Tracking performance limitations in LTI multivariable discrete-timesystems

In this paper, we investigate tracking properties of linear shift-invariant feedback control systems. We consider the standard unity feedback configuration, and use the energy of an error signal as a measure of tracking ability. Our main goal is to understand the fundamental limitation on tracking performance, which can arise due to the nonminimum phase zeros, unstable poles, and time delays in the plant, and which varies with input reference signals. We consider step, ramp, and sinusoidal signals, and for each type of the signals we derive a closed form expression for the minimum tracking error attainable by any stabilizing controller. Our results display an explicit dependence of the tracking error on nonminimum phase zeros, unstable poles, and in particular the coupling between the directions of the poles and zeros, and those of the input reference signal, upon which a number of useful conclusions can be drawn. One interesting outcome is that not only zero and pole locations affect tracking performance, but their directional properties also play an important role. The paper provides a nontrivial extension of the previously available results to discrete-time systems, with a consideration on broader classes of reference input

Tracking performance limitations in LTI multivariable discrete-timesystems

In this paper, we investigate tracking properties of linear shift-invariant feedback control systems. We consider the standard unity feedback configuration, and use the energy of an error signal as a measure of tracking ability. Our main goal is to understand the fundamental limitation on tracking performance, which can arise due to the nonminimum phase zeros, unstable poles, and time delays in the plant, and which varies with input reference signals. We consider step, ramp, and sinusoidal signals, and for each type of the signals we derive a closed form expression for the minimum tracking error attainable by any stabilizing controller. Our results display an explicit dependence of the tracking error on nonminimum phase zeros, unstable poles, and in particular the coupling between the directions of the poles and zeros, and those of the input reference signal, upon which a number of useful conclusions can be drawn. One interesting outcome is that not only zero and pole locations affect tracking performance, but their directional properties also play an important role. The paper provides a nontrivial extension of the previously available results to discrete-time systems, with a consideration on broader classes of reference input

Asymptotic tracking performance of sampled-data systems

This paper studies the tracking performance of sampled-data control systems. We consider the problem of tracking a step reference input by a sampled-data controller, and the goal is to minimize the integral square of the error between the output and input signals. Under this criterion, of particular interest is to investigate whether and when a degradation in the tracking performance may result, due to the use of sampled-data controllers, and whether such a degradation, where it does exist, can be remedied by a sufficiently fast sampler. The degradation thus constitutes a gap between the optimal performance achievable by continuous-time controllers and that by optimal sampled-data controllers. It is shown that for plants with relative degree greater than one, a performance loss does take place and it can never be recovered despite that the sampler is allowed to operate arbitrarily fast. This performance loss is seen to be fundamental of the sampling and hold mechanism, rather than from the plant itself. It is also shown that for plants with relative degree one, the loss can indeed. be retrieved with a sufficiently fast sampler

On the algorithmic unsolvability of some stability problems forhybrid systems

We define two stability problems for a class of hybrid systems containing asynchronous iterative processes and prove these problems are algorithmically unsolvable. Furthermore, we also show some reachability problems for asynchronous iterative processes are algorithmically unsolvabl

Концепції мовної гри як теоретичні засади організації навчально-ігрової діяльності

У статті розглянуто лінгвофілософські й лінгвістичні концепції мовної гри як підґрунтя організації навчально-ігрової діяльності в системі українськомовної освіти. На основі наукового осмислення окреслено зміст понять "гра", "навчально-ігрова діяльність", "мовна гра". Шляхом аналізу наукової літератури й синтезу теоретичних ідей визначено принципи побудови й реалізації навчально-методичної системи, спрямованої на формування мовної особистості школяра в навчально-ігровій діяльності

Seeing the world through non rose-colored glasses: anxiety and the amygdala response to blended expressions

Anxious individuals have a greater tendency to categorize faces with ambiguous emotional expressions as fearful (Richards et al., 2002). These behavioral findings might reflect anxiety-related biases in stimulus representation within the human amygdala. Here, we used functional magnetic resonance imaging (fMRI) together with a continuous adaptation design to investigate the representation of faces from three expression continua (surprise-fear, sadness-fear, and surprise-sadness) within the amygdala and other brain regions implicated in face processing. Fifty-four healthy adult participants completed a face expression categorization task. Nineteen of these participants also viewed the same expressions presented using type 1 index 1 sequences while fMRI data were acquired. Behavioral analyses revealed an anxiety-related categorization bias in the surprise-fear continuum alone. Here, elevated anxiety was associated with a more rapid transition from surprise to fear responses as a function of percentage fear in the face presented, leading to increased fear categorizations for faces with a mid-way blend of surprise and fear. fMRI analyses revealed that high trait anxious participants also showed greater representational similarity, as indexed by greater adaptation of the Blood Oxygenation Level Dependent (BOLD) signal, between 50/50 surprise/fear expression blends and faces from the fear end of the surprise-fear continuum in both the right amygdala and right fusiform face area (FFA). No equivalent biases were observed for the other expression continua. These findings suggest that anxiety-related biases in the processing of expressions intermediate between surprise and fear may be linked to differential representation of these stimuli in the amygdala and FFA. The absence of anxiety-related biases for the sad-fear continuum might reflect intermediate expressions from the surprise-fear continuum being most ambiguous in threat-relevance

Design And Implementation Of A Java Based Distributed Control System Over The Internet: A Tele-Laboratory System

In this paper, design and implementation of a Java based distributed control system over the Internet, is discussed. The main goal of the project is the development of a tele-laboratory system, which enables one to do experiments on equipments located at remote sites, by using the Internet. The main motivation for this project is the success of the well-known Australian tele-robot system. Following their success, many researchers tried to build web based laboratory systems. Being able to do a laboratory experiment over the Internet is a great convenience, leads to higher collaboration between researchers, and enables students to use the laboratory equipment whenever and wherever they want, as long as a computer with Internet connection is available. Despite these advantages, doing a laboratory experiment over the Internet is not as simple as doing it on site, and involves many new challenges. First of all, during the experiment one should be able to change laboratory equipment parameters, controller parameters, and system inputs remotely. Furthermore, there should be a high-speed data collection system, which can send the collected data to the remote computer for, graphical display. The most important requirement. is the need for a high-speed control loop executed with strict real-time requirements. Finally, a live video connection is necessary so that one can also watch the laboratory equipment and its response as live video. In this paper, we will discuss how we address these challenges, and in which aspects the proposed structure is an improvement of the existing tele-laboratory implementations around the world

Design of a multi-threaded distributed telerobotic framework

A telerobotic system consists of master (client) and slave (server) stations which are usually connected by a computer network. A reliable real-time connection between master and slave systems is proposed using Distributed Components (.NET Remoting). This has a number of benefits such as software reusability, ease of extensibility, debugging, and data encapsulation. It is based on most advanced software tools like NET Framework that promise definite advantages over DCOM (Distributed Component Object Model) and RPC (Remote Procedure Call), previously used for distributed applications. The components communicate with each other using NET Remoting and SOAP (Simple Object Access Protocol) that automatically handle the network resources and data transfer while isolating the components from network protocol issues. This enhances the data security as well as facilitates easy deployment. Implementing telerobotics using the proposed approach gives the advantage of a multi-threaded execution needed to effectively realize multi-streaming of force, command and stereo data over a LAN

Design of a multi-threaded distributed telerobotic framework

A telerobotic system consists of master (client) and slave (server) stations which are usually connected by a computer network. A reliable real-time connection between master and slave systems is proposed using Distributed Components (.NET Remoting). This has a number of benefits such as software reusability, ease of extensibility, debugging, and data encapsulation. It is based on most advanced software tools like NET Framework that promise definite advantages over DCOM (Distributed Component Object Model) and RPC (Remote Procedure Call), previously used for distributed applications. The components communicate with each other using NET Remoting and SOAP (Simple Object Access Protocol) that automatically handle the network resources and data transfer while isolating the components from network protocol issues. This enhances the data security as well as facilitates easy deployment. Implementing telerobotics using the proposed approach gives the advantage of a multi-threaded execution needed to effectively realize multi-streaming of force, command and stereo data over a LAN