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Multivariable Control Systems ECSE 6460. Fall 2009 Lecture 26: 4 December 2009. Uncertain MIMO Plant. G p (s). Frequency Response. Feedback Control Loop. K(s). G p (s). +. -. practically zero steady state error for step reference rise time less than 1 second overshoot less than 5%
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Multivariable Control SystemsECSE 6460 Fall 2009 Lecture 26: 4 December 2009
Uncertain MIMO Plant Gp(s)
Feedback Control Loop K(s) Gp(s) + - • practically zero steady state error for step reference • rise time less than 1 second • overshoot less than 5% • robustly for any value of c
Menu for the day • Representing the uncertainty • a la unstructured uncertainty • a la structured uncertainty • Assessment of robust stability • a la unstructured uncertainty • a la structured uncertainty • Assessment of robust stability • a la unstructured uncertainty • a la structured uncertainty
Unstructured Uncertainty Wo(s) D(s) Output uncertainty + G(s) + Wi(s) D(s) Input uncertainty + + G(s)
Output Uncertainty Wo(s) D(s) Output uncertainty + G(s) + We need to select a weight such that:
Input Uncertainty Wi(s) D(s) Input uncertainty + + G(s) We need to select a weight such that:
Weight Wo(s) Refer to uncert1.m
Structured Uncertainty Ws(s) D relax to + G(s) +
Assessment of Robustness • In this topic, we first design a controller for the nominal system, then we assess the robustness properties of the system. • Two control designs are explored, decentralized inverse-based, and H-infinity synthesis. K(s) Gp(s) + -
Decentralized Inverse Based Based on nominal plant model Refer to decent.m
H synthesis for nominal plant • Use S/T synthesis with: Refer to hinf_ex.m
Robust Stability Assessment Unstructured Uncertainty Wo(s) D(s) + K(s) G(s) + + -
Robust Stability Assessment Wo(s) + K(s) G(s) + -
Robust Stability Assessment Refer to decent.m
Robust Stability Assessment Refer to hinf_ex.m
Robust Stability Assessment Structured Uncertainty Ws(s) D + K(s) + G(s) + -
Robust Stability Assessment Structured Uncertainty Ws(s) + K(s) + G(s) + -
Structured Singular Value Peak at 0.130 For decentralized controller
Structured Singular Value Peak at 0.150
Nominal Performance Refer to hinf_ex.m
Robust Performance Assessment Unstructured Uncertainty Wo(s) + + K(s) G(s) WP(s) + + -
Robust Performance Assessment Unstructured Uncertainty Wo(s) + + K(s) G(s) WP(s) + + -
Robust Performance Assessment Structured Uncertainty Ws(s) + + K(s) G(s) WP(s) + + -
Robust Performance Assessment Structured Uncertainty Ws(s) + + K(s) G(s) WP(s) + + -