Strictly Positive Real Problem with Observers

In English We study the extension of what class of linear time invariantplants may be transformed into SPR systems introducingan observer. It is shown that for the open loopstable systems a cascaded observer achieves the result.For the open loop unstable systems an observer-basedfeedback is required to success. In general any system stabilizableand observable may be transformed into an SPRsystem. This overcomes the old conditions of minimumphase and relative degree one. The result is illustratedwith some examples.