In this paper we develop a robust controller based on variable structure systems (VSS) control theory for the stabilization of a class of Underactuated Mechanical Systems. This controller is based on a noncollocated partial feedback linearization of the underactuated system with a particular choice of the additional control for which the design is made using the sliding mode approach. Simulatio...

The lecture presents an overview of some recent results of the work carried out at Alta on the hydrodynamic design and rotordynamic fluid forces of cavitating turbopumps for liquid propellant feed systems of modern rocket engines. The reduced order models recently developed for preliminary geometric definition and noncavitating performance prediction of tapered-hub axial inducers and centrifuga...

We study hexagon patterns in non-Boussinesq convection of a thin rotating layer of water. For realistic parameters and boundary conditions we identify various linear instabilities of the pattern. We focus on the dynamics arising from an oscillatory side-band instability that leads to a spatially disordered chaotic state characterized by oscillating (whirling) hexagons. Using triangulation we ob...

The whirling helical structure obtained when pouring honey onto toast may seem like an easy enough problem to solve at breakfast. Specifically, one would hope that a quick back-of-the-envelope scaling argument would help rationalize the observed behaviour and predict the coiling frequency. Not quite: multiple forces come into play, both in the part of the flow stretched by gravity and in the co...

In this paper we develop an intelligent controller on the basis of Genetic Algorithms for the stabilization of a class of Underactuated Mechanical Systems. First we develop a static State Feedback Controller with inner noncollocated partial feedback linearization loop to stabilize the nominal system. Second, we develop a Genetic algorithm controller to maintain system stabilization and to adapt...

Motivated by diverse phenomena in cellular biophysics, including bacterial flagellar motion and DNA transcription and replication, we study the overdamped nonlinear dynamics of a rotationally forced filament with twist and bend elasticity. Competition between twist injection, twist diffusion, and writhing instabilities is described by coupled PDEs for twist and bend evolution. Analytical and nu...

“Voys Lessons: Whirling Words in Chaucer’s ‘House of Rumour’” examines the lability of sound and its use in the dissemination, transposition, and authorship of stories within The House of Fame , a text exemplifying the mobility and flexibility of misused or unhinged words, as expressed through sound as opposed to text. By engaging the use and interpretation of sound in contrast to words, this n...

The investigation of the parameters in screw surfaces whirling process is presented. equation trajectory relative movement workpiece and cutter parametric form taking into account ring along obtained. Appropriate graphs are plotted, which allow to make conclusion that increasing rotational speed results decrease thickness metal layer, cut during one period contact between cutter. It also show o...

Toroidal vortices are whirling disturbances rotating about a ring-shaped core while advancing in the direction normal to ring orifice. commonly found nature and being studied wide range of disciplines. Here we report experimental observation photonic toroidal vortex as new solution Maxwell's equations with use conformal mapping. The helical phase twists around closed loop leading an azimuthal l...