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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]

• The manuscript is focused on efficiency analysis of parabolic dish collector systems, working in a range of low/medium temperatures, which is of great importance in industrial practice. • A comparison of several receivers (flat-plane and cavity) has been performed, based on a detailed modeling of the radiant power losses due to reradiation, convection and conduction losses. • In practice, the flat-plate receiver should be used with some care, since its temperature is very high in the zones of high concentration. An open cavity solves this problem with the biggest reduction of temperature, but has a relatively modest increasing of thermal efficiency. It is found that the cavity receiver with a cover is the most efficient with an increasing up to a 20% with respect to the flat-plate receiver, with a very significative reduction of the cavity temperature. Application of parabolic dish collector systems working in a range of low/medium temperatures is of great importance in industrial practice. In this work, a thermal efficiency analysis will be performed for different receivers such as a flat-plate receiver and a cavity receiver (with and without a glass cover). Most of the previous receivers analyses found in the literature have been performed for applications with high temperatures. Moreover, a detailed analysis including losses such as reradiation, natural and forced convection, and conduction, have been performed, developing new correlations for natural and forced convention. The obtained results are discussed in detail, obtaining a significant increasing of efficiency of the cavity receivers against the flat-plat receiver with much less working temperatures: up to 20 % for the covered cavity receiver in comparison with the flat-plate receiver, with a temperature reduction at the receiver of more than 450 ° C. [ABSTRACT FROM AUTHOR]

This article investigates the asymptotic stability of impulsive delay dynamical systems (IDDS) by using the Lyapunov–Krasovskii method and looped-functionals. The proposed conditions reduce the conservatism of the results found in the literature by allowing the functionals to grow during both the continuous dynamics and the discrete dynamics. Sufficient conditions for asymptotic stability in the form of linear matrix inequalities (LMI) are provided for the case of impulsive delay dynamical systems with linear and time-invariant (LTI) base systems (non-impulsive actions). Several numerical examples illustrate the effectiveness of the method. [ABSTRACT FROM AUTHOR]

A novel method to tune a Proportional–Integral (PI) compensator for an integrating plus dead time (IPDT) process, in presence of interval parametric uncertainty, is presented. The design is based on optimization of load disturbance rejection with constraints on the magnitude of the sensitivity and complementary sensitivity functions, that must be satisfied for any element belonging to a set of plants. Instead of solving this problem with a brute force approach (grid the uncertainty set), we prove that this problem can be solved by considering only two plants. That lets us to obtain a tuning rule, after using some approximations. To conclude, some examples will be given in order to elucidate the usefulness of the proposed tuning rule. [ABSTRACT FROM AUTHOR]

A novel representation of reset control systems with a zero-crossing resetting law, in the framework of hybrid inclusions, is postulated. The well-posedness and stability issues of the resulting hybrid dynamical system are investigated, with a strong focus on how non-deterministic behavior is implemented in control practice. Several stability conditions have been developed by using the eigenstructure of matrices related to the periods of the reset interval sequences and by using Lyapunov function-based conditions. [ABSTRACT FROM AUTHOR]

Abstract: The reset band is a simple idea, and a must in practice, to improve reset compensation by adding extra phase lead in a feedback loop. However, a formal treatment of how the reset band can affect stability and performance of a reset control system is still an open issue. This work approaches the problem of the existence and stability of limit cycles of reset control systems with reset band. A frequency domain approach is given by using standard methods based on the describing function. In addition, closed-form expressions have been obtained for the describing function of arbitrary order full reset compensators with and without reset band. [Copyright &y& Elsevier]

Abstract: This work presents results on the stability of time-delay systems under reset control. The case of delay-dependent stability is addressed, by developing a generalization of previous stability results for reset systems without delay, and also a generalization of the delay-independent case. The stability results are derived by using appropriate Lyapunov–Krasovskii functionals, obtaining LMI (Linear Matrix Inequality) conditions and showing connections with passivity and positive realness. The stability conditions guarantee that the reset action does not destabilize the base LTI (Linear Time Invariant) system. Several interpretations are given for these conditions in terms of impulsive control, which provide insights into the potentials of reset control. [Copyright &y& Elsevier]

Abstract: The objective of this work is to study the stability of systems with backlash, from an input–output point of view. In the first part, an analysis is addressed. This analysis provides not only conditions for boundedness of the loop signals, but also results on existence of solutions, based on Schauder fixed point theorem. In the second part, the system is studied using an or conic sector approach. The backlash graph is confined into certain conic sector, which is shown to be optimum or maximal. The conic inequality induces frequencial conditions on the linear part, which are further relaxed introducing dynamic multipliers. In the third part, both and techniques are combined reaching a final criterion which results in a Popov-like stability condition. [Copyright &y& Elsevier]

This work develops a new reset-based feedback controller that stabilizes a double integrator plant, in finite-time under a finite-jerk restriction (that is without jumps in acceleration). It is proved that these objectives can be achieved by a second order controller with adequate jerk resettings and a special crossing manifold. The solution is justified with the help of an intuitive geometrical approach (spherical projection of trajectories). The nominal solution is robustified as a hybrid system and simulations show satisfactory performance under output disturbances and state measurement uncertainty. The proposal is compared to several finite-time controllers previously developed in the literature. [ABSTRACT FROM AUTHOR]