Survey on time-delay approach to networked control

This paper provides a survey on time-delay approach to networked control systems (NCSs). The survey begins from a brief summary on fundamental network-induced issues in NCSs and the main approaches to the modelling of NCSs. In particular, a comprehensive introduction to time-delay approach to sampled-data and networked control is provided. Then, recent results on time-delay approach to event-triggered control are recalled. The survey highlights time-delay approach developed to modelling, analysis and synthesis of NCSs, under communication constraints, with a particular focus on Round-Robin, Try-once-discard and stochastic protocols. The time-delay approach allows communication delays to be larger than the sampling intervals in the presence of scheduling protocols. Moreover, some results on networked control of distributed parameter systems are surveyed. Finally, conclusions and some future research directions are briefly addressed

Speed-Accuracy Trade-Offs and General Systems Performance Theory: Novel Application to Fitts’ Law and Beyond

Speed-accuracy trade-offs have long been of interest in human performance. General Systems Performance Theory (GSPT) was motivated by human performance measurement and modeling needs. It has subsequently been applied in those and other areas. In GSPT, all system performance attributes are modeled using a resource construct. Systems are characterized by multi-dimensional performance capacity envelopes (PCEs). The systems of interest here are considered to possess limited speed and accuracy performance resources defining a two-dimensional PCE. When considering human movement, relevance to Fitts’ law was conjectured. In multiple Fitts’ paradigm tasks, we found a near-perfect correlation between Index of Performance (IP) and PCE area. An almost exact prediction was obtained when scaled by Fitts\u27 index of task difficulty (ID). While the well-known Fitts’ law equation does not contain accuracy explicitly, the GSPT-derived expression (CPS-A= ID • Speed • Accuracy) contains both speed (motions/s) and accuracy (hits/attempts). Concepts are applicable beyond human movement; e.g., to visual, auditory, or other information processing types

PerformanceMeasurementandPrediction inaDistributedTeleroboticsSystem

Indevelopingteleroboticssystems,itisdesirable tobeabletopredicttheeectofaddingorreplacing systemcomponentsontheoverallsystem'sperfor-mancecapacities.Byappropriatelystressingperfor-mancedimensionsofasystemandcharacterizing itsbehavior,wecandevelopamodelthatwillde-scribethesystemquantitativelyintermsofitstotal available\performanceresources".Iftheresource availabilityisgreaterthanorequaltotheresource demandsforagiventask,wecanpredictsuccessful completionforthetask.Usingthisapproach,wecan characterizenewintelligentcomponentsandpredict theirperformanceinagiventask.Resultsofatele-operationexperimentareincludedwhichyieldasys-temperformancecapacityenvelopeforatelerobotics system. 1Introduction Thetermteleroboticshasbeenusedtorepresent humancontrolofremotesubsystems,includingsu-pervisorycontrolofautonomouscomponents[2].In general,theevaluationofteleroboticssystemshas beentask-oriented.Thatis,cananoperatorac-complishaparticulartaskandhowlongdoesit take[4]?Althoughthisprovidesanindicationof whetherthesystemworksforthatparticulartask, itdoesnothingtocharacterizetheperformanceof thecomponentsorindicatewherethelimitations andweaknessesexist.Italsodoesnotgenerallypro-videinformationwhichcouldbeusedtopredictthe ThisworkhasbeensupportedbyNASAundergrant numbersNAG9-461andNCC2-517,bytheStateofTexas underTATPgrants999903-267and999903-095,andbyth

Aortic valve mechanics

Model and animal experiments emphasized the relevance of presence and flexibility of aortic sinuses in valve closure. In dogs the asymmetric deformation of aortic ring and the commissure displacements during the cardiac cycle were quantified. Finite element modelling made clear that the leaflet bundles are essential for a homogeneous stress distributio