Stable open loop poles: to cancel or not to cancel?

Stable plant poles can either be shifted by feedback, or they can be approximately canceled by a controller. While it is known that the canceling design impacts on the transients due to input disturbances, it seems little appreciated that the alternative, i.e. the shifting design, impacts on closed...

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Bibliographic Details
Main Authors: Graebe, S.F., Middleton, R.H.
Format: Conference Proceeding
Language:English
Subjects:
Australia
Control systems
Feedback loop
Industrial control
Open loop systems
Output feedback
Polynomials
Robustness
State feedback
Transfer functions
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Summary:Stable plant poles can either be shifted by feedback, or they can be approximately canceled by a controller. While it is known that the canceling design impacts on the transients due to input disturbances, it seems little appreciated that the alternative, i.e. the shifting design, impacts on closed loop robustness. In this paper we show that shifting stable poles, rather than canceling them, increases the l/sub 1/, H/sub /spl infin// and the point-wise in frequency norms of the complementary sensitivity. Thus, the choice to either cancel or shift any one stable pole emerges as a design issue that requires a deliberate trade-off between input disturbance response and robustness.
ISSN:0191-2216
DOI:10.1109/CDC.1995.478749