Identifying and mitigating residual vibrations in wave-based control of lumped, flexible systems

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Wave-based control (WBC) is a technique for motion control of under-actuated flexible sys-tems. It envisages actuator motion as launching a motion wave into the system, while simulta-neously absorbing any wave returning from the system. For rest-to-rest motion the net launch displacement is set at half the target displacement. In absorbing the returning wave and vibra-tions, WBC moves the system the remaining distance to the target, with zero steady-state error. The focus of this paper is on very small residual vibrations around the target position which can endure for a long time after arrival at target. This issue was discovered through a recent devel-opment within WBC context on controlling complex two-dimensional, mass-spring, beam-like arrays. To date their existence has been unidentified. This paper investigates and interprets the nature of these vibrations, explains and identifies them based on wave ideas, and finally offers a new wave-based approach to mitigate or suppress them. It also discusses their implication, not just for WBC but for the general problem of control of flexible systems

Dynamic political contexts and power asymmetries: the cases of the Blue Nile and the Yarmouk Rivers

This paper explores the evolving patterns of hydropolitical relations in the dynamic contexts of Yarmouk and Blue Nile Rivers in comparison. The analysis aims at shedding light over the complex implications that recent political and social changes have aroused for the water disputes between Jordan and Syria on the one hand, and Ethiopia and Egypt on the other. In both basins, cooperative efforts toward the integrated management of transboundary waters have been only partially effective and largely undermined by the perpetuation of unilateral actions by riparian states. In the case studies, the lack of a basin-wide vision over the control and use of shared waters has resulted in disputes among the basin states and ultimately in an unsustainable, unfair, and unwise utilization of the resources. This paper argues that a substantive and effective integration of national water policies is unlikely to occur, unless power asymmetries are properly addressed in order to overcome the likelihood of hegemonic regimes

Hydropolitics and issue-linkage along the Orontes River Basin: an analysis of the Lebanon–Syria and Syria–Turkey hydropolitical relations

The Orontes River Basin is among the least researched transboundary water basins in the Middle East. The few studies on the Orontes have two main theoretical and empirical shortcomings. First, there is a lack of critical hydropolitics studies on this river. Second, those studies focus on either the Turkish–Syrian or Lebanese–Syria relations rather than analysing the case in a holistic way. Gathering both primary (international agreements, government documents, political statements and media outlets) and secondary sources, this paper seeks to answer how could Syria, as the basin hydro-hegemon, impose its control on the basin? This study argues that the lack of trilateral initiatives, which is also reflected in academic studies, is primarily due to asymmetrical power dynamics. Accordingly, Syria played a dual-game by excluding each riparian, Turkey and Lebanon, and it dealt with the issue at the bilateral interaction. Syria has used its political influence to maintain water control vis-à-vis Lebanon, while it has used non-cooperation with Turkey to exclude Turkey from decision-making processes. The paper also argues that the historical background and the political context have strongly informed Syria’s water policy. Finally, given the recent regional political developments, the paper finds that Syria’s power grip on the Orontes Basin slowly fades away because of the changes in the broader political context

An enhanced control technique for the elimination of residual vibrations in flexible-joint manipulators

One method used to reduce or eliminate residual vibrations is to modify the input signal by using previously determined system parameters. In order to eliminate the residual vibration completely, these system parameters must be very accurately determined. In real systems, achieving such accuracy may not always be possible. To address this problem and to provide a solution, a new residual vibration elimination method is introduced in this study, which has proven to be useful especially in cases of uncertain parameters of estimated or predicted systems. It is shown that the technique is capable of handling high levels of uncertainty and is able to successfully eliminate or reduce residual vibrations in flexible systems. In this approach, the desired position of the system is primarily divided into two equal parts, and the generated input signal is used to eliminate vibration. This study presents theoretical and experimental results of the techniques applied to a flexible mechanical system; a comparative study of robustness performance is also provided. Simulation and experimental results show that the oscillations are considerably decreased with a high degree of robustness in the presence of uncertainty regarding system parameters. © 2014 Journal of Mechanical Engineering. All rights reserved

Experimental investigation of performance and emission parameters changes on diesel engines using anisole additive

Trans tech publications2013 2nd International Conference on Mechanical Design and Power Engineering, ICMDPE 2013 --29 November 2013 through 30 November 2013 -- Beijing --In this study, effect of anisole additive into the diesel fuel on performance and emission parameters of diesel engines was investigated. Instead of structural changes which are more difficult and expensive, development of fuel technologies is preferred to provide reduction on exhaust gas emissions which are harmful to environment and human health. Therefore, in this experimental study, anisole was used as additive into diesel fuel with the volumetric ratio of 1,5%, 3% and 5%. The performance characteristics and exhaust emissions of a four cylinder, four stroke, naturally aspirated, water cooled, direct injection compression ignition engine fueled with modified fuels were analyzed. Engine was subjected constant speed, full load conditions during tests. Engine power, torque, specific fuel consumption, carbon monoxide, nitrogen oxide and carbon dioxide emissions were measured and results were evaluated. Changes in performance parameters were negligible for all ratios of modified fuels except specific fuel consumption. Finally, while carbon monoxide gas emissions were increased with anisole additive, carbon dioxide and nitrogen oxide gas emissions were decreased. © (2014) Trans Tech Publications, Switzerland

Comparison of robust input shapers for elimination of residual vibrations

Trans tech publications2013 2nd International Conference on Mechanical Design and Power Engineering, ICMDPE 2013 --29 November 2013 through 30 November 2013 -- Beijing --Input shaping is a feedforward control technique for improving the settling time and positioning accuracy, while minimizing residual vibrations. Shaped command profiles are generated by convolving a sequence of impulses. To design an input shaping controller, estimates of the system natural frequency and damping ratio are required. However, real systems cannot be modeled exactly, making the robustness to modeling errors an important consideration. Many robust input shapers have been developed, but robust shapers typically have longer durations that slow the system response. This creates a compromise between shaper robustness and rise time. This paper analyses the compromise between shaper duration and robustness for several robust input shapers. © (2014) Trans Tech Publications, Switzerland