No description available.

Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: William Singhose; Committee Member: John-Paul Clarke; Committee Member: Kok-Meng Lee; Committee Member: Patricio Vela; Committee Member: Rhett Mayor.

The rapid movement of machines is a challenging control problem because it often results in high levels of vibration. As a result, flexible machines are typically moved relatively slowly to avoid such vibration. Therefore, motion-induced vibration limits the operational speed of the system. Input shaping is one method that eliminates motion-induced vibrations by intelligently designing the reference command such that system vibration is cancelled. It has been successfully implemented on a number of systems, including bridge and tower cranes. The implementation of input shaping on cranes provides a substantial increase in the operational efficiency. Unfortunately, most cranes, once erected, have limited or no base mobility. This limits their workspace. The addition of base mobility could help extend the operational effectiveness of cranes and may also expand crane functionality. Mobile cranes may also be better suited for use in harsh and/or distant environments. Teleoperation of oscillatory systems, such as cranes, then becomes another avenue for advancement of crane functionality. Base mobility in cranes presents both additional control challenges and operational opportunities. A crane with base mobility is redundantly actuated (overactuated), such that multiple combinations of actuators can be used to move a payload from one location to another. This opens the possibility for the selection of a combination of actuation that provides both rapid motion and limited system vibration. The extension of input shaping into this operational domain will provide a method to maximize effective actuation combinations. Toward addressing these issues, new multi-input shaping methods were developed and applied to a mobile, portable tower crane. During this development, a firm understanding of robust input shaping techniques and the compromises inherent to input shaper design was formed. In addition, input shaping was compared to other command generation techniques, namely lowpass and notch filtering, and proven to be superior for vibration reduction in mechanical systems. Another, new class of input shapers was also introduced that limit the input shaper induced overshoot in human operated systems. Finally, a series of crane operator studies investigated the application of input shaping techniques to teleoperated cranes. These studies suggested that input shaping is able to dramatically improve remote crane operator performance.

Les grues à tour sont des engins de levage utilisés de manière cyclique sur les chantiers de construction. De ce fait, la prise en compte du phénomène de fatigue dans le dimensionnement des charpentes de grue est primordiale. La fatigue est usuellement considérée dans les normes au moyen de règles déterministes ayant pour but de garantir l’intégrité de la structure sous diverses conditions d’utilisation. Bien que cette approche fournisse des résultats satisfaisants dans la plupart des cas, celle-ci ne permet pas d’évaluer le niveau de fiabilité des éléments de charpente en fonction de leur durée d’exploitation. De ce point de vue, les approches probabilistes permettent de pallier cette difficulté en proposant des outils pertinents servant à caractériser et à propager les incertitudes liées à la fatigue au travers d’un modèle mécanique. Une approche probabiliste originale permettant la prise en compte des incertitudes liées à la fatigue dans le dimensionnement des charpentes de grues à tour est proposée dans ce manuscrit. La méthode proposée est basée sur la définition de deux densités de probabilité représentant respectivement les variabilités liées à la résistance des joints soudés d’une part, et les nombreuses dispersions associées à la sollicitation des éléments de charpente d’autre part. La définition de la densité de probabilité de résistance repose sur la capitalisation d’un grand nombre de résultats d’essais d’endurance sur structures soudées, tandis que la définition de la distribution de sollicitation est basée sur une modélisation à deux niveaux tenant compte de divers jeux de données collectés sur chantier. Les résultats de l’analyse de fiabilité présentée dans ce manuscrit démontrent la pertinence des approches probabilistes dans le cadre du dimensionnement en fatigue des éléments de charpente de grue à tour. / Tower cranes are lifting appliances which are cyclically used on construction sites. Thus, the consideration of the fatigue phenomenon in the design of crane structural members is essential. This phenomenon is usually taken into account in standards by means of deterministic rules enabling to ensure structural safety under various operating conditions. Although it provides satisfactory results in most cases, the deterministic approach do not enable to evaluate the reliability of crane structural members according to their operating time. From this point of view, probabilistic approaches allow to overcome this difficulty by proposing relevant tools enabling to characterize and propagate uncertainties related to fatigue through a mechanical model. An original probabilistic approach enabling the consideration of the uncertainties related to crane members fatigue design is proposed in this manuscript. It relies on the definition of two probability density functions related respectively to the strength variability of crane welded joints on one hand, and the dispersion of operating conditions (stress) on this other hand. The definition of the strength distribution stems from the capitalization of various welded joint fatigue test results, while the characterization of the stress distribution relies on the analysis of various data sets coming from crane monitoring performed on different construction sites. The results coming from the reliability analysis presented in this manuscript show the relevance of probabilistic approaches in the frame of tower crane structural members fatigue design.