Avoiding space robot collisions utilizing the NASA/GSFC tri-mode skin sensor

Sensor based robot motion planning research has primarily focused on mobile robots. Consider, however, the case of a robot manipulator expected to operate autonomously in a dynamic environment where unexpected collisions can occur with many parts of the robot. Only a sensor based system capable of generating collision free paths would be acceptable in such situations. Recently, work in this area has been reported in which a deterministic solution for 2DOF systems has been generated. The arm was sensitized with 'skin' of infra-red sensors. We have proposed a heuristic (potential field based) methodology for redundant robots with large DOF's. The key concepts are solving the path planning problem by cooperating global and local planning modules, the use of complete information from the sensors and partial (but appropriate) information from a world model, representation of objects with hyper-ellipsoids in the world model, and the use of variational planning. We intend to sensitize the robot arm with a 'skin' of capacitive proximity sensors. These sensors were developed at NASA, and are exceptionally suited for the space application. In the first part of the report, we discuss the development and modeling of the capacitive proximity sensor. In the second part we discuss the motion planning algorithm

Material Strength in Polymer Shape Deposition Manufacturing

Shape Deposition Manufacturing (SDM) is a layered manufacturing process involving an iterative combination of material addition and material removal. Polymer SDM processes have used castable thermoset resins to build a variety of parts. The strength of such parts is determined by the bulk material properties of the part materials and by their interlayer adhesion. This paper describes tensile testing of three thermoset resins used for SDM - two polyurethane resins and one epoxy resin. Both monolithic specimens and specimens with two interlayer !nterfaces were tested. Interlayer tensile strengths were found to vary greatly among the three matenals, from 5-40 MPa.Mechanical Engineerin

Enhancing Ionic Conductivity of Bulk Single Crystal Yttria-Stabilized Zirconia by Tailoring Dopant Distribution

We present an ab-initio based kinetic Monte Carlo model for ionic conductivity in single crystal yttria-stabilized zirconia. Ionic interactions are taken into account by combining density functional theory calculations and the cluster expansion method and are found to be essential in reproducing the effective activation energy observed in experiments. The model predicts that the effective energy barrier can be reduced by 0.15-0.25 eV by arranging the dopant ions into a super-lattice.Comment: Submitted to Phys. Rev. Lett. on 8/3/2010 (in review

Project MAXWELL: Towards Rapid Realization of Superior Products

We describe a new methodology for the design and manufacture of mechanical components. The methodology is a synergism of a new, mathematically rigorous procedure for the concurrent design of shape and material composition of components, and a new manufacturing process called MD* for their realization. The concurrent design strategy yields information about the global shape of the component and its material composition. The fabrication of such designs with novel microstructural configurations require unconventional manufacturing processes. MD* is a shape deposition process for the free-form fabrication of parts from single or composite materials and is ideally suited for realizing the aforementioned designs. Project MAXWELL, therefore, promotes the use of layered manufacturing beyond prototyping tasks and offers the possibility of their integration into the mainstream product development and fabrication process..Mechanical Engineerin

Manufacturing Mechatronics Using Thermal Spray Shape Deposition

A new technology for manufacturing mechatronics is described. The technique is based on recursive masking and deposition of thermally sprayed materials. Using these methods, mechanical structures can be created that embed and interconnect electronic components. This results in highly integrated mechatronic devices. A simple, electromechanical artifact was designed and produced to assess the feasibility of these techniques. The details and limitations of this project will be discussed. Areas of future research are identified which are aimed at realizing the full potential of this emerging manufacturing process.Mechanical Engineerin

Avoiding space robot collisions utilizing the NASA/GSFC tri-mode skin sensor

A capacitance based proximity sensor, the 'Capaciflector' (Vranish 92), has been developed at the Goddard Space Flight Center of NASA. We had investigated the use of this sensor for avoiding and maneuvering around unexpected objects (Mahalingam 92). The approach developed there would help in executing collision-free gross motions. Another important aspect of robot motion planning is fine motion planning. Let us classify manipulator robot motion planning into two groups at the task level: gross motion planning and fine motion planning. We use the term 'gross planning' where the major degrees of freedom of the robot execute large motions, for example, the motion of a robot in a pick and place type operation. We use the term 'fine motion' to indicate motions of the robot where the large dofs do not move much, and move far less than the mirror dofs, such as in inserting a peg in a hole. In this report we describe our experiments and experiences in this area

Representation of acoustic communication signals by insect auditory receptor neurons

Despite their simple auditory systems, some insect species recognize certain temporal aspects of acoustic stimuli with an acuity equal to that of vertebrates; however, the underlying neural mechanisms and coding schemes are only partially understood. In this study, we analyze the response characteristics of the peripheral auditory system of grasshoppers with special emphasis on the representation of species-specific communication signals. We use both natural calling songs and artificial random stimuli designed to focus on two low-order statistical properties of the songs: their typical time scales and the distribution of their modulation amplitudes. Based on stimulus reconstruction techniques and quantified within an information-theoretic framework, our data show that artificial stimuli with typical time scales of >40 msec can be read from single spike trains with high accuracy. Faster stimulus variations can be reconstructed only for behaviorally relevant amplitude distributions. The highest rates of information transmission (180 bits/sec) and the highest coding efficiencies (40%) are obtained for stimuli that capture both the time scales and amplitude distributions of natural songs. Use of multiple spike trains significantly improves the reconstruction of stimuli that vary on time scales <40 msec or feature amplitude distributions as occur when several grasshopper songs overlap. Signal-to-noise ratios obtained from the reconstructions of natural songs do not exceed those obtained from artificial stimuli with the same low-order statistical properties. We conclude that auditory receptor neurons are optimized to extract both the time scales and the amplitude distribution of natural songs. They are not optimized, however, to extract higher-order statistical properties of the song-specific rhythmic patterns