Tech Briefs

Measurement and Controls Data Acquisition System

Measurement and Controls Data Acquisition System (MCDAS) is an application program that integrates the functions of two stand-alone programs: one for acquisition of data, the other for controls.

Posted in: Software, Briefs

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2D/3D Visual Tracker for Rover Mast

A visual-tracker computer program controls an articulated mast on a Mars rover to keep a designated feature (a target) in view while the rover drives toward the target, avoiding obstacles. Several prior visual tracker programs have been tested on rover platforms; most require very small and well-estimated motion between consecutive image frames — a requirement that is not realistic for a rover on rough terrain. The present visual-tracker program is designed to handle large image motions that lead to significant changes in feature geometry and photometry between frames. When a point is selected in one of the images acquired from stereoscopic cameras on the mast, a stereo triangulation algorithm computes a three-dimensional (3D) location for the target. As the rover moves, its body-mounted cameras feed images to a visual-odometry algorithm, which tracks two-dimensional (2D) corner features and computes their old and new 3D locations. The algorithm rejects points, the 3D motions of which are inconsistent with a rigid-world constraint, and then computes the apparent change in the rover pose (i.e., translation and rotation). The mast pan and tilt angles needed to keep the target centered in the field-ofview of the cameras (thereby minimizing the area over which the 2D-tracking algorithm must operate) are computed from the estimated change in the rover pose, the 3D position of the target feature, and a model of kinematics of the mast. If the motion between the consecutive frames is still large (i.e., 3D tracking was unsuccessful), an adaptive view-based matching technique is applied to the new image. This technique uses correlation-based template matching, in which a feature template is scaled by the ratio between the depth in the original template and the depth of pixels in the new image. This is repeated over the entire search window and the best correlation results indicate the appropriate match. The program could be a core for building application programs for systems that require coordination of vision and robotic motion.

Posted in: Software, Briefs

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Implementing Access to Data Distributed on Many Processors

A reference architecture is defined for an object-oriented implementation of domains, arrays, and distributions written in the programming language Chapel.

Posted in: Software, Briefs

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Dual Common Planes for Time Multiplexing of Dual-Color QWIPs

With external control, commercial single-color readout integrated circuits could be used. A proposed improved method of externally controlled time multiplexing of the readouts of focal plane arrays of pairs of stacked quantum well infrared photodetectors (QWIPs) that operate in different wavelength bands is based on a dual detector common plane circuit configuration. The method would be implemented in a QWIP integrated-circuit chip hybridized with a readout integrated circuit (ROIC) chip.

Posted in: Semiconductors & ICs, Briefs

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MMIC Power Amplifier Puts Out >40 mW From 75 to 110 GHz

This amplifier operates over the full frequency band of the WR-10 waveguide. A three-stage monolithic microwave integrated circuit (MMIC) W-band amplifier has been constructed and tested in a continuing effort to develop amplifiers as well as oscillators, frequency multipliers, and mixers capable of operating over wide frequency bands that extend above 100 GHz. There are numerous potential uses for MMICs like these in scientific instruments, radar systems, communication systems, and test equipment operating in this frequency range. This amplifier can be characterized, in part, as a lower-frequency, narrower band, higher-gain version of the one described in “Power Amplifier With 9 to 13 dB of Gain from 65 to 146 GHz” (), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 44. This amplifier includes four InP high-electron-mobility transistors (HEMTs), each having a gate periphery of 148 µm. In the third amplifier stage, two of the HEMTs are combined in parallel to maximize the output power. The amplifier draws a current of 250 mA at a supply potential of 2.5 V.

Posted in: Semiconductors & ICs, Briefs

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Design and Selection Considerations for High-Temperature Aerospace Accelerometers

Considerations include material selection, construction, and radiation tolerance. Accelerometers used for shock and vibration measurement in extreme environments require special consideration in the design and manufacturing process. Certain unique applications can require the same accelerometer to function from -54 to 649 °C (-65 to 1,200 ° F). This might include such applications as vibration measurement on gas turbine engines, in flight, or in test cells; rocket motor vibration measurements; and thruster vibration. These accelerometers also may need to function in nuclear radiation environments, and possibly in a combination of temperature extremes and radiation. This might include nuclear power generation or space vehicle applications. Materials and construction must then be selected not only to enhance high temperature performance, but also to allow operation in the presence of gamma and neutron radiation

Posted in: Physical Sciences, Briefs

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Microscale Regenerative Heat Exchanger

Materials and dimensions are chosen to optimize performance at microscale. The device illustrated in Figure 1 is designed primarily for use as a regenerative heat exchanger in a miniature Stirling engine or Stirling-cycle heat pump. A regenerative heat exchanger (sometimes called, simply, a “regenerator” in the Stirling-engine art) is basically a thermal capacitor: Its role in the Stirling cycle is to alternately accept heat from, then deliver heat to, an oscillating flow of a working fluid between compression and expansion volumes, without introducing an excessive pressure drop. These volumes are at different temperatures, and conduction of heat between these volumes is undesirable because it reduces the energy-conversion efficiency of the Stirling cycle. Hence, among the desired characteristics of a regenerative heat exchanger are low pressure drop and low thermal conductivity along the flow axis.

Posted in: Physical Sciences, Briefs

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