Simulation and Control Aspects of FHT

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Simulation and Control Aspects of FHT

• M. V. Sivaselvan
• CO-PI CU-NEES
• Assistant Professor
• Dept. of Civil, Environmental and Architectural
  Eng.
• University of Colorado at Boulder
• siva_at_colorado.edu

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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Multi-story Building
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(No Transcript)
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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Use of hybrid simulation
Laboratory Testing
Hybrid Simulation is useful for
qualification/proof-of-concept testing when the
interaction of a component with its surroundings
needs to be accurately represented

• Examine the performance of a component in its
  host environment
• Proof of concept tests
• Interaction with surroundings may significantly
  modify input
• Hybrid simulation is useful

• Hybrid simulation not very useful for this
  purpose
• Some kind of computation-in-the-loop with
  geometric reasoning about state-space may be
  possible

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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Feedback interaction in reality
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
Substructure 2 Physical
Work Conjugate Boundary Condition
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In hybrid simulation however
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
Actuator / Transfer Device
Substructure 2 Physical
Work Conjugate Boundary Condition
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In hybrid simulation however
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
Actuator / Transfer Device
Sensor
Substructure 2 Physical
Work Conjugate Boundary Condition
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In hybrid simulation however
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
Natural Physical Feedback
Actuator / Transfer Device
Sensor
Substructure 2 Physical
Work Conjugate Boundary Condition
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In hybrid simulation however
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
Natural Physical Feedback
Actuator / Transfer Device
Sensor
Actuator Feedback
Substructure 2 Physical
Work Conjugate Boundary Condition
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In hybrid simulation however
External Input (Eg. Ground Motion)
Substructure 1 Computational
Boundary Condition
NEW DYNAMICS
Natural Physical Feedback
Actuator / Transfer Device
Sensor
Actuator Feedback
Substructure 2 Physical
Work Conjugate Boundary Condition
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Challenges

• These additional dynamics create significant
  problems
• When the structure to be simulated is lightly
  damped, almost always renders the system unstable
• Need to develop control algorithms to make hybrid
  simulation possible
• Causality ? Design of such algorithms requires
  knowledge about physical substructure (predictive
  model, implicit integration etc.) ? This is a
  conflict ? Robustness of algorithm with respect
  to modeling of the physical substructure
• A numerical algorithm need not be causal, a
  hybrid simulation algorithm does

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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Hybrid Simulation
Pseudo-dynamic
Dynamic
Has no inertia effects of interest
Has significant inertia effects

• More practical applications necessitate this form
  of hybrid simulation
• My research is in this area

• Born from the displacement-based finite element
  one of the elements is now physical !
• Algorithms also reflect this
• If in addition, there are no frequency-dependent
  behavior is the physical substructure can be
  done as slowly as we want to

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Hybrid Simulation
Pseudo-dynamic
Dynamic
Real-time
Slow
Hybrid simulation with Shaking Tables
CU NEES Site
CU NEES Site
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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Recall
External Input
Substructure 1 Computational
Boundary Condition
Motivation Want actuator to behave the same way
as Substructure 1
Natural Physical Feedback
Actuator / Transfer Device
Sensor
Actuator Feedback
Substructure 2 Physical
Work Conjugate Boundary Condition
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Introduce a controller
External Input
Substructure 1 Computational
Boundary Condition
Controller
Natural Physical Feedback
Actuator / Transfer Device
Actuator Feedback
Substructure 2 Physical
Work Conjugate Boundary Condition
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Introduce a controller
External Input
Substructure 1 Computational
Boundary Condition
Controller
Natural Physical Feedback
Actuator / Transfer Device
Actuator Feedback
Substructure 2 Physical
Work Conjugate Boundary Condition
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Model Reference Control

• Controller designed so that does the same
  thing as
• Part implemented in the computer

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Another Approach
Internal Model Control - IMC
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Equivalence of different approaches

• The two approaches can be shown to be shown to be
  different parametrizations of a 2 DOF controller
• Each offers a different perspective
• MRC useful in design
• IMC useful in robustness analysis

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CU FHT Algorithm

• Computer implementation of IMC

Discretize at 10 ms
Discretize at 1 ms
CU FHT Algorithm !! (Shing et. al., 2005)
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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Hybrid Simulation with a Shaking Table

• Necessary when physical substructure has
  distributed mass

• In many cases of practical interest for hybrid
  simulation, mass is distributed and there is no
  such natural way of lumping the mass for
  substructuring.
• Examples
• Nonstructural components in civil structures
• Payloads in aerospace structures
• Machine components
• Dams, chimneys and other continuum civil
  structures
• Soil / fluid-structure interaction
• The interface device must be able to dynamically
  excited a system with distributed mass shaking
  table

Physical substructure has no masses of
significance, hence no inertia effects (Hence
pseudo-dynamic)
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Outline

• What is hybrid simulation?
• Why do it?
• Challenges in implementing a hybrid simulation
  system
• Types of hybrid simulation
• Hybrid simulation algorithms architecture and
  equivalence
• Hybrid testing with shaking tables
• Current and planned work, Conclusions

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Hybrid Testing with Shaking Tables

• 1.5 m x 1.5 m working area
• /- 200 mm dynamic stroke
• Frequency range 0-50 Hz
• Maximum payload 2000 kg
• Maximum Acceleration 1.0-2.9 g
• Maximum Velocity 1 m/s
• Will give CU structures lab capability to perform
  such hybrid simulations as listed in the previous
  slide
• Collaboration with MTS Systems

Hybrid Simulation Configurations
Combination of Shaking Table and External Actuator
Shaking Table Only
Response Feedback
Response Feedback
Computational Substructure
External Actuator
Physical Substructure
Physical Substructure
Physical Substructure
Reaction Wall
Shaking Table
Shaking Table
Computational Substructure
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Conclusions

• Hybrid simulation online combination of
  computation and physical experimentation
• Useful for qualification/proof-of-concept testing
  when the interaction of a component with its
  surroundings needs to be accurately represented
• Challenge added dynamics and feedback paths
  created by the transfer system/actuator applying
  that applied interface conditions between the two
  substructures.
• More difficult in dynamic hybrid simulation where
  physical substructure has significant inertia (as
  opposed to pseudo-dynamic)
• Algorithms based on a control-systems perspective
  offer more promise than those motivated by the
  finite element method