Reduced Bandwidth for Remote Vehicle Operations

Oak Ridge National Laboratory staff have developed a video compression system for low-bandwidth remote operations. The objective is to provide real-time video at data rates comparable to available tactical radio links, typically 16 to 64 thousand bits per second (kbps), while maintaining sufficient quality to achieve mission objectives. The system supports both continuous lossy transmission of black and white (gray scale) video for remote driving and progressive lossless transmission of black and white images for remote automatic target acquisition. The average data rate of the resulting bit stream is 64 kbps. This system has been demonstrated to provide video of sufficient quality to allow remote driving of a High-Mobility Multipurpose Wheeled Vehicle at speeds up to 15 mph (24.1 kph) on a moguled dirt track. The nominal driving configuration provides a frame rate of 4 Hz, a compression per frame of 125:1, and a resulting latency of ~1s. This paper reviews the system approach and implementation, and further describes some of our experiences when using the system to support remote driving

Microfabrication of Optically Flat Silicon Micro-Mirrors for Fully Programmable Micro-Diffraction Gratings

AbstractWe have fabricated and characterized a Fully Programmable Micro-Diffraction Grating (FPMDG) with 64 silicon micro-mirrors for spectral shaping in the visible and near-infrared wavelength range. The FPMDG arrays of 50μm and 80μm wide and 700μm long silicon micro-mirrors have been fabricated in a process based on anodic bonding of an 8μm-SOI wafer and a borosilicate glass wafer. The detrimental bending of the micro-mirrors during electrostatic actuation has been minimized through separation of the mechanical and optical sections of the device. Flexures incorporating serpentine structures have been used to reduce the actuation dependence on length and thickness. Independent addressing of the micro-mirrors with negligible cross-talk and with bending of the micro-mirrors smaller than 0.14μm over 700μm have been demonstrated

Thermal Characterization of Polycrystalline CVD Diamond Thin Films

An experimental thermal characterization method is developed for high thermal conductivity thin films. The method utilizes Ta/Pt resistors on microfabricated free-standing thin film structures both for heating and temperature monitoring at different positions on the structures. The steady-state temperature at the heater and the sensor positions are monitored as a function of the power dissipated by the heater under vacuum environment, and the thermal conductivity is estimated by comparing these results to FEA and/or analytical models. The developed method is used to characterize the thermal conductivity of various different CVD diamond films of different grain sizes and films thicknesses. The measured thermal conductivity values range from 15 W/m·K to 300 W/m·K, which are at least one order of magnitude lower than that of natural diamond. It is also shown that the thermal conductivity of such films in the in-plane direction increases with increasing grain size and film

SCALABLE CASCADED SNAP-IN ACTUATORS FOR LARGE-STROKE DISPLACEMENTS

This paper will focus on the design, and first measurements of a cascaded in-plane parallel plate snap-in actuator. The actuator is based on a rather simple microfabrication process and can achieve a total displacement of several tenths of microns. Compared to classical noncascaded transducer device based on parallel plates or comb-drive actuator, the actuation voltage is relatively low due to the snap-in phenomenon of electrostatic actuators. The electromechanical response of such a device is sequential. The fabricated 4-stage device shows a total stroke of 75 μm at 60 V. It is possible to easily increase the total stroke of the actuator by increasing the number of stages. Only one input electrode is required. Simulations with CoventorWare showed easy scalability of the concept for up to 19 stages with a total displacement of 350 μm

A microchip optomechanical accelerometer

The monitoring of accelerations is essential for a variety of applications ranging from inertial navigation to consumer electronics. The basic operation principle of an accelerometer is to measure the displacement of a flexibly mounted test mass; sensitive displacement measurement can be realized using capacitive, piezo-electric, tunnel-current, or optical methods. While optical readout provides superior displacement resolution and resilience to electromagnetic interference, current optical accelerometers either do not allow for chip-scale integration or require bulky test masses. Here we demonstrate an optomechanical accelerometer that employs ultra-sensitive all-optical displacement read-out using a planar photonic crystal cavity monolithically integrated with a nano-tethered test mass of high mechanical Q-factor. This device architecture allows for full on-chip integration and achieves a broadband acceleration resolution of 10 \mu g/rt-Hz, a bandwidth greater than 20 kHz, and a dynamic range of 50 dB with sub-milliwatt optical power requirements. Moreover, the nano-gram test masses used here allow for optomechanical back-action in the form of cooling or the optical spring effect, setting the stage for a new class of motional sensors.Comment: 16 pages, 9 figure

Centrality dependence of charged hadron transverse momentum spectra in d+Au collisions at sqrt(s_NN) = 200 GeV

We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt(s_NN) = 200 GeV. The spectra were obtained for transverse momenta 0.25 < p_T < 6.0 GeV/c, in a pseudorapidity range of 0.2 < eta < 1.4 in the deuteron direction. The evolution of the spectra with collision centrality is presented in comparison to p+pbarcollisions at the same collision energy. With increasing centrality, the yield at high transverse momenta increases more rapidly than the overall particle density, leading to a strong modification of the spectral shape. This change in spectral shape is qualitatively different from observations in Au+Au collisions at the same energy. The results provide important information for discriminating between different models for the suppression of high-p_T hadrons observed in Au+Au collisions.Comment: 5 pages, 4 figures, submitted to PR