1. Structural Dynamics & Vibration Control Lab. 1 대용량 20 톤 MR 유체 감쇠기의 새로운 동적 모델 정형조, 한국과학기술원 건설환경공학과 최강민, 한국과학기술원 건설환경공학과 Guangqiang Yang, University of Notre Dame, USA Billie F. Spencer, Jr., University of Notre Dame, USA 이인원, 한국과학기술원 건설환경공학과 한국전산구조공학회 춘계 학술발표회 서울대학교, 서울 2002 년 4 월 13 일

2. Structural Dynamics & Vibration Control Lab. 2 Outline MR Damper Experimental Setup Experimental Results Quasi-Static Modeling of MR Dampers Dynamic Modeling of MR Damper System Conclusions

3. Structural Dynamics & Vibration Control Lab. 3 Introduction Although, MR fluids were discovered in the late of 1940s, commercial applications were not developed until the Lord Corporation pioneered small-scale devices for vehicular applications in the 1990s. Partnering with the Lord Corporation in the mid 90s, Univ. of Notre Dame (Prof. Spencer) sought to develop large-scale devices for civil infrastructural applications.

4. Structural Dynamics & Vibration Control Lab. 4 Magnetorheological Fluid Damper F Magnetic Choke MR Fluid MR Damper Experimental Setup

5. Structural Dynamics & Vibration Control Lab. 5 Prototype 20-Ton MR Fluid Damper Thermal Expansion Accumulator LORD Rheonetic TM Seismic Damper MR-9000 MR Fluid 3-Stage Piston Diameter: 20 cm Stroke: 16 cm Power: < 50 watts, 22 volts

6. Structural Dynamics & Vibration Control Lab. 6 LORD Rheonetic TM Seismic Damper MR-9000 Diameter: 20 cm Stroke: 16 cm Power: < 50 watts, 22 volts Prototype 20-Ton MR Fluid Damper

7. Structural Dynamics & Vibration Control Lab. 7 Experimental Setup (Yang 2001)

8. Structural Dynamics & Vibration Control Lab. 8 Performance Testing Experimental Results (Yang 2001)

9. Structural Dynamics & Vibration Control Lab. 9 Force-Displacement Tests under Triangular Excitation Velocity: 6 cm/sec

10. Structural Dynamics & Vibration Control Lab. 10 Damper Force-Displacement and Force-Velocity Relationships under Sinusoidal Excitation Displacement Excitation: 1 inch, 0.5 Hz

11. Structural Dynamics & Vibration Control Lab. 11 Frequency-Dependent Tests 1 inch displacement excitation 2 A input current

12. Structural Dynamics & Vibration Control Lab. 12 Constant Peak Velocity Tests Displacement excitation with peak velocity of 8 cm/s and input current of 2 A

13. Structural Dynamics & Vibration Control Lab. 13 Quasi-Static Models for MR Dampers* Insufficient to describe the MR damper behavior under dynamic loading. * Yang 2001

14. Structural Dynamics & Vibration Control Lab. 14 Dynamic model of the current driver. –Current driver has shown to be more effective than the common voltage-driven power supply in reducing MR damper response time. Dynamic model of the MR damper itself. Dynamic Model of MR Damper System The dynamic model of the MR damper system is necessary for simulation of damper behavior and structural vibration control simulation with MR dampers.

15. Structural Dynamics & Vibration Control Lab. 15 Dynamic Model of Current Driver Differential equation between i com and i is

16. Structural Dynamics & Vibration Control Lab. 16 Dynamic Model of Current Driver Identified transfer function between i com and i is

17. Structural Dynamics & Vibration Control Lab. 17 Experimental Verification

18. Structural Dynamics & Vibration Control Lab. 18 Experimental Verification

19. Structural Dynamics & Vibration Control Lab. 19 MR Damper Response Analysis Displacement Lag Force Overshoot Force Roll-Off

20. Structural Dynamics & Vibration Control Lab. 20 MR Dampers Response Analysis Force Roll-Off Additional Loops Force Overshoot

21. Structural Dynamics & Vibration Control Lab. 21 Proposed Dynamic Model of MR Dampers

22. Structural Dynamics & Vibration Control Lab. 22 Proposed Dynamic Model

23. Structural Dynamics & Vibration Control Lab. 23 Damper Response with Random Displacement Excitation and Constant Current Damper Response with an Input Current of 2 A

24. Structural Dynamics & Vibration Control Lab. 24 Generalization for Fluctuating Current Six parameters are assumed to vary with the input current, which are , a 1, a 2, m, n, f 0. A first-order low-pass filter is utilized to accommodate the dynamics involved in the MR fluid reaching rheological equilibrium

25. Structural Dynamics & Vibration Control Lab. 25 Experimental Verification DisplacementExcitation Input Current

26. Structural Dynamics & Vibration Control Lab. 26 Damper Response Experimental Verification

27. Structural Dynamics & Vibration Control Lab. 27 Conclusions Magnetorheological fluid dampers are one of the most promising smart damping technologies. Full-scale MR dampers can be effectively realized. Proposed dynamic model of MR damper systems is effective in describing the nonlinear MR damper behavior under dynamic loading.