Grasp Analysis Tools for Synergistic Underactuated Robotic Hands

Despite being a classical topic in robotics, the research on dexterous robotic hands still stirs a lively research activity. The current interest is especially attracted by underactuated robotic hands where a high number of degrees of freedom (DoFs), and a relatively low number of degrees of actuation co-exist. The correlation between the DoFs obtained through a wise distribution of actuators is aimed at simplifying the control with a minimal loss of dexterity. In this sense, the application of bio-inspired principles is bringing research toward a more conscious design. This work proposes new, general approaches for the analysis of grasps with synergistic underactuated robotic hands.After a review of the quasi-static equations describing the system, where contact preload is also considered, two different approaches to the analysis are presented. The first one is based on a systematic combination of the equations. The independent and the dependent variables are defined, and cause-effect relationships between them are found. In addition, remarkable properties of the grasp, as the subspace of controllable internal force and the grasp compliance, are worked out in symbolic form. Then, some relevant kinds of tasks, such as pure squeeze, spurious squeeze and kinematic grasp displacements, are defined, in terms of nullity or non-nullity of proper variables. The second method of analysis shows how to discover the feasibility of the pre-defined tasks, operating a systematic decomposition of the solution space of the system. As a result, the inputs to be given to the hand, in order to achieve the desired system displacements, are found. The study of the feasible variations is carried out arriving at the discovery of all the combinations of nullity and/or non-nullity variables which are allowed by the equations describing the system. Numerical results are presented both for precision and power grasps, finding forces and displacements that the hand can impose on the object, and showing which properties are preserved after the introduction of a synergistic underactuation mechanism

Exact N=2 Supergravity Solutions With Polarized Branes

We construct several classes of exact supersymmetric supergravity solutions describing D4 branes polarized into NS5 branes and F-strings polarized into D2 branes. These setups belong to the same universality class as the perturbative solutions used by Polchinski and Strassler to describe the string dual of N=1* theories. The D4-NS5 setup can be interpreted as a string dual to a confining 4+1 dimensional theory with 8 supercharges, whose properties we discuss. By T-duality, our solutions give Type IIB supersymmetric backgrounds with polarized branes.Comment: 22 pages. v2 - references added, details clarifie

Biomimetic grasp planning for cortical control of a robotic hand

In this paper we outline a grasp planning system designed to augment the cortical control of a prosthetic arm and hand. A key aspect of this system it the ability to combine online user input and autonomous planning to enable the execution of stable grasping tasks. While user input can ultimately be of any modality, the system is being designed to adapt to partial or noisy information obtained from grasp-related activity in the primate motor cortex. First, principal component analysis is applied to the observed kinematics of physiologic grasping to reduce the dimensionality of hand posture space and simplify the planning task for on-line use. The planner then accepts control input in this reduced-dimensionality space, and uses it as a seed for a hand posture optimization algorithm based on simulated annealing. We present two applications of this algorithm, using data collected from both primate and human subjects during grasping, to demonstrate its ability to synthesize stable grasps using partial control input in real or near-real time

A Path Integral Approach To Noncommutative Superspace

A path integral formula for the associative star-product of two superfields is proposed. It is a generalization of the Kontsevich-Cattaneo-Felder's formula for the star-product of functions of bosonic coordinates. The associativity of the star-product imposes certain conditions on the background of our sigma model. For generic background the action is not supersymmetric. The supersymmetry invariance of the action constrains the background and leads to a simple formula for the star-product.Comment: Latex 13 pages. v2: references and footnotes adde

Synthetic Data Generation and Defense in Depth Measurement of Web Applications

Measuring security controls across multiple layers of defense requires realistic data sets and repeatable experiments. However, data sets that are collected from real users often cannot be freely exchanged due to privacy and regulatory concerns. Synthetic datasets, which can be shared, have in the past had critical flaws or at best been one time collections of data focusing on a single layer or type of data. We present a framework for generating synthetic datasets with normal and attack data for web applications across multiple layers simultaneously. The framework is modular and designed for data to be easily recreated in order to vary parameters and allow for inline testing. We build a prototype data generator using the framework to generate nine datasets with data logged on four layers: network, file accesses, system calls, and database simultaneously. We then test nineteen security controls spanning all four layers to determine their sensitivity to dataset changes, compare performance even across layers, compare synthetic data to real production data, and calculate combined defense in depth performance of sets of controls

On The Interaction Of D0-Brane Bound States And RR Photons

We consider the problem of the interaction between D0-brane bound state and 1-form RR photons by the world-line theory. Based on the fact that in the world-line theory the RR gauge fields depend on the matrix coordinates of D0-branes, the gauge fields also appear as matrices in the formulation. At the classical level, we derive the Lorentz-like equations of motion for D0-branes, and it is observed that the center-of-mass is colourless with respect to the SU(N) sector of the background. Using the path integral method, the perturbation theory for the interaction between the bound state and the RR background is developed. We discuss what kind of field theory may be corresponded to the amplitudes which are calculated by the perturbation expansion in world-line theory. Qualitative considerations show that the possibility of existence of a map between the world-line theory and the non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are corrected, very small change

Interaction between M2-branes and Bulk Form Fields

We construct the interaction terms between the world-volume fields of multiple M2-branes and the 3- and 6-form fields in the context of ABJM theory with U($N$)$\times$U($N$) gauge symmetry. A consistency check is made in the simplest case of a single M2-brane, i.e, our construction matches the known effective action of M2-brane coupled to antisymmetric 3-form field. We show that when dimensionally reduced, our couplings coincide with the effective action of D2-branes coupled to R-R 3- and 5-form fields in type IIA string theory. We also comment on the relation between a coupling with a specific 6-form field configuration and the supersymmetry preserving mass deformation in ABJM theory.Comment: 30 pages, version to appear in JHE