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Sensory Substitution using
Custom-Made Robotic Systems

Effect of Environmental Noise on Discrimination Performance

Oct 2009 - Present

Johns Hopkins University, Haptics Laboratory

I created a model to describe how humans perceive stiffness that accounts for both human perception capabilities and external environment rendering capabilities. I am currently testing the model, using human subject data, to test its validity.

Role of Visual and Proprioceptive Motion Feedback in Discrimination Task

May 2006 - Present

Johns Hopkins University, Haptics Laboratory

Experimental Setup

I created a robotic system and conducted a human subjects study to investigate the importance of proprioceptive motion feedback during a discrimination task. This study compares the Weber fraction for human perception in three conditions: visual motion, proprioceptive motion, and their combination. I non-invasively controlled the perception of proprioceptive motion feedback in unimpaired individuals using a virtual environment and a custom-designed, torque controlled haptic interface for the right index finger. Psychometric curves and Weber fractions were generated from an experiment in which users palpated pairs of springs and attempted to identify the spring with higher stiffness. To account for slight trial-to-trial variations in the relationship between force and position in the proprioceptive feedback conditions, the analysis uses measurements of actual rendered stiffness, rather than commanded stiffness. Results indicate that having the sense of proprioceptive motion is more useful than not sensing it. (PDF) YouTube Video

Value of Visual and Proprioceptive Motion Feedback During Targeting Task

Sep 2006 - May 2007

Johns Hopkins University, Haptics Laboratory

Targeting Task Setup

Controlling the motion of an upper-limb proshesis without visual feedback is extremely difficult because the wearer does not know the prosthesis' configuration. We designed an experiment to determine the relative importance of visual and haptic position feedback during targeted force-based motion by non-amputee human subjects as an analogy to prosthetic use. Subjects control the angle of a virtual proxy through an admittance relationship by generating torque at the MCP joint of the right index finger. During successive repetitions of a target acquisition task, the proxy's state is selectively conveyed to the user through graphical display and finger motion. Performance metrics for each feedback condition provide insights on the role of haptic position feedback and may help guide the development of future upper-limb prostheses. (PDF)

Human Performance in a Knob-Turning Task

Sep 2004 - Mar 2007

Johns Hopkins University, Haptics Laboratory

Knob-Turning Task

Knob turning is a common task that should influence the design of human-machine interfaces such as prosthetic arms, teleoperated robots, and virtual environments. In this work, I created a robotic system and designed a human subject study to investigate turning strategies in a knob-turning task. The study examines the following metrics for a specified knob rotation: turning strategy, including arm motions used and number of grasps made, time used to complete the motion, and maximum applied forces and torques. The subject's task was to rotate a one-degree-of freedom haptic knob at least 270 degrees for two angles of attack (hand parallel versus perpendicular to the plane of the knob), three knob sizes, and three motor gains. Principal results from this study indicate that humans change their turning strategy depending on the knob-turning difficulty, and apply forces and torques in directions that are not conducive to the task.(PDF)

Analysis of Human Movement

Jan 2003 - May 2004

University of Pennsylvania, Vestibular Ocular Motor Research Laboratory

Human MOI Work

Vestibular disorders cause an estimated two million US adults to suffer from dizziness or difficulty with balance and more than one half of accidental deaths among the elderly. The focus of this work was to better understand the vestibular ocular reflex (VOR) and its contribution to orienting oneself with the ground. The VORs respond to the rotation of the head with eye movements in the opposite direction, allowing one to maintain a fixed gaze on an object while the head is in motion. By gaining a better understanding of the VOR behavior, treatment methods to those with vestibular disorders and post-flight treatment of astronauts can be improved. The goal of my specific project was to demonstrate the importance of the ankle proprioceptors on head and trunk balance. This was to be achieved by quantifying the dynamics of the body in a pivot turn. A right pivot turn was defined as a right foot driven clockwise 180-degree turn with the left leg planted on the ground. I revised a pivot turn model into a more mathematically and anatomically accurate one and performed experiments of my own design, collecting additional pivot turn data and utilizing a torsion pendulum to collect and verify further dynamic values. I completed this project by creating a simulation that supported my hypothesized pivot turn model. (PDF)