3,097 research outputs found

    Event-driven displays for manipulator control

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    The problem of constructing event-related information displays from multidimensional data generated by proximity, force-torque and tactile sensors integrated with the terminal device of a remotely controlled manipulator is considered. Event-driven displays are constructed by using appropriate algorithms acting on sensory data in real time. Event-driven information displays lessen the operator's workload and improve control performance. The paper describes and discusses several event-driven display examples that were implemented in the JPL teleoperator project, including a brief outline of the data handling system which drives the graphics display in real time. The paper concludes with a discussion of future plans to integrate event-driven displays with visual (TV) information

    Displays for supervisory control of manipulators

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    The problem of displaying information generated by sensors attached to the terminal device of a remotely controlled manipulator is considered. The sensors under consideration are proximity, force-torque, tactile and slip-page sensors. The paper describes and evaluates several examples that have been implemented in the JPL teleoperator project using audio and graphic displays of information generated by four proximity sensors attached to a manipulator end effector. Design schemes are also discussed related to the display of information generated by a six-dimensional force-torque sensor, a multipoint proportional tactile sensor, and a directional slippage sensor. The paper concludes with a discussion of future integrated displays of visual (TV) and handbased sensor information

    Ion implantation and low-temperature epitaxial regrowth of GaAs

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    Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ion‐implanted GaAs and the crystal quality following capless furnace annealing at low temperature (∼400 °C). The implantation‐induced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 Å. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (<400 Å) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the low‐temperature annealing of GaAs

    A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers

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    We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs~1×10^(–17) W Hz^(–1/2). Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz^(–1/2) to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility

    Some recent results in aerospace vehicle trajectory optimization techniques

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    Algorithms and computation techniques for solving trajectory optimization problem

    Epitaxial regrowth of thin amorphous GaAs layers

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    Channeling and transmission electron microscopy have been used to investigate the parameters that govern the crystal quality following capless funace annealing at low temperature (~ 400 °C) in ion-implanted GaAs. From the results obtained, we concluded that the crystal quality after annealing depends strongly on the thickness of the amorphous layer generated by ion implantation and the number of residual defects increases linearly with the thickness of the implanted layer. Single-crystal regrowth free of defects detectable by megaelectron volt He + channeling was achieved for a very thin amorphous layer (<~ 400 Å)
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