled seismic data are applied to the tested structure. Finally, the usefulness of the suggested semi-active control technique in mitigating earthquake structural vibration is demonstrated clearly in the compared controlled and uncontrolled responses.

Seismic control of a smart structure with semiactive tuned mass damper and adaptive stiffness property

AbstractTo reduce structural responses under earthquake excitations effectively and improve their resilience, a smart structure with a semiactive tuned mass damper (STMD) on the top story and a semiactive adjustable stiffness device (SASD) on the first story which contributes to the structural adaptive stiffness property is developed in this study. The SASD consists of a diamond spring device composed of four linear springs and an electromagnetic actuator, which can change the angle of the diamond device and therefore retune the stiffness. Two typical STMDs developed previously are reviewed first, which are diamond device‐based STMD with variable stiffness and damping and pendulum‐type STMD with variable frequency and eddy current damping, respectively. Numerical results show that the proposed STMD has a better control performance than passive‐tuned mass damper and STMD with variable stiffness or damping acting independently. To enhance the seismic protection of the structure with an STMD on the top story further, based on the principle of base isolation, a diamond device‐based SASD is applied to the first story. The linear quadratic Gaussian‐based variable stiffness algorithm for SASD is proposed. A 10‐story building is presented as a case study. The variable stiffness range of SASD is discussed in detail, while it is found that a ±50% variable stiffness range achieves the best earthquake mitigation. Control effects of different numbers of SASD implemented along the height of the building are compared as well. Numerical results show that with the increase in the number of SASDs, the earthquake mitigation effect is better; however, the magnitude of the increase is decreasing. The smart structure with the combined SASD and STMD has an excellent seismic protection performance and is better than with SASD or STMD acting independently. Meanwhile, it is found that the proposed combination has a similar control effect to four SASDs installed from the first story to the fourth story, respectively, while it can reduce the number of additional electromechanical systems and the influence on the use function of the building.

Performance analysis of magnetorheological plastomer dampers with different annular shear gaps

Magnetorheological plastomer (MRP) dampers are controllable semi-active smart devices, which are commonly used in the field of vehicle suspension systems, structural engineering, aerospace engineering and military equipment. This study was conducted to numerically investigate the performance of MRP dampers with different annular shear gap sizes. The MRP used in the analysis consisted of 60% Carbonyl Iron Powder (CIP) and 40% Polyurethane Matrix (MRP60). The focus of the analysis was on the MRP60 flow behaviour in the annular shear gap region, where the induced magnetic field generated a range of dynamic damping forces depending on the size of the annular shear gap. The numerical simulation involved an integration of the finite element analysis (FEA) to examine the magnetic field in the annular shear gap region as well as the computational fluid dynamics (CFD) analysis to simulate the damping characteristics of the MRP damper. The relationship between the yield stress and the magnetic flux density for MRP60 was used for the analysis. The results of the FEA showed that as the size of the annular shear gap increased, the magnetic flux density and the yield stress decreased. From the CFD results, it was observed that the damping force decreased as a result of increasing the size of annular shear gap.

Intelligent Control Methodology for Smart Highway Bridge Structures Using Optimal Replicator Dynamic Controller

Control algorithms are an essential part of effective semi-active vibration control systems used for the protection of large structures under dynamic loading. Adaptive control algorithms, which are data-driven methods, have recently been developed to replace model-based control algorithms, thus improving efficiency. The dynamic parameters of semi-actively controlled infrastructures will change after significant vibration loading. As a result, these structures require real-time, effective control actions in response to changing conditions, which classical controllers are unable to provide. To improve the efficiency of the semi-active controller, the optimal control algorithm was developed in this study. The algorithm is the integration of the replicator dynamics with an improved non-dominated sorting genetic algorithm (NSGA), which is NSGA-II. The optimal parameters of replicator dynamics (total resources, growth rate, and fitness function), which represent the behavior of the actuators, were obtained through a multi-objective optimization process. The new control system was then used to reduce the vibrations of the isolated highway bridge, which is equipped with semi-active control devices known as MR dampers. Moreover, the current study improved the performance of the structural control system with minimum energy consumption by assigning a specific growth rate to each control device. In order to reduce the vibrations of the highway bridge, the results show that the performance of the optimal replicator controller is better than the performance of the classical control algorithms. Doi: 10.28991/CEJ-2023-09-01-01 Full Text: PDF

Experimental investigation of Magneto-rheological damper

In recent years, intensive research works are concentrated on the development of semi-active control devices. A semi-active control system can also be explained as a system that mainly requires a small external power source for functioning and applies the motion of the structure to generate the control forces. A semi-active control system typically begins from a passive control system, which is followed by a change to permit the flexibility of mechanical properties. The mechanical properties of the semi-active control devices may be modified depending upon the response from the excitation and/or from the calculated reaction. Magneto-rheological (MR) dampers are a type of a semi-active control device that, in the presence of Magneto-rheological (MR) fluid, responds to the applied vibrations. This type of damper has copper winding in it, forming an electronic circuit internally with a combination of MR fluids. The effectiveness of MR damper greatly depends on the command voltage to the copper winding. In the present study, the response of MR Damper to the command voltage, and the excitation frequency is experimentally evaluated. MR damper is supported by a wall mounting rigid fixture and connected to a shake table by a fixing unit. The voltage is varied from 0 V - 10 V with an interval of 2 V. Command voltages is applied to the MR damper with the help of voltage regulator and digital multi meter. The effect of excitation frequency is also studied (1 Hz – 8 Hz). While conducting the experimental work, acceleration values are obtained through the Data acquisition system. These acceleration values are integrated to get the velocity and displacement response. The relation between the displacement, velocity, acceleration of the MR damper, and the frequency of shake table and command voltage is studied. From the experimental work, it is observed that the displacement response of the damper is effectively controlled by increasing the command voltage.