Adaptive Robust Control For Dual Stage Hard Drives

1
Adaptive Robust Control For
Dual Stage Hard Drives
in GOD we trust

• ????? ?????? ???? ???? ???? ???? ??? ???

Dr. Hamid D. Taghirad
???? ???? ?????? ??????? ???????? ???? ??????
??? ????? ??????? ????? ????????? ????
H.H.Eghrary MS Student of Electrical
Engineering K.N.Toosi Univ.
2
2end Seminar Presentation
Sunday, August 12,2007
Introduction to Adaptive Robust Control

• Obstacles for Control Algorithm Design

• Strategies for Performance Improvement

• Adaptive Robust Control (ARC) For a HDD

?Adaptive Control
?Robust Control

• ARC via Discontinuous Projection

• ARC via Smooth Projection

• Desired Compensation ARC

3
Obstacles for Control Algorithm Design

• Inherent Nonlinearity

• Unknown But Reproducible
• for example Unknown parameters
• Unreproducable
• for example
• model Disturbance

• Modeling Uncertainty

4
Strategies for Performance Improvement

• Nonlinear Analysis And Synthesis

?Deal With Nonlinearity Directly Nonlinear
Control
Effective for both reproducible and none
Reproducible Uncertainities

• Fast Robust Feedback

• Controled Learning For Uncertainity Reduction

Effective for Reproducible Uncertainities
5
Adaptive Robust Control (ARC)
Robust
Adaptive

• Reduce the model uncertainty
• Zero Tracking Error
• (Without High gain Feedback)

• Attenuate the effect of model uncertainties
  through
• robust feedback.
• Instantaneous
• Reaction

• Drawbacks
• Transient Performance of the system is not Clear.
• Unknown Nonlinear functions such as external
  disturbances are not considered.

• Drawbacks
• Transient Performance of the system is not Clear.
• Unknown Nonlinear functions such as external
  disturbances are not considered.

6
Deterministic Robust Control
Adaptive Control
Conflicts

• Use to Design Base Line Controller

• Used to Design Supervisor

Guarantee ?Transient Performance
?Prescribed final tracking accuracy
Improved ?Asymptotic Input Tracking
7
Conventional Adaptation Law ? Estimated
Parameters May not be Bounded
Conflicts
Deterministic Robust Control ? Requires
Bounds On Uncertainties
Modify The Conventional Adaptation Law
Bounded Estimation Parameters
8
Adaptive Robust Control For Hard Disk Drive
Servo System
Problem Formulation
9
Robust Control scheme
Adaptive Control scheme
10
Stability Analysis
?Lyapanov Function
Adaptive Control scheme
Parameter Estimation
Estimation Error
11
Results

• Limitations Of Adaptive Control

• Transient Performance is Unknown

• Uncertain nonlinearity are not Considered

12
Robust Control scheme
More In Detail

• Error Dynamics

? Choose The such that
13
Stability Analysis
?Lyapanov Function
Choose small such that
Stable
14

• Tracking Error

• Steady State Error

15
Decrease for decreasing Steady State Error
Parameter Adaptation
16
Adaptive Robust Control
17
Conflicts
Conventional Adaptation Law ? Estimated
Parameters May not be Bounded
REMIND
Deterministic Robust Control ? Requires
Bounds On Uncertainties
Modify The Conventional Adaptation Law
Bounded Estimation Parameters
18
Adaptive Robust Control Via Discontinuous
Projection
19
Remains in
Increases
Decreases
Remains in
Parameter Uncertainty Bounded via Adaptation
Progress
Robust Control Problem Solved
20
Adaptive Robust Control Via Smooth Projection
There is a Lyapanov Function
Stability is Guaranteed
21
Desired Compensation ARC
Desired Trajectory
Remind ARC Scheme
Real Parameter Measurement (Measurement Noise)
Dynamic Stabilizing Feedback
Static Feedback
22
Desired Compensation ARC
Regressors Dose not Depend On Measurements

• Eliminate Measurement Noise Effect on Parameter
  Adaptation
• Off-Line Regressors Calculation

Fast Error Dynamic and Parameter Adaptation
Facilitate Control Gain Tuning Process due to
Separation of Robust Control And Parameter
Adaptation