Concept for a large master/slave-controlled robotic hand

A strategy is presented for the design and construction of a large master/slave-controlled, five-finger robotic hand. Each of the five fingers will possess four independent axes each driven by a brushless DC servomotor and, thus, four degrees-of-freedom. It is proposed that commercially available components be utilized as much as possible to fabricate a working laboratory model of the device with an anticipated overall length of two-to-four feet (0.6 to 1.2 m). The fingers are to be designed so that proximity, tactile, or force/torque sensors can be imbedded in their structure. In order to provide for the simultaneous control of the twenty independent hand joints, a multilevel master/slave control strategy is proposed in which the operator wears a specially instrumented glove which produces control signals corresponding to the finger configurations and which is capable of conveying sensor feedback signals to the operator. Two dexterous hand master devices are currently commercially available for this application with both undergoing continuing development. A third approach to be investigated for the master control mode is the use of real-time image processing of a specially patterned master glove to provide the respective control signals for positioning the multiple finger joints

RF Pulse Design for Parallel Excitation in MRI.

Parallel excitation in MRI uses localized coils driven by independent RF waveforms as a mechanism for spatially encoding RF energy deposition. Because localized coil (or sensitivity) encoding is imposed instantaneously, one can create shorter pulses by trading gradient encoding for sensitivity encoding. However, the parallel pulse design problem is complicated by the non-Fourier nature of sensitivity encoding and the potential for patient-dependent problem inputs, requiring pulses to be designed rapidly online. In this project, I investigate novel techniques for parallel RF pulse design, with a focus on fast and general methods. I first propose a model-based iterative small-tip-angle pulse design method that is facilitated by a linear Fourier analysis of small-tip-angle excitation. It allows the user to rapidly design pulses with compensation for non-idealities such as main field inhomogeneities. We show in simulations and experiments that it produces pulses of higher accuracy than competing methods. The non-linear large-tip-angle regime requires more complex pulse design methods. To address this problem, I also investigate two fast large-tip-angle pulse design methods. Both are formulated as a series of Bloch simulations interleaved with small-tip-angle pulse designs whose results sum to produce accurate large-tip-angle pulses. Small-tip-angle pulse designs use approximate linear models for the perturbations induced by adding a small-tip-angle pulse to a large-tip-angle pulse. The first method uses the Fourier small-tip-angle equation as a linear model. We demonstrate that it is fast, robust and simple to implement, but it has some drawbacks, such as the inability to control excitation phase, that are addressed by the second method. The second method is based on a novel analytical linearization of the Bloch equation about an RF pulse. While more complex than the first method, we show that it produces pulses of higher accuracy, and can be applied to a broader range of pulse design problems. Both methods produce large-tip-angle pulses of higher accuracy than small-tip-designed pulses that are scaled to produce large-tip-angles.Ph.D.Biomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58521/1/wgrissom_1.pd

Additive angle method for fast large-tip-angle RF pulse design in parallel excitation

Current methods for parallel excitation RF pulse design are based on the small-tip-angle approximation, which provides a computationally efficient means of pulse calculation. In general, pulses designed with those methods are inaccurate when scaled to produce large-tip angles, and methods for large-tipangle pulse design are more computationally demanding. This paper introduces a fast iterative method for large-tip-angle parallel pulse design that is formulated as a small number of Bloch equation simulations and fast small-tip-angle pulse designs, the results of which add to produce large-tip-angle pulses. Simulations and a phantom experiment demonstrate that the method is effective in designingmultidimensional large-tip-angle pulses of high excitation accuracy, compared to pulses designed with small-tip-angle methods. Magn Reson Med 59:779–787, 2008. © 2008 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58569/1/21510_ftp.pd

Ultra-high spatial resolution BOLD fMRI in humans using combined segmented-accelerated VFA-FLEET with a recursive RF pulse design

Purpose To alleviate the spatial encoding limitations of single-shot EPI by developing multi-shot segmented EPI for ultra-high-resolution fMRI with reduced ghosting artifacts from subject motion and respiration. Methods Segmented EPI can reduce readout duration and reduce acceleration factors, however, the time elapsed between segment acquisitions (on the order of seconds) can result in intermittent ghosting, limiting its use for fMRI. Here, "FLEET" segment ordering--where segments are looped over before slices--was combined with a variable flip angle progression (VFA-FLEET) to improve inter-segment fidelity and maximize signal for fMRI. Scaling a sinc pulse's flip angle for each segment (VFA-FLEET-Sinc) produced inconsistent slice profiles and ghosting, therefore, a recursive Shinnar-Le Roux (SLR) RF pulse design was developed (VFA-FLEET-SLR) to generate unique pulses for every segment that together produce consistent slice profiles and signals. Results The temporal stability of VFA-FLEET-SLR was compared against conventional-segmented EPI and VFA-FLEET-Sinc at 3 T and 7 T. VFA-FLEET-SLR showed reductions in both intermittent and stable ghosting compared to conventional-segmented and VFA-FLEET-Sinc, resulting in improved image quality with a minor trade-off in temporal SNR. Combining VFA-FLEET-SLR with acceleration, we achieved a 0.6-mm isotropic acquisition at 7 T--without zoomed imaging or partial Fourier--demonstrating reliable detection of BOLD responses to a visual stimulus. To counteract the increased repetition time from segmentation, simultaneous multi-slice VFA-FLEET-SLR was demonstrated using RF-encoded controlled aliasing. Conclusions VFA-FLEET with a recursive RF pulse design supports acquisitions with low levels of artifact and spatial blur, enabling fMRI at previously inaccessible spatial resolutions with a "full-brain" field of view.Comment: 51 pages (including supplement), 8 main figures, 6 supporting figures. For supporting videos (8), please visit https://github.com/aveberman/vfa-fleet. Note: this work has been accepted for publication at Magnetic Resonance in Medicin

Underwater Optical Wireless Communications Link for Short-Range Data Transmission: A Proof of Concept Study

Gemstone Team OPTICThe purpose of this thesis is to lay the groundwork for the development of a cost-effective Underwater Optical Wireless Communications system. Currently, one of the largest barriers to the expansion of underwater enterprise and research is a lack of high-speed wireless communication systems. Wireless communication underwater is essential for safety, improving aquatic technology, and many other marine ventures, yet it is still technologically limited. Current methods, such as acoustic communication, are often power inefficient, cumbersome, and expensive. The proposed system would enable scuba divers and researchers to bridge the technological gaps in available underwater data transmission systems. This paper proposes using visible light to wirelessly transmit data underwater. Visible light is an effective carrier wave underwater due to its large bandwidth and low absorption coefficient. Using light emitting diodes, silicon PIN photodetectors, waterproof enclosures, and consumer-grade microcontrollers, a model for the development of a wireless optical communications system is proposed. The system also adopts a modular design which allows each component to evolve as needed. The proposed system can transmit and receive audio and vitals signals underwater, illustrating the potential of a technology that could make diving and other underwater endeavors safer and more efficient. Furthermore, the proposed data link shows the potential for this technology to be used in other underwater applications that were previously limited by data speeds or mobility. Above all, this technology seeks to build upon existing knowledge of optical wireless communication and advance the field of underwater science and technology