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A dual‐rate control system is a hybrid system composed of continuous‐time and discrete‐time elements with two sampling frequencies. In this work, a new frequency domain analysis and design approach, based on the quantitative feedback theory is developed, to cope with robust stability and robust tracking specifications. Tracking specifications are considered not only in the discrete‐time but also in continuous‐time, that allow a precise description of the intersample behavior (ripples), and characterization of frequencies below and beyond the Nyquist frequencies. Several illustrative examples and a case study has been developed. [ABSTRACT FROM AUTHOR]

When in a digital control strategy there are samples lost due to limitations, different multirate (MR) control options can be used for solving the problem: Dual-rate inferential control (IC) and model-based dual-rate control (MBDR). The objective of this contribution is to analyze, compare, and to assess their behavior under different perspectives. Is a dual-rate inferential control better than a model-based dual-rate control? Both options lead to a periodically time-varying discrete-time system and for this reason a lifted modeling is considered. An efficient algorithm is used for computing a MR system's frequency response for these control structures. The robust performance and disturbance effects are studied in detail under sample losses and process uncertainty, and some considerations are reported. A new QFT (quantitative feedback theory) procedure for dual-rate systems analysis is also described. Analysis and simulation examples and experimental results for UGV path tracking are introduced in this work, revealing that MBDR outperforms IC when the model contains important uncertainties. • A frequency analysis is used to compare dual-rate strategies for slow measured systems. • New application of quantitative feedback theory techniques to dual-rate systems. • A discussion of robust stability and performance on practical problems is reported. • Under important model uncertainties, model-based dual-rate control is the best option. • Dual-rate control reveals energy saving in a low-cost mobile robot control application. [ABSTRACT FROM AUTHOR]

In this work we propose a new family of fractional order structures, composed of so-called Fractional order Complex pole-based Terms (FCTs), to be used for Quantitative Feedback Theory (QFT) loop shaping. The choice of this kind of structure is discussed, and its ability to approach the optimal solution (close-to-optimality) is shown by comparing the results obtained by FCT-based structures to other fractional structures introduced previously in the literature. The ability of FCT-based structures to solve QFT problems is shown by solving a benchmark robust control problem. [ABSTRACT FROM PUBLISHER]