•A novel compact rotary MR damper with variable stiffness and variable damping characteristics was designed and prototyped for the seat suspension.•The nonlinear stiffness control scheme can avoid ...the end-stop impact and dissipate vibration energy.•The no-jerk skyhook damping control scheme can reduce the vibration amplitude.•The vibration attenuation performance of the seat suspension was largely improved by the VSVD rotary MR damper.
Long-term vibration poses a threat to drivers’ health and affects their ride performance. Furthermore, large-magnitude vibration and sudden shocks may even result in end-stop impacts, raising the drivers’ injury risk. To reduce the vibration and avoid end-top impacts, this paper presents an innovative seat suspension installed with variable stiffness and variable damping (VSVD) rotary magnetorheological (MR) dampers. At first, a novel compact VSVD rotary MR damper was designed and prototyped for the suspension, making the suspension’s stiffness and damping controllable. Then, with two identical VSVD MR dampers were installed, the prototyped seat suspension was characterised by an MTS test frame to verify its capabilities of variable stiffness and damping. A control strategy consisting of a nonlinear stiffness control and a no-jerk skyhook damping control was also designed. Finally, the vibration attenuation performance of the seat suspension was numerically and experimentally evaluated under three vibration excitations, i.e., harmonic excitation, bump excitation, and random excitation. Both numerical and experimental results indicate that the vibration control performance of the seat suspension can be significantly improved by the VSVD rotary MR dampers.
Magnetorheological fluids involve multi-physics phenomena which are manifested by interactions between structural mechanics, electromagnetism and rheological fluid flow. In comparison with analytical ...models, numerical models employed for magnetorheological fluid applications are thought to be more advantageous, as they can predict more phenomena, more parameters of design, and involve fewer model assumptions. On that basis, the state-of-the-art numerical methods that investigate the multi-physics behaviour of magnetorheological fluids in different applications are reviewed in this article. Theories, characteristics, limitations and considerations employed in numerical models are discussed. Modelling of magnetic field has been found to be rather an uncomplicated affair in comparison to modelling of fluid flow field which is rather complicated. This is because, the former involves essentially one phenomenon/mechanism, whereas the latter involves a plethora of phenomena/mechanisms such as laminar versus turbulent rheological flow, incompressible versus compressible flow, and single- versus two-phase flow. Moreover, some models are shown to be still incapable of predicting the rheological nonlinear behaviour of magnetorheological fluids although they can predict the dynamic characteristics of the system.
Overshoot and long settling time are two common problems of the positioning control for robotic arms. To solve the positioning control problems, an innovative variable stiffness and variable damping ...(VSVD) magnetorheological (MR) actuation system for robotic arms was designed, prototyped and evaluated in this paper. The system can reduce the overshoot and settling time of the robotic arm with less energy consumption by controlling the stiffness and damping of its VSVD unit. A robotic arm with the VSVD actuation system was developed and prototyped. In order to evaluate the performance of the system, a step route and a customised route were designed for the robotic arm system to trace. Under these two routes, the positioning control performances of the VSVD robotic arm were evaluated numerically and experimentally with the control modes of uncontrolled, VD, VS and VSVD, respectively. Both the numerical and experimental results demonstrated that the VSVD control mode works best in general with less overshoot, settling time and energy consumption, indicating that the proposed VSVD actuation system can serve as a good candidate to solve the positioning control problems of robotic arms.
To enhance the effect of reducing suspension vibration and harvesting the vertical vibration energy of cars, a research was conducted on an energy-regenerative suspension with magnetorheological ...dampers (MRDs). First, an innovative structure of energy-regenerative dampers was developed, as well as mathematical and simulation models of the damping force and energy harvest. Subsequently, simulation experiments and bench tests were conducted. Based on these, mathematical models of a two-degree-of-freedom semi-active suspension were built, and a whale optimization algorithm- proportional integral derivative (WOA-PID) control algorithm was designed. Simulation experiments were conducted on the working conditions of white-noise and impact road surfaces. The obtained results indicate that the energy-regenerative dampers considered in this study have a certain energy-regenerative capability, and the WOA-PID algorithm exerts an optimal controlling effect on the suspension.
Magnetorheological dampers have been used in automotive industry and civil engineering applications for shock and vibration control for some time. While such devices are known to provide reliable ...shock and vibration suppression, there exist emerging applications in which the magnetorheological dampers have to be optimized in terms of power consumption and overall weight (e.g. energy-efficient electric vehicles). Utilizing traditional optimal design approaches to tackle those issues can sometimes lead to convergence problems such as getting trapped in a local extremum and failing to converge to the global optimum. Furthermore, manufacturing limitations are usually not taken into account in the optimization process which may hamper achieving an optimal design. In this article, we present a method for optimal design of magnetorheological dampers by utilizing mathematical optimization and finite element analysis. The proposed method avoids infeasible solutions by considering physical constraints such as fabrication limitations and tolerances. This approach takes every single feasible solution into account so that the final solution would be the global extremum of the optimization cost function. The proposed approach is applied to optimize a complex magnetorheological damper structure with different types of materials such as steel and AlNiCo. In particular, we present the design of a valve-mode magnetorheological damper with AlNiCo integrated as its core. A magnetorheological damper prototype is manufactured based on the proposed optimization method and tested experimentally.
Suspension systems are one of the most critical components of transportation vehicles. They are designed to provide comfort to the passengers to protect the chassis and the freight. Suspension ...systems are normally provided with dampers that mitigate these harmful and uncomfortable vibrations. In this paper, we explore two control methodologies (in time and frequency domain) used to design semiactive controllers for suspension systems that make use of magnetorheological dampers. These dampers are known because of their nonlinear dynamics, which requires the use of nonlinear control methodologies for an appropriate performance. The first methodology is based on the backstepping technique, which is applied with adaptation terms and H ∞ constraints. The other methodology to be studied is the quantitative feedback theory (QFT). Despite QFT is intended for linear systems, it can still be applied to nonlinear systems. This can be achieved by representing the nonlinear dynamics as a linear system with uncertainties that approximately represents the true behavior of the plant to be controlled. The semiactive controllers are simulated in MATLAB/Simulink for performance evaluation.
Studies conducted after Northridge and Kobe earthquakes have shown that brittle failures in connections and members of structures led to extensive and catastrophic damage. Consequently, evaluation of ...critical points in a structure, controlling, and mitigating the seismic responses of structures, and avoiding structural damage such as low-cycle fatigue are needed. In this study, an adaptive control algorithm is used to reduce the low-cycle fatigue damage in two benchmark structures equipped with MR dampers. First, optimum parameters of the adaptive control method, called the Simple Adaptive Control Method (SACM), are calculated. The effectiveness of using SACM to mitigate the structural response of a three-story benchmark structure and a twenty-story benchmark structure under earthquake is studied. Finally, reducing fatigue damage on those structures subjected to various earthquakes is examined to extend the fatigue life of the structures.
To calculate the cumulative fatigue, the rain-flow counting technique is used. In order to validate the developed nonlinear models, natural frequencies and displacement response of a three-story structure subjected to three different earthquakes are compared with the values presented in the reference studies. A numerical search method is used to minimize the ratio of cumulative fatigue and maximum ratio of roof displacement in each structure. The results show that the adaptive control system can reduce fatigue damage in elements, and fatigue life could be extended in structures. Also, the effects of using the semi-active adaptive control approach on dynamic characteristics of a structure are studied.
•The assessment of existing viaducts built without the concepts of seismic engineering is mandatory for the in force standards.•The combined use of semi-active dampers, friction pendulum devices and ...seismic early warning system, is investigated for an existing viaduct.•The linking between dampers and early warning system is realized using a control algorithm for a calibration of devices.•The effectiveness and robustness of the investigated strategy is compared with a consolidate anti-seismic technology.•The results attested that the approach proposed results in a more robust seismic behavior of the structure.
The seismic events occurred in recent years have highlighted the extreme vulnerability of a large part of existing Italian highway infrastructure. The principal skeleton of Italian highway network was built during the mid-century, where the knowledge of seismic engineering was still limited. Also, the old age of structures with the need of seismic assessment, is forcing highway stakeholders to give an answer to a strategic query: should thousands of highway bridges be destroyed and re-built with in force regulations, or do they just need a retrofit? The objective of this work is to reply concretely to that issue, investigating the combined use of a dissipative smart-passive control strategy and an innovative isolation system to protect seismically excited structures. It is based on the use of seismic early warning information (SEWI) to optimally calibrate variable dampers for a higher reduction of the structural response. In particular, the adoption of dissipative magnetorheological (MR) dampers calibrated according to the forecasted value of the seismic peak ground acceleration, and a new adaptive control algorithm, are herein proposed. Moreover, to reduce the influence of support devices in the global viaduct behavior, a prototype of double concave friction pendulum (DCFP), with a very low value of friction coefficient, is implemented. The effectiveness and robustness of the DCFPs system with smart-passive MR dampers driven by the SEWI, are demonstrated with reference to an existing Italian highway viaduct for the first time. The results of non-linear time history analysis using seismic registrations of natural events are then compared with a consolidate passive technique characterized by lead rubber bearings (LRB), applied to the same structure. The control technique results were promising for the ease of implementation for structures, effectiveness, even compared with a widespread passive system and robustness, given an estimate of the incoming earthquake by a seismic early warning system.
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