1,721,043 research outputs found
Antiwindup-aware PI Autotuning
No full textThis manuscript addresses the problem of “tuning the antiwindup mechanism” of PI(D) controllers, an issue seldom addressed in the literature but yielding improvement and reducing undesired large-transient behaviours if tackled correctly. A previously proposed framework is extended and related to both alternative antiwindup implementations and tuning methods, resulting in more methodological insight on the matter, and guidelines to set up the extension of a given method to include antiwindup. Simulation examples are reported to illustrate the achievable advantages
Automating efficiency-targeted approximations in modelling and simulation tools: Dynamic decoupling and mixed-mode integration
No full textModelling and simulation nowadays permeate virtually any engineering activity, requiring tools capable of managing complex models efficiently. Nonetheless, whereas modern modelling languages and tools allow to construct such models even on lightweight platforms (e.g., a laptop), the same is not true when it comes to numerically integrate those models. For the latter purpose, modellers usually pursue efficiency by resorting to approximation and reduction techniques. However, such techniques are unnatural to include in modelling and simulation tools. This is particularly true with object-oriented ones, which on the other hand are the most interesting for dealing with complexity from the model construction viewpoint. This paper presents a novel approximation technique that can be easily included in modelling and simulation tools, and relates the proposal to literature alternatives so as to evidence its peculiarities. An extended manipulation toolchain is also proposed, allowing for the introduction of other (classical) efficiency-targeted approximation techniques, within a unified framework. Some application examples illustrate the achieved advantages and motivate the major design choices from an operational viewpoint
PI/PID autotuning with contextual model parametrisation
No full textIn model-based PI/PID tuning regulators, the same set of I/O data and the same tuning rule can produce very different results, depending just on the procedure used to parametrise the process model. The problem is seldom addressed, but extremely relevant for the acceptability of model-based autotuners in the applications. This manuscript proposes a methodology to treat the model parametrisation and regulator tuning phases jointly, so as to circumvent said problem with affordable process stimulation and computational effort. The methodology can be generalised to different regulator structures, and even employed
to devise new tuning rules
Disturbance rejection in autotuners: An assessment method and a rule proposal
No full textDisturbance rejection is a primary objective in many industrial control loops, thus a relevant goal for autotuning controllers. Nonetheless, autotuning has invariantly to cope with a reduced amount of process information. As a consequence, with the standard single-loop structure typically adopted in the addressed context, effective disturbance rejection calls for strong feedback, and therefore the solutions available to date fall sometimes short of perfection. This paper discusses the matter basically from a methodological standpoint, evidencing some structural reasons for the observed shortcomings. The result is a synthesis approach improving rejection performance with respect to existing and well established tuning rules, on a rigorously sound basis. Simulation examples are presented to support the proposal
Model reduction of switched affine systems: a method based on balanced truncation and randomized optimization
No full textThis paper proposes an approach to build a reduced order model for a Switched Affine (SA) system. The main idea is to transform the SA system into an equivalent Switched Linear (SL) system with state reset, and then apply balanced truncation to each mode and redefine the reset maps so as to best reproduce the free evolution of the system output. A randomized method is proposed for order selection in the case when the input is stochastic and one is interested in reproducing the output of the original SA system over a finite time-horizon. The performance of the approach is shown on a benchmark example
Model reduction of switched affine systems
Full text linkThis paper addresses model reduction and extends balanced truncation to the class of switched affine systems with endogenous switching. The switched affine system is rewritten as a switched linear one with state resets that account for the affine terms.
Balanced truncation can then be applied to each mode dynamics, independently. As a result, different reduced state vectors are associated with the different modes, and reset maps are here appropriately redefined so as to account and compensate for this mismatch, possibly preserving the continuity of the output. The overall behavior of the reduced switched system is determined by both the selected reduction per mode and the adopted reset maps. In this paper, we consider a stochastic setting and propose a randomized method for the selection of the reduced order. The performance of the proposed approach is illustrated through a multi-room temperature control example
A model partitioning method based on dynamic decoupling for the efficient simulation of multibody systems
No full textThe presence of different time scales in a dynamic model significantly hampers the efficiency of its simulation. In multibody systems the fact is particularly relevant, as the mentioned time scales may be very different, due for example to the coexistence of mechanical components controlled by electronic drive units, and may also appear in conjunction with significant nonlinearities. This paper proposes a systematic technique, based on the principles of dynamic decoupling, to partition a model based on the time scales that are relevant for the particular simulation studies to be performed, and as transparently as possible for the user. In accordance with said purpose, peculiar to the technique is its neat separation in two parts: a structural analysis of the model, that is general with respect to any possible simulation scenario, and a subsequent decoupled integration, which can conversely be (easily) tailored to the study at hand. Also, since the technique does not aim at reducing but rather at partitioning the model, the state space and the physical interpretation of the dynamic variables are inherently preserved. Moreover, the proposed analysis allows to define some novel indices relative to the separability of the system, thereby extending the idea of “stiffness” in a way that is particularly keen to its use for the improvement of simulation efficiency, be the envisaged integration scheme monolithic, parallel, or even based on co-simulation. Finally, thanks to the way the analysis phase is conceived, the technique is naturally applicable to both linear and nonlinear models. The paper contains a methodological presentation of the proposed technique, that is related to alternatives available in the literature so as to evidence the peculiarities just sketched, and some application examples, illustrating the achieved advantages and motivating the major design choice from an operational viewpoint
- …
