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Free fatty acids (FFA) have gained research interest owing to their functions in both local and systemic immune regulation. Changes in the serum levels of anti‐inflammatory short chain fatty acids (SCFA), primarily derived from the gut microbiota, and pro‐inflammatory medium (MCFA) and long (LCFA) chain fatty acids, derived from either the gut microbiota or the diet, have been associated with autoimmunity. Circulating FFA were retrospectively analysed by a gas chromatography–mass spectrometry method in the serum of 18 patients with pemphigus vulgaris (PV) at the baseline and 6 months (n = 10) after immunosuppressive treatments, and 18 healthy controls (HC). Circulating FFA were correlated with the Pemphigus Disease Area Index (PDAI) and serum concentrations of interferon‐gamma (IFN‐γ), Interleukin (IL)‐17A, IL‐5, IL‐10 and IL‐21. Principal Component analysis computed on FFA abundances revealed significant differences in the profile of SCFA (p = 0,012), MCFA (p = 0.00015) and LCFA (p = 0,035) between PV patients and HC, which were not significantly changed by immunosuppressive treatments. PV patients showed a significantly lower serum concentration of propionic (p < 0.0005) and butyric (p < 0.0005) acids, SCFA with anti‐inflammatory functions, while hexanoic (p < 0.0005) and hexadecanoic (p = 0.0006) acids, pro‐inflammatory MCFA and LCFA respectively, were over‐represented. Treatments induced a significant decrease of hexanoic (p = 0.035) and a further increase of hexadecanoic (p = 0.046) acids. Positive correlations emerged between IFN‐γ and acetic acid (Rho = 0.60), IFN‐γ and hexanoic acid (Rho = 0.46), IL‐5 and both hexadecanoic acid (Rho = 0.50) and octadecanoic acid (Rho = 0.53), butyric acid and PDAI (Rho = 0.53). PV was associated with a remarked imbalance of circulating FFA compared to HC. The serum alterations of SCFA, MCFA, and LCFA may contribute to promoting inflammation in PV. Deeper insights into the immunomodulatory functions of these molecules may pave the way for personalized dietary interventions in PV patients. [ABSTRACT FROM AUTHOR]

This article proposes a new switched adaptive control design for uncertain switched systems with composite (time‐driven and state‐dependent) switching and shows its applicability in switched impedance control. A composite switched adaptive control design, consisting of the direct switched adaptive control and the indirect switched adaptive control counterpart, is developed to improve the control performance. Specifically, a new stability condition for composite switching is proposed by making use of differential matrix equations and Sylvester matrix equations, which are a generalization of Lyapunov matrix equations. The design results in a time‐varying multiple Lyapunov function that is decreasing at the switching instants. From the theoretical point of view, the relevance of this work is the construction of the adaptive laws that guarantee asymptotic tracking error and asymptotic estimation for the direct and indirect switched adaptive control loops, respectively. From the practical point of view, the relevance of this work is validated in a new switched impedance control for the robot interaction with uncertain and discontinuous environments. [ABSTRACT FROM AUTHOR]

This article studies the extremum seeking control (ESC) problem for a class of constrained nonlinear systems. Specifically, we focus on a family of constraints that allows to reformulate the original nonlinear system in the so‐called input–output normal form. To steer the system to optimize a performance function without knowing its explicit form, we propose a novel numerical optimization‐based extremum seeking control (NOESC) design consisting of a constrained numerical optimization method and an inversion‐based feedforward controller. In particular, a projected gradient descent algorithm is exploited to produce the state sequence to optimize the performance function, whereas a suitable boundary value problem accommodates the finite‐time state transition between each two consecutive points of the state sequence. Compared to available NOESC methods, the proposed approach (i) can explicitly deal with output constraints; (ii) can consider a direct dependence on the states of the internal dynamics in the performance function; (iii) the internal dynamics do not have to be necessarily stable. The effectiveness of the proposed ESC scheme is shown through extensive numerical simulations and design of antilock braking systems. [ABSTRACT FROM AUTHOR]

Summary: We propose a new reinforcement learning method in the framework of Recursive Least Squares‐Temporal Difference (RLS‐TD). Instead of using the standard mechanism of eligibility traces (resulting in RLS‐TD(λ)), we propose to use the forgetting factor commonly used in gradient‐based or least‐square estimation, and we show that it has a similar role as eligibility traces. An instrumental variable perspective is adopted to formulate the new algorithm, referred to as RLS‐TD with forgetting factor (RLS‐TD‐f). An interesting aspect of the proposed algorithm is that it has an interpretation of a minimizer of an appropriate cost function. We test the effectiveness of the algorithm in a Policy Iteration setting, meaning that we aim to improve the performance of an initially stabilizing control policy (over large portion of the state space). We take a cart‐pole benchmark and an adaptive cruise control benchmark as experimental platforms. [ABSTRACT FROM AUTHOR]

In this study, the authors study adaptive synchronisation in networks with Kuramoto units whose parameters are unknown and where measurements are quantised over the communication network (therefore information is limited). They show that, for an undirected connected graph, synchronisation is enabled via appropriate adaptive protocols that counteract the effect of heterogeneity, uncertainty and quantised information. In particular, to address heterogeneity and uncertainty, appropriate adaptive laws are designed to drive the network to frequency synchronisation; to address quantised information, a dynamic quantiser is introduced and embedded into the adaptive mechanism via a zooming‐based approach (therefore with hybrid dynamics). The resulting protocol ends up being an adaptive hybrid synchronisation strategy that can be distributed throughout the network: the quantiser is co‐designed with the controller, as typical for zooming‐based quantisation. The proposed integrated adaptation+quantisation protocol guarantees asymptotic synchronisation to a desired frequency, which is shown via an appropriately designed distributed Lyapunov function. Numerical simulations are also used to demonstrate the effectiveness of the proposed protocol. [ABSTRACT FROM AUTHOR]

Summary: This paper establishes a novel online fault detection and identification strategy for a class of continuous piecewise affine (PWA) systems, namely, bimodal and trimodal PWA systems. The main contributions with respect to the state‐of‐the‐art are the recursive nature of the proposed scheme and the consideration of parametric uncertainties in both partitions and in subsystems parameters. In order to handle this situation, we recast the continuous PWA into its max‐form representation and we exploit the recursive Newton‐Gauss algorithm on a suitable cost function to derive the adaptive laws to estimate online the unknown subsystem parameters, the partitions, and the loss in control authority for the PWA model. The effectiveness of the proposed methodology is verified via simulations applied to the benchmark example of a wheeled mobile robot. [ABSTRACT FROM AUTHOR]

Summary: This paper addresses the problem of asymptotic tracking for switched linear systems with parametric uncertainties and dwell‐time switching, when input measurements are quantized due to the presence of a communication network closing the control loop. The problem is solved via a dynamic quantizer with dynamic offset that, embedded in a model reference adaptive control framework, allows the design of the adaptive adjustments for the control parameters and for the dynamic range and dynamic offset of the quantizer. The overall design is carried out via a Lyapunov‐based zooming procedure, whose main feature is overcoming the need for zooming out at every switching instant, in order to compensate for the possible increment of the Lyapunov function at the switching instants. It is proven analytically that the resulting adjustments guarantee asymptotic state tracking. The proposed quantized adaptive control is applied to the piecewise linear model of the NASA Generic Transport Model aircraft linearized at multiple operating points. [ABSTRACT FROM AUTHOR]

Recursive least squares (RLS) for control, which is tackled by Baldi, Zhang, and Liu in the framework of Recursive Least Squares-Temporal Difference (RLS-TD), using an instrumental variable perspective. As compared to conventional adaptive control, robust adaptive control aims to provide robustness against unmodeled dynamics, coupling effects, and other endogenous and exogenous disturbances. State-dependent uncertainties without a priori bounds: Shukla, Roy, and Gupta consider an adaptive control problem in which the uncertainties cannot be bounded a priori by any constant, but should be tackled in their state-dependent nature. [Extracted from the article]

SUMMARY A recently proposed adaptive control scheme with mixing involves the use of precalculated candidate controllers whose output is weighted on the basis of the parameter estimates generated by an online parameter estimator. It has been shown analytically and demonstrated in simulations that adaptive control with mixing exhibits good performance for the regulation case in the presence of modeling errors, disturbances, and time delays. The transient performance, however, depends on the initial conditions of the parameter estimator, and for some initial conditions, the transient oscillations may not be acceptable in certain applications. In this paper, we combine the controller mixing strategy with a multiple parameter estimation architecture plus a hysteresis switching logic selecting the parameter estimates that generate the smaller estimation errors to decide the mixing of the controllers. We show analytically that this approach, referred to as multiestimator adaptive mixing control, achieves stability and stability robustness, and we demonstrate using extensive simulations that the scheme achieves consistently better transient performance than the original adaptive mixing control. In addition, we extend the design and analysis to be applicable to the tracking case where the output is required to track a nonzero reference signal. The stability and performance of the proposed scheme in the presence of unmodeled dynamics and bounded disturbances have also been analyzed and demonstrated using a numerical example. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hybrid systems have been attracting considerable attention in recent years because of their ability to model complex physical systems with both continuous and discrete dynamic behavior. 2 Zhang X, Wang J, Wu M, Xu Z. Robust quasi-time-dependent control for switched time-delay systems with performance guarantee. 15 Fan S, Yan H, Huang L, Yang C. Design and optimization of a novel fast distributed Kalman consensus filtering algorithm. [Extracted from the article]