Mike Stilman Ph.D.

Assistant Professor
College of Computing
School of Interactive Computing
Georgia Tech
85 5th Street NW TSRB 240
Atlanta, GA 30332


404.385.3184

Robot Dribbling

CS225A (2001): I worked with Anita Lillie and Drew Baglino to create a ball dribbling controller for a Puma 560. We replaced the end effector with a compliant half-cylindrical tube that structurally kept the ball in a plane. The feedback controller gathered information from a three axis force torque sensor and determined appropriate behavior for the arm. The controller consisted of two modules:
  • Hit the ball down on contact
  • Move sideways to give the ball spin
The latter control was particularly exciting since it used friction to move the the ball back towards the center. This made is possible to return to vertical dribbling from states that would be unrecoverable under the assumptions of rigid body dynamics.

Video: [DivX] [MP4]



Robot Catch

(2002) We looked into the problem of two Puma arms performing a throw and catch task. The catching robot is not aware of the intentions of the throwing robot and must catch the ball via visual servoing. The relative proximity of the robots requires early detection and extrapolation of the ball path for the catcher to reach the ball.

Vision was performed using a Small Vision System (SVS) stereo camera that extracted stereo information of the scene at 30fps. We localized the ball using a blob finding algorithm in the range data. The robot also used its force sensor to detect whether the ball had been acquired successfully.

By instructing the pitcher to throw randomly in a designated workspace area we achieved over 10 consecutive catches. After each trial the catcher autonomously returned the ball to the pitcher.

Video: [DivX] [MP4]



Real-Time Stereo Tracking [Project Webpage]

CS225B: (2002) Seungbum Koo, Anton Dizhur and I developed an active contour algorithm that tracked multiple subjects in real time. The tracker mainted contours around targets such as people moving in a three dimensional lab setting. Our algorithm operated on disparity data acquired from an SRI Small Vision System camera.

Active contour models, such as those in the Snake algorithm, use intensity gradients from images to fit contours to underlying features of objects. Each snake-like contour has internal and external energy which it tries to minimize. External energy is the effect of gradients pulling the contours to a close fit of features. Minimizing internal energy keeps the contours tight and smooth.

Video: [DivX] [MP4]


Artificial Intelligence

(2001-2003) Before my research in spatial reasoning I looked into robots that think logically. My work with Professor John McCarthy and his Formal Reasoning Group studied effects that actions have on the world. One result summarized how effects could be classified according to previous knowledge and feasibility. This gave an intuitive solution to the frame problem for planning expressed in first-order logic.

M. Stilman. Causality Revisited: Reifying Effects Stanford University Dept. of Computer Science, Formal Reasoning Group Tech. Report, Aug. 2001 [PDF]

I also participated in Professor Eyal Amir's project on partitioning and reasoning. The goal was to increase the efficiency of reasoning about sets of axioms by localizing problems to subsets of axioms. My contributions were in software development and algorithm optimization for partitioning tools.


Dynamic Balancing [Anybots Webpage]

ANYBOTS (2003) Between Stanford and CMU I joined a unique company started by Dr. Trevor Blackwell in Mountain View, CA. Anybots' goal is to develop dynamically balancing humanoid robots that can operate in human enviornments. When I joined Anybots, Trevor had built the pneumatic biped Dexter. We worked together on designing control algorithms to make the robot balance. The challenge was to provide long term stability against disturbances with inherently compliant pneumatic actuators.

During my time at Anybots we achieved stable balancing and began initial steps towards walking. Recently, however, Trevor has succeeded in prolonged walking control of the biped. Please visit the Anybots webpage for these exciting new results.


3D Game Development

CS248: (2003) Mike Liu and I set out to create the ultimate 3D arcade game for the PC. This action packed project engages the player in motorcycle combat where riding, performing stunts and destroying enemies all contribute the score.

Creating a video game was educational and challenging. The complete project involved modeling the physics of motorcyle riding, weapon balistics and particle systems for explosions. Each component required attention to both physical realism and intuitive game play. Furthermore, we designed a control system for smooth, critically damped camera motion that would follow the rider and provide additional distance/panning during turns and stunts.