1,721,199 research outputs found
A new perspective proposal for preemptive feedback scheduling
No full textA novel way to formalise the problem of preemptive feedback scheduling is presented, based on discrete-time linear dynamic systems. Despite its extreme simplic- ity, the obtained formalism is suitable both for representing (and therefore dynamically analysing) existing scheduling methods, and for synthesizing new ones in a totally system- theoretical perspective. Also, by further specialising the class of systems employed, the modelling complexity can be scaled and tailored to the particular problem to be addressed. Examples are reported to explain and support the above claims, including some (simple) new scheduling policies
Esercizi di Fondamenti di Automatica
No full textRaccolta di esercizi a supporto dei corsi di base di Automatica
Benchmark analysis of a control-theoretical approach to feedback scheduling
No full textA feedback-based approach to process scheduling in a single-processor system was recently proposed, that deeply relies on the control theory for its entire design. In this work a literature benchmark is used to compare said approach to classical ones, with particular reference to the real-time case. Two are the main results. First, in the case of a schedulable process set, the proposed “control-theoretical” design yields similar performance with comparable or lower time complexity with respect to classical approaches. Second, and more relevant, if the required CPU utilisation transiently exceeds the unity, the proposed approach allows for a significantly better system recovery (measured in terms of deadline misses) once said utilisation returns feasible
The PI+p Controller Structure and its Tuning
No full textThis manuscript is part of a long-term research, aimed at establishing methodologically grounded relationships between model- and relay-based tuning of industrial regulators, and at consequently deriving synthesis procedures that couple the advantages of model-based tuning to the simplicity and clarity of relay-based identification. In this work, the addressed controller structure is the ‘‘PI+p”, i.e., a PI augmented with an additional, stable pole. The advantages of using the combined model-relay-based approach on that structure are evidenced, by means of both simulation and experimental results
Implementation and evaluation of a control-theoretical scheduler
No full textRecent papers have demonstrated that process schedulers can be designed entirely as feedback controllers—quite novel an approach with respect of the way the control theory is typically applied to computing systems. This work takes a more technological attitude with respect to the methodological ones just quoted. The real- isation of a control-theoretical process scheduler on a kernel written for a microcon- troller is briefly described, and a small sample is presented of the tests performed to assess its correct operation, and to evidence the advantages that the underlying ap- proach yields over classical ones
Object-oriented modelling of starch mashing for simulation-based control studies
No full textIn the production of beer, good temperature control of the starch mashing phase is very important for both the final product quality and the process efficiency. A precise tuning of the said control is, however, complicated by the highly non-linear nature of the process, and often also by the actuation scheme. Based on suitably extended literature models, this article shows how object-oriented modelling and simulation (OOMS) can be used to devise a solution to the above problem. A mashing model is first derived along the OOMS approach, and then the said model is coupled to a control representation of scalable detail, including a quasi replica of the control code. Doing so allows one to easily create and maintain hybrid overall models that are suitable for system studies on the design and assessment of both the control strategy and the process instrumentation, with particular reference to the use of on–off actuation in conjunction with modulating control
Object-oriented Modelling of Industrial PID Controllers
No full textThis paper presents a library of (PID) controller models adopting the object-oriented approach, and written in Modelica. Peculiar to this work is that controllers are represented both as dynamic continuous-time and digital models, achieving consistence between the two and accounting for the functionalities of typical industrial implementations. This allows the designer to use realistic controllers, maintaining the possibility of choosing the continuous-time or digital (event based) representation. The former allows for example for variable-step simulation, to the advantage of efficiency, while the latter represents very realistically the actual control system’s operation, clearly at the cost of more simulation time. Beside standard PI and PID controls, in this work also autotuning is (initially) considered, and some application examples are reported to show how the presented library can ease system studies involving (PID) controls
The PID+p Controller Structure and its Contextual Autotuning
No full textA previous paper addressed the “PI + p” controller (a PI augmented with an additional, stable pole) and demonstrated its advantages over standard PIs, particularly if tuned with a combined model-relay-based method along the “contextual” approach proposed in another recent work. This manuscript extends the scenario to the PID + p structure, with obvious meaning, and applies the contextual approach to its autotuning. Benchmark tests and a quite realistic simulation example support the proposal
Task Scheduling: a Control-theoretical Viewpoint for a General and Flexible Solution
Full text linkAbstract in UndeterminedThis manuscript presents a new approach to the design of task scheduling algorithms, where system-theoretical methodologies are used throughout. The proposal implies a significant perspective shift with respect to mainstream design practices, but yields large payoffs in terms of simplicity, flexibility, solution uniformity for different problems, and possibility to formally assess the results also in the presence of unpredictable run-time situations. A complete implementation example is illustrated, together with various comparative tests, and a methodological treatise of the matter
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