Stabilization of delayed teleoperation systems using time domain passivity control

It is known that time delay in bilateral teleoperation can drive a system to instability. Time Domain Passivity Control (TDPC) deals with the stabilization of haptic interfaces in teleoperation using the notion of passivity directly in the continuous time variables like force and velocity. In this work, first it is shown that TDPC can be extended to stabilize the time-delayed teleoperation by considering the communication channel as an active component and then, to design passivity controllers for it on master side using a Kalman filter based recursive prediction of slave side energy. However, such a scheme is prone to large corrective impulses generated by passivity controllers as the scheme only comes into effect when the net energy goes negative, while on other time instants it stays out of the control loop in order to provide maximally transparent teleoperation. These impulses degrade the performance of teleoperator. It is thus further proposed, that the derivative of net energy should also be computed in real-time, and as soon as this term becomes negative, indicating a decline in the net energy, the passivity controllers should immediately compensate this active behavior. This forces the system to always dissipate energy and thus stop the occasional accumulation of a large amount of negative energy. In addition to that, parabolic power integration is employed to provide non-linear estimation of net energy in the communication channel. The above developed approach is then used to stabilize time-varying delays. In order to provide a time-base for the predictor, a first order one-step ahead prediction of RTT (Round Trip Time) is used. Beta distributed and TrueTime network simulator based delays are used to evaluate the system performance. Simulation results are given showing the efficacy of the proposed approach.Es ist bekannt, dass eine Zeitverzögerung in bilateraler Teleoperation ein System bis zur Instabilität führen kann. Time Domain Passivity Control (TDPC) behandelt die Stabilisierung von haptischen Ein- und Ausgabegeräten mittels der Idee von Passivität (Passivity), bezogen auf die stetigen Zeitvariablen wie Kraft und Geschwindigkeit. In dieser Arbeit wurde zuerst demonstriert, dass die Erweiterung des Konzeptes von TDPC für die Stabilisierung der zeitverzögerten Teleoperation eingesetzt werden kann, falls der Kommunikations-Kanal als ein aktives Bauteil angesehen wird. Anschließend wird ein auf einem rekursiven Kalman-Filter basierender Passivitäts-Controller entwickelt, der die Gesamtenergie des Slavesystems vorhersagt. Durch diese Vorgehensweise werden jedoch große Impulse durch den Passivitäts-Controller erzeugt, weil dieser ausschließlich dann aktiv wird, falls die Energie im Netz negativ wird. Ist die Energie im Netz positiv, ist der Regelkreis nicht aktiv, damit die Übertragung der Signale über das Kommunikationsnetz nicht beeinflusst wird. Diese Impulse können die Funktion eines Teleoperators stark beeinträchtigen. Es wird deshalb vorgeschlagen, die Ableitung der Energie im Netz in Echtzeit zu berechnen, damit, sobald die Ableitung negativ wird, was einen Abfall der Energie andeutet, der Passivitäts-Controller aktiv eingreifen kann, um das Netz wieder zu stabilisieren. Dies erzwingt eine ständige Verminderung der Energie im System, und somit ist das System gegen die zeitweise Akkumulation von großen negativen Energiemengen abgesichert. Darüber hinaus wird eine parabolische Integration eingesetzt, um die nicht-lineare Schätzung der Gesamtenergie im Kommunikations-Kanal zu gewährleisten. Der oben entwickelte Ansatz wird dazu benutzt, um stochastische Totzeiten zu stabilisieren. Um eine Zeitbasis für die Schätzung der Netzenergie zu erhalten, wird die Rundreisezeit (RTT: Round Trip Time) mit Hilfe eines Prädiktors erster Ordnung geschätzt. Basierend auf der Betaverteilung und einem Programm namens ,,TrueTime network simulator werden Totzeiten benutzt, um die Systemstabilität zu überprüfen. Simulationsergebnisse zeigen die Wirksamkeit des vorgeschlagenen Verfahrens

STR-956: PRESTRESSED TIMBER STRUCTURES FOR MULTI-STORIED BUILDINGS: FROM THEORY TO PRACTICE

A new generation of buildings have been designed in recent years with an innovative structural system developed in New Zealand over the last decade. Conventional post-tensioning is combined with timber structures made of engineered wood products to produce highly efficient systems suitable for supporting long floor spans. The moment connections are particularly useful in structures designed for seismic regions. The post-tensioning ensures self-centering in addition to ductility provided by additional energy dissipating elements within the connections. Extensive experimental and numerical studies have confirmed the expected performance of the systems and design procedures have been developed for practical applications. A summary of the evolution of the concept and developments are presented here. The concept has already been applied in design of a number of structures within and outside New Zealand. The applications are reviewed with discussion on the details implemented. The system has excellent prospect of emerging as a practical alternative for multi-storied timber buildings. Arrangements have been made recently to utilize the technology in North America and initiatives are currently underway for implementation in Canada

On-Road Vehicular Emission Inventory in View of Its Distribution Over Dhaka City, Bangladesh: A Bottom-Up Modelling Approach to Support Sustainability Assessment

The study aims to account emissions from the vehicular sources of Dhaka city, more specifically, for the major roads of the city. Transport sector being one of the highest contributors of air emissions in the city makes it important to investigate the factors that catalyse the on-road emissions and acts as constraints in attaining environmental sustainability. Due to several reasons, on road congestion level is very high in the city that reduces the fuel efficiency of the vehicles. The research tends to reflect the fact while accounting the emissions with a meso scale bottom-up modelling approach, where the road by road vehicle characteristics are considered. The study estimated emissions of criteria pollutants, greenhouse gases and toxic substances by adopting a bottom-up technique to cover the major roads of the city in the current state of operation, where the actual moving pattern of the vehicles on different city roads were considered. Detailed survey was conducted in the Dhaka city roads in the year 2012 to collect diurnal traffic volume, speed profiles and vehicle composition. In general, the results suggested that the roads with higher traffic volume coupled with traffic congestion contributed at a higher rate to the emission load. The increasing trend of private vehicles along with uncontrolled traffic movement keeps the city under the threat of the harmful level of emission if proper management strategy is not adopted. As considering the detailed system-data can offer greater proximity to identify the key areas of concern, the methodological approach of this research can be adopted by others as well concerned with the on-road vehicular emissions, and can work towards attaining sustainability by reducing emissions and increasing fuel efficiency. Keywords: Emission inventory; bottom-up modelling; vehicle speed profile; Dhaka city, Banglades

Non-profit Sector in Pakistan: Government Policy and Future Issues

The non-profit sector remains relatively small and underdeveloped in Pakistan. During the decade of the 1990s, it has demonstrated some nascent growth resulting from a number of favourable factors like the return to democracy, the growing push towards deregulation and privatisation, the process of globalisation and the emergence of international coalitions of civil society and the deterioration in the financial position of governments which has limited the public provision of social services. The objective of this paper is to examine the role played by government policy in fostering this process of growth of the non-profit sector of Pakistan and to review the key issues faced by the sector at this time. Of particular concern are, first, the overall posture of the government towards the non-profit sector, the types of policies in place, and the underlying philosophy or principles that guide policy-making. Second, the forms of support to the non-profit sector by different levels of government. Third, the posture of international organisations and supranational governments towards local non-profit organisations and, forth, the major issues facing the non-profit sector at the present time. The objective of this paper is to analyse government policy towards the nonprofit sector in Pakistan over the last two decades and review some major issues facing the sector at the present time. It is important to note that analysis presented here does not cover the period of current government.

Simple and efficient solutions to the problems associated with acoustic echo cancellation

This dissertation is a collection of papers that addresses several important problems associated with acoustic/line echo cancellation (AEC/LEC), specifically double-talk and echo-path change detection. A double-talk detector is used to freeze AEC filter\u27s adaptation during periods of near-end speech. This dissertation presents three different novel double-talk detection schemes. Simulations demonstrate the efficiency of the proposed algorithms --Abstract, page iii

Fatigue Life of Pultruded and Hand Lay-Up GFRP Exposed to Different Environmental Conditions.

The use of unidirectional Glass Fiber Reinforced Polymer (GFRP) composites to reinforce glulam beams in tension has been proven by researchers at University of Maine and others to improve both allowable strength and ductility. The addition of 3% E-glass FRP has been shown to increase the allowable flexural strength by as much as 100%. These promising findings can be used in practice only if the GFRP will maintain a major proportion of its strengthfstiffness mechanical properties over the life of the structure. This study focuses on the fatigue life of two types of E-glasslphenolic GFRP (hand lay-up and pultruded) with special emphasis on the effect of environmental degradation on the fatigue life of pultruded GFRP. Fatigue life of pultruded GFRP was evaluated after treatment in salt water, hot water, freezethaw, and UV weathering. Static tests indicate that hot water (45°C) causes the higher reduction in tensile strength. The Young\u27s modulus did not change significantly for any of the exposed specimens. Fatigue tests were conducted at constant amplitude at a frequency of 20H2, and S-N curves were developed for each exposure group. The results show that except for UV weathering, the fatigue life of all the exposed specimens exhibited slight statistically significant improvement for low stress fatigue tests. Residual strength tests conducted at 10% of ultimate strength exhibited no statistically significant (a=0.05) reduction in tensile strength or modulus at 3 million cycles of fatigue. The fatigue data was plotted using S-N diagrams and modeled using Loglinear equations. From the models, allowable strength for design purposes was recommended using statistical analysis. One-sided lower 95% tolerance limit for 95% of the population (5% LTL) were developed for pultruded control and hand lay-up specimens

Comparison of actinides and fission products recycling scheme with the normal plutonium recycling scheme in fast reactors

Multiple recycling of actinides and non-volatile fission products in fast reactors through the dry re-fabrication/reprocessing atomics international reduction oxidation process has been studied as a possible way to reduce the long-term potential hazard of nuclear waste compared to that resulting from reprocessing in a wet PUREX process. Calculations have been made to compare the actinides and fission products recycling scheme with the normal plutonium recycling scheme in a fast reactor. For this purpose, the Karlsruhe version of isotope generation and depletion code, KORIGEN, has been modified accordingly. An entirely novel fission product yields library for fast reactors has been created which has replaced the old KORIGEN fission products library. For the purposes of this study, the standard 26 groups data set, KFKINR, developed at Forschungszentrum Karlsruhe, Germany, has been extended by the addition of the cross-sections of 13 important actinides and 68 most important fission products. It has been confirmed that these 68 fission products constitute about 95% of the total fission products yield and about 99.5% of the total absorption due to fission products in fast reactors. The amount of fissile material required to guarantee the criticality of the reactor during recycling schemes has also been investigated. Cumulative high active waste per ton of initial heavy metal is also calculated. Results show that the recycling of actinides and fission products in fast reactors through the atomics international reduction oxidation process results in a reduction of the potential hazard of radioactive waste

Advanced raman amplification techniques for high capacity and broadband coherent optical transmission systems

This thesis presents a detailed study of different advanced Raman fibre laser (RFL) based amplification schemes and the development of novel broadband distributed and discrete Raman amplifiers in order to improve the transmission performance of modern high capacity, long-haul coherent optical systems. The numerical modelling of different Raman amplifier techniques including power distribution of signal, pump and noise components, RIN transfer from pump to signal, broadband gain optimization and so on have been described in details.The RIN and noise performances of RFL based distributed Raman amplifiers (DRAs) with different span lengths, forward pump powers and input reflection levels have been characterized experimentally. It has been shown through coherent transmission experiment that, in order to improve pump power efficiency, a low level of input reflection up to ~10% can be allowed without increasing the Q factor penalty > 1dB due to additional signal RIN penalty.A novel broadband (>10nm) first order Raman pump is developed for use as a forward pump in long-haul transmission experiment. Significant signal RIN mitigation up to 10dB compared with conventional low RIN, narrowband sources was obtained for bidirectional DRA schemes. Long-haul coherent transmission experiments with 10×120Gb/s DP-QPSK system were carried out in are circulating loop setup using the proposed broadband pump in bidirectional and backward only pumping configurations. The maximum transmission reach up to ~8330km was reported with first order broadband pumped bidirectional DRA, with transmission reach extensions of 1250km and1667km compared with conventional backward only and first order semiconductor pumped bidirectional pumping scheme respectively.Finally, a novel design of bidirectional broadband distributed DRA is proposed to reduce the noise figure tilt and improve the WDM transmission performances. Furthermore, broadband discrete Raman amplifier schemes in dual stage configuration are also shown for high gain, high output power, low noise and low nonlinear performance

Joint Planck and WMAP Assessment of Low CMB Multipoles

The remarkable progress in cosmic microwave background (CMB) studies over past decade has led to the era of precision cosmology in striking agreement with the $\Lambda$CDM model. However, the lack of power in the CMB temperature anisotropies at large angular scales (low-$\ell$), as has been confirmed by the recent Planck data also (up to $\ell=40$), although statistically not very strong (less than $3\sigma$), is still an open problem. One can avoid to seek an explanation for this problem by attributing the lack of power to cosmic variance orcan look for explanations i.e., different inflationary potentials or initial conditions for infl ation to begin with, non-trivial topology, ISW effect etc. Features in the primordial power spectrum (PPS) motivated by the early universe physics has been the most common solution to address this problem. In the present work we also follow this approach and consider a set of PPS which have features and constrain the parameters of those using WMAP 9 year and Planck data employing Markov-Chain Monte Carlo (MCMC) analysis. The prominent feature of all the models of PPS that we consider is an infra-red cut off which leads to suppression of power at large angular scales. We consider models of PPS with maximum three extra parameters and use Akaike information criterion ($AIC$) and Bayesian information criterion ($BIC$) of model and Bayesian information criterion ($BIC$) of model selection to compare the models. For most models, we find good constraints for the cut off scale $k_c$, however, for other parameters our constraints are not that good. We find that sharp cut off model gives best likelihood value for the WMAP 9 year data, but is as good as power law model according to $AIC$. For the joint WMAP 9+Planck data set, Starobinsky model is slightly preferred by $AIC$ which is also able to produce CMB power suppression up to $\ell\leq30$ to some extent.Comment: 27 pages, 10 figures, 3 tables, matches with the published version, abstract is shortened to keep it within arXiv's limit (1920 characters