• [2012-07-13]

  Date posted: May 4, 2012 Simultaneous Three-Dimensional Impacts with Friction and Compliance

 Title：Simultaneous Three-Dimensional Impacts with Friction and Compliance Lecturer：Yan-Bin Jia Time： 9:30 am Date:  May 9，2012.   Venue：Conference Room 212, Building No.1, Engineering College Host：Prof. Cai-Shan Liu   Abstract：     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. This talk will discuss computation of tangential impulse from normal impulse at a colliding point between two bodies in the presence of tangential compliance and friction. 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. It will also 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. Within a state, (normal) impulses are coupled differentially subject to relative stiffnesses at the active contact points and the strain energies stored there. Such coupling may cause restart of compression from restitution during a single impact. The two impact models are integrated, with one copy of the compliance model placed at each contact with a physical experiment for the massé shot, which is a difficult trick in billiards.

About the speaker：
    Yan-Bin Jia received his PHD in Robotics from Carnegie Mellon University in 1997. He is an associate professor of mechanical engineering at the University of Nebraska-Lincoln (UNL). His research interests include modeling and grasping of deformable objects, simultaneous impacts with compliance, billiard robots, and shape localization, recognition, and reconstruction from tactile data. and Nanostructures. Yan-Bin Jia received the US National Science Foundation CAREER Award in 2002.