10,998 research outputs found

    SAW torque transducers for disturbance rejection and tracking control of multi-inertia servo-drive systems

    Get PDF
    The paper proposes a resonance ratio control (RRC) technique for the coordinated motion control of multi-inertia mechanical systems, based on the measurement of shaft torque via a SAW-based torque sensor. Furthermore, a new controller structure, RRC plus disturbance feedback is proposed, which enables the controller to be designed to independently satisfy tracking and regulation performance. A tuning method for the RRC structure is given based on the ITAE index, normalized as a function of the mechanical parameters enabling a direct performance comparison between a basic proportional and integral (PI) controller. The use of a reduced-order state observer is presented to provide a dynamic estimate of the load-side disturbance torque for a multi-inertia mechanical system, with an appraisal of the composite closed-loop dynamics. It is shown that the integrated formulation of the tuning criteria enables lower bandwidth observers to be implemented with a corresponding reduction in noise and computational load. The control structures are experimentally validated via a purpose designed test facility and demonstrate significant improvement in dynamic tracking performance, whilst additionally rejecting periodic load side disturbances, a feature previously unrealisable except by other, high-gain control schemes that impose small stability margins

    STREETS: an agent-based pedestrian model.

    Get PDF
    8-11 Septembe

    Observer based tuning techniques and integrated SAW torque transducers for two-inertia servo-drive systems

    Get PDF
    A controller design and tuning methodology is proposed that facilitates the rejection of periodic load-side disturbances applied to a torsional mechanical system, whilst simultaneously compensating for the disturbance observer's inherent phase delay, thereby facilitating the used of lower bandwidth, practically realisable, disturbance observers. The merits of implementing both a full- and reduced order observer, is investigated, with the latter being implemented with a new low-cost, high-bandwidth torque sensing device based on surface acoustic wave technolog

    Time-averaged single sided ventilation rates and thermal environment in cooling mode for a low energy retrofit envelope

    Get PDF
    Non-invasive, scalable, building retrofit solutions are very attractive deep renovation techniques to improve energy efficiency in existing buildings; this includes natural ventilation for cooling due to the low impact nature of the installation. However, a number of criteria that are important to natural ventilative cooling strategies can be substantially altered as a result of an external retrofit solution. This paper investigates this experimentally; it presents ventilation rate and internal thermal environment results from full scale testing of a modular, scalable, external low energy retrofit envelope solution applied to an existing 1970s precast concrete building in Ireland. Experimental results of time averaged single sided ventilation rates for three different ventilation opening configurations in a retrofitted office space during a warm and low wind summer period are analysed and compared to a single configuration control space. Results show that the highest time averaged ventilation rates were measured in the control space although a similar distribution was present in one retrofit opening configuration. Analysis of tracer concentration decay fluctuation profiles during tests suggest increased unsteady flow effects in the control space compared to all retrofit configurations. This is likely due to the different responses to turbulent diffusion processes and wind pressure fluctuations at the window opening compared to the louvred retrofit design. Zone thermal stratification and diurnal temperature variation within the control and retrofit spaces were measured during each ventilation rate test and also continuously for an extended period. Results show that vertical temperature differences have been substantially reduced following the retrofit works with all δTs values within recommended acceptable limits.The original pilot project works was supported through a grant from the Department of Education and Skills, Ireland

    Agent-based models and individualism: is the world agent-based?

    Get PDF
    Agent-based models (ABMs) are an increasingly popular tool in the social sciences. This trend seems likely to continue, so that they will become widely used in geography and in urban and regional planning. We present an overview of examples of these models in the life sciences, economics, planning, sociology, and archaeology. We conclude that ABMs strongly tend towards an individualist view of the social world. This point is reinforced by closer consideration of particular examples. This discussion pays attention to the inadequacy of an individualist model of society with reference to debates in social theory. We argue that because models are closed representations of an open world it is important that institutions and other social structures be explicitly included, or that their omission be explained. A tentative explanation for the bias of ABMs is offered, based on an examination of early research in artificial intelligence and distributed artificial intelligence from which disciplines the approach is derived. Some implications of these findings are discussed. We indicate some useful research directions which are beginning to tackle the individualism issue directly. We further note that the underlying assumptions of ABMs are often hidden in the implementation details. We conclude that such models must be subject to critical examination of their assumptions, and that model builders should engage with social theory if the approach is to realise its full potential

    Zebra battery technologies for all electric smart car

    Get PDF
    This paper describes the operational behaviour and advantages of the high temperature, sodium nickel chloride (Zebra) battery, for use in all electric urban (city) vehicles. It is shown that an equivalent parallel electrical circuit can be employed to accurately simulate the electrochemical behaviour inherent in the most recent generation of Zebra cells. The experimental procedure is outlined and summary attributes of the investigation validated by both simulation studies, and experimentally, via measurements from a prototype battery module intended for use in an all electric smart ca

    The impact of sloshing on the intra-group medium and old radio lobe of NGC 5044

    Full text link
    We present temperature and abundance maps of the central 125 kpc of the NGC 5044 galaxy group, based an a deep XMM-Newton observation. The abundance map reveals an asymmetrical abundance structure, with the centroid of the highest abundance gas offset ~22 kpc northwest of the galaxy centre, and moderate abundances extending almost twice as far to the southeast than in any other direction. The abundance distribution is closely correlated with two previously-identified cold fronts and an arc--shaped region of surface brightness excess, and it appears that sloshing, induced by a previous tidal encounter, has produced both the abundance and surface brightness features. Sloshing dominates the uplift of heavy elements from the group core on large scales, and we estimate that the southeast extension (the tail of the sloshing spiral) contains at least 1.2x10^5 solar masses more iron than would be expected of gas at its radius. Placing limits on the age of the encounter we find that if, as previously suggested, the disturbed spiral galaxy NGC 5054 was the perturber, it must have been moving supersonically when it transited the group core. We also examine the spectral properties of emission from the old, detached radio lobe southeast of NGC 5044, and find that they are consistent with a purely thermal origin, ruling out this structure as a significant source of spectrally hard inverse-Compton emission.Comment: 10 pages, 8 figures, 2 tables, accepted for publication in MNRAS; updated references and fixed typos identified at proof stag

    Robust quantum state engineering through coherent localization in biased-coin quantum walks

    Get PDF
    We address the performance of a coin-biased quantum walk as a generator for non-classical position states of the walker. We exploit a phenomenon of coherent localisation in the position space --- resulting from the choice of small values of the coin parameter and assisted by post-selection --- to engineer large-size coherent superpositions of distinguishable position states of the walker. The protocol that we design appears to be remarkably robust against both the actual value taken by the coin parameter and strong dephasing-like noise acting on the spatial degree of freedom. We finally illustrate a possible linear-optics implementation of our proposal, suitable for both bulk and integrated-optics platforms.Comment: 7 pages, 7 figure
    corecore