Semi-active Devices Research Articles

Friction observer-based hybrid controller for a seat suspension with semi-active electromagnetic damper

This paper proposes a hybrid controller for a seat suspension equipped with an advanced electromagnetic damper (EMD) system to meet the requirement with vibration isolation and energy saving. The friction of seat suspension has considerable influence on the system dynamic. Applying a constant model to describe the friction is unreliable due to the long term wear and tear. Therefore, an observer is designed to estimate seat suspension friction, and it is used to compensate for the frictional influence in a H∞ controller. The friction observer applies the acceleration, relative displacement and circuit current, which are measurable in engineering. Then, a hybrid controller is further proposed, in which the low-frequency vibration is controlled with the friction observer-based H∞ controller, and the system will switch to passive state with low damping at high frequency based on the dominant frequency of the vibration. In order to validate the effectiveness of the proposed friction observer, the Bouc-Wen friction model is selected to describe actual seat suspension friction, and it is compared with the estimated friction by the observer. Experimental results show that the friction observer has similar performance and less computational complexity compared with the Bouc-Wen friction model. The effectiveness of the proposed hybrid controller is validated on a six-degree of freedom vibration platform with the bump and random excitation. This friction observer-based hybrid controller is helpful for the engineering application as it applies practically measurable variables as feedback and considers the performance of the semi-active device in reality.

Performance enhancement in cable vibration energy harvesting employing inerters: Full‐scale experiment

Harvesting cable vibration energy via electromagnetic dampers has been demonstrated as potential power supplies for wireless sensor networks or semi-active control devices. However, how the inerter enhances the energy harvesting performance of the electromagnetic damper when applied to a bridge stay cable remains largely unknown. This paper presents a full-scale experimental study on harvesting the vibration energy of a 135 m-long cable using an electromagnetic inertial mass damper (EIMD). The EIMD integrates an electromagnetic damper and an inerter. A numerical model of the cable-EIMD system was also established using Matlab/Simulink for performance analysis. In the free vibration test, the EIMD could achieve the peak output power of 61.52 W and average output power of 13.80 W, when the inerter and the load resistance are optimized, considering an initial displacement of 100 mm near the mid-span of the cable. The corresponding energy harvesting efficiency was up to 25.31%. However, the energy harvesting performance of the EIMD degrades under ultra-small-amplitude vibration conditions due to the overlarge parasitic damping induced by Coulomb friction. Besides, experimental data uncover a 53.08% increase of average output power due to the inerter used, while numerical results indicate a tremendous increase of output power up to 126.1% because of assuming low parasitic damping. The EIMD with the optimal parameters (inertance, damping coefficient, and load resistance) can provide superior energy harvesting performance owing to the energy amplification mechanism induced by the inerter.

Force tracking model and experimental verification on a novel magnetorheological damper with combined compensator for stay cables of bridge

As one of the most promising semi-active control devices, magnetorheological (MR) damper has received significant attention in the past few decades because it can offer the adaptability of active control devices in the absence of the associated large power sources. In this study, a new single-rod MR damper with combine volume compensator are proposed, and the design method of combined compensator with independent functions of volume compensation and compensation force is proposed. Then the dynamic tests of the single-rod MR damper are carried out to demonstrate its working performance. The identified sigmoid model is adopted as forward model to characterize the performance of the MR damper. And the force tracking method is put forward by performing inverse of the forward model. Finally, the force tracking simulation of the optimal LQR control force for the stay cable is given to show its feasibility.

An Electromagnetic Variable Inertance and Damping Seat Suspension With Controllable Circuits

This article proposes a novel semiactive electromagnetic device with the capability of variable inertance and damping (VIVD) and an energy storage priority control (ESPC) strategy for vibration reduction of vehicle seat suspensions. The VIVD device can control its inertance and damping by adjusting resistances in a variable admittance (VA) circuit different from the traditional mechanical damper. The circuit and mechanical dynamics model of the VIVD seat suspension is analyzed and verified with tests, and the energy storage characteristic and controllability of the VIVD device are explored. Also, the frequency response characteristics of the VIVD device are derived from the admittance characteristics of the VA circuit. For the semiactive VIVD seat suspension, an H∞ controller is designed to obtain the desired control force. An ESPC strategy is proposed to make the electromagnetic force of the VIVD device track the desired control force. The test results show that the VIVD seat suspension can successfully suppress the seat's vibration, which is better than the traditional variable damping seat suspension performance. Under the random excitation, the root means square acceleration of the VIVD seat is reduced by 32.99% compared with a passive seat. This new semiactive VIVD device shows great potential in engineering applications.

Modified Adaptive Negative Stiffness Device with Variable Negative Stiffness and Geometrically Nonlinear Damping for Seismic Protection of Structures

Adaptive negative stiffness device is one of the promising seismic protection devices since it can generate seismic isolation effect through negative stiffness when it is mostly needed and achieve similar vibration mitigation as a semi-active control device. However, the adaptive negative stiffness device generally combined with linear viscous damping underpins the drawback of degrading the vibration isolation effect during the high-frequency region. In this paper, a modified adaptive negative stiffness device (MANSD) with the ability to provide both lateral negative stiffness and nonlinear damping by configuring linear springs and linear viscous dampers is proposed to address the above issue. The negative stiffness and nonlinear damping are realised through a linkage mechanism. The fundamentals and dynamic characteristics of a SDOF system with such a device are analyzed and formulated using the Harmonic Balance Method, with a special focus on the amplitude–frequency response and transmissibility of the system. The system with damping nonlinearity as a function of displacement and velocity has been proven to have attractive advantages over linear damping in reducing the transmissibility in the resonance region without increasing that in the high-frequency region. The effect of nonlinear damping on suppressing displacement and acceleration responses is numerically verified under different sinusoidal excitations and earthquakes with different intensities. Compared with linear damping, the MANSD with nonlinear damping could achieve additional reductions on displacement and acceleration under scaled earthquakes, especially intensive earthquakes.

Developing a semi-active adjustable stiffness device using integrated damage tracking and adaptive stiffness mechanism

Recently, the passive negative stiffness device (PNSD) is used to decrease the shear force in the structure by providing an apparent yielding in the entire system. Usually, due to extreme environmental factors the structure is damaged which leads to disrupt the PNSD performance; so that, the shear force and permanent irreversible deformation increase remarkably in the structure. This study proposes a new controller and develops a semi-active adjustable stiffness device (SASD) based on the combination of a damage detection method and the semi-active control strategy. The stiffness of the SASD is retuned based on the identified damages in the structure. The performance of the proposed controller are evaluated through numerical examples. By comparing with passive and uncontrolled cases, results show that the SASD is robust against any changes in the structural characteristics of the system and effectively decreases the dynamic responses and the damage severity caused to the structure simultaneously.

Study on integrated response-based adaptive strategies for control and placement optimization of multiple magneto-rheological dampers-controlled structure under seismic excitations

The application and optimization of control systems with multiple magneto-rheological dampers integrated into a civil engineering structure is a challenging task. The performance of the control system is strongly linked with the location and arrangement of control devices, and the optimal placement of control devices is inherently linked with the performance objective of the control algorithm. Therefore, for semi-active control devices, the placement algorithm should be well rooted within the control algorithm, for effective structural control. This article proposes response-based adaptive control strategies embedded with the device location optimization algorithm. The acceleration and inter-story drift responses of the structure are considered as the performance objective for two separate control strategies. The flexibility of this approach lies in the fact that the design algorithm for control and location of magneto-rheological dampers can be engineered based on the performance criteria of the system. This study involves numerical simulation of an actual five-story framed structure. The simulation results indicated that the seismic performance of the structure is strongly linked with the number, placement of the magneto-rheological damper, and the performance objective of the control strategy used. Also, the configuration and corresponding control provided by the response-based adaptive strategies performed better than the configuration predicted by the benchmark genetic algorithm using the H2/LQG controller.

Semi Active Seat Suspension System using Modified Intelligent Active Force Control

This paper presents a modified intelligent active force control (AFC) control strategy in a semi active seat suspension system. The main actuator studied in this research is the Magneto-rheological (MR) damper. Since a semi-active device like MR damper can only dissipate energy so a modified version of AFC controller is needed. The modified AFC controller main function is to determine the appropriate control force. A Heaviside Step Function (HSF) is used to ensure the MR damper produce the desired damping force according to the control force generated by AFC controller. The phenomenological Bouc-Wen is used to study the effectiveness of the new AFC controller taking into account the dynamic response of the damper. Sinusoidal signals simulated as vibration sources are applied to the seat suspension system to investigate the improvement of ride comfort as well as to ascertain the new AFC controller robustness. Comparison of body acceleration signals from the passive suspension with AFC controller semi active seat suspension system shows up to to 45% improvement to the occupant ride comfort under different vibration intensities.

Development of a hybrid control algorithm for effective reduction of drift in multispan isolated bridges

This study aimed to develop a hybrid control algorithm for semiactive control devices to effectively control the drift caused by seismic loads in the superstructure of an isolated multispan bridge. First, bridge behavior was simulated using the Newmark method to select a semiactive control device that would be appropriate for the bridge structure. An optimal control force was selected to control the displacement and relative displacement of each superstructure element. Next, an equation of motion that employed a stochastic linearization capable of representing the nonlinearity beyond the structural linear limits was used. Further, a Bouc–Wen model was designed to simulate the nonlinearity of the structure model and the control device to configure the control logic. A hybrid control algorithm was developed to overcome the disadvantages of the clipped-optimal and Lyapunov control algorithms, which show excellent control effectiveness but experience problems during nonlinear control along with extreme manual control problems owing to their use of the Heaviside step function. The two control algorithms were used individually to make judgments, and the results of each were used to produce a three-stage signal (min., max., median). The performance of the proposed control method with the developed algorithm was verified through experimental tests. The developed hybrid control algorithm improved the performance of the two individual control algorithms and effectively controlled the behavior of multispan bridges.

A semi-active variable equivalent stiffness and inertance device implemented by an electrical network

Semi-active devices have been widely investigated and applied due to their advantages in control systems. However, for satisfying complicated applications, some semi-active devices need to be capable of controlling multiple mechanical properties, which is hard to implement with a mechanical network considering the space limitation. In this paper, a semi-active variable equivalent stiffness and inertance (VESI) device is developed by an electrical network and an electromagnetic device instead of a mechanical system. Due to that the inerter and spring can store energy, the dynamic control of their mechanical properties without the external power to compensate the stored energy will cause the system discontinuity, which will affect the control performance. Therefore, the variable damping (VD) device is applied to connect with spring or inerter in series to obtain variable equivalent stiffness or inertance properties. Then, according to the force-current analogy, an electrical “VESI” network is designed to simulate the mechanical VESI network. An electromagnetic device equips with the variable electrical system can achieve the VESI mechanical properties, which is validated with experiments. The imaginary part of the admittance of the proposed device can vary to the positive phase and also the negative phase by controlling two resistors. The application of VESI device in the vehicle is investigated and analysed. A semi-active control strategy is designed for vibration control and rollover prevention of vehicles with VESI suspensions. According to the simulation result, the proposed semi-active system can significantly improve the vibration reduction performance at both vertical and roll directions; also, it can decrease the roll angel when vehicles in the cornering maneuver. Besides, the semi-active VESI device with an electrical network has the advantages in installation and maintenance. It has great potential in practical applications.

Adaptive neuro-fuzzy and simple adaptive control methods for full three-dimensional coupled buildings subjected to bi-directional seismic excitations

Attenuation of three-dimensional coupled buildings under bi-directional seismic excitations using semi-active control devices is pursued in this paper. Multiple magneto-rheological (MR) dampers are employed to connect two adjacent buildings at multiple levels for real-time control of the structural responses. The MR dampers are managed by adaptive neuro-fuzzy inference systems (ANFIS) and simple adaptive control (SAC) methods so a comparison between the performance of both controllers can be made. The displacement feedback type is used for both control methods to design the closed-loop action. The structural system modeled as two three-dimensional buildings connected by frame elements in which the MR dampers are implemented. The equations of motions of the three-dimensional model are formulated by assuming that each floor diaphragm is rigid in its own plane but flexible in the vertical coordinate. Each link is assumed to have three degrees-of-freedom two translational and one rotational at its ends. The adaptive neuro-fuzzy inference system is designed based on Sugeno-type model. Seven triangular membership functions are chosen to fuzzify the input crisp data in the fuzzy logic controller. The training data for ANFIS are generated by the Linear Quadratic Regulator (LQR) under white-noise disturbance. For the simple adaptive controller, LQR is also used to generate the desired trajectories of the reference-model. Numerical simulations are carried out for both symmetrical and asymmetrical coupled buildings under eleven pairs of major earthquakes. The results show that both ANFIS and SAC can deal very successfully with modeling complexities associated with full three-dimensional models subjected to multi-excitations. In terms of seismic responses reduction, both methods have shown a great potential in enhancing the structural performance under seismic activities.

User-centred assistive SystEm for arm Functions in neUromuscuLar subjects (USEFUL): a randomized controlled study

BackgroundUpper limb assistive devices can compensate for muscular weakness and empower the user in the execution of daily activities. Multiple devices have been recently proposed but there is still a lack in the scientific comparison of their efficacy.MethodsWe conducted a cross-over multi-centric randomized controlled trial to assess the functional improvement at the upper limb level of two arms supports on 36 patients with muscular dystrophy. Participants tested a passive device (i.e., Wrex by Jaeco) and a semi-active solution for gravity compensation (i.e., Armon Ayura). We evaluated devices’ effectiveness with an externally-assessed scale (i.e., Performance of the Upper Limb-PUL-module), a self-perceived scale (i.e., Abilhand questionnaire), and a usability scale (i.e., System Usability Scale). Friedman’s test was used to assess significant functional gain for PUL module and Abilhand questionnaire. Moreover, PUL changes were compared by means of the Friedman’s test.ResultsMost of the patients improved upper limb function with the use of arm supports (median PUL scores increase of 1–3 points). However, the effectiveness of each device was related to the level of residual ability of the end-user. Slightly impaired patients maintained the same independence without and with assistive devices, even if they reported reduced muscular fatigue for both devices. Moderately impaired patients enhanced their arm functionality with both devices, and they obtained higher improvements with the semi-active one (median PUL scores increase of 9 points). Finally, severely impaired subjects benefited only from the semi-active device (median PUL scores increase of 12 points). Inadequate strength was recognized as a barrier to passive devices. The usability, measured by the System Usability Scale, was evaluated by end-users “good” (70/100 points) for the passive, and “excellent” (80/100 points) for the semi-active device.ConclusionsThis study demonstrated that assistive devices can improve the quality of life of people suffering from muscular dystrophy. The use of passive devices, despite being low cost and easy to use, shows limitations in the efficacy of the assistance to daily tasks, limiting the assistance to a predefined horizontal plane. The addition of one active degree of freedom improves efficacy and usability especially for medium to severe patients. Further investigations are needed to increase the evidence on the effect of arm supports on quality of life and diseases’ progression in subjects with degenerative disorders.Trial registration clinicaltrials.gov, NCT03127241, Registered 25th April 2017. The clinical trial was also registered as a post-market study at the Italian Ministry of Health.

Improving curving performance of a straddle type monorail vehicle by using semi-active devices

Improving curving performance of a straddle type monorail vehicle by using semi-active devices

Application of the resettable semi-active damper device for macro modelling of confined semi-interlocking masonry walls

In previous research by the authors, the semi-interlocking masonry (SIM) was investigated as infill panels for framed structures and its favourable seismic performance was established through laboratory tests. Confined semi-interlocking masonry (CSIM) is a new application of SIM that aims to enhance earthquake performance of confined masonry buildings. Numerical simulations are performed to estimate the structural capacity of CSIM buildings. Micro and macro-modelling strategies are two major approaches for numerical simulation of masonry buildings. This paper proposes a macro-model for CSIM buildings by using a resettable semi-active damper model to simulate the behaviour of the SIM panel. The hysteretic performance of CSIM walls using the proposed macro-model was compared with the load-displacement pushover curve resulting from the FEA micro-modelling approach. The acceptable match between the responses of CSIM walls obtained from the micro and the macro-model confirmed the capability of the proposed model to capture the capacity of CSIM walls.

The Effects of Mathematical Modelling of Magneto-rheological Dampers on Its Control Performance: A Comparative Study Between the Modified Bouc-Wen and the Maxwell Nonlinear Slider Hysteretic Models

Input voltage of Magneto Rheological (MR) dampers is the only controllable parameter as a semi-active control device. Therefore, voltage selection has an important role in control procedure via MR dampers. In many of semi-active control algorithms, a mathematical modelling method is required for determining the MR damper voltage at each time instant. As a result, applying different mathematical modelling methods can lead to different voltages for the MR damper, which subsequently results in different control performance. In the present research, the effects of mathematical modelling method of an MR damper hysteretic behaviour on its control performance were investigated. The most exact and common Maxwell nonlinear slider and modified Bouc-Wen hysteretic models were employed through a nonlinear comparative numerical study. A building structure was utilized for numerical investigations. A ten-story office building steel structure is excited by seven acceleration time histories. Nonlinear instantaneous optimal control and linear quadratic regulator controllers were utilized as two active-based semi-active algorithms. Results of nonlinear investigations showed an obvious difference between the Maxwell nonlinear slider and the modified Bouc-Wen models from the control performance viewpoint. Outputs show a very slight better performance for the MNS model in reducing the nonlinear responses.

Load balancing and neural dynamic model to optimize replicator dynamics controllers for vibration reduction of highway bridge structures

Earthquakes cause irreparable damages to the built environment, which has led bridge engineers to develop structural control systems to mitigate damage and improve vibration reduction in real-time. Among control systems, base isolation is one of the most commonly used passive control strategies for seismic protection of civil structures. Yet, it lacks real-time adaptability, has lower energy dissipation, and poor performance during near-fault earthquakes. To overcome these limitations, a hybrid control system comprised of semi-active magneto-rheological (MR) dampers and passive base isolation bearings is installed at the deck and piers for vibration reduction of highway bridge structures. This paper, inspired by evolutionary game theory and artificial intelligence, proposes data-driven replicator dynamic control algorithms to distribute the command voltage to the current driver of the semi-active MR dampers. It incorporates a load balancing strategy to reallocate additional resources. To achieve a high-performance design of the game-theory-inspired controllers, a patented neural dynamic model is used to optimize the control parameters. The evaluation of the proposed methodology uses a benchmark control problem based on the 91/5 highway bridge in Southern California subjected to near-field earthquake accelerograms. The performance of five different proposed controllers is compared with conventional Lyapunov and fuzzy logic control algorithms using 21 performance criteria. Results show the load balancing capability of the proposed control algorithms to mitigate the vibrations experienced by the bridge structure and further increase the durability of semi-active devices. The novelty of the methodology impacts how game-theory controllers make control decisions among multiple devices in engineering problems.

Seismic Performance Evaluation of a Recently Developed Magnetorheological Damper: Experimental Investigation

Magnetorheological (MR) dampers have the ability to mitigate natural hazards for structures due to their high energy dissipation features with low power demand. This feature has made the MR damper one of the most popular semiactive damping devices. The present work validates the performance of a single-story reinforced concrete (RC) frame using a reduced scale 10 kN capacity multiple coil MR damper that has recently been developed by the authors. To conduct this test, MR fluid is synthesized and the proposed multicoil MR damper was designed and fabricated. Three RC frames were cast and tested using a loading frame with a capacity of 50 kN. This frame was subjected to earthquake excitation with MR damper placed diagonally at 0 A current, 3 A current, and without MR damper for a better comparison. The comparative performance indicated the reductions in displacements, increase of forces, and changes in crack patterns. The proposed semiactive damper can, therefore, be used effectively as a seismic resilient device in reducing the structural responses in the regions of moderate to high seismicity.

Parametric Study of Damping Characteristics of Magneto-Rheological Damper: Mathematical and Experimental Approach

The present research work is a part of a project was a semi-active structural control technique using magneto-rheological damper has to be performed. Magneto-rheological dampers are an innovative class of semi-active devices that mesh well with the demands and constraints of seismic applications; this includes having very low power requirements and adaptability. A small stroke magneto-rheological damper was mathematically simulated and experimentally tested. The damper was subjected to periodic excitations of different amplitudes and frequencies at varying voltage. The damper was mathematically modeled using parametric Modified Bouc-Wen model of magneto-rheological damper in MATLAB/SIMULINK and the parameters of the model were set as per the prototype available. The variation of mechanical properties of magneto-rheological damper like damping coefficient and damping force with a change in amplitude, frequency and voltage were experimentally verified on INSTRON 8800 testing machine. It was observed that damping force produced by the damper depended on the frequency as well, in addition to the input voltage and amplitude of the excitation. While the damping coefficient (c) is independent of the frequency of excitation it varies with the amplitude of excitation and input voltage. The variation of the damping coefficient with amplitude and input voltage is linear and quadratic respectively. More ever the mathematical model simulated in MATLAB was in agreement with the experimental results obtained.

Parameter identification of Bouc–Wen dynamic model for magnetorheological shimmy damper based on improved simulated annealing algorithm

Magnetorheological (MR) shimmy damper has a good application prospect in aircraft landing gear shimmy control as a semi-active vibration control device; however, its non-linear and hysteretic characteristics bring difficulties to the control and restrict performance. It is necessary to develop a dynamic model of the damper that can effectively show these characteristics. This study is based on the experimental data of the damping force characteristics of MR shimmy damper with different control currents. Bouc–Wen model, apply to describe non-linear and hysteretic characteristics, was selected to establish the dynamic model of damping force, displacement and velocity. This study proposed an improved simulated annealing (SA) algorithm, which can improve the efficiency of identification, to identify the parameters of the model. Comparing with the original algorithm, the improved SA algorithm has the same solution quality and better performance in computational efficiency. The relationships between the identified parameters and the control current were obtained by curve fitting, and the experimental data with different amplitudes and frequencies are used to verify the result. It is shown that the established model can accurately show the dynamic characteristics of the damper under different excitation.

Physical modeling and experimental verification of magneto-rheological damper under medium and high frequency excitation

As a promising semi-active device, magneto-rheological damper has been widely used in low-frequency vibration isolation fields (within 20 Hz) such as bridge damping and building seismic resistance. Recently, the application of magneto-rheological damper has extended to medium and high frequency fields such as satellite and power engine vibration control, accompanied with an urgent need of detailed understanding of its output characteristics. In this paper, a comprehensive physical model is established to analyze dynamic performance of the magneto-rheological damper. The model, derived from both Poiseuille and Couette flow, aims to describe the relationship between the flow rate and pressure difference. The compressibility of the magneto-rheological fluid, the inertia of both the fluid and piston assembly, and the friction are involved to capture the medium and high frequency dynamics of the damping force. Theoretical calculation and simulation verification of magnetic circuit are conducted. Then the experiment based on a self-made prototype is carried out. The results show that the damping force calculated by proposed physical model matches well with the experimental results across the predefined range of frequency and coil current levels.