Optimal placement of binary actuators in deformable optical systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 111-113).Recently, exploration has been conducted into the applicability of binary mechatronics to active figure correction in large optical systems such as space telescopes and ground-based solar-thermal concentrators. This Thesis will continue this exploration. The information-theoretic requirements of the corrective commands required in active optics will be explored to understand the dimensionality of the continuous workspace sampled by binary actuation. In both the minimal expected error and the minimal computation time sense, the optimal discrete workspace is the uniform discrete distribution. A rigorous analogy between binary mechatronics and discrete random variables will be used to show that this optimal workspace is achievable by a linear superposition of actuators with exponentially decreasing influences on the optical surface. It will be proven that elasticity can be exploited to construct mechanisms where constant magnitude actuators exhibit exponentially decaying influences on certain parts of the mechanism, allowing for designs where individual binary actuators correspond to binary bits of the required deformation. A planar truss mechanism designed with this philosophy will be presented and shown to have independent kinematic control of multiple adjacent displacements on its top side. Finally, this design will be shown extend to three dimensions in a manner applicable to optical figure correction. Due to the complexity of mechanisms that meet the optimality criteria, only theoretical analysis will be presented.by Roman Geykhman.S.M

Proprioceptive localization for a quadrupedal robot on known terrain

We present a novel method for the localization of a legged robot on known terrain using only proprioceptive sensors such as joint encoders and an inertial measurement unit. In contrast to other proprioceptive pose estimation techniques, this method allows for global localization (i.e., localization with large initial uncertainty) without the use of exteroceptive sensors. This is made possible by establishing a measurement model based on the feasibility of putative poses on known terrain given observed joint angles and attitude measurements. Results are shown that demonstrate that the method performs better than dead-reckoning, and is also able to perform global localization from large initial uncertainty

The effect of differential color refraction on astrometric observations of Solar System bodies and Earth satellites from ground-based optical telescopes

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 289-300).Earth's atmosphere is optically dispersive and subjects astrometric observations from ground-based optical telescopes to systematic bias from differential color refraction (DCR). This bias is evident in Minor Planet Center observations of asteroids with known spectral types and in observations of GPS and GLONASS satellites. DCR bias is on the order of 0.1 arcsec, and until recently, őxed-pattern star catalog errors exceeded this level. With the release of the Gaia DR2 star catalog in April of 2018, catalog error is no longer dominant and the systematic error ŕoor in ground-based astrometry is deőned by DCR.Unaccounted-for DCR bias in observations can introduce a small but statistically signiőcant bias into the estimate of Keplerian mean motion of inner Solar System asteroids, reduce the probability of successfully observing a stellar occultation by a Kuiper Belt Object, and in rare pathological cases can mean the difference between predicting an impact or a miss by a hazardous asteroid. DCR in observations of geostationary satellites can introduce a large bias into the estimate of solar radiation pressure area-to-mass ratio in a single-night orbit őt and tens of meters of error into an orbit prediction derived from several nights of observation.Measurements of the 2017 near-Earth ŕyby of the asteroid 3122 Florence from MIT and MIT Lincoln Laboratory facilities in Westford, MA and Socorro, NM suggest that narrow passbands are insufficient to mitigate DCR, and measurements of a sample of geostationary satellites' spectra at the US Naval Observatory Flagstaff Station show that the DCR bias of active satellites can vary by up to 0.1 arcsec over half an hour. While the DCR of őducial stars is predictable from catalog data, satellites' DCR must be measured directly. To that end, a slitless spectrograph was deployed at the Firepond Optical Facility in Westford, MA and observed GPS and GLONASS satellites over seven nights. Using that data, I demonstrate DCR compensation yielding a 60% reduction in bias and 30% reduction in noise in astrometric residuals relative to color-agnostic processing when all atmosphere-induced effects (stellar DCR, target DCR, and parallactic refraction) are accounted for."Supported by the National Aeronautics and Space Administration (NASA) and the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) under Air Force Contract No. FA8702-15-D-0001"--Page 3.by Roman O. Geykhman.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Aeronautics and Astronautic