Stability Considerations in the Synthesis of Time-Varying Feedback Systems

In a recent paper
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the synthesis technique proposed by Guillemin for liniear stationary systems
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was extended for nonstationary feedback systems. It is to be expected, however, that stability problems may arise when applying the method for unstable or nonminimum phase plants, as it does in the time-invariant case. In this investigation it is shown that stability of the system can be assured by imposing constraints in the open-loop differential equation. These constraints are seen to be analogous to those of the time-invariant case.