Kalman-variant estimators for state of charge in lithium-sulfur batteries

Lithium-sulfur batteries are now commercially available, offering high specific energy density, low production costs and high safety. However, there is no commercially-available battery management system for them, and there are no published methods for determining state of charge in situ. This paper describes a study to address this gap. The properties and behaviours of lithium-sulfur are briefly introduced, and the applicability of ‘standard’ lithium-ion state-of-charge estimation methods is explored. Open-circuit voltage methods and ‘Coulomb counting’ are found to have a poor fit for lithium-sulfur, and model-based methods, particularly recursive Bayesian filters, are identified as showing strong promise. Three recursive Bayesian filters are implemented: an extended Kalman filter (EKF), an unscented Kalman filter (UKF) and a particle filter (PF). These estimators are tested through practical experimentation, considering both a pulse-discharge test and a test based on the New European Driving Cycle (NEDC). Experimentation is carried out at a constant temperature, mirroring the environment expected in the authors' target automotive application. It is shown that the estimators, which are based on a relatively simple equivalent-circuit–network model, can deliver useful results. If the three estimators implemented, the unscented Kalman filter gives the most robust and accurate performance, with an acceptable computational effort

Safe Policy Synthesis in Multi-Agent POMDPs via Discrete-Time Barrier Functions

A multi-agent partially observable Markov decision process (MPOMDP) is a modeling paradigm used for high-level planning of heterogeneous autonomous agents subject to uncertainty and partial observation. Despite their modeling efficiency, MPOMDPs have not received significant attention in safety-critical settings. In this paper, we use barrier functions to design policies for MPOMDPs that ensure safety. Notably, our method does not rely on discretization of the belief space, or finite memory. To this end, we formulate sufficient and necessary conditions for the safety of a given set based on discrete-time barrier functions (DTBFs) and we demonstrate that our formulation also allows for Boolean compositions of DTBFs for representing more complicated safe sets. We show that the proposed method can be implemented online by a sequence of one-step greedy algorithms as a standalone safe controller or as a safety-filter given a nominal planning policy. We illustrate the efficiency of the proposed methodology based on DTBFs using a high-fidelity simulation of heterogeneous robots.Comment: 8 pages and 4 figure

Cyber-Democracy or Cyber-Hegemony? Exploring the Political and Economic Structures of the Internet as an Alternative Source of Information

Although government regulation of the Internet has been decried as undercutting free speech, the control of Internet content through capitalist gateways???namely, profit-driven software companies???has gone largely uncriticized. The author argues that this discursive trend manufactures consent through a hegemonic force neglecting to confront the invasion of online advertising or marketing strategies directed at children. This study suggests that ???inappropriate content??? (that is, nudity, pornography, obscenities) constitutes a cultural currency through which concerns and responses to the Internet have been articulated within the mainstream. By examining the rhetorical and financial investments of the telecommunications business sector, the author contends that the rhetorical elements creating ???cyber-safety??? concerns within the mainstream attempt to reach the consent of parents and educators by asking them to see some Internet content as value laden (sexuality, trigger words, or adult content), while disguising the interests and authority of profitable computer software and hardware industries (advertising and marketing). Although most online ???safety measures??? neglect to confront the emerging invasion of advertising/marketing directed at children and youth, the author argues that media literacy in cyberspace demands such scrutiny. Unlike measures to block or filter online information, students need an empowerment approach that will enable them to analyze, evaluate, and judge the information they receive.published or submitted for publicatio

Have Milk Fat Preferences Shifted? Structural Analysis of New York Milk Consumption

Consumption of lowfat and skim milk has increased substantially over the past decade. This study investigates whether the change is due to price and expenditure effects or to a more fundamental preference change in milk demand. Parametric and nonparametric analytical approaches provide a comprehensive analysis of structural change in milk consumption in New York State. A nonparametric approach first finds evidence of structural change. A parametric likelihood-ratio test then confirms the existence of structural change using a Kalman filter specification. The value of this technical analysis of milk preferences is its implication for labeling initiatives. Milk fat labels have allowed consumers to act on a new set of preferences, thereby improving consumer welfare.Food Consumption/Nutrition/Food Safety,