Nonlinear observation in fuel cell systems: a comparison between disturbance estimation and High-Order Sliding-Mode techniques

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/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.Peer ReviewedPostprint (author's final draft

Finite-Time Consensus with Disturbance Rejection by Discontinuous Local Interactions in Directed Graphs

In this technical note we propose a decentralized discontinuous interaction rule which allows to achieve consensus in a network of agents modeled by continuous-time first-order integrator dynamics affected by bounded disturbances. The topology of the network is described by a directed graph. The proposed discontinuous interaction rule is capable of rejecting the effects of the disturbances and achieving consensus after a finite transient time. An upper bound to the convergence time is explicitly derived in the technical note. Simulation results, referring to a network of coupled Kuramoto-like oscillators, are illustrated to corroborate the theoretical analysis

Distributed parameter nonlinear state observer with unmatched disturbance estimation for PEMFC systems

In this paper a nonlinear state observer based on a distributed parameter model is proposed for a proton exchange membrane fuel cell (PEMFC). The estimation technique is implemented using a model-based nonlinear observer with a nonlinear disturbance observer in parallel. To implement the model, a finite element discretisation is performed to take advantage of the boundary conditions of the problem and also to apply lumped systems theory in the observer synthesis procedure. By means of this double observation technique it is possible to reconstruct the gases concentrations internal states in the gas channels of the PEMFC in the presence of disturbances. The reaction rates and water transport terms that cross the membrane are considered as unknown unmatched disturbances of the model, henceforth the implementation of a disturbance observer to estimate them. Simulation results of the proposed solution are provided and discussed.Peer ReviewedPostprint (author’s final draft

Control of oxygen excess ratio in a PEM fuel cell system using high-order sliding-mode controller and observer

The main objective of this manuscript is to design a high-order sliding-mode observer to provide finite time estimation of unmeasurable states (x4 : oxygen mass, x5 : nitrogen mass) together with the oxygen excess ratio (ratio of the input oxygen ow to the reacted oxygen ow in the cathode). This is done by applying second-order sliding modes through either super twisting or suboptimal controllers to control the proton exchange membrane fuel cell's breathing. The estimated oxygen excess ratio is controlled in a closed-loop system using 2 distinct sliding-mode approaches: a cascaded super twisting controller and a single-loop suboptimal structure. Simulation results are presented to make a quantitative comparison between the cascade and the single-loop configuration. The results verify that the cascade provides accurate reference tracking while the single-loop presents faster convergence

State estimation in fuel cell systems : a sliding mode approach

In this paper, a nonlinear distributed parameter observer (NDOP) is developed for the estimation of the internal condi-tions of a proton exchange membrane fuel cell (PEMFC). In particular, the estimation of the internal concentration values for different gas species is studied. A novel high order sliding mode (HOSM) estimation technique, based on a distributed parameter model of a PEMFC is developed to reconstruct the internal variables. The observer includes the estimation of the reaction and water transport terms, which are considered as disturbances of the PEMFC estimation model. Since the approach is based on a distributed parameter model representation of the PEMFC, the observer is capable of reconstruct the full internal profile of the estimated variables. The performance and robustness of the proposed observation technique is tested through a simulation example around different operation points.Peer ReviewedPostprint (author's final draft

Cascade Control of PM DC Drives Via Second-Order Sliding-Mode Technique

Abstract-This paper presents a novel scheme for the speed/ position control of permanent-magnet (PM) dc motor drives. A cascade-control scheme, based on multiple instances of a secondorder sliding-mode-control (2-SMC) algorithm, is suggested, which provides accurate tracking performance under large uncertainty about the motor and load parameters. The overall control scheme is composed of three main blocks: 1) a 2-SMC-based velocity observer which uses only position measurements; 2) a 2-SMC-based velocity control loop that provides a reference command current; and 3) a 2-SMC-based current control loop generating the reference voltage. The proposed scheme has been implemented and tested experimentally on a commercial PM dc motor drive. The experimental results confirm the precise and robust performance and the ease of tuning and implementation, featured by the proposed scheme. Index Terms-Cascade control, dc motor drives, second-order sliding-mode (2-SM) control (2-SMC), SM differentiators

Wetland selection, niche breadth and overlap in 10 duck species wintering in northern Campania (Italy)

Analysis of the selection index, the niche breadth and the niche overlap of 10 species of wintering ducks in 11 wetland areas of the Campania region between January 2003 and 2015 revealed that the distribution of the species in the examined sites was not casual. In fact, each species actively chose their wintering area. Using selection index, we were able to measure the species’ preferences and non-preferences for the 11 examined sites. By calculating Shannon-Wiener entropy and its normalized value (Evenness), we determined niche breadth; the Morisita index allowed us to check niche overlap