307 research outputs found
The automatic validation tool for PDDL2.1
The 3rd International Planning Competition [1] was a great success and a cornerstone to this success was the initial definition of a semantics for the language used in the competition, PDDL2.1. This created a general understanding of the semantics of the domains defined using this language and therefore a general understanding of what constitutes a valid plan. With this consensus on what a valid plan is it was possible to implement an automatic plan validator, VAL. This tool conveys what is a valid plan in PDDL2.1 to anyone developing a planner using this language, as well as providing extra information in a L ATEX report featuring graphs of changing numerical values and a Gantt chart (see figure 2). Actions With Continuous Effects A numerical quantity that can be changed, a function in PDDL, is called a primitive numerical expression (PNE). These PNEs can have continuous change initiated with changes made to the values of their (time) derivatives by durative actions. The effect starts at the beginning of the durative action and ends at the end of the durative action. The introduction of continuous change creates two further complications to the discrete temporal model: 1) Continuous changes can interact with one another, and 2) Invariant conditions may depend on values that are continuously changing. The key extension to the discrete temporal model is that interactin
Validating plans with exogenous events
We are concerned with the problem of deciding the validity of a complex plan involving interacting continuous activity. In these situations there is a need to model and reason about the continuous processes and events that arise as a consequence of the behaviour of the physical world in which the plan is expected to execute. In this paper we describe how events, which occur as the outcome of uncontrolled physical processes, can be taken into account in determining whether a plan is valid with respect to the domain model. We do not consider plan generation issues in this paper but focus instead on issues in domain modelling and plan validation
VAL : automatic plan validation, continuous effects and mixed initiative planning using PDDL
This paper describes aspects of our plan validation tool, VAL. The tool was initially developed to support the 3rd International Planning Competition, but has subsequently been extended in order to exploit its capabilities in plan validation and development. In particular, the tool has been extended to include advanced features of PDDL2.1 which have proved important in mixed-initiative planning in a space operations project. Amongst these features, treatment of continuous effects is the most significant, with important effects on the semantic interpretation of plans. The tool has also been extended to keep abreast of developments in PDDL, providing critical support to participants and organisers of the 4th IPC
Lithium-ion battery thermal-electrochemical model-based state estimation using orthogonal collocation and a modified extended Kalman filter
This paper investigates the state estimation of a high-fidelity spatially
resolved thermal- electrochemical lithium-ion battery model commonly referred
to as the pseudo two-dimensional model. The partial-differential algebraic
equations (PDAEs) constituting the model are spatially discretised using
Chebyshev orthogonal collocation enabling fast and accurate simulations up to
high C-rates. This implementation of the pseudo-2D model is then used in
combination with an extended Kalman filter algorithm for differential-algebraic
equations to estimate the states of the model. The state estimation algorithm
is able to rapidly recover the model states from current, voltage and
temperature measurements. Results show that the error on the state estimate
falls below 1 % in less than 200 s despite a 30 % error on battery initial
state-of-charge and additive measurement noise with 10 mV and 0.5 K standard
deviations.Comment: Submitted to the Journal of Power Source
Identifiability of generalised Randles circuit models
The Randles circuit (including a parallel resistor and capacitor in series
with another resistor) and its generalised topology have widely been employed
in electrochemical energy storage systems such as batteries, fuel cells and
supercapacitors, also in biomedical engineering, for example, to model the
electrode-tissue interface in electroencephalography and baroreceptor dynamics.
This paper studies identifiability of generalised Randles circuit models, that
is, whether the model parameters can be estimated uniquely from the
input-output data. It is shown that generalised Randles circuit models are
structurally locally identifiable. The condition that makes the model structure
globally identifiable is then discussed. Finally, the estimation accuracy is
evaluated through extensive simulations
The dynamics of collaboration networks and the history of general relativity, 1925â1970
This paper presents a novel methodology for defining and analyzing the dynamics of the collaboration networks of scientists working on general relativity from the mid-1920sâ1970. During these four and a half decades the status of the theory underwent a radical transformation: from a marginal theory before the mid-1950s to a pillar of modern physics. To investigate this passageâknown as the renaissance of general relativityâwe used a definition of collaboration networks broader than the co-authorship relations retrievable from online datasets. We constructed a multilayer network, in which each layer represents a different kind of collaboration. After having analyzed the evolution over time of specific parameters of the co-authorship network, we investigated the effects of adding one type of collaboration edge at a time, in a cumulative fashion, on the values of these parameters and on the topology of the collaboration network through time, including rapid shifts in the dynamic evolution of the largest component. This analysis provides robust quantitative evidence that a shift in the structure of the relativity collaboration network occurred between the late 1950s and the early 1960s, when a giant component started forming. We interpret this shift as the central social dynamic of the renaissance process and then identify its central actors. Our analysis disproves common explanations of the renaissance process. It shows that this phenomenon was not a consequence of astrophysical discoveries in the 1960s, nor was it a simple by-product of socio-economic transformations in the physics landscape after World War II
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Radially resolved measurement of stator heat transfer in a rotor-stator disc system
This paper describes a new experimental method for measuring stator heat transfer in a rotorâstator disc system using an electrical heater array. The system is partially blocked at the periphery, with radial outflow of rotor-pumped air from an inlet at stator centre. The aim is to improve thermal performance prediction for air-cooled disc type electrical machines. Local Nusselt numbers were measured for 0.63e5 for all gap ratios. Increased Nusselt numbers at the periphery are observed for all Reθ and G because of the ingress of ambient air along the stator due to the rotor pumping effect
Detection and Isolation of Small Faults in Lithium-Ion Batteries via the Asymptotic Local Approach
This contribution presents a diagnosis scheme for batteries to detect and
isolate internal faults in the form of small parameter changes. This scheme is
based on an electrochemical reduced-order model of the battery, which allows
the inclusion of physically meaningful faults that might affect the battery
performance. The sensitivity properties of the model are analyzed. The model is
then used to compute residuals based on an unscented Kalman filter. Primary
residuals and a limiting covariance matrix are obtained thanks to the local
approach, allowing for fault detection and isolation by chi-squared statistical
tests. Results show that faults resulting in limited 0.15% capacity and 0.004%
power fade can be effectively detected by the local approach. The algorithm is
also able to correctly isolate faults related with sensitive parameters,
whereas parameters with low sensitivity or linearly correlated are more
difficult to precise.Comment: 8 pages, 2 figures, 3 tables, conferenc
A parametric open circuit voltage model for lithium ion batteries
The financial support of EPSRC UK and Jaguar Land Rover Ltd is gratefully acknowledged.We present an open circuit voltage (OCV) model for lithium ion (Li-ion) cells, which can be parameterized by measurements of the OCV of positive and negative electrode half-cells and a full cell. No prior knowledge of physical parameters related to particular cell chemistries is required. The OCV of the full cell is calculated from two electrode sub-models, which are comprised of additive terms that represent the phase transitions of the active electrode materials. The model structure is flexible and can be applied to any Li-ion cell chemistry. The model can account for temperature dependence and voltage hysteresis of the OCV. Fitting the model to OCV data recorded from a Li-ion cell at 0°C, 10°C, 20°C, 30°C and 40°C yielded high accuracies with errors (RMS) of less than 5 mV. The model can be used to maintain the accuracy of dynamic Li-ion cell models in battery management systems by accounting for the effects of capacity fade on the OCV. Moreover, the model provides a means to separate the cell's OCV into its constituent electrode potentials, which allows the electrodesâ capacities to be tracked separately over time, providing an insight into prevalent degradation mechanisms acting on the individual electrodes.Publisher PDFPeer reviewe
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