Modeling and Control of Magnetorheological Dampers for Seismic Response Reduction
Summary (2 min read)
Introduction
- The tragic consequences of the recent earthquakes in Kobe, Japan and in Los Angeles, California have underscored, in terms of both human and economic factors, the tremendous importance of the way in which buildings and bridges respond to earthquakes.
- To date, active structural control has been successfully applied in over twenty commercial buildings and more than ten bridges (during erection) [20].
- Yet there are a number of serious challenges that remain before active control can gain general acceptance by the engineering and construction professions at large.
- Semi-active control devices potentially offer the reliability of passive devices, yet maintain the versatility and adaptability of fully active systems.
MR Damper Behavior and Modeling
- Magnetorheological fluids recently developed by the Lord Corporation [3–7] (see alsohttp:// www.rheonetic.com/mrfluid/) have many attractive features, including high yield strength, low viscosity and stable hysteretic behavior over a broad temperature range.
- Moreover, MR fluids can operate at temperatures from –40 to 150oC with only slight variations in the yield stress.
- The measured forces are shown as a function of time in Fig. 2a, the force-displacement loops are shown in Fig. 2b, and the force-velocity loops are shown in Fig. 2c.
- The simple mechanical idealizations of the MR damper depicted in Fig. 3 has been shown to accurately predict the behavior of the prototype MR damper over a broad range of inputs [42].
- A constrained nonlinear optimization was used to obtain the 14 model parameters in Eqs. (1– 8).
Clipped-Optimal Control Algorithm Development
- Previous researchers have found semi-active control systems can potentially achieve the majority of the performance of fully active systems [25, 33, 35, 44].
- To date, most of the current active structural control strategies for aseismic protection have been based on either full-state feedback (i.e., all structural displacements and velocities) or on velocity feedback.
- Consider a seismically excited structure controlled with a single MR damper.
- The measurement equation is given by (10) where is the vector of measured outputs, and is the measurement noise vector.
- When the MR damper is providing the desired optimal force (i.e., ), the voltage applied to the damper should remain at the present level.
Numerical Example
- The performance of the clipped-optimal control algorithm presented in the previous section is now evaluated through numerical simulation.
- The structural measurements used for calculating the desired control force include the absolute accelerations of the three floors of the structure, and the displacement of the MR damper (i.e., ).
- The peak structural responses to the El Centro earthquake are given in Table 2.
- Notice that these performance gains are achieved by the semi-active controller while requiring smaller control forces than are required in the passive-on case.
- Interestingly, the forces applied by the MR damper operating in semi-active mode are often smaller than those corresponding to the damper operating in the passive-on mode, again indicating that larger damping forces do not always produce better results.
Conclusions
- The performance of a semi-active control system based on newly developed magnetorheological (MR) fluid dampers has been studied.
- A recently reported model for the MR damper was presented which is capable of predicting the response of the MR damper over a wide range of loading conditions and command voltages, and a clipped-optimal controller was proposed for control implementation.
- Excellent results were obtained when this strategy was applied to control a model of a seismically excited three-story scaled building model.
- Similar results have been obtained experimentally [11, 16].
- Finally, note that the algorithms that explicitly incorporate actuator dynamics and controlstructure interaction into the control design process may offer additional controlled performance gains [12].
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References
2,377 citations
"Modeling and Control of Magnetorheo..." refers background in this paper
...where the evolutionary variable is governed by [45]...
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745 citations
"Modeling and Control of Magnetorheo..." refers background in this paper
...In the last decade, significant effort has been devoted to the possibility of employing various control strategies in the design of engineering structures to increase their safety and reliability against strong earthquakes [20, 22–24, 39]....
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710 citations
"Modeling and Control of Magnetorheo..." refers background or methods in this paper
...Magnetorheological (MR) dampers are new semi-active control devices that use MR fluids to provide controllable dampers that are quite promising for civil engineering applications [8, 15, 42]....
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...3 has been shown to accurately predict the behavior of the prototype MR damper over a broad range of inputs [42]....
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...This paper first presents a recently developed model for a prototype MR damper [42] that has been studied in the Structural Dynamics and Control / Earthquake Engineering Laboratory ( http://www....
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...Dyke, Spencer, Sain & Carlson August 1, 1996 3 filled with an MR fluid [42]....
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574 citations
"Modeling and Control of Magnetorheo..." refers background in this paper
...Magnetorheological fluids recently developed by the Lord Corporation [3–7] (see also http:// www....
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Frequently Asked Questions (19)
Q2. What have the authors stated for future works in "Modeling and control of magnetorheological dampers for seismic response reduction" ?
Efforts are currently underway to investigate this possibility.
Q3. What is the force-velocity relationship of the MR damper?
At 0 V the MR damper primarily exhibits the characteristics of a viscous device (i.e., the force-displacement relationship is approximately elliptical, and the force-velocity relationship is nearly linear).
Q4. How long can the damper be operated?
The peak power required is less than 10 watts, which could allow the damper to be operated continuously for more than an hour on a small camera battery.
Q5. What are the advantages of semi-active control devices?
Semi-active control devices potentially offer the reliability of passive devices, yet maintain the versatility and adaptability of fully active systems.
Q6. What is the description of MR dampers?
They offer highly reliable operation at a modest cost and can be viewed as fail-safe in that they become passive dampers should the control hardware malfunction.
Q7. How many buildings have been successfully constructed?
To date, active structural control has been successfully applied in over twenty commercial buildings and more than ten bridges (during erection) [20].
Q8. What is the displacement of the MR damper?
Because the MR damper is attached between the first floor and the ground, its displacement is equal to the displacement of the first floor of the structure relative to the ground, i.e., in Eqs. (1–4).
Q9. Why did the semi-active controller perform better than the passive-off and passive-on control?
Because the semi-active system has the ability to vary its properties to more effectively control the structure, the clipped optimal controller performed better than both the passive-off and passive-on control systems.
Q10. Why is the MR damper unable to be operated continuously for more than an hour?
This behavior is primarily due to the time the MR fluid in the damper takes to reach rheological equilibrium and the time lag associated with the dynamics of driving the electromagnet in the MR damper.
Q11. How long does the MR damper take to rise?
The rise time (defined as the time required to go from 10% to 90% of the final value) in the force generated by the MR damper during a constant velocity test when a step in the voltage is applied to the current driver is approximately 8 msec.
Q12. What is the way to induce the MR damper to produce the desired control force?
If the magnitude of the force produced by the damper is smaller than the magnitude of the desired optimal force and the two forces have the same sign, the voltage applied to the current driver is increased to the maximum level so as to increase the force produced by the damper to match the desired control force.
Q13. What are some of the common types of semi-active devices?
Various semi-active devices have been proposed which utilize forces generated by surface friction or viscous/viscoelastic-plastic fluids to dissipate vibratory energy in a structural system.
Q14. What is the performance of the semi-active control system?
The performance of the semi-active control system employing the MR damper was found to be modestly better in reducing peak displacements than that of the linear active controller, indicating that the semi-active control system is capable of not only approaching, but surpassing, the performance of linear active control system, while only requiring a small fraction of the power that is required by the active controller.
Q15. What is the way to control the MR damper?
When the MR damper is providing the desired optimal force (i.e., ), the voltage applied to the damper should remain at the present level.
Q16. What is the way to measure the displacement of a structure?
Because accelerometers can readily provide reliable and inexpensive measurement of accelerations at arbitrary points on the structure, development of control methods based on acceleration feedback is an ideal solution to this problem and will be presented subsequently.
Q17. What are the structural measurements used for calculating the desired control force?
The structural measurements used for calculating the desired control force include the absolute accelerations of the three floors of the structure, and the displacement of the MR damper (i.e., ).
Q18. What is the definition of a semi-active control device?
According to presently accepted definitions, a semi-active control device is one which cannot input energy into the system being controlled.
Q19. What is the equation of motion for a MR damper?
Assuming that the forces provided by the MR damper are adequate to keep the response of the primary structure from exiting the linear region, then the equations of motion can be written as(9)ż