752 research outputs found
Group and total dissipativity and stability of multi-equilibria hybrid automata
Full text linkComplex systems, which consist of different interdependent and interlocking subsystems, typically have multiple equilibrium points associated with different set points of each operation mode. These systems are usually interpreted as switched systems, or in general, as hybrid systems. Surprisingly, the consideration of multiple equilibria is not common in hybrid systems’ literature, being typically focused on the study of stability and dissipativity properties for switched systems whose subsystems share the same equilibrium point. This paper will expand the discussion to the case of having multiple co-existing equilibrium points for hybrid systems modelled as hybrid automata, which are more general than switched systems. A classification of equilibria for hybrid automata is offered, and some stability related properties are shown for them. Moreover, some dissipativity-related properties are studied. The chief idea of our approach is to identify stable and dissipative components as group of discrete locations within the hybrid automaton. Two examples are used to illustrate our conclusions
Sampled-data adaptive control for a class of nonlinear systems with parametric uncertainties
Full text linkSampled-data control systems have been prevailing in various applications, in parallel with the development of digital computers and its applications in control activities. Moreover, adaptation has proved to improve performance of a control algorithm, particularly when uncertainties involve in the model of the systems. In this paper, a stabilization problem for a class of nonlinear systems with parametric uncertainties is addresses. A discrete-time adaptation algorithm constructed based directly on the discrete-time model of the system is proposed. This adaptation algorithm is then used for constructing a discrete-time controller to stabilize (in a semiglobal practical sense) the original continuous-time system in closed-loop, in a sampled-data set-up. This proposed direct discrete-time technique is shown to improves the closed-loop performance of the system, compared to applying a discrete-time adaptive control which is obtained through emulation design (by means of sample and hold). An example is presented to illustrate the result, to show the advantages of this direct discrete-time design for sampled-data implementatio
Coloured graphlet profiles as a predictor of career length in scientific co-authorship networks
No full textGraphlets, or induced motifs, have long been used to find important medium-scale structures in directed networks. We present a method using the composition of coloured graphlets in ego-networks to characterise nodes. We give an example application using our technique to predict the numbers of years researchers are active from their collaboration networks, and compare our success with simpler metrics; particularly, we find that the use of coloured graphlets improves predictiveperformance compared to colour-blind graphlets; that 4-star graphlets centred on an author are predictors of a long career, and that this effect is not degenerate to centralities
Coloured graphlet profiles as a predictor of career length in scientific co-authorship networks
No full textGraphlets, or induced motifs, have long been used to find important medium-scale structures in directed networks. We present a method using the composition of coloured graphlets in ego-networks to characterise nodes. We give an example application using our technique to predict the numbers of years researchers are active from their collaboration networks, and compare our success with simpler metrics; particularly, we find that the use of coloured graphlets improves predictiveperformance compared to colour-blind graphlets; that 4-star graphlets centred on an author are predictors of a long career, and that this effect is not degenerate to centralities
Coloured graphlet profiles as a predictor of career length in scientific co-authorship networks
No full textGraphlets, or induced motifs, have long been used to find important medium-scale structures in directed networks. We present a method using the composition of coloured graphlets in ego-networks to characterise nodes. We give an example application using our technique to predict the numbers of years researchers are active from their collaboration networks, and compare our success with simpler metrics; particularly, we find that the use of coloured graphlets improves predictiveperformance compared to colour-blind graphlets; that 4-star graphlets centred on an author are predictors of a long career, and that this effect is not degenerate to centralities
DYVERSE: From formal verification to biologically-inspired real-time self-organizing systems
No full textTo predict the future of scientific thought and technological advance is a challenging venture, but it seems probable that progress lies in the multi-disciplinary approach. Multi-disciplinary research is a manner of sharing ideas across specialized areas in order to find answers to new technological challenges. The complexity of today’s technological applications means that automated and semiautomated processes have become proportionately more complicated. With consumers demanding more from automated services, the necessity for safety-critical and resilient systems – that is, systems capable of preserving stability and recovering from shock – becomes more pressing. The challenge is to accurately test the performance of complex systems, and, if necessary, to modify their behavior to meet desired specifications. But complexity is not only on the outside. The most safety-critical, resilient, and robust system of all is the human body. Could the lessons learned in engineering be applied to healthcare? Surprisingly, from the mathematical perspective, there are common features and dynamical behaviors in the synchronization of swarm satellites and, for example, the self-organization of cells in living organisms. Behind the surface appearance of each system are underlying patterns and points of similarity. Typically, they are highly nonlinear systems, and combine continuous and discrete, smooth and abrupt dynamics. Their combined dynamics can be interpreted as a hybrid dynamical system. DYVERSE is a computational-dynamical framework for the modeling, analysis and control of complex control systems under the framework of hybrid systems, and stands for the DYnamically-driven VERification of Systems with Energy considerations. DYVERSE methodology aims to bring together formal computational tools, dynamical systems theory and control engineering methodologies to advance the understanding of systems interconnected in a non-regular and nontrivial manner
DYVERSE: From formal verification to biologically-inspired real-time self-organizing systems
No full textTo predict the future of scientific thought and technological advance is a challenging venture, but it seems probable that progress lies in the multi-disciplinary approach. Multi-disciplinary research is a manner of sharing ideas across specialized areas in order to find answers to new technological challenges. The complexity of today’s technological applications means that automated and semiautomated processes have become proportionately more complicated. With consumers demanding more from automated services, the necessity for safety-critical and resilient systems – that is, systems capable of preserving stability and recovering from shock – becomes more pressing. The challenge is to accurately test the performance of complex systems, and, if necessary, to modify their behavior to meet desired specifications. But complexity is not only on the outside. The most safety-critical, resilient, and robust system of all is the human body. Could the lessons learned in engineering be applied to healthcare? Surprisingly, from the mathematical perspective, there are common features and dynamical behaviors in the synchronization of swarm satellites and, for example, the self-organization of cells in living organisms. Behind the surface appearance of each system are underlying patterns and points of similarity. Typically, they are highly nonlinear systems, and combine continuous and discrete, smooth and abrupt dynamics. Their combined dynamics can be interpreted as a hybrid dynamical system. DYVERSE is a computational-dynamical framework for the modeling, analysis and control of complex control systems under the framework of hybrid systems, and stands for the DYnamically-driven VERification of Systems with Energy considerations. DYVERSE methodology aims to bring together formal computational tools, dynamical systems theory and control engineering methodologies to advance the understanding of systems interconnected in a non-regular and nontrivial manner
Parameters Controller Selection Through Bifurcation Analysis in a Piecewise-smooth System
Full text linksmooth (PWS) systems can be ineffective if an additional bifurcationanalysis is not made. Due to the presence of discontinuities,PWS systems present a wide variety of standard and non-standard bifurcations.Safe ranges of system and controller parameters can be establishedlest these bifurcations appear. This is studied by means of asimplified torsional model of an oilwell drillstring of three degrees offreedom (DOF). A PID-type controller is applied. The bifurcation analysisof the open-loop and the closed-loop systems is used to choose thecontroller parameters for which non-desired bit sticking situations areavoided. The control goal of driving the rotary velocities to a constantpositive value is achieved despite the existence of a sliding motion
Parameters Controller Selection Through Bifurcation Analysis in a Piecewise-smooth System
No full textsmooth (PWS) systems can be ineffective if an additional bifurcationanalysis is not made. Due to the presence of discontinuities,PWS systems present a wide variety of standard and non-standard bifurcations.Safe ranges of system and controller parameters can be establishedlest these bifurcations appear. This is studied by means of asimplified torsional model of an oilwell drillstring of three degrees offreedom (DOF). A PID-type controller is applied. The bifurcation analysisof the open-loop and the closed-loop systems is used to choose thecontroller parameters for which non-desired bit sticking situations areavoided. The control goal of driving the rotary velocities to a constantpositive value is achieved despite the existence of a sliding motion
- …
