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| Received:July 13, 2006Revised:December 03, 2008 |
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| Ill-conditioned stable inversion arising from singularly perturbed zero dynamics |
| Xuemei GUO, Guoli WANG |
| (School of Information Science and Technology, Sun Yat-Sen University, Guangzhou Guangdong 510275, China) |
| Abstract: |
| The ill-conditioned stable inversion is studied for slightly nonminimum phase systems whose zero dynamics is singularly perturbed, that is, the relative degree is ill-defined. For these systems, we show that there exists an inherent limitation in the bandwidth of a reference trajectory to be tracked when a well-conditioned feedforward input via stable inversion is sought. We assert that, when the violation of this limitation occurs, the so-called reference trajectory redesign is called for. Our analysis results can provide an explicit assessment as well as useful guidance for the reference trajectory redesign if needed. |
| Key words: Nonminimum phase Ill-defined relative degree Stable inversion Singularly perturbed zero dynamics |