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ABSTRACT: In this paper, we present exact analysis for the worst case response time of the general multiframe (MF) task model executing
on a uniprocessor according to the fixed priority scheduling scheme. The analysis is developed in four stages. Firstly, we
present the basic response time analysis where we optimize the number of frames that have to be considered in such analysis;
we show how their number can be significantly reduced by eliminating non critical frames that are dominated by other frames.
Secondly, we extend this analysis to be applicable to MF tasks with arbitrary deadlines. Thirdly, the basic analysis is extended
to cope with frame specific deadlines. Lastly, the two models of frame specific deadlines and arbitrary deadlines are combined
and the relative analysis is presented. An optimal priority assignment scheme for the frame specific deadline scenario is
also presented in this paper.
Real-Time Systems 04/2012; 43(2):119-146. · 0.74 Impact Factor
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ABSTRACT: Timed Circus is a compact extension to Circus, that is, it inherits only the CSP part of Circus while introducing time. Although it looks much like timed CSP from the viewpoint of syntax, its semantics is very different from that of timed CSP because it uses a complete lattice in the implication ordering instead of the complete partial order of the standard failures-divergences model of CSP. The complete lattice gives rise to a number of strange processes which violate some axioms of CSP, especially when the miracle (the top element) and SKIP meet time. In this paper, compared with timed CSP, we will extensively explore such strange processes which turn out to be very useful in specifying a distinct property that "something must occur". Finally, we use a simple example to demonstrate how our model can contribute to modelling temporal behaviours with multiple time scales in complex systems.
Engineering of Complex Computer Systems (ICECCS), 2011 16th IEEE International Conference on; 05/2011
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ABSTRACT: Wireless sensor networks have become increasingly common in everyday applications due to decreasing technology costs and improved product performance, robustness and extensibility. Wearable physiological monitoring systems have been utilized in a variety of studies, particularly those investigating ECG or EMG during human movement or sleep monitoring. These systems require extensive validation to ensure accurate and repeatable functionality. Here we validate the physiological signals (EMG, ECG and GSR) of the SHIMMER (Sensing Health with Intelligence, Modularity, Mobility and Experimental Reusability) against known commercial systems. Signals recorded by the SHIMMER EMG, ECG and GSR daughter-boards were found to compare well to those obtained by commercial systems.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: Body-worn kinematic sensors have been widely proposed for use in portable, low cost, ambulatory monitoring of gait. Such sensor based systems could avoid the need for high-cost laboratory-based methods for measurement of gait. We aimed to evaluate an adaptive gyroscope-based algorithm for automated temporal gait analysis using body-worn wireless gyroscopes. Temporal gait parameters were calculated from initial contact (IC) and terminal contact (TC) points derived from gyroscopes, contained in wireless sensors on the left and right shanks, using a newly developed adaptive algorithm. Gyroscope data from nine healthy adult subjects performing four walks at three different speeds were then compared against data acquired simultaneously using two force-plates. Results show that the mean true error between the adaptive gyroscope algorithm and force-plate was -5.5±7.3 ms and 40.6±19.2 ms for IC and TC points respectively; the latter representing a consistent, systematic error of this magnitude that may be intrinsic to shank-mounted gyroscopes. These results suggest that the algorithm reported here could form the basis of a robust, portable, low-cost system for ambulatory monitoring of gait.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: Applying new sensing technology to healthcare maybe part of a solution to the financial and demographic crisis facing global healthcare systems. Researchers applying new approaches to noninvasive patient monitoring and diagnostics are assisted by the features of Sensing Health with Intelligence, Modularity, Mobility and Experimental Reusability (SHIMMER™), a flexible sensing platform. Integrated peripherals, open software, modular expansion, specific power management hardware, and a library of applications supported with platform validation provide SHIMMER with advantages over many other medical research platforms.
IEEE Sensors Journal 10/2010; · 1.52 Impact Factor
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ABSTRACT: The correctness of a real-time system depends on not only the system's output but also on the time at which results are produced. A hard real-time system is required to complete its operations before all its timing deadlines. For a given task set, it is very useful in an engineering context to know what changes to period (interarrival time) can be made to a task that will deliver a schedulable system. In this paper, we address the sensitivity analysis (parameter calculations) of task period for EDF scheduled systems on a uniprocessor. We prove that a minimum task period can be determined by a single pass of the QPA algorithm. This algorithm provides exact and efficient sensitivity analysis for arbitrary deadline real-time systems. The approaches developed for task parameter computations are therefore as efficient as QPA, and are easily incorporated into a system design support tool.
Computer Science and Information Technology (ICCSIT), 2010 3rd IEEE International Conference on; 08/2010
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ABSTRACT: Development of a flexible wireless sensor platform for measurement of biomechanical and physiological variables related to functional movement would be a vital step towards effective ambulatory monitoring and early detection of risk factors in the ageing population. The small form factor, wirelessly enabled SHIMMER platform has been developed towards this end. This study is focused assessing the utility of the SHIMMER for use in ambulatory human gait analysis. Temporal gait parameters derived from a tri-axial gyroscope contained in the SHIMMER are compared against those acquired simultaneously using the CODA motion analysis system. Results from a healthy adult male subject show excellent agreement (ICC(2, k) > 0.85) in stride, swing and stance time for 10 walking trials and 4 run trials. The mean differences using the Bland and Altman method for stance, stride and swing times were 0.0087, 0.0044 and -0.0061 seconds respectively. These results suggest that the SHIMMER is a versatile cost effective tool for use in temporal gait analysis.
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: This paper derives closed form upper bounds on the response times of tasks in fixed priority real-time systems. These bounds are valid for tasks with arbitrary deadlines, release jitter, and blocking. Response time upper bounds are given for tasks that are scheduled pre-emptively, cooperatively with intervals where pre-emption is deferred, and non-preemptively. The set of upper bounds for n tasks can be computed in O(n) time, providing a linear-time sufficient schedulability test, applicable to complex commercial real-time systems.
Real-Time Systems Symposium, 2008; 01/2009
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ABSTRACT: An exact scheduling test for AM multiframe tasks executing on a uniprocessor according to the fixed priority scheduling scheme is presented in this paper. The test is given as a generalization of the exact worst case response time of AM multiframe tasks in two directions. First is an improvement of the exact analysis to be applicable to systems that are subjected to release jitter. Whilst the second is to cope with the arbitrary deadline scenario. A combined analysis of both scenarios is also introduced in this paper.
Emerging Technologies and Factory Automation, 2008. ETFA 2008. IEEE International Conference on; 10/2008
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ABSTRACT: This paper focuses on resource sharing in hierarchical fixed priority pre-emptive systems where a number of separate applications, each with its own server, reside on a single processor. It defines the hierarchical stack resource policy, an appropriate global resource access policy that bounds priority inversion and also limits interference due to overruns during resource access. The paper provides detailed response time analysis enabling the schedulability of application servers and tasks to be determined for systems with local and global resource access. This analysis is applicable to real-world systems where server-based applications need mutually exclusive access to shared resources such as communications buffers, peripheral devices, operating system calls and data structures shared with interrupt handlers
Real-Time Systems Symposium, 2006. RTSS '06. 27th IEEE International; 01/2007
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ABSTRACT: This paper focuses on the hierarchical scheduling of systems where a number of separate applications reside on a single processor. It addresses the particular case where fixed priority pre-emptive scheduling is used at both global and local levels, with a server associated with each application. Using response time analysis, an exact schedulability test is derived for application tasks. This test improves on previously published work. The analysis is extended to the case of harmonic tasks that can be bound to the release of their server. These tasks exhibit improved schedulability indicating that it is advantageous to choose server periods that enable some tasks to be bound to the release of their server. The use of periodic, sporadic and deferrable servers is considered with the conclusion that the simple periodic server dominates both sporadic and deferrable servers when the metric is application task schedulability.
Real-Time Systems Symposium, 2005. RTSS 2005. 26th IEEE International; 01/2006
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S.M. Smith,
P.E. An,
K. Holappa,
J. Whitney, A. Burns,
K. Nelson,
E. Heatzig,
O. Kempfe,
D. Kronen,
T. Pantelakis,
E. Henderson,
G. Font,
R. Dunn,
S.E. Dunn
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ABSTRACT: The Advanced Marine Systems Lab at Florida Atlantic University has
developed a new ultramodular plastic mini autonomous underwater vehicle
(AUV), called the Morpheus, for littoral military and coastal
oceanographic sampling, survey, and mapping. The name Morpheus was
chosen because the Greek god Morpheus could change shape or "morph." The
higher degree of modularity of the Morpheus AUV allows it to "morph" or
change its size and components for different applications. This vehicle
is composed of modular injection-molded plastic pressure vessels and a
cabling system that allow the modules to be rearranged without rewiring
bulkheads. The plastic pressure vessels are inexpensive, inherently
mass-producible, extremely corrosion-resistant, and have low magnetic
signatures. The pressure vessels are small but are sized to fit most
standard electronic board standards. The mini AUV can be anywhere from 4
to 10 ft in length, depending on its mission. The vehicle architecture
is an adaptation of the Ocean Explorer AUV system and uses an ANSI 709.1
(LonTalk) distributed control network for connecting all sensors and
actuator subsystems as smart nodes. The modularity in containers,
control, and power makes this vehicle rapidly reconfigurable and easy to
repair or upgrade. This paper will present details of the motivation,
design, and construction of the new mini AUV. The Morpheus was deployed
during the summer of 2000 in field exercises for very shallow and
shallow water mine counter measures. Some results from these tests will
be presented
IEEE Journal of Oceanic Engineering 11/2001; · 0.95 Impact Factor
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ABSTRACT: The scheduling scheme “shortest remaining processing
time” (SRPT) has the advantage that it minimises mean response
times. We present feasibility tests for SRPT that will enable this
scheduling approach to be used for real time systems. Examples are given
of task sets that are schedulable under SRPT but not by fixed priority
based scheduling
Real-Time Systems, 1997. Proceedings., Ninth Euromicro Workshop on; 07/1997
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ABSTRACT: Synchrotron radiation interferences between small dipoles in the
very low (visible) frequency range have been studied at the LEP
diagnostic mini-wiggler. Their understanding allowed a substantial
brightness gain by adequate layout modifications. The phenomenon is
described analytically in terms of time coherence effects. This serves
as a basis for further detailed numerical simulations of the experiment
by means of stepwise ray-tracing, and allows precise interpretation of
the spectral, polarization and intensity measurements collected at LEP.
It also provides guidelines for SR diagnostic at the injection energy in
LHC
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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ABSTRACT: The lifetimes of coasting beams in LEP are computed from the
difference of the bunch currents measured during a time interval of a
few seconds. The quality of these measurements is presently limited by
the noise figure of the bunch to bunch acquisition system. This paper
describes comparative studies on the acquisition system in order to
improve the noise figure by one order of magnitude. For this purpose
three different principles, i.e., integrating measurements, peak hold
circuits with internal timing (autotrigger) or peak hold circuits with
external timing were studied. The paper describes the results of these
studies
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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ABSTRACT: As the real-time computing industry moves away from static cyclic executive-based scheduling towards more flexible process-based scheduling, so it is important for current scheduling analysis techniques to advance and to address more realistic application areas. This paper extends the current analysis associated with static priority pre-emptive based scheduling; in particular it derives analysis for tasks with arbitrary deadlines that may suffer release jitter due to being dispatched by a tick driven scheduler. We also consider bursty sporadic activities, where tasks arrive sporadically but then execute periodically for some bounded time. The paper illustrates how a window-based analysis technique can be used to find the worst-case response time of a task set, and shows that the technique can be easily extended to cope with realistic and complex task characteristics.
Real-Time Systems 01/1994; 6(2):133-151. · 0.74 Impact Factor
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ABSTRACT: This paper addresses the problem of jointly scheduling tasks with
both hard and soft time constraints. We present a new analysis which
builds upon previous research into slack stealing algorithms. Our
analysis determines the maximum processing time which may be stolen from
hard deadline periodic or sporadic tasks, without jeopardising their
timing constraints. It extends to tasks with characteristics such as
synchronization, release jitter and stochastic execution times, as well
as forming the basis for a family of optimal and approximate slack
stealing algorithms
Real-Time Systems Symposium, 1993., Proceedings.; 01/1994
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ABSTRACT: It is noted that in many hard real-time systems, the set of
functions that a system is required to provide may change over time. One
way of providing this change is to allow currently running hard
real-time tasks to be deleted or changed, or new tasks to be added. The
authors define this change as a mode change, and seek to guarantee a
priori the timing constraints of all tasks across the change from one
mode to another. The authors derive a scheduling theory for static
priority preemptive scheduling that can be used to make such guarantees.
The schedulability test discussed could easily be incorporated into
engineering support tools. The authors also discuss some of the
approaches that could be taken to extend the analysis to cope with more
complex and interesting scheduling problems, and to handle distributed
hard real-time systems
Real-Time Systems Symposium, 1992; 01/1993
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ABSTRACT: A distributed hard real time system can be composed from a number of communicating tasks. One of the difficulties with building such systems is the problem of where to place the tasks. In general there are P
T ways of allocating T tasks to P processors, and the problem of finding an optimal feasible allocation (where all tasks meet physical and timing constraints) is known to be NP-Hard. This paper describes an approach to solving the task allocation problem using a technique known as simulated annealing. It also defines a distributed hard real-time architecture and presents new analysis which enables timing requirements to be guaranteed.
Real-Time Systems 05/1992; 4(2):145-165. · 0.74 Impact Factor
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B. Bouchet,
C. Bovet, A. Burns,
J. Camas,
G. Ferioli,
C. Fischer,
R. Jung,
Q. King,
K.H. Kissler,
J. Koopman,
J. Mann,
H. Michel,
R. Schmidt,
L. Vos
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ABSTRACT: Two sets of wire scanners, each for measuring the horizontal and vertical profile, are installed in LEP in a straight section where the dispersion in both planes is zero. The authors present the design and discuss some limitations of the instrument. A carbon fiber with a diameter of 36 mu m moves through the beam with a speed of about 0.5 m/s. The bremsstrahlung photons generated by the passage of the wire through the beam are detected in scintillators located 80-m downstream. During the first months of LEP operation, the fibers were destroyed occasionally. The various causes, tests and remedies are discussed. At injection energy a significant blowup of the beam results from the wire scan and has to be taken into account for the estimation of the genuine emittance. A model of this blowup is proposed, where the effect is renormalized on the actual measured data. This provides an effective data treatment to obtain the unperturbed beam size.< >
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE; 06/1991
