Finding antipodal point grasps on irregularly shaped objects

Two-finger antipodal point grasping of arbitrarily shaped smooth 2-D and 3-D objects is considered. An object function is introduced that maps a finger contact space to the object surface. Conditions are developed to identify the feasible grasping region, F, in the finger contact space. A “grasping energy function”, E , is introduced which is proportional to the distance between two grasping points. The antipodal points correspond to critical points of E in F. Optimization and/or continuation techniques are used to find these critical points. In particular, global optimization techniques are applied to find the “maximal” or “minimal” grasp. Further, modeling techniques are introduced for representing 2-D and 3-D objects using B-spline curves and spherical product surfaces

A Rapidly Reconfigurable Robotics Workcell and Its Applictions for Tissue Engineering

This article describes the development of a component-based technology robot system that can be rapidly configured to perform a specific manufacturing task. The system is conceived with standard and inter-operable components including actuator modules, rigid link connectors and tools that can be assembled into robots with arbitrary geometry and degrees of freedom. The reconfigurable "plug-and-play" robot kinematic and dynamic modeling algorithms are developed. These algorithms are the basis for the control and simulation of reconfigurable robots. The concept of robot configuration optimization is introduced for the effective use of the rapidly reconfigurable robots. Control and communications of the workcell components are facilitated by a workcell-wide TCP/IP network and device level CAN-bus networks. An object-oriented simulation and visualization software for the reconfigurable robot is developed based on Windows NT. Prototypes of the robot systems configured to perform 3D contour following task and the positioning task are constructed and demonstrated. Applications of such systems for biomedical tissue scaffold fabrication are considered.Singapore-MIT Alliance (SMA

Nuclear matter symmetry energy and the neutron skin thickness of heavy nuclei

Correlations between the thickness of the neutron skin in finite nuclei and the nuclear matter symmetry energy are studied in the Skyrme Hartree-Fock model. From the most recent analysis of the isospin diffusion data in heavy-ion collisions based on an isospin- and momentum-dependent transport model with in-medium nucleon-nucleon cross sections, a value of $L=88\pm 25$ MeV for the slope of the nuclear symmetry energy at saturation density is extracted, and this imposes stringent constraints on both the parameters in the Skyrme effective interactions and the neutron skin thickness of heavy nuclei. Predicted thickness of the neutron skin is $0.22\pm 0.04$ fm for $$Pb, $0.29\pm 0.04$ fm for $^{132}$Sn, and $0.22\pm 0.04$ fm for $$Sn.Comment: 6 pages, 4 figures, 1 table, revised version, to appear in PR

Moving HomePlug to Industrial Applications with Power-Line Communication Network

Home networking is becoming an attractive application not only for the Internet access but also for home automation. Being a high-speed and dominant standard presently, HomePlug has an important role in home LAN connecting to the Internet. For industrial applications, the Power Line Communication also has significant advances. However, the PHY/MAC technology provided by HomePlug still cannot be employed with some critical features such as real time performance, implications in the event of link and node loss. In this paper, the characteristics of HomePlug PHY/MAC, the property of power line channel, as well as the noise features of power line are analyzed. Based on HomePlug, a model of high level real-time protocol applied to industrial environment is proposed. The protocol simultaneously belongs to layer two and three, and can support real-time implementation with no loss and small delay according to the requirement in PLC networks, for targeting to develop a real time network with high speed power line media and advanced modulation.Singapore-MIT Alliance (SMA

Precessionless spin transport wire confined in quasi-two-dimensional electron systems

We demonstrate that in an inversion-asymmetric two-dimensional electron system 2DES with both Rashba and Dresselhaus spin-orbit couplings taken into account, certain transport directions on which no spin precession occurs can be found when the injected spin is properly polarized. By analyzing the expectation value of spin with respect to the injected electron state on each space point in the 2DES, we further show that the adjacent regions with technically reachable widths along these directions exhibit nearly conserved spin. Hence a possible application in semiconductor spintronics, namely, precessionless spin transport wire, is proposed.Comment: 3 pages, 4 figures, to be appeared in Journal of Applied Physics, Proceedings of the 50th MMM Conferenc