Implementation of algebraic controllers for non-conventional sampled-data systems

Abstract

Nowadays, in industrial control applications, is rather usual to sample and update different variables at different rates, although it is common to consider all these activities equally and regularly spaced on time. These applications are implemented on real-time operating systems by decomposing them into several tasks in such a way that pre-emption and blocking may appear due to task priorities and resource sharing. This could imply the presence of delays, leading to a non-regular periodic behaviour and, as a result, the control performance can be degraded. In order to undertake this problem, a solution based on a modelling methodology for non-conventional sampled-data systems is proposed. This technique permits the consideration of any cyclic sampling pattern. Thus, these delays can be considered in the modelling step, and later on, a non-conventional controller based on this model can be designed. In this way, if the considered non-conventional control system is implemented assuming a real-time operating system (Tornado-VxWorks, in this case), a clear performance improvement can be observed.

A retunable PID multi-rate controller for a networked control system

“…Even if the argumentation for state and output equations has been made for t 2 ½0; NT, it is, of course, trivial to extend it to t 2 ½kNT; ðk þ 1ÞNT (as appearing in (9) and (10), in fact) so U becomes U k and Y becomes Y k , in the forms (7) and (8).…”

“…In this context, the consideration of a dual-rate controller might be useful: as it is directly connected to the actuator, it can work at a faster rate than the network which provides the measurements. Dual-rate controllers in linear time-invariant setups have been considered, for instance, in an internal-model inferential structure in [16], in an algebraic transfer function setting in [8], or in a state-space representation in [14].…”

Non-uniform sampling strategies for digital control

“…In addition, Albertos and Crespo (1999) and Cuenca, Salt, and Albertos (2007) surveyed and proposed improvements in control design techniques under non-uniform sampling schemes mainly concentrating on assessing the effects of variations of the intended uniform sample rate due to scheduling and multitasking timing constraints. The authors examined industrial perspectives for real-time control with nonuniform sampling and deduced that due to the complexity of modern control systems, sample update irregularities become inevitable.…”

Multirate control with incomplete information over Profibus-DP network

“…The control law proposal is developed from a gain scheduling multirate control strategy Sala et al (2009) properly adapted to this advanced specific case. Other works related to this field can be found in Xie et al (2013), Khan et al (2012), Peñarrocha et al (2012), Cuenca et al (2007), Lall and Dullerud (2001), Salt and Albertos (2005), Salt et al (2011), .…”