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Screw Geometry and Recent Advances in Spatial Kinematics


Dr. Dimiter Zlatanov < zlatanov@gmc.ulaval.ca >
Universite Laval

May 7, 2003 at  11:30 AM
437

The first years of the new century have brought significant discoveries in the theory and synthesis of spatial mechanisms. Whole new classes of parallel kinematic chains, with four or five degrees of freedom, have been invented. Less than a decade ago, experts could name only a few parallel devices ensuring full translational or rotational motion of a tool. Now, these mechanism families have have been joined by scores of new members, some with remarkable properties. It has become known that mobility of a kinematic chain can undergo amazing transformations at certain special configurations, called constraint singularities, which serve as gateways between seemingly unrelated operation modes. Just as remarkable are the research methods that made them possible. No computers, no symbolic or numerical manipulations were involved --- only careful geometric reasoning, aided mostly by the theory of screws. The purpose of this talk is to present some of the discoveries and show the value of the relevant methodology to researchers and designers alike. As an illustration, the screw systems of freedoms and constraints will be applied to reveal the mobility properties of parallel mechanisms.