Piled Higher and Deeper

I'm pleased to announce that Dr. Steven Knight Charles successfully defended his PhD Thesis today with a time of 6 years 10 months and 6 days (including the 3 years he spent "training" during his Master's work). At the finish line he was rewarded with an aluminum foil PhD medal, a warming blanket, and banana, apple, and water to help him regain the vitamins and hydration he lost during this mega-marathon. As you can see, a PhD is well worth it!

Here are the members of Steven's committee (from left to right). Don't let their congenial smiles fool you--they made sure to put Steven sufficiently through the ringer. Seriously, we are very grateful for their support and attention.

Thesis Advisor and Committee Chairman:Neville Hogan, Professor, Mechanical Engineering, Brain and Cognitive Sciences, MIT

Committee Members:Emilio Bizzi, Institute Professor, MITRobert Howe, Professor, School of Engineering and Applied Sciences, Harvard UniversityPeter L. Strick, Professor, Neurobiology, Psychiatry, University of Pittsburgh

Steven's labmates were extremely kind and even brought doughnuts and coffee to the defense to keep the committee members at bay. : ) Here's how we party at MIT--it's not a celebration unless you're surrounded by machines and lab equipment

Thanks for the cake, Newman Lab. We couldn't be more proud of Dr. Charles!

And for the nerd in you, we present Steven's abstract:

Thesis Defense:

It’s All in the Wrist: A Quantitative Characterization of Human Wrist Control

Steven Charles
MIT Miller Room (1-114)
Thursday, July 10th, 10 am

Over the past three decades, much research in motor neuroscience has focused on understanding how humans make coordinated reaching movements, yielding valuable insight into the planning and control of reaching movements, and establishing a foundation for robot-assisted rehabilitation. The goal of my doctoral research has been to provide a quantitative characterization of humans’ wrist rotations, paving the way for intelligent robot-assisted wrist rehabilitation. More specifically, my research has characterized the kinematics and dynamics of wrist rotations, and discussed implications for planning and control.

Kinematics: It has long been known that humans tend to make relatively straight reaching movements, suggesting that reaching movements are primarily under kinematic control of hand position. Are wrist rotations also under kinematic control of the hand? Using a motion capture system, it was found that wrist rotations exhibit a pattern with significantly more path curvature and variability than reaching movements (p ≤ 0.001). While the increased path curvature could lead one to believe that wrist rotations may not be under kinematic control of hand position, this work provides evidence that the curvature is instead due to imperfect peripheral execution.

Dynamics: In order to determine the exact cause of path curvature, an anatomically accurate, mathematical model of the wrist was developed, including recent measurements of passive wrist stiffness. Combining experimentally measured kinematics from human subjects with the wrist model revealed that moderately-sized wrist rotations can be approximated by a very simple model with virtually no loss in accuracy. Interaction torques, for which the nervous system compensates in reaching movements, are present but negligible in wrist rotations. Rather, wrist rotation dynamics are dominated by stiffness, which was shown to be the likely cause of path curvature.