This result has been extended to the parameter space so that one can determine the stability margin, in terms of ranges of parameter variations, of the closed loop system when the nominal stabilizing controller is given. This stability margin can be enlarged by a choice of better stabilizing controller.The second problem this report describes is the lower order stabilization problem.Even though the wide range of stabilizing controller design methodologies are available in both the state space and the transfer function domains, all of these methods produce unnecessarily high order controllers.The motivation of the problem is as follows.In practice, the stabilization is only one of many requirements to be satisfied.Therefore, if the order of a stabilizing controller is excessively high, one can normally expect to have a even higher order controller upon the completion of design such as inclusion of dynamic response requirements, etc. Therefore, it is reasonable to have a lowest possible order stabilizing controller first and then adjust the controller to 3 meet additional requirements.In this report, the algorithm of designing a lower order stabilizing controller is given. The algorithm is not necessarily produce the minimum order controller, however the algorithm is theoretically logical and some simulation results show that the algorithm works in general.The above two problems have been solved and published. These are found in Appendix A and B. Finally, some remarks and on going research are briefly discussed. To appear.
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DISCUSSIONS AND DIRECTIONS OF RESEARCHThe stability margin in the parameter space is in general more practical than one in the coefficient space. When parameters enter into coefficients of characteristic polynomial linearly, the stability margin is exact. However, when parameters enter in nonlinear fashion which is the general facts in practical systems, the margin seems to be conservative.The results show that the transfer function approach (or polynomial frame-
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ABSTRACTThis paper treats the robust stability issue using the characteristic polynomial, for two different cases. First in coefficient space with respect to perturbations in the coefficients of the characteristic polynomial, and then for a control system containing perturbed parameters in the transfer function description of the plant.
This paper outlines the technical approach adopted to meet the specifications laid down for the '2001 Future Energy Challenge (FEC)' organized by the Department of Energy and IEEE in August 2001. Abstract -In this paper, the development of a low cost fuel cell inverter system is detailed. The approach consists of a three-terminal push-pull DC-DC converter to boost the fuel cell voltage (48V) to f2OOVDC. A four switch (IGBT) inverter is employed to produce 120V/240V, 60Hz AC outputs. High performance, easy manufacturability, lower component count., safety and cost are addressed. Protection and diagnostic features form an important part of the design. Another highlight of the proposed design is the control strategy, which allows the inverter to adapt to the requirements of the load as well as the power source (fuel cell). A unique aspect of the design is the use of the TMS320LF2407 DSP to control the inverter. Two sets of lead-acid batteries are provided on the high voltage DC bus to supply sudden load demands. Efficient and smooth control of the power drawn from the fuel cell and the high voltage battery is achieved by controlling the front end DC-DC converter in current mode. The paper details extensive experimental results of the proposed design on DOE National Energy Technology Laboratory (NETL) Fuel Cell.
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