Electro-thermal modeling of a Rogowski coil sensor system

This paper focuses on the electro-thermal modeling of an electrical current sensor, based on the Rogowski Coil transducer. We exploit the multi-domain capabilities of VHDL-AMS together with geometrical Finite Element Analysis (FEA) to create a time-dependent parametrical model which is able to compute concurrently the thermal and electrical variables of the system. This is particularly convenient for evaluating the temperature effect in the analogue and digital signal processing of the sensor. Some key geometrical and inner material properties of the sensor and its environment, which are difficult, or even impossible to simulate dynamically in a classical lumped-element model, are taken into account in the proposed model. This modeling technique can be used to improve the accuracy in the design of the self-calibration circuit of the sensor.

Of Choices, Failures and Asynchrony: The Many Faces of Set Agreement

Dan Alistarh, Seth Gilbert, Rachid Guerraoui

Set agreement is a fundamental problem in distributed computing in which processes collectively choose a small subset of values from a larger set of proposals. The impossibility of fault-tolerant set agreement in asynchronous networks is one of the seminal results in distributed computing. The complexity of set agreement in synchronous networks has also been a significant research challenge. Real systems, however, are neither purely synchronous nor purely asynchronous. Rather, they tend to alternate between periods of synchrony and periods of asynchrony. In this paper, we analyze the complexity of set agreement in such a “partially synchronous” setting, presenting the first (asymptotically) tight bound on the complexity of set agreement in such systems. We introduce a novel technique for simulating, in fault-prone asynchronous shared memory, executions of an asynchronous and failure-prone message-passing system in which some fragments appear synchronous to some processes. We use this technique to derive a lower bound on the round complexity of set agreement in a partially synchronous system by a reduction from asynchronous wait-free set agreement. We also present an asymptotically matching algorithm that relies on a distributed asynchrony detection mechanism to decide as soon as possible during periods of synchrony. By relating environments with differing degrees of synchrony, our simulation technique is of independent interest. In particular, it allows us to obtain a new lower bound on the complexity of early deciding k-set agreement complementary to that of [12], and to re-derive the combinatorial topology lower bound of [13] in an algorithmic way.

Springer2009

Of Choices, Failures and Asynchrony: The Many Faces of Set Agreement

Dan Alistarh, Seth Gilbert, Rachid Guerraoui

Set agreement is a fundamental problem in distributed computing in which processes collectively choose a small subset of values from a larger set of proposals. The impossibility of fault-tolerant set agreement in asynchronous networks is one of the seminal results in distributed computing. In synchronous networks, too, the complexity of set agreement has been a significant research challenge that has now been resolved. Real systems, however, are neither purely synchronous nor purely asynchronous. Rather, they tend to alternate between periods of synchrony and periods of asynchrony. Nothing specific is known about the complexity of set agreement in such a ``partially synchronous'' setting. In this paper, we address this challenge, presenting the first (asymptotically) tight bound on the complexity of set agreement in such systems. We introduce a novel technique for simulating, in a fault-prone asynchronous shared memory, executions of an asynchronous and failure-prone message-passing system in which some fragments appear synchronous to some processes. We use this simulation technique to derive a lower bound on the round complexity of set agreement in a partially synchronous system by a reduction from asynchronous wait-free set agreement. Specifically, we show that every set agreement protocol requires at least

\floor{t}{k} + 2

synchronous rounds to decide. We present an (asymptotically) matching algorithm that relies on a distributed asynchrony detection mechanism to decide as soon as possible during periods of synchrony. From these two results, we derive the size of the minimal window of synchrony needed to solve set agreement. By relating synchronous, asynchronous and partially synchronous environments, our simulation technique is of independent interest. In particular, it allows us to obtain a new lower bound on the complexity of early deciding

k

-set agreement complementary to that of~\cite{Gafni2005}, and to re-derive the combinatorial topology lower bound of~\cite{Herlihy2006} in an algorithmic way.

2012

Electro-thermal virtual prototyping of a Rogowski Coil sensor system

Juan Sebastian Rodriguez Estupinan, Alain Vachoux

An electro-thermal model of a Rogowski Coil sensor system is here described. A co-design methodology between VHDL-AMS and Finite Element Analysis (FEA) has been used for modeling the entire system. The proposed modeling strategy uses geometrical FEA to complete a time-dependent parametrical heat transfer model, which can be implemented in VHDL-AMS or in any other similar hardware description language. This is especially useful for performing simulations with the embedded signal processing electronics of the sensor. Important geometrical, environmental and inner material properties of the Rogowski Coil sensor system, which are difficult, or even impossible to simulate dynamically in a classical lumped-element model, are taken into account indirectly in the proposed model. This allows to study the cross-domain effects in the complete system.

IEEE2015

Of Choices, Failures and Asynchrony: The Many Faces of Set Agreement

Dan Alistarh, Seth Gilbert, Rachid Guerraoui

Set agreement is a fundamental problem in distributed computing in which processes collectively choose a small subset of values from a larger set of proposals. The impossibility of fault-tolerant set agreement in asynchronous networks is one of the seminal results in distributed computing. In synchronous networks, too, the complexity of set agreement has been a significant research challenge that has now been resolved. Real systems, however, are neither purely synchronous nor purely asynchronous. Rather, they tend to alternate between periods of synchrony and periods of asynchrony. Nothing specific is known about the complexity of set agreement in such a ``partially synchronous'' setting. In this paper, we address this challenge, presenting the first (asymptotically) tight bound on the complexity of set agreement in such systems. We introduce a novel technique for simulating, in a fault-prone asynchronous shared memory, executions of an asynchronous and failure-prone message-passing system in which some fragments appear synchronous to some processes. We use this simulation technique to derive a lower bound on the round complexity of set agreement in a partially synchronous system by a reduction from asynchronous wait-free set agreement. Specifically, we show that every set agreement protocol requires at least

\floor{t}{k} + 2

k

-set agreement complementary to that of~\cite{Gafni2005}, and to re-derive the combinatorial topology lower bound of~\cite{Herlihy2006} in an algorithmic way.

2012