Steady-State Bumpless Transfer Under Controller Uncertainty: Methodology and Applications
Zheng, Kai
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https://hdl.handle.net/2142/83868
Description
Title
Steady-State Bumpless Transfer Under Controller Uncertainty: Methodology and Applications
Author(s)
Zheng, Kai
Issue Date
2006
Doctoral Committee Chair(s)
Bentsman, Joseph
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
Bumpless transfer refers to smooth transfer between dynamic controllers without inducing undesirable transients in plant outputs. To achieve bumpless transfer, a transfer operator must be designed to stabilize the off-line controller to be switched in and enforce that the values of the output signal of the off-line controller are equal to those of the online one prior to controller transfer. It is found, however, that the leading transfer operator synthesis techniques, represented by the steady-state LQ bumpless transfer technique proposed by Turner and Walker, are incapable of providing convergence of the output of the off-line controller to that of the online one, prohibiting bumpless transfer, under the presence of controller uncertainty. The latter is defined to be the mismatch between the controller model and the actual implemented controller. To address this problem, a novel state/output feedback bumpless transfer topology is proposed that employs the nominal state of the offiine controller and, through the use of an additional controller/model mismatch compensator, also the actual offline controller output. A corresponding bumpless transfer design procedure along with the supporting theory is developed and rigorously shown to be applicable to a large class of systems. Furthermore, the unique structure of the state/output bumpless transfer topology is discovered and shown to give rise to the realization of robust bumpless transfer in the limit through a novel hybrid mode of behavior---robustly controlled discrete transition. The attainment of the latter completely eliminates the need for any performance/robustness trade-off in the transfer operator design and provides arbitrarily fast convergence of the off-line controller output to that of the online one, removing a key obstacle to acceptance by practitioners of the technique proposed. Thus a complete methodology for steady-state bumpless transfer under controller uncertainty is developed. Finally, the methodology is successfully utilized in two important applications: (1) full operating range robust control of a boiler/turbine unit, and (2) high performance robust linear hybrid control of an induction motor.
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