FeedNetBack - D05.04 - Design methodologies for event-based control systems

This is a Deliverable Report for the FeedNetBack project (www.feednetback.eu). Networked Control Systems (NCS) are systems in which the sensors or/and the actuators communicate with the controller through a network. Energy saving and robustness to unreliable channels are major challenges in networked control, notably in wireless scenarios. Energy efficiency and in particular asynchronous design methodologies are studied in this deliverable. The presence of a channel between the sensors measuring the plant and the controller generating the control inputs implies that the measurements should be quantized. As a preliminary step, the problem of finding a stabilizing policy with quantized measurements and bounded control inputs is considered. It is common to assume that the different nodes of a Network Control System use a periodic synchronized clock, this simplifies the model which may take into account some transmission delays. However, this assumption is strong and energy consuming. Indeed, the periodic sampling time is often chosen to ensure given performance in the worst case scenario, wasting energy when the system is running around its working point. To relax the assumption of synchronized nodes, the rest of the deliverable introduces two asynchronous design methodologies, event-based and self-triggered methodologies. The former consists in limiting the transmissions between the nodes when a given condition holds, or, in other words, when an event occurs. Not only this approach relaxes the assumption of synchronized nodes, but it also limits the transmissions which save energy. In the following, event-based approach is applied to a feedback control case and an estimation case. However, by its nature, event-based approach forces the communicating node to watch for the occurrence of the triggering event. This is relaxed in self-triggered approach where each node decides, at the end of an action (e.g. measuring, transmitting, controlling), when the next action will take place. In between these times, the node usually goes to down mode to save energy. In the last part of this deliverable, this approach is applied to a variable sample rate control and to the case of IEEE 802.15.4 protocol

On event-based PI control of first-order processes

In this paper the design of an event-based proportional-integral (PI) control scheme for stable first-order processes is considered. A novel triggering mechanism which decides the transmission instants based on an estimate of the PI control signal is proposed. This mechanism addresses some side-effects that have been discovered in previous event-triggered PI proposals, which trigger on the process output. In the proposed scheme, the classic PI controller is further replaced with PIDPLUS, a promising version of PI controller for networked control systems. Although PIDPLUS has been introduced to deal with packet losses and time delays, and, to the best of our knowledge, a stability analysis of the closed-loop system where such a controller is used has never been performed, here the performance of such a controller in an event-based fashion are analyzed, and a stability analysis is further provided. The proposed event-based scheme ensures set-point tracking and disturbance rejection as in classic time-periodic implementations of PI controller, while greatly reducing the number of sensor transmissions. The theoretical results are validated by simulations, where the benefits in using PIDPLUS in combination with the proposed PI event-based triggering rule are shown.QC 20121016</p

Energy-efficient sampling of networked control systems over IEEE 802.15.4 wireless networks

Self-triggered sampling is an attractive paradigm for closed-loop control over energy-constrained wireless sensor networks (WSNs) because it may give substantial communication savings. The understanding of the performance of self-triggered control systems when the feedback loops are closed over IEEE 802.15.4 WSNs is of major interest, since the communication standard IEEE 802.15.4 is the de-facto reference protocol for energy-efficient WSNs. In this paper, a new approach to control several processes over a shared IEEE 802.15.4 network by self-triggered sampling is proposed. It is shown that the sampling time of the processes, the protocol parameters, and the scheduling of the transmissions must be jointly selected to achieve a good performance of the closed-loop system and an energy-efficient utilization of the network. The challenging part of the proposed analysis is ensuring globally uniformly ultimately boundedness of the controlled processes while providing efficient scheduling of the process state transmissions. Such a scheduling is difficult when asynchronous multiple control loops share the network, because transmissions over IEEE 802.15.4 are allowed only at certain time slots. The proposed approach establishes that the joint design of self-triggered samplers and the network protocol (1) ensures globally uniformly ultimately boundedness of each control loop, (2) reduces the number of sensor transmissions, and (3) increases the sleep time of the transmitting nodes. A new dynamic scheduling problem is proposed for the joint control of each process and network protocol adaptation. An algorithm is derived, which adapts the network parameters according to the self-triggered sampler of every control loop. Numerical examples illustrate the analysis and show the benefits of the approach. It is concluded that self-triggered control strategies over WSNs ensure desired control performance, reduce the network utilization, and reduce energy consumption only if the protocol parameters are appropriately regulated.QC 20130129</p

The possibility of promoting the emotional response of the youngest pre-school child to the literary work at the preschool stage

Darba tēma: Jaunākā pirmsskolas vecuma bērna emocionālās atsaucības veicināšanas iespējas literāro darbu iepazīšanas procesā pirmskolā. Pētījuma mērķis: Pētīt jaunākā pirmsskolas vecuma bērna emocionālās atsaucības veicināšanas iespējas literāro darbu iepazīšanas procesā pirmsskolā. Darbs sastāv no divām daļām – teorētiskās un empīriskās daļas. Teorētiskā daļa – ir sniegts emociju vispārīgs raksturojums, izzināti paņēmieni emocionālās atsaucības veicināšanai pirmsskolā, sniegts jaunākā pirmsskolas vecuma bērnu attīstības raksturojums, analizēta literāro darbu ietekme uz emocionālās atsaucības veidošanos. Empīriskā daļa – veikta novērošana jaunākā pirmsskolas vecuma bērnu grupā literārā darba iepazīšanas procesa laikā, analizēti un apkopoti iegūtie dati. Pētījuma gaitā apstiprinājās izvirzītā hipotēze, ka literāro darbu iepazīšanas procesā jaunākā pirmsskolas vecuma bērnu emocionālā atsaucība tiek veicināta, ja tiek izvēlēti vecumposmam, bērnu vajadzībām, izpratnei un interesēm atbilstoši literārie darbi, ir apstiprinājusies, jo emocionālo atsaucību veicina atbilstoši izvēlēti literārie darbi, kā arī pozitīva, nepiespiesta gaisotne literārā darba iepazīšanas laikā. Darba apjoms: 48 lpp., darbam pievienoti 12 attēli, 4 tabulas, 1 pielikums. Izmantoti 46 literatūras avoti. Atslēgas vārdi: jaunākais pirmsskolas vecums, emocijas, emocionālā atsaucība, literārie darbi.  Theme of work: The possibility of promoting the emotional response of the youngest preschool child to the literary work at the preschool stage. Purpose of the research: To study the possibilities of promoting the emotional response of the youngest preschool child to the study process of the literary work in the preschool. The work consists of two parts - the theoretical and empirical. The theoretical part is a general description of emotions, identified and selected techniques for promoting emotional responsiveness in the preschool. It contains a description of the youngest preschoolers’ development process, and the influence of literary works on the formation of emotional responsiveness. Empirical part - observation and pilot work in the group of the youngest preschoolers during the process of getting acquainted with the literary work, analyzed and summarized data obtained. The research confirmed the work hypothesis: the emotional responsiveness of the youngest preschool children is promoted in the process of getting acquainted with literature, when choosing the literary works appropriate to the children's age, needs, understanding and interests. Preschooler’s emotional responses are promoted as well as by positive, an uncompressed atmosphere while reading a literary work. Content of work: 48 pages, 12 pictures, 4 tables added, 46 literary sources used, 1 addendum. Keywords: the youngest preschool age, emotions, emotional responsiveness, literary works.

FeedNetBack - D05.04 - Design methodologies for event-based control systems

This is a Deliverable Report for the FeedNetBack project (www.feednetback.eu). Networked Control Systems (NCS) are systems in which the sensors or/and the actuators communicate with the controller through a network. Energy saving and robustness to unreliable channels are major challenges in networked control, notably in wireless scenarios. Energy efficiency and in particular asynchronous design methodologies are studied in this deliverable. The presence of a channel between the sensors measuring the plant and the controller generating the control inputs implies that the measurements should be quantized. As a preliminary step, the problem of finding a stabilizing policy with quantized measurements and bounded control inputs is considered. It is common to assume that the different nodes of a Network Control System use a periodic synchronized clock, this simplifies the model which may take into account some transmission delays. However, this assumption is strong and energy consuming. Indeed, the periodic sampling time is often chosen to ensure given performance in the worst case scenario, wasting energy when the system is running around its working point. To relax the assumption of synchronized nodes, the rest of the deliverable introduces two asynchronous design methodologies, event-based and self-triggered methodologies. The former consists in limiting the transmissions between the nodes when a given condition holds, or, in other words, when an event occurs. Not only this approach relaxes the assumption of synchronized nodes, but it also limits the transmissions which save energy. In the following, event-based approach is applied to a feedback control case and an estimation case. However, by its nature, event-based approach forces the communicating node to watch for the occurrence of the triggering event. This is relaxed in self-triggered approach where each node decides, at the end of an action (e.g. measuring, transmitting, controlling), when the next action will take place. In between these times, the node usually goes to down mode to save energy. In the last part of this deliverable, this approach is applied to a variable sample rate control and to the case of IEEE 802.15.4 protocol

Wireless ventilation control for large-scale systems: the mining industrial case

This paper describes a new industrial case on automation, for large scale systems with high environmental impact: the mining ventilation control systems. Ventilation control is essential for the operation of a mine in terms of safety (CO and NOx regulation) and energy optimization. We first discuss a novel regulation architecture, highlighting the interest for a model-based control approach and the use of distributed sensing capabilities thanks to a wireless sensor network (WSN). We propose a new model for underground ventilation. The main components of the system dynamics are described with time-delays, transmission errors, energy losses and concentration profiles. Two different modelbased control approaches, which can embody the complex dynamics of the system, are proposed. The first one resorts to a nonlinear model predictive control strategy (receding horizon) and aims to energy minimization thanks to a continuous operation of the fans. The second one, based on a hybrid description of the model and fans operation, provides automatic verification of the wireless control thanks to abstraction techniques. These control strategies are compared with simulations, in terms of regulation efficiency, energy consumption and need for computational capabilities. The industrial case description and control strategies open new vistas for the development of global system approaches that allow for the optimization of energy consumption of complex large-scale systems. Copyright c