Computer science colloquia: Yan-bin Jia
| Date/Time: | Thursday, 27 Sep 2012 at 3:40 pm |
|---|---|
| Location: | B29 Atanasoff |
| Cost: | Free |
| Phone: | 515-294-6516 |
| Channel: | College of Liberal Arts and Sciences |
| Categories: | Lectures |
| Actions: | Download iCal/vCal | Email Reminder |
Impact happens when two or more bodies collide, generating very large impulsive forces in a very short period of time during which kinetic energy is first absorbed and then released after some loss. The phenomenon is common in our daily life, and indispensible in robotic manipulation tasks in which objects and/or manipulators move at high speeds. Applied research using impact has been hindered by underdeveloped computational foundations for rigid body collision.
When two bodies collide, impulse accumulates at their contact point. In the first part of this talk, Jia will discuss computation of tangential impulse from normal impulse at the contact in the presence of tangential compliance and friction. The contact point is modeled as a massless particle able to move tangentially on one body while connected to an infinitesimal region on the other body via three orthogonal springs. Impact and contact mode analyses can be carried out using normal impulse rather than time as the only independent variable, unlike in the previous work. This is due to the ability of updating the energies stored on the three springs.
When three or more bodies collide, normal impulses at individual contact points are coupled differentially subject to relative stiffnesses at the active contact points and the strain energies stored there. In the second part of the talk, Jia will introduce a state transition diagram to model a frictionless multi-body collision. Each state describes a different topology of the collision characterized by the set of instantaneously active contacts. A change of state happens when a contact disappears at the end of restitution, or when a disappeared contact reappears as the relative motion of two bodies goes from separation into penetration. Impulses grow along a bounded curve with first-order continuity, and converge during the state transitions.
To solve a multi-body collision problem, the two impact models are integrated, with one copy of the compliance model placed at each contact. The entire system is driven by one normal impulse that switches among the contacts. Jia will conclude by comparing model predictions to a physical experiment for the massé shot, which is a difficult trick in billiards.
Jia's research interests include robotics, modeling and grasping of deformable objects, multiple impacts with compliance, and shape localization, recognition, and reconstruction from tactile data. Jia received the U.S. National Science Foundation CAREER Award in 2002. He was an associate editor of the IEEE Transactions on Automation Science and Engineering in 2008-2011. He also served on the Conference Editorial Board of the IEEE Robotics and Automation Society from 2006 to 2008, and was a co-editor of a Special Issue (on Tactile Presence) of the International Journal of Robotics Research in 2000. His papers were a semi-finalist for the Best Conference Paper Award, a finalist for the Anton Philips Best Student Paper Award, at the IEEE International Conferences on Robotics and Automation in 1996 and 1998, respectively, and a finalist for IEEE Transactions on Robotics King-Sun Fu Memorial Best Paper Award in 2010. Jia received the B.S. degree in Computer Science from University of Science and Technology of China in 1988, and the M.S. and Ph.D. degrees in Robotics from Carnegie Mellon University in 1993 and 1997, respectively.