Auto-Calibration%20and%20Control%20Applied%20to%20Electro-Hydraulic%20Valves

1
Auto-Calibration and Control Applied to
Electro-Hydraulic Valves

• A Ph.D. Thesis Proposal
• Presented to the Faculty of the
• George Woodruff School of Mechanical Engineering
• at the Georgia Institute of Technology
• By
• PATRICK OPDENBOSCH
• Committee Members
• Nader Sadegh (Co-Chair, ME)
• Wayne Book (Co-Chair, ME)
• Chris Paredis (ME)
• Bonnie Heck (ECE)
• Roger Yang (HUSCO Intl.)

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

3
INTRODUCTION

• CURRENT APPROACH
• Electronic control
• Use of solenoid Valves
• Energy efficient operation
• New electrohydraulic valves
• Conventional hydraulic spool valves are being
  replaced by assemblies of 4 independent valves
  for metering control

Low Pressure
High Pressure
Spool Valve
Spool piece
Spool motion
Piston
Piston motion
4
INTRODUCTION

• CURRENT APPROACH
• Electronic control
• Use of solenoid Valves
• Energy efficient operation
• New electrohydraulic valves
• Conventional hydraulic spool valves are being
  replaced by assemblies of 4 independent valves
  for metering control

Valve motion
Low Pressure
High Pressure
Piston motion
5
INTRODUCTION

• ADVANTAGES
• Independent control
• More degrees of freedom
• More efficient operation
• Simple circuit
• Ease in maintenance
• Distributed system
• No need to customize

Valve motion
Low Pressure
High Pressure
Piston motion
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INTRODUCTION

• METERING MODES
• Standard Extend
• Standard Retract
• High Side Regeneration
• Low Side Regeneration
• DISADVANTAGES
• Nonlinear system
• Complex control

Valve motion
Low Pressure
High Pressure
Piston motion
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INTRODUCTION
Coil Cap
Adjustment Screw

• POPPET ADVANTAGES
• Excellent sealing
• Less faulting
• High resistance to contamination
• High flow to poppet displacement ratios
• Low cost and low maintenance

Modulating Spring
Input Current
Coil
Armature
Pilot Pin
Control Chamber
Armature Bias Spring
U.S. Patents (6,328,275) (6,745,992)
Pressure Compensating Spring
Main Poppet
Forward (Side) Flow
Reverse (Nose) Flow
8
INTRODUCTION
Coil Cap
Adjustment Screw

• Electro-Hydraulic Poppet Valve (EHPV)
• Poppet type valve
• Pilot driven
• Solenoid activated
• Internal pressure compensation
• Virtually zero leakage
• Bidirectional
• Low hysteresis
• Low gain initial metering
• PWM current input

Modulating Spring
Input Current
Coil
Armature
Pilot Pin
Control Chamber
Armature Bias Spring
U.S. Patents (6,328,275) (6,745,992)
Pressure Compensating Spring
Main Poppet
Forward (Side) Flow
Reverse (Nose) Flow
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INTRODUCTION

• VALVE CHARACTERIZATION
• Flow Conductance Kv
• or

10
INTRODUCTION

• FORWARD MAPPING
• REVERSE MAPPING

Side to nose
Forward Kv at different input currents A
Nose to side
Reverse Kv at different input currents A
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INTRODUCTION

• MOTIVATION
• Need to control valves KV
• Currently done by inversion of the steady-state
  input/output characteristics
• Requires individual offline calibration

• CHALLENGES
• Online learning of steady state and transient
  characteristics
• Online estimation of individual Kv.
• ADVANTAGES
• No individual offline calibration
• Design need not be perfect and sufficiently
  fast
• Maintenance scheduling can be implemented from
  monitoring and detecting the deviations from the
  normal pattern of behavior.

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

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PROBLEM STATEMENT

• PURPOSE
• Develop a general theoretical framework for
  auto-calibration and control of general nonlinear
  systems. It is intended to explore the
  feasibility of the online learning of the
  systems characteristics while improving its
  transient and steady state performance without
  requiring much a priori knowledge of such system.
  
• APPLICATION
• This framework is applied to a hydraulic system
  composed of electro-hydraulic valves in an effort
  to study the applicability of having a
  self-calibrated system.

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PROBLEM STATEMENT

• RESEARCH QUESTIONS
• How well can the systems mappings be learned
  online while at the same time trying to achieve
  good state tracking performance?
• How can the tracking error dynamics be maintained
  stable while applying learning and estimation on
  the system?
• How is the learning affected by input saturation
  and time-varying dynamics?
• In particular for the EHPVs, how well can the
  forward and reverse flow mappings be learned?
• How can the learned mappings be used for fault
  detection?

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

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OBJECTIVES

• THEORETICAL
• Development of a general formulation for control
  of nonlinear systems with parametric uncertainty
  and time-varying characteristics
• Development of a formulation for auto-calibration
  of nonlinear systems
• Study of learning dynamics online along with
  fault diagnosis
• Improve Kv control of EHPVs

• EXPERIMENTAL
• Analysis and validation on the effectiveness of
  the proposed method
• Study of the accuracy of the auto-calibration and
  possible drift problems
• Development of computationally efficient
  algorithms
• Development of a nonlinear observer for state
  estimation for unmeasurable states

17
PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

18
RELEVANT WORK REVIEW

• CONTROL
• Sadegh, N., (1995), A nodal link perceptron
  network with applications to control of a
  nonholonomic system, IEEE Transactions on Neural
  Network, Vol. 6, No. 6, pp. 1516-1523.
• Sadegh, N., (1998), A multilayer nodal link
  perceptron network with least squares training
  algorithm, International Journal of Control, Vol.
  70, No. 3, pp. 385-404.

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RELEVANT WORK REVIEW
Sadegh (1995)

• The plant is linearized about a desired
  trajectory
• A Nodal Link Perceptron Network (NLPN) is
  employed in the feedforward loop and trained with
  feedback state error
• The control scheme needs the plant Jacobian and
  controllability matrices obtained offline
• Approximations of the Jacobian and
  controllability matrices can be used without
  loosing closed loop stability.

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RELEVANT WORK REVIEW
Sadegh (1998)

• Nodal Link Perceptron Network (NLPN)
• Functional approximation is achieved by the
  scaling of basis functions
• The class of basis functions are to be selected
  as well as their weights are to be trained so
  that the functional approximation error is within
  prescribed bounds

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RELEVANT WORK REVIEW

• FLOW OBSERVER
• O'hara, D.E., (1990), Smart valve, in Proc
  Winter Annual Meeting of the American Society of
  Mechanical Engineers pp. 95-99
• Book, R., (1998), "Programmable electrohydraulic
  valve", Ph.D. dissertation, Agricultural
  Engineering, University of Illinois at
  Urbana-Champaign
• Garimella, P. and Yao, B., (2002), Nonlinear
  adaptive robust observer for velocity estimation
  of hydraulic cylinders using pressure measurement
  only, in Proc ASME International Mechanical
  Engineering Congress and Exposition pp. 907-916

22
RELEVANT WORK REVIEW

• O'hara (1990), Book (1998)
• Concept of Inferred Flow Feedback
• Requires a priori knowledge of the flow
  characteristics of the valve via offline
  calibration

Squematic Diagram for Programmable Valve
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RELEVANT WORK REVIEW

• Garimella and Yao (2002)
• Velocity observer based on cylinder cap and rod
  side pressures
• Adaptive robust techniques
• Parametric uncertainty for bulk modulus, load
  mass, friction, and load force
• Nonlinear model based
• Discontinuous projection mapping
• Adaptation is used when PE conditions are
  satisfied

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RELEVANT WORK REVIEW

• Liu and Yao (2005)
• Modeling of valves flow mapping
• Online approach without removal from overall
  system
• Combination of model based approach,
  identification, and NN approximation
• Comparison among automated modeling, offline
  calibration, and manufacturers calibration

25
RELEVANT WORK REVIEW

• HEALTH MONITORING
• Polycarpou and Vemuri (1995)
• Selmic and Lewis (2000)
• Linear modeling techniques
• NN for nonlinear identification

Failure Detection and Accommodation Monitoring
off-nominal behavior
Multimodel Failure Detection
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RELEVANT WORK REVIEW

• HEALTH MONITORING
• Polycarpou, M.M. and Vemuri, A.T., (1995),
  Learning methodology for failure detection and
  accommodation, IEEE Control Systems, Vol. No.
  pp. 16-24.
• Selmic, R.R. and Lewis, F.L., (2000),
  Identification of nonlinear systems using rbf
  neural networks Application to multimodel
  failure detection, in Proc XVI International
  Conference on "Material flow, machines, and
  devices in industry"

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

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PROPOSED RESEARCH

• AUTO-CALIBRATION AND CONTROL
• k 0,1,2 (discrete-time index)
• 0 ui iUMAX, i 1,2,,m
• Set of admissible states
• Set of admissible inputs

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PROPOSED RESEARCH

• AUTO-CALIBRATION AND CONTROL
• k 0,1,2 (discrete-time index)
• 0 ui iUMAX, i 1,2,,m
• The control purpose is to learn the input
  sequence uk that forces the states of the
  system xk to follow a desired state trajectory
  dxk as k?8
• PROPOSED Adaptive approach without requiring
  detailed knowledge about the systems model

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PROPOSED RESEARCH

• SQUARE NONLINEAR SYSTEM
• ASSUMPTIONS
• The system is strongly controllable
• The system is strongly observable
• The functions F and H are continuously
  differentiable

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PROPOSED RESEARCH

• SQUARE NONLINEAR SYSTEM
• DEFINITIONS
• Jacobian Matrix
• Controllability Matrix
• Observability Matrix

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PROPOSED RESEARCH

• SQUARE NONLINEAR SYSTEM
• CONTROL DESIGN
• Tracking Error
• Error Dynamics

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PROPOSED RESEARCH

• SQUARE NONLINEAR SYSTEM
• CONTROL DESIGN
• Error Dynamics
• Deadbeat Control Law

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PROPOSED RESEARCH

• SQUARE NONLINEAR SYSTEM
• CONTROL DESIGN
• Deadbeat Control Law
• Proposed Control Law

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PROPOSED RESEARCH

• Proposed Control Law

Nominal inverse mapping
Estimation of Jacobian and controllability
Feedback correction
inverse mapping correction
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PROPOSED RESEARCH
Nominal inverse mapping
Inverse Mapping Correction
uk
xk
NLPN
PLANT
dxk
Adaptive Proportional Feedback
Jacobian Controllability Estimation
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PROPOSED RESEARCH

• ESTIMATION APPROACHES
• Modified Broyden

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PROPOSED RESEARCH

• ESTIMATION APPROACHES
• Recursive Least Squares

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PROPOSED RESEARCH

• APPLICATION
• Kv Observer

For each valve
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PROPOSED RESEARCH

• APPLICATION
• Health Monitoring
• Failures sensor fault, wear of the mating parts,
  contamination, break of a component, or component
  stiction
• Assess valves behavior with respect to the
  nominal behavior.
• Establish the criteria to declare faulting on the
  valves by studying the deviations from the
  nominal pattern.

Kv as a Function of Input Current Deviations
from Nominal Patterns
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PROPOSED RESEARCH

• THEORETICAL TASKS
• Work on the convergence properties of the
  estimated matrices
• Perform analysis about the closed loop stability
  of the overall system.
• Work on a nonlinear observer for the valves flow
  conductances.

• EXPERIMENTAL TASKS
• Hydraulic testbed setup
• Sensor integration, calibration, and filtering
  design
• Data acquisition and analysis
• Validation of theory
• Compare the performance under learning to that of
  fixed input/output mapping

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

43
PRELIMINARY WORK
Implemented Nominal Mapping

• NONLINEAR 1ST ORDER DISCRETE TIME SYSTEM

Comparison implemented and true steady state
mapping
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PRELIMINARY WORK
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PRELIMINARY WORK
Closed-loop and open-loop performance
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PRELIMINARY WORK
Estimated Jacobian and Controllability
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PRELIMINARY WORK

• MORE INFORMATION AT
• Opdenbosch, P. and Sadegh, N., (2005), Control of
  discrete-time systems via online learning and
  estimation, in Proc IEEE/ASME International
  Conference on Advanced Intelligent Mechatronics
  pp. 975-980

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PRELIMINARY WORK

• Single EHPV learning control being investigated
  at Georgia Tech
• Controller employs Neural Network in the
  feedforward loop with adaptive proportional
  feedback
• Satisfactory results for single EHPV used for
  pressure control

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PRELIMINARY WORK
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PRELIMINARY WORK

• Initial test response, no NLPN learning

Flow Conductance
Estimated Jacobian and Controllability
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PRELIMINARY WORK

• EHPV response with NLPN learning

Flow Conductance
Estimated Jacobian and Controllability
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PRELIMINARY WORK

• MORE INFORMATION AT
• Opdenbosch, P. and Sadegh, N., (2005), Control of
  electro-hydraulic poppet valves via online
  learning and estimation, in Proc ASME
  International Mechanical Engineering Congress and
  Exposition, IMECE (Accepted)

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

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EXPECTED CONTRIBUTIONS

• An alternative methodology for control system
  design of nonlinear systems with time-varying
  characteristics and parametric uncertainty.
• A method to estimate and learn the flow
  conductance of the valve online.
• Guidelines to experimentally use this control
  methodology and health monitoring efficiently in
  the area of electro-hydraulic control.

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PRESENTATION OUTLINE

• INTRODUCTION
• PROBLEM STATEMENT
• OBJECTIVES
• REVIEW OF MOST RELEVANT WORK
• PROPOSED RESEARCH
• PRELIMINARY WORK
• EXPECTED CONTRIBUTIONS
• CONCLUSION

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CONCLUSIONS

• The proposed control methodology combines
  adaptive proportional feedback control with
  online corrected feedforward compensation
• The input/output mapping of the system can be
  easily extracted via a functional approximator on
  the feedforward compensation
• Extensive knowledge about the dynamics of the
  system are not needed a priori for satisfactory
  performance
• The proposed method is to be employed in a
  Wheatstone bridge arrangement of novel
  Electro-Hydraulic Poppet Valves seeking a
  self-calibrated system