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DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

The value of norm-based control synthesis methodologies heavily depends on the quality of the model at hand. The acquisition of low-order control oriented models however is often a non-trivial task. This paper pursuits the nonparametric synthesis of optimal controllers while omitting parametrization of the plant. As a result, the actual parametrization is performed on the controller such that no data-reduction is performed without knowledge of closed-loop relevant behavior.The synthesis of frequency response coefficients of an optimal controller for a sampled version of the mixed-sensitivity problem is considered. To convexify the problem, the actual optimization is performed over the frequency response coefficients of the Youla parameter Qi. Using the Youla parameter, the set of stabilizing controllers is mapped onto the set of stable transfer functions. The main contribution of this paper is the derivation of algebraic constraints over Qi that guarantee the existence of a rational stable interpolant over the points Qi. Simulations shows that the frequency response coefficients found via the proposed approach show similar behavior as model based methods.

Due to the demand for higher accuracy and lower acoustic noise levels, there is a growing interest for active vibration suppression in industrial application. Many control concepts have been proposed in this field that are suited to introduce damping in systems with a large number of modes. However tuning is often focussed on reduction of one dominant mode. Such control approaches are less transparent when several dominant modes are involved.A combined loop-shaping and root-locus tuning approach is proposed to reduce several dominant modes with low-order controllers. The tuning approach is experimentally evaluated on a vibrating plate using piezo's for both sensing and actuating. Based on the given tuning rules and trade-offs, a SISO feed-back controller is designed and implemented. This low authority control approach shows that besides local performance, also the global damping of the plate is improved which consequently results in reduction of vibration levels over the whole plate for a broad range of frequencies. As a results, acoustic noise radiation is reduced significantly.

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