Adaptive modal damping for advanced LIGO suspensions

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 179-183).Gravitational waves are predicted to exist by Einstein's Theory of General Relativity. The waves interact extremely weakly with the surrounding universe so only the most massive and violent events such as supernovae and collisions of black holes or neutron stars produce waves of sufficient amplitude to consider detecting. The Laser Interferometer Gravitational-Wave Observatory (LIGO) aims to pick up the signals from these very faint waves. LIGO directs much of its effort to the areas of disturbance rejection and noise suppression to measure these waves. The work in this thesis develops an adaptive modal damping control scheme for the suspended optics steering the laser beams in the LIGO interferometers. The controller must damp high quality factor mechanical resonances while meeting strict noise and disturbance rejection requirements with the challenges of time varying ground vibrations, many coupled degrees of freedom, process noise, and nonlinear behavior. A modal damping scheme is developed to decouple the complex system into many simpler systems that are easily controlled. An adaptive algorithm is then built around the modal damping scheme to automatically tune the amount of damping applied to each mode to achieve the optimal trade-off between disturbance rejection and noise filtering for all time as the non-stationary stochastic disturbances evolve. The adaptation is tuned to provide optimal sensitivity to astrophysical sources of gravitational waves. The degree of sensitivity improvement is analyzed for several classes of these sources.by Brett Noah Shapiro.Ph.D

Modal control with state estimation for advanced LIGO quadruple suspensions

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 124-126).Gravitational waves are predicted to exist by Einstein's General Theory of Relativity. These waves are distortions of space-time which until now have remained outside the realm of possible detection, due to their incredibly weak interactions. Now, due to newly built highly sensitive observatories, such as the Laser Interferometer Gravitational Wave Observatory (LIGO), these detections are now believed to be possible and may occur in the very near future. The research discussed here is on an active control system for the quadruple pendulum, from which the mirrors of the LIGO interferometer are suspended. This pendulum is a chain of four masses used to provide seismic isolation of the mirrors at the level of 10-19 m Hz-1/2 at 10 Hz. Because the pendulum is so quiet above 10 Hz, the sensor noise used in the active control is not trivial. Thus, the purpose of this research is to optimize a control scheme that has high gain at the resonant frequencies of the pendulum to provide damping while at the same time rolling the gain off to virtually zero at the limit of the gravitational wave detection band less than half a decade away. This requirement is very difficult to achieve with classical control design techniques. The alternative method explored here is a type of modal control with state estimation where incomplete sensor information is reconstructed and mathematically decomposed into modal responses. The modal responses can be thought of as simple single degree of freedom oscillators that are very easy to control. In this way, a few highly complicated controllers are traded for a larger collection of reasonably simple ones that are easy to design for each mode. Damping vs. noise injection can then be optimized by tailoring the control gain on each mode.by Brett N. Shapiro.S.M

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Search for gravitational waves from binary black hole inspiral, merger, and ringdown

We present the first modeled search for gravitational waves using the complete binary black-hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data, taken between November 2005 and September 2007, for systems with component masses of 1–99M⊙ [1-99 M circled dot operator] and total masses of 25–100M⊙ [25-100 M circled dot operator]. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for 19M⊙≤m1 [19 M circled dot operator greater than or equal to m subscript 1], m2≤28M⊙ [m subscript 2 greater than or equal to 28 M circled dot operator] binary black-hole systems with negligible spin to be no more than 2.0  Mpc-3 {Mpc superscript -3] Myr-1 [Myr superscript -1] at 90% confidence.National Science Foundation (U.S.)United States. National Aeronautics and Space AdministrationCarnegie TrustLeverhulme TrustDavid & Lucile Packard FoundationResearch CorporationAlfred P. Sloan Foundatio