Hyung-Jo Jung Sejong University, Korea Hyung-Jo Jung Sejong University, Korea Kang-Min Choi Korea Advanced Inst. of Science and Tech. Kang-Min Choi Korea Advanced Inst. of Science and Tech. Sang-Won Cho Korea Advanced Inst. of Science and Tech. Sang-Won Cho Korea Advanced Inst. of Science and Tech. In-Won Lee University of Western Ontario, Canada In-Won Lee University of Western Ontario, Canada University of San Diego, July 11-13, 2006 An MR Damper-based Control System Introducing Electromagnetic Induction Part Fourth World Conference on Structural Control and Monitoring (4WCSCM)

OUTLINE Introduction Introduction Proposed Control System Proposed Control System Numerical Verification Experimental Verification Experimental Verification Conclusions Conclusions Dynamics and Smart Structures Lab., Sejong Univ., KOREA

Background Background INTRODUCTION INTRODUCTION  Smart damping systems (i.e., semiactive control systems): - reliability of passive systems; adaptability of active systems - smart damping devices: variable stiffness damper, variable - smart damping devices: variable stiffness damper, variable friction damper, MR/ER damper, etc. friction damper, MR/ER damper, etc.  An MR damper-based control system is one of the promising smart damping systems, because of its mechanical simplicity, high dynamic range, low operating power requirements, environmental robustness, and so on. Dynamics and Smart Structures Lab., Sejong Univ., KOREA

3 Conventional MR Damper-based System Conventional MR Damper-based System MR damper  A control system including sensors, a controller and an external power source  Difficult to install and maintain the conventional system, especially in the cases of large-scale structures such as high-rise buildings and long-span bridges INTRODUCTION INTRODUCTION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 4 Possible Solutions Possible Solutions  Application of advanced technologies such as power harvesting and wireless sensor networks  Development of passively operated control systems with adaptability and high performance with adaptability and high performance  Etc. INTRODUCTION INTRODUCTION One of the promising systems is the smart passive control system proposed by Cho et al. (2005). One of the promising systems is the smart passive control system proposed by Cho et al. (2005). * S.W. Cho, H.J. Jung, and I.W. Lee, “Smart passive system based on magnetorheological damper,” Smart Mater. Struct., 14, , 2005.

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 5 Objectives Objectives  To introduce a newly developed MR damper- based control system.  To numerically and experimentally verify the effectiveness of the proposed control effectiveness of the proposed control system for seismic protection of building system for seismic protection of building structures. structures. INTRODUCTION INTRODUCTION

Conventional MR Damper-based Control System MR Damper controller power source command current PROPOSED CONTROL SYSTEM Control System sensor Dynamics and Smart Structures Lab., Sejong Univ., KOREA

7  An EMI system consists of permanent magnet and coils.  It changes the kinetic energy of the reciprocation motion of the MR damper to the electric energy according to the Faraday’s law of induction. Proposed MR Damper-based Control System Proposed MR Damper-based Control System MR damper with Electromagnetic induction (EMI) system MR damper with Electromagnetic induction (EMI) system MR Damper damper deformation magnetic field induced current PROPOSED CONTROL SYSTEM EMI system

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 8 Proposed MR Damper-based Control System Proposed MR Damper-based Control System MR damper with Electromagnetic induction (EMI) system MR damper with Electromagnetic induction (EMI) system Conventional System Control system including sensors, controller, and power supply EMI system consisting of permanent magnet and coils Proposed System PROPOSED CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 9  Adaptability: damping characteristics of MR damper vary with strength of external load  Simplicity: no power source, no controller, and no sensors Advantages of Proposed Control System Advantages of Proposed Control System PROPOSED CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 10 SMART Advantages of Proposed Control System Advantages of Proposed Control System  Adaptability: damping characteristics of MR damper vary with strength of external load  Simplicity: no power source, no controller, and no sensors PROPOSED CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 11 PASSIVE Advantages of Proposed Control System Advantages of Proposed Control System  Adaptability: damping characteristics of MR damper vary with strength of external load  Simplicity: no power source, no controller, and no sensors SMART PROPOSED CONTROL SYSTEM

NUMERICAL VERFICATION Dynamics and Smart Structures Lab., Sejong Univ., KOREA Three-story Building (Dyke et al. 1996) MR damper

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 13  Proposed MR damper-based control system - SPC-D: EMI part designed to reduce drifts - SPC-A: EMI part designed to reduce accelerations  Conventional smart damping system - CO-D: clipped-optimal algorithm to reduce drifts - CO-A: clipped-optimal algorithm to reduce accelerations Control Systems Compared NUMERICAL VERFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 14  Normalized peak responses under four historic earthquakes El Centro Hachinohe Kobe Northridge Peak Accel.Peak Drift CO-D CO-A SPC-D SPC-A NUMERICAL VERFICATION Simulation Results

Three-story Building Model Installed EMI System Three-story Building Model Installed EMI System EXPERIMENTAL VERIFICATION Dynamics and Smart Structures Lab., Sejong Univ., KOREA

16 Ground Input Motion (Scaled El Centro Earthquake) Ground Input Motion (Scaled El Centro Earthquake) EXPERIMENTAL VERIFICATION - 진동대 입력 하중 : 40% El Centro earthquake (PGA: g) 20% El Centro earthquake (PGA: g) 30% Hachinohe earthquake (PGA: g) 20% Kobe earthquake (PGA: g) 10% Northridge earthquake (PGA: g)

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 17 EXPERIMENTAL VERIFICATION Experimental Results: Movie Clips Experimental Results: Movie Clips

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 18 EXPERIMENTAL VERIFICATION Experimental Results: Passive-mode Case Experimental Results: Passive-mode Case Peak Acceleration at 3 rd floor Peak Drift between 2 nd and 3 rd floors  Passive-off: 0 Volt  Passive-optimal: 3 Volt  Passive-on: 10 Volt

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 19 Optimal EXPERIMENTAL VERIFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 20 Experimental Results: Acceleration at 3 rd Floor Experimental Results: Acceleration at 3 rd Floor EXPERIMENTAL VERIFICATION Passive-on (10Volt) Smart passive

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 21 EXPERIMENTAL VERIFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 22 EXPERIMENTAL VERIFICATION Experimental Results: Comparison Experimental Results: Comparison Peak Acceleration at 3 rd floor Peak Drift between 2 nd and 3 rd floors

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 23 EXPERIMENTAL VERIFICATION

Proposed MR Damper-based Control System Compact, simple, and cost-effective.Compact, simple, and cost-effective. Adaptable to external loads.Adaptable to external loads. Shows the comparable performance to a conventional smart system using clipped optimal algorithm in numerical simulation.Shows the comparable performance to a conventional smart system using clipped optimal algorithm in numerical simulation. Shows the comparable performance to optimal passive case in preliminary experiment.Shows the comparable performance to optimal passive case in preliminary experiment. CONCLUSIONS Dynamics and Smart Structures Lab., Sejong Univ., KOREA

Thank You for Your Attention! Dynamics and Smart Structures Lab., Sejong Univ., KOREA

26  Determination of coil turns for solenoid  By varying two parameters, S a and S i S a : summation of peak acceleration at each floor S i : summation of peak interstory drift at each floor which are normalized by uncontrolled responses which are normalized by uncontrolled responses  Using envelope of maximum value of S a and S i for El Centro, Hachinohe, Kobe earthquakes  Two EMI systems are designed: EMI-A from S a and EMI-D from S i Design of EMI System NUMERICAL VERFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 27  Faraday’s law of induction  : induced electromotive force from EMI system n: number of turns of coil  B : magnetic flux B: magnetic field A: cross area w : width of the area covered by magnetic field x : damper deformation (1) Estimation of induced voltages by EMI system SMART PASSIVE CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 28 where :damper deformation : width of area covered by magnetic field (15) (16) (17) EMI system SMART PASSIVE CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 29  If we assume as below - Magnetic field: 1.2 T (Tesla) - Turns of solenoid : 900 turns/m - Area of cross section: 13.2 (cm 2 ) - Velocity of stroke: 9 cm/s (max. value of uncontrolled) Length : 5cm Area : 13.2cm 2 SMART PASSIVE CONTROL SYSTEM

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 30 Variations of S a Envelope of max. responses Coil turns/m SaSa Hachinohe Kobe El Centro Coil turns/m SiSi Hachinohe Kobe El Centro EMI-A : 2.6  10 4 EMI-D : 2.2  10 4 Max. envelope of S a Max. envelope of S i NUMERICAL VERFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 31  Induced voltages for various earthquakes by EMI system Time (sec) Voltage (V) Time (sec) EL Centro Kobe Hachinohe Northridge Results NUMERICAL VERFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 32 Normalized accelerations at each floor Normalized accelerations at each floor EL Centro Kobe Hachinohe Northridge Floor level Normalized accel. Floor level Clipped-D Clipped-A EMI-D EMI-A NUMERICAL VERFICATION

Dynamics and Smart Structures Lab., Sejong Univ., KOREA 33 Normalized accel. EL Centro Kobe Hachinohe Northridge Floor level Clipped-D Clipped-A EMI-D EMI-A Normalized interstory drifts at each floor Normalized interstory drifts at each floor NUMERICAL VERFICATION