1,741,256 research outputs found
Ensuring consistency in scalable-detail models for DT-based control
No full textDigital Twins (DTs for short) are a powerful aid for creating, assessing and maintaining control strategies. This use of DTs however requires that the physical entities to control be described at different levels of detail. For example, simple I/O models are used to compute parameters of modulating controllers, more time-accurate ones may be required to set up and assess logic controls, high-accuracy, possibly nonlinear ones may serve for overall strategy verification, and for software-in-the-loop testing, also the host computing/network architecture needs representing. In such a complex scenario, guaranteeing that all the descriptions of all elements are consistent with one another is a relevant problem. We discuss this matter and propose a solution, in the form of a modelling paradigm where - as a novel contributions - relationships (in a sense analogous to what the term means in database theory) can be instated and enforced. This allows to create and maintain knowledge based made of interrelate data and models, embracing all the major DT interpretations proposed so far in the literature, or said more explicitly, combining data-driven and model-driven DTs in a single framework. We also provide an illustrative example
Fine-Grained Dynamic Resource Allocation for Big-Data Applications
Full text linkMany big-data applications are batch applications that exploit dedicated frameworks to perform massively parallel computations across clusters of machines. The time needed to process the entirety of the inputs represents the application's response time, which can be subject to deadlines. Spark, probably the most famous incarnation of these frameworks today, allocates resources to applications statically at the beginning of the execution and deviations are not managed: to meet the applications' deadlines, resources must be allocated carefully. This paper proposes an extension to Spark, called dynaSpark, that is able to allocate and redistribute resources to applications dynamically to meet deadlines and cope with the execution of unanticipated applications. This work is based on two key enablers: containers, to isolate Spark's parallel executors and allow for the dynamic and fast allocation of resources, and control-theory to govern resource allocation at runtime and obtain required precision and speed. Our evaluation shows that dynaSpark can (i) allocate resources efficiently to execute single applications with respect to set deadlines and (ii) reduce deadline violations (w.r.t. Spark) when executing multiple concurrent applications
Efficient control-oriented modelling of heterogeneous large-scale computer cooling systems
No full textThe power of modern computing equipment, from small devices such as laptops through a variety of cases up to entire data centres, makes cooling vital. Especially in large-scale systems, delivering the right cooling to the right place at the right time is crucial for both computing performance and energy efficiency. As such, modern cooling systems require a lot of controls. Given the many cases to face, designing and assessing such controls requires tools to rapidly and modularly build and manage computationally efficient simulation models, sometimes concentrating on the thermal policies aboard on a chip, sometimes on the cooling of a rack, sometimes on an entire date centre with its fluid conditioning and transport machinery, and so forth. Though technology exist to address many such cases individually, a holistic approach to embrace them all within a unified modelling methodology and workflow is still the subject of research. In this paper we distil our experience over the last years, and discuss how a solution based on joining purpose-specific chip modelling (using the 3D-ICE simulator) and Equation-Based Object-Oriented Modelling (employing the Modelica language) can help the joint design of a computing system and its cooling
Harmonising and integrating the Digital Twins multiverse: A paradigm and a toolset proposal
Full text linkDigital Twins are of paramount relevance in the Industry 4.0 framework. However, the idea of Digital Twin has many different interpretations. These are tied to the intended use of a Digital Twin, thus to the viewpoint of the involved professionals (process designers, control specialists, managers, and so on). The said interpretations are often highly incompatible with one another, since they can involve as heterogeneous entities as a CAD drawing and a neural network. A convergence of Digital Twin interpretations is desirable, to take full profit of the contained knowledge. In this research we argue that this desired convergence cannot be found at the same abstraction level of the available Digital Twin interpretations, and calls for a higher one. We consequently propose a paradigm – that we name Digital Multiverse – to comprehend the major Digital Twin interpretations not only in the sense of data integration, which is the goal of promising complementary ideas like that of Asset Administration Shell, but also by establishing and enforcing consistency rules that involve both data and models. We also show some examples to support the usefulness and viability of our proposal
Teaching to design control applications with coordinated modulating and logic functions
No full textIn the literature on control education, a minority of papers concern logic control. Out of this minority, an even smaller one addresses the problem of designing an application composed of both modulating and logic control functions, interacting and coordinating with one another. In the opinion of the authors this is a gap to be filled, as it easily leads to an inefficient use of the available development tools, and sometimes results in cumbersome design and poor maintainability. In this paper we discuss the matter, and propose a compact teaching activity based on the experience gathered along the last years
A Multitransmission Event-Based Architecture for Energy-Efficient Autotuning Wireless Controls
No full textWe propose a periodic event-based control scheme in which, when the sensor triggers an event, also past and subsequent values of the controlled variable are transmitted. We employ this idea to obtain a stability condition independent of the used event-triggering mechanism. In turn, we exploit this independence to devise a methodology for extending existing controller (auto)tuning rules to the event-based setting and provide an example with the internal model control PID (IMC-PID) rule. We then abstract the functionalities that a wireless sensor node has to offer for implementing our scheme and finally present such a node, physically realized in a completely hardware-based form to the advantage of both energy efficiency and security. Simulations results and experiments with the so-obtained control architecture (wireless sensor node plus event-based IMC-PID) are reported
Wireless synchronisation as a control problem embedded in new-generation networked automation systems
Full text linkIn the present and rapidly evolving industrial scenario, wireless networked controls are gaining importance. This brings about new problems concerning the use of the radio channel, as well as the energy efficiency of the involved devices (often running on battery). We argue that such problems, among which a fundamental one is clock synchronisation, should be addressed by dedicated control structures embedded in the used hardware/software architecture, and that the construction of the said controls should follow strictly system-theoretical principles to the maximum extent. In this paper, building on previous experience, we present such a synchronisation solution together with a formal model for its operation, also accounting for non-idealities in the reference time base. Some experimental results are reported to support the statements made
Event-Based Control Enters the Real-Time World: Perspectives and Pitfalls
Full text linkIn the last years, event-based control techniques have been gaining a steadily increasing importance owing to the advantages they bring, such as reduced network traffic, low actuator wear, reduced energy consumption of the involved devices. Applying the event-based paradigm in the context of real-time control opens up new opportunities, but introduces new challenges as well. In this paper we provide an overview of both opportunities and challenges, outlining the major problems to be tackled and as a consequence future research directions
On the criticality of the model parametrisation method in industrial autotuning controllers
No full textWith reference to model-based (auto)tuning, we discuss the somehow overlooked role of the procedure used to parametrise the chosen process model structure. We evidence the detrimental effect of neglecting that procedure, particularly when evaluating/comparing tuning rules, thus when setting up a tuning procedure for a given application. We finally formulate a proposal for choosing the best model parametrisation procedure, in a given set, based on the information available in the tuning phase, and on the selected control quality indicator(s)
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