Projects
Research toolboxes, a robotic art collaboration, and other things built along the way.
A Matlab toolbox for the analysis and design of hybrid systems based on the looped-functional framework. Implements stability analysis and controller synthesis for impulsive, switched, sampled-data, and periodic systems with convex, LMI-based conditions.
An artistic project: a robotic arm holds a brush at its tip and writes the word sens (French for meaning, sense, feeling, or direction) in ink that disappears once dry, over and over again. An idea from Markus Buser that I helped develop, exhibited in Dans quel sens? at FabrikCulture.
The arm was designed by Roland Bitterli and built by Claude Gacon using two leadscrews for the arm angles, driven by NEMA 17 stepper motors, plus a third NEMA 17 with a belt drive for lateral rotation. Electronics: Arduino UNO with a CNC shield and three A4988 drivers. No sensors. A kinematic model gave Cartesian coordinates from joint angles, and Newton's method inverted it. Calibration used direct measurements and linear fitting from motor angles to arm angles. Around 200 unevenly-spaced points on the word sens were stored in fixed-point polar coordinates to save memory.
The hard parts were drift accumulation (no encoders), brush dynamics on the floor that could stall motors or shift the robot, and the difference in friction between a dry and a wet brush, the latter dragging the trajectory off course. The brush mount was adapted to give a degree of vertical compliance.