Alessandro Pilloni

Observer-Based Air Excess Ratio Control of a PEM Fuel Cell System via High-Order Sliding Mode

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.

Finite-time consensus for a network of perturbed double integrators by second-order sliding mode technique

This paper considers the problem of achieving consensus in a network of agents whose dynamics consist of perturbed double integrators. The considered class of perturbations is a bounded additive uncertainty, different for each agent, and such that the maximal magnitude is the only information available a-priori. Agents are supposed to interact through an undirected, static and connected, communication topology. The main contribution of the present work is a discontinuous local interaction rule which is able to provide finite time consensus while completely rejecting the effect of the perturbations. The local interaction rule, whose performance is investigated by Lyapunov approach, is accompanied by a set of simple tuning rules for setting the algorithms parameters. Simulation results demonstrate the effectiveness of the suggested scheme.

Consensus-Based Control for a Network of Diffusion PDEs With Boundary Local Interaction

In this technical note the problem of driving the state of a network of identical agents, modeled by boundary-controlled heat equations, towards a common steady-state profile is addressed. Decentralized consensus protocols are proposed to address two distinct problems. The first problem is that of steering the states of all agents towards the same constant steady-state profile which corresponds to the spatial average of the agents initial condition. The second problem deals with the case where the controlled boundaries of the agents dynamics are corrupted by additive persistent disturbances. To achieve synchronization between agents, while completely rejecting the effect of the boundary disturbances, a nonlinear sliding-mode based consensus protocol is proposed. Simulation results are presented to support the effectiveness of the proposed algorithms.

Recent advances in sliding-mode based consensus strategies

In this paper we present a review of our recent advancements in consensus-based cooperative control by using sliding-mode concepts for networked systems. In particular, strategies for achieving consensus in networks of persistently perturbed agents with static and switching network topologies, which can be disconnected for intervals of time, are discussed. We consider both first and second order agent models. Convergence proofs are carried out by means of non-smooth Lyapunov analysis and simulative results are presented to corroborate the theoretical results.

Parameter tuning and chattering adjustment of Super-Twisting sliding mode control system for linear plants

A simple procedure for tuning the parameters of the Super-Twisting (STW) second-order sliding mode control (2-SMC) algorithm, used for the feedback control of uncertain linear plants, is presented. When the plant relative degree is higher than one, it is known [10] that a self-sustained periodic oscillation takes place in the feedback system. The purpose of the present work is that of illustrating a systematic procedure for control tuning based on Describing Function (DF) approach guaranteeing pre-specified frequency and magnitude of the resulting oscillation. The knowledge of the plants Harmonic Response (magnitude and phase) at the desired chattering frequency is the only required prior information. By means of a simulation example, we show the effectiveness of the proposed procedure.

Finite-time consensus with disturbance attenuation for directed switching network topologies by discontinuous local interactions

In this paper we investigate the properties of a decentralized consensus algorithm for a network of continuous-time integrators subject to unknown-but-bounded persistent disturbances. The proposed consensus algorithm is based on a discontinuous local interaction rule. Under certain restrictions on the directed switching topology of the communication graph, it is proven that after a finite transient time the agents achieve an approximated consensus condition by attenuating the destabilizing effect of the disturbances. Lyapunov analysis is carried out for characterizing the performance of the suggested algorithm. Simulative analysis are illustrated and commented to validate the developed result.

Decentralized State Estimation in Connected Systems

Abstract This paper considers the problem of state estimation and unknown input reconstruction of a class of connected heterogeneous LTI MIMO systems. Local high order sliding mode observers at each node of the network are designed for this purpose. The proposed method, under some network structural conditions, is inherently robust, nonlinear and totally independent of the time-varying network topology. Knowledge of the number of nodes that belong to the network is not required. At the supervisory level, decentralized control signals are computed based on the state estimates in order to operate the networking synchronization. By mean of simulation, the effectiveness of the proposal procedure is shown.

Robust Finite-Time Frequency and Voltage Restoration of Inverter-Based Microgrids via Sliding-Mode Cooperative Control

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.

Robust FDI in induction motors via second order sliding mode technique

This paper proposes a novel approach to detect the presence of broken bars in the rotor of a squirrel cage induction motor (SCIM). A mathematical model of the SCIM capturing both the healthy and faulty operating conditions of the motor is introduced, and a model-based FDI observer, based on second order sliding modes (2-SMs), is presented. Appropriate theoretical arguments are invoked to demonstrate that the suggested FDI observer is capable of detecting the occurrence of the Broken Bar Fault (BBF) condition by relying on stator current and shaft speed measurements, which can be easily achieved in practice. Additionally, the proposed observer provides an exponentially convergent estimation of the rotor fluxes and of the the external load torque. The proposed scheme has been experimentally tested by means of a commercial Siemens 1.1-kW three-phase SCIM. The experimental results confirm the robust performance featured by the suggested methodology.

Detection of rotor broken bar and eccentricity faults in induction motors via second order sliding mode observer

This paper provides a novel approach for detecting certain abnormal operating conditions in squirrel cage induction motors (SCIMs). A mathematical model of the faulty operating mode is derived with the rotor broken bars and the rotor eccentricity being the faults of interest. To detect the fault occurrence, an appropriate FDI observer, based on second order sliding modes, is presented and analyzed by Lyapunov methods. The ability of the suggested FDI observer to produce suitable residual signals which allow a reliable threshold-based fault detection is shown. Once the fault is detected, dedicated FFT analysis of the residuals allows the classification of the fault. The proposed scheme has been verified by real implementation tests using measurements taken from certain commercial three-phase SCIMs intentionally damaged in order to reproduce the fault scenarios of concern. Experimental results confirm the reliability of the suggested framework.