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This present article addresses the feedback control design problem of in-line liquid flow heating units used to process silicon wafers in the semiconductor industry. A physics-based model is developed to describe the thermal behavior of the heater and the liquid circulating in it. Under sensible approximations, process dynamics are shown to be governed by a coupled partial differential equation (PDE)/ordinary differential equation (ODE) system. A boundary control law capable of steering the fluid temperature to the desired set-point value while rejecting matched disturbances is developed. The proposed boundary control is sliding-mode-based and makes use of boundary measurements only. The convergence properties of the closed-loop system are formally demonstrated by means of Lyapunov-based analysis. In addition, the input-to-state stability (ISS) properties of the closed-loop system with respect to nonmatching boundary disturbances are investigated. To corroborate the theoretical findings, this article additionally presents the experimental results with the proposed controller implemented in the closed loop on a real in-line heating unit. [ABSTRACT FROM AUTHOR]

Summary: The position and attitude control of a six‐degree‐of‐freedom vehicle is dealt with in this paper. The actuation system is assumed to consist of a set of mono‐directional devices suitably located and directed. The model of the system is characterized by a large amount of uncertainties, disturbances and measurement errors. The state is assumed fully available and the navigation problems generating smooth references for the state trajectories are supposed already solved. A new attitude guidance algorithm has been developed to enhance robustness with respect to a class of nonsmooth measurement errors. The use of the simplex‐based sliding mode methodology reveals to be simultaneously suitable for the design of the actuation system (position and orientation of the actuators) and the implementation of the control strategy. The chattering phenomenon is strongly attenuated by the introduction of integrators in the input channel and, consequently to this choice, a suitable mechanism to avoid the unbounded growth of the individual thrust of the actuators is designed, while at the same time, achieving a direct control of power losses. The performances of the proposed control scheme are demonstrated by simulation by using mathematical models available in the literature. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel control strategy to perform the exact finite-time restoration among voltages and frequencies of an islanded inverter-based microgrid. The problem is attacked from a cooperative-based control perspective inspired to the tracking consensus paradigm. Ad hoc chattering-free sliding-mode-based distributed algorithms are designed to enhance the underlying robustness and convergence properties of the system with respect to the existing solutions. Particularly, the restoration is achieved while dispensing with the knowledge of the distributed generators’ models and parameters. Performance of the control system is analyzed by Lyapunov tools, and a simple set of tuning rules are derived. The effectiveness of the proposed scheme is verified by simulations on a realistic inverter-based microgrid modelization. [ABSTRACT FROM PUBLISHER]

The aim of this research is to develop and test in a simulation environment an advanced model-based control solution for a proton exchange membrane fuel cell (PEMFC) system. A nonlinear model-predictive control (NMPC) strategy is proposed to maximize the active catalytic surface area at the cathode catalyst layer to increase the available reaction area of the stack and to avoid starvation at the catalyst sites. The PEMFC stack model includes a spatial discretization that permits the control strategy to take into account the internal conditions of the system. These internal states are estimated and fed to the NMPC via a nonlinear distributed parameters observer. The air-fed cathode of the PEMFC simulation model includes a two-phase water model for better representation of the stack voltage. The stack temperature is regulated through the use of an active cooling system. The control strategy is evaluated in an automotive application using a driving cycle based on the New European Driving Cycle profile as the case study. [ABSTRACT FROM AUTHOR]

In this paper, a novel adaptive second-order sliding mode technique to optimize the efficiency of certain types of variable-speed wind turbines is developed and analyzed. A revisited form of a recent adaptation algorithm is proposed to deal with the characteristics and control requirements of wind energy conversion systems (WECS), particularly model uncertainties and fast disturbances due to gusty wind effects. The revisited algorithm is based on appropriate receding horizon adaptation time windows rather than on fixed, adjacent, and nonoverlapping ones. This modification, which enhances the reactivity of the adaptation strategy against fast varying uncertainties, represents the main theoretical novelty of this paper. The proposed approach is successfully used to control a doubly fed induction-generator-based wind turbine topology proving its suitability for this application area. The novel adaptive controller is extensively assessed through computer simulations over a full-order realistic model of the WECS under study. [ABSTRACT FROM AUTHOR]

This paper compares two Nonlinear Distributed Parameter Observers (NDPO) for the observation of a Proton Exchange Membrane Fuel Cell (PEMFC). Both NDPOs are based on the discretisation of distributed parameters models and they are used to estimate the state profile of gas concentrations in the anode and cathode gas channels of the PEMFC, giving detailed information about the internal conditions of the system. The reaction and water transport flow rates from the membrane to the channels are uncertainties of the observation problem and they are estimated throughout all the length of the PEMFC without the use of additional sensors. The first observation approach is a Nonlinear Disturbance Observer (NDOB) for the estimation of the disturbances in the NDPO. In the second approach, a novel implementation of a High-Order Sliding-Mode (HOSM) observer is developed to estimate the true value of the states as well as the reaction terms. The proposed observers are tested and compared through a simulation example at different operating points and their performance and robustness is analysed over a given case study, the New European Driving Cycle. [ABSTRACT FROM AUTHOR]

This paper deals with a high-order sliding mode (HOSM) approach to the observer-based output feedback control of a proton exchange membrane (PEM) fuel cell (FC) system consisting of a compressor, a supply manifold, an FC stack, and a return manifold. The treatment is based on a lumped parameter nonlinear modeling of the PEM FC system under study. The suggested scheme assumes the availability for measurements of readily accessible quantities such as the compressor angular velocity, the load current, and the supply and return manifold pressures. The control task is formulated in terms of regulating the oxygen excess ratio (which is estimated by a nonlinear finite-time converging HOSM observer) to a suitable set-point value by using, as adjustable input variable, the compressor supply voltage. The proposed observer embeds an original synergic combination between second- and third-order sliding mode (SM) algorithms. The controller also uses a second-order SM algorithm complemented by a novel tuning procedure, supported by local linearization and frequency-domain arguments, which allows the designer to enforce a practical SM regime with some prespecified and user-defined characteristics. Thoroughly discussed simulations results certify the satisfactory performance of the proposed approach. [ABSTRACT FROM PUBLISHER]