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Graduate Students Seminar Series

The ME Graduate Student Seminar Series GSSS is an independent, student-organized, bi-weekly series of seminars where graduate students from the Department of Mechanical Engineering at Vanderbilt University can present their ongoing research, improve their presentation skills, and receive feedback from their fellow students. The format allows one or two students to present depending on speakers availability. Pizza and drinks will be provided for all attendees. If you are willing to share your work send an e-mail to This e-mail address is being protected from spambots. You need JavaScript enabled to view it indicating your preferred date. Critiques and complaints are welcome and they might be evaluated ;-).

We thank the staff of the Department of Mechanical Engineering for the logistic and all the following speakers for past and future presentations:

04/20/2011

Roger Goldman
Advanced Robotics and Mechanism Applications Laboratory

Abstract - Novel minimally invasive surgical paradigms accessing deep surgical sites present a new challenge of safe instrument insertion and navigation. This paper addresses this challenge by presenting a new framework for compliant motion control of multi-backbone continuum robots subject to whole-arm contacts. This control framework does not rely on knowledge of contact locations along the length of a continuum robot. Instead, the forces at joint level are applied as controller inputs to generate compliant motion. The paper first presents a new mapping of the external wrenches to a generalized force in the configuration space of a single-stage multi-backbone continuum robot. A closed-form analytic expression for the passive stiffness of a multi-backbone continuum robot segment is also presented. A controller, robust to uncertainties of the system model, is proposed to provide compliant motion of the continuum robot segment by using the generalized force and stiffness definitions. Stability, convergence, and controller properties are shown through experimental validation. The presented framework defines a method for providing compliant motion to continuum robots without explicit knowledge of the environment. We believe this work enables new control algorithms for rapidly deployable surgical robots and supports novel surgical paradigms by increasing safety during unstructured interaction with flexible anatomy.


03/16/2011

Alexander Pedchenko
Laboratory for the Design and Control of Energetic Systems

Design and Finite Element Modeling of High Energy Density Strain Energy Accumulator

Abstract - In 2006, approximately 75 billion gallons of gasoline were consumed by passenger cars in the United States. This astounding figure emphasizes the importance of increasing fuel economy of mass-produced consumer vehicles. The push to reduce gas consumption has resulted in numerous proposed remedies such as the use of hydrogen fuel cells, solar power, and regenerative braking (RB). RB has already seen commercial implementation on vehicles such as the Toyota Prius. Its purpose is to recover a portion of the energy that is usually lost in slowing down a vehicle with conventional brake pads, allowing to salvage as much as half of the energy used for subsequent acceleration. Currently, RB on passenger vehicles is almost universally electrical. The possibility of achieving significant gains in power capture rate for a RB system which implements hydraulic components instead of electrical ones encouraged research and development of hydraulic regenerative braking (HRB). This technology has already been successful integrated onto heavy vehicles, such as garbage trucks and buses, resulting in fuel saving on the scale of 25-30% in city driving (e.g, Hydraulic Launch Assist by Ford and Eaton). The objective of this research is to assess the feasibility of the migration of HRB to the light passenger vehicle sector.


02/23/2011

Brian Lawson
Center for Intelligent Mechatronics

Stability Enhancement for Transfemoral Amputees Using a Powered Knee and Ankle Prosthesis

Abstract - In recent years several companies and researchers have begun to consider the possibility of bringing powered lower limb prostheses to market. Current literature suggests that such prostheses have the ability to enhance the mobility of amputees through reduced metabolic cost of transport, faster self-selected walking speed, and improved symmetry of gait. In addition to these benefits, we are investigating the degree to which adding both power and intelligence to a lower limb prosthetic device can enhance the stability of the amputee. The loss of proprioception and active power generation in the lower limb result in both lower balance confidence among amputees and a significantly increased rate of falls and injuries. I will be discussing two projects currently under way which aim to address these issues. The first project is the implementation of a new standing controller for a powered transfemoral prosthesis that incorporates both intent recognition and ground adaptation based on inertial measurements. The second project is the incorporation of active stumble recovery behaviors into the walking controller of the prosthesis. These behaviors are based upon the reactions seen in healthy subjects according to the biomechanics literature.


02/09/2011 - 12:00pm - Room 132

Nathan Grady
Laser Diagnostics and Combustion Lab

Hydroxyl Tagging Velocimetry in a Supersonic Flow Over a Ramped-Wall Cavity Flameholder with an Upstream Strut

Abstract - Supersonic air flow over a wall cavity with a rear ramp both with and without an upstream strut was studied with Hydroxyl Tagging Velocimetry (HTV). HTV is a non-intrusive means of measuring gas velocity by producing a hydroxyl tag from water vapor via a two step process: 1) the “write” phase where water molecules are dissociated into OH+H, 2) the “read” phase where after a fixed time delay the OH field is interrogated with planar laser-induced fluorescence. An 11x11 OH grid was used to obtain velocities at ~120 grid points. Mean and RMS fluctuation velocity profiles both with and without the strut were analyzed and compared to each other and to a rectangular cavity studied by other authors. In the ramped-cavity, increased recirculation and turbulence was observed over the ramp compared to the rectangular cavity, and the shear layer both grew more slowly and was lower into the cavity. Once the strut was installed, it was observed that cavity recirculation along the centerline increased relative to the no-strut configuration and extended above the step. Furthermore, expansion waves off the top of the strut and weak compression waves off the back of the strut were observed. Finally, shear layer vorticity in the wake region of the strut was analyzed.

Furui Wang
Robotics and Autonomous Systems Laboratory

Robot-Assisted Upper-Limb Rehabilitation After Stroke

Abstract - Millions of people are affected by stroke every year. Rehabilitation after a stroke has been shown to be effective for many stroke survivors. However, intensive rehabilitation is both resource-intensive and costly. Initial research suggests that robot-assisted stroke rehabilitation can be effective, cost-efficient and the treatment can be made individualized and adaptive. As a result, more versatile robotic systems are being developed to impart rehabilitation in a more efficient and human-like manner. In this seminar, I will discuss the design and development of robotic systems along with new rehabilitation paradigms for stroke rehabilitation that we are working on at Robotics and Autonomous Systems Laboratory.


01/26/2011 - 12:00pm - Room 132

Jenna Toennies
Medical & Electromechanical Design Laboratory

Wireless Insufflation and Educational Haptics

Abstract -The first part of the talk will focus on illustrating the feasibility of wireless insufflation from a capsule endoscope. The success of traditional endoscopy in diagnosing diseases of the Gastrointestinal Tract can be attributed to the clear view of the intestinal lumen that can be achieved through insufflation. The ability to distend tissue and view the entire intestinal lumen is challenging for current capsule endoscopes, however, which lack this ability to insufflate. Further, insufflation has the potential to enhance active capsule locomotion by reducing the resistance to movement imposed by the deflated lumen. I will discuss experiments designed to evaluate the amount of gas a capsule must produce to have a beneficial impact on visualization and locomotion in the colon before describing experiments evaluating how much gas can be generated from a given volume of catalyzed Hydrogen Peroxide. The second part of the talk will focus on the use of a haptic touchscreen to convey graphical and mathematical concepts through aural and/or vibratory tactile feedback, with an emphasis on using such a display for teaching visually impaired students concepts that are traditionally learned almost entirely visually.I will describe initial feasibility studies using a commercially available haptic touchscreen to display grids, points, lines, and shapes – some of the first visual graphical entities students encounter in K-12 mathematics education. The user studies conducted evaluate perception of these objects through solely haptic feedback, solely auditory feedback, and combinations of the two.


11/03/2010 - 12:00pm - Room 132

Dustin House
Computational Flow Physics Lab

Electrophoretic trajectory of a colloidal sphere eccentrically positioned in a bent cylinder

Abstract - Streamlines representing flow devoid of particles are used as a convenient method of predicting the trajectory of particles driven through a microchannel by electrophoresis. However, the validity of this approach is not clear when the channel geometry is non-trivial and when the particle size is large compared to the characteristic length scale of the channel. To address this issue, we have developed an accurate numerical approach based on the boundary-element method to solve the coupled electric field, flow and particle motion. From this, we simulate a spherical particle moving within a bent cylindrical channel and investigate how the particle's trajectory deviates from that of its predicted streamline when using the previously stated approach

Bo Yin
Computational Flow Physics Lab

Numerical simulation of fluid-solid and fluid-fluid interactions by combining two different immersed-boundary methods

Abstract - Two-phase flows in various industrial applications often occur ingeometries. To simulate this type of flows, we have combined two different immersed-boundary methods to handle the fluid-fluid and the fluid-solid interfaces separately. For the fluid-fluid interface, a diffuse-interface method is employed where the discontinuities of the material properties and the traction jump are all regularized using an approximate Dirac's Delta function. For the fluidsolid interface, ghost nodes and a local flow reconstruction are employed to complement the finite-difference discretization and to incorporate the boundary conditions. A single-block Cartesian mesh is used to discretize the entire domain. Both 2D and 3D codes have been implemented.


10/20/2010 - 12:00pm - Room 132

Caleb Rucker
Medical & Electromechanical Design Laboratory

Modeling Tendon-Actuated Continuum Robots

Abstract - This presentation will begin with a brief overview of some of the work done in the MED lab on active cannula robot modeling and control. Then, recent work on modeling tendonactuated robots will be  described in detail. This work provides a new kinematic model for a continuum robot with embedded tendons routed in arbitrary curved paths along its length. The modeling also accounts for large  nonlinear deformations of the robot due to externally applied point and distributed wrenches, as well as the distributed dynamics. An experiment demonstrating the accuracy of the approach will also be  described to conclude the talk.

Marc Ramsey
Laser Diagnostics and Combustion Lab

Velocity Measurements in the Shock Pattern of a Supersonic Rocket Plume and Energetic Cavitation Collapse

Abstract - The cap shock pattern is observed in the plume of over-expanded thrust optimized rocket nozzles at the low pressure ratios that occur during start-up and shut-down transients, and is a precursor to dangerous instabilities. Detailed measurements of the 2D velocity field are presented here and compared with computational results. Measurements are obtained with hydroxyl tagging velocimetry, in which molecular tags are written into the flow by laser photodissociation and tracked by laser induced fluorescence. The 1D dynamics of a spherical gas bubble in a liquid are well characterized by theory which predicts an intriguing inertial collapse. In routine experiments, a 50  bubble driven to collapse with a pressure of only one atmosphere reaches 60,000 atmospheres and ~5000 K at stagnation, emitting light and a strong shock wave. A new method is proposed to apply stronger driving and reach stagnation pressures of millions of atmospheres, conditions of interest to the field of high energy density physics.


10/06/2010 - 12:00pm - Room 132

Andrea Bajo
Advanced Robotics and Mechanism Applications Laboratory

Methods and Algorithms for Enabling Safe Interaction of Continuum Robots with the Environment

Abstract - The aim of this talk is to present ongoing research at the A.R.M.A. Lab on modeling and control of multi-backbone continuum robots for enhancing safe interaction with the environment. Methods, algorithms, simulations, and experimental results for contact detection, estimation of contact location, mixed configuration and joint space feedback control, and complaint insertion will be discussed. The audience will be provided with the theoretical background on screw theory, statics, direct kinematics, instantaneous kinematics, and control of continuum robots, motion control, motion tracking, force perception, and sensor registration.

 
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