3D Ultrafast Shear Wave Absolute Vibro-Elastography using a Matrix Array Transducer

3D ultrasound imaging provides more spatial information compared to conventional 2D frames by considering the volumes of data. One of the main bottlenecks of 3D imaging is the long data acquisition time which reduces practicality and can introduce artifacts from unwanted patient or sonographer motion. This paper introduces the first shear wave absolute vibro-elastography (S-WAVE) method with real-time volumetric acquisition using a matrix array transducer. In SWAVE, an external vibration source generates mechanical vibrations inside the tissue. The tissue motion is then estimated and used in solving a wave equation inverse problem to provide the tissue elasticity. A matrix array transducer is used with a Verasonics ultrasound machine and frame rate of 2000 volumes/s to acquire 100 radio frequency (RF) volumes in 0.05 s. Using plane wave (PW) and compounded diverging wave (CDW) imaging methods, we estimate axial, lateral and elevational displacements over 3D volumes. The curl of the displacements is used with local frequency estimation to estimate elasticity in the acquired volumes. Ultrafast acquisition extends substantially the possible S-WAVE excitation frequency range, now up to 800 Hz, enabling new tissue modeling and characterization. The method was validated on three homogeneous liver fibrosis phantoms and on four different inclusions within a heterogeneous phantom. The homogeneous phantom results show less than 8% (PW) and 5% (CDW) difference between the manufacturer values and the corresponding estimated values over a frequency range of 80 Hz to 800 Hz. The estimated elasticity values for the heterogeneous phantom at 400 Hz excitation frequency show average errors of 9% (PW) and 6% (CDW) compared to the provided average values by MRE. Furthermore, both imaging methods were able to detect the inclusions within the elasticity volumes

Data for model validation summary report. A summary of data for validation and benchmarking of recovery boiler models

One of the tasks in the project was to obtain data from operating recovery boilers for the purpose of model validation. Another task was to obtain water model data and computer output from University of British Columbia for purposes of benchmarking the UBC model against other codes. In the course of discussions on recovery boiler modeling over the course of this project, it became evident that there would be value in having some common cases for carrying out benchmarking exercises with different recovery boiler models. In order to facilitate such a benchmarking exercise, the data that was obtained on this project for validation and benchmarking purposes has been brought together in a single, separate report. The intent is to make this data available to anyone who may want to use it for model validation. The report contains data from three different cases. Case 1 is an ABBCE recovery boiler which was used for model validation. The data are for a single set of operating conditions. Case 2 is a Babcock & Wilcox recovery boiler that was modified by Tampella. In this data set, several different operating conditions were employed. The third case is water flow data supplied by UBC, along with computational output using the UBC code, for benchmarking purposes

Haptic interface control-design issues and experiments with a planar device

Describes the haptic rendering of a virtual environment by drawing upon concepts developed in the area of teleoperation. A four-channel teleoperation architecture is shown to be an effective means of coordinating the control of a 3-DOF haptic interface with the simulation of a virtual dynamic environmen

Vision-based relative navigation for formation flying of spacecraft

The objective of this paper is to develop a robust and efficient approach for relative navigation and at-titude estimation of spacecraft flying in formation. The approach developed here uses information from a new optical sensor that provides a line of sight vector from the master spacecraft to the secondary satel-lite. The overall system provides a novel, reliable, and autonomous relative navigation and attitude determi-nation system, employing relatively simple electronic circuits with modest digital signal processing require-ments and is fully independent of any external systems. State estimation is achieved through an optimal ob-server design, which is analyzed using a Lyapunov and contraction mapping approach. Simulation results in-dicate that the combined sensor/estimator approach provides accurate relative position and attitude esti-mates

OPTIMIZATION-BASED TELEOPERATION CONTROLLER DESIGN

This paper addresses issues of performance and stability robustness specifications and trade-offs, and computational techniques in optimization-based teleoperation controller design. With Youla's Q-parametrization of stabilizing controllers, a transparency measure, defined as the H1 distance to the ideal teleoperator model, and a robust stability constraint, defined as positive realness of the transmitted admittance to the environment, are convex in the free design parameters. Therefore, the controller design problem can be formulated as a convex optimization problem. The limit of performance achievable with the designed controller, and thus the exact form of the trade-offs between performance and robust stability, can be computed numerically. The solution procedure is illustrated by a design example for a motion-scaling teleoperation system

Lorentz Levitation Technology: A New Approach to Fine Motion Robotics, Teleoperation, Haptic Interfaces, and Vibration Isolation

Recently, a new technology for stably levitating and controlling the position and orientation of a rigid body has been introduced. A unique feature is the use of Lorentz forces rather than the usual Maxwell forces as in magnetic bearings. The Lorentz force approach, which uses the force experiencedbyaconductor in a magnetic #eld, is seen to have several advantages. After an initial exploration phase and periodoffeasibility study, a number of potentially important applications are emerging. Among them are a way to provide #ne compliant motion for assembly, to provide high #delity force#torque feedback for teleoperation and virtual reality haptic interfaces, and to isolate sensitive payloads from environmental vibrational disturbances, either in spaceoronearth. In this paper we will discuss recent work intended to demonstrate the e#cacy of Lorentz levitation technology for these application areas.