Graphical servo simulations in C in a UNIX environment, and mathematical modeling of servo performance in the C programming language were done by me. I designed a Multibus interface for an XY servo positioning system involving digital logic and parallel interfaces. Also, I redesigned the Eurocard servo controllers into a form that was easily analyzed mathematically and whose behavior I could predict, with demonstrated higher performance and superior characteristics. Two cards were used, one to control film feed and another to control lens movement, each sperately tuned for its unique inertial load.

ALso, I designed a servo simulator test instrument and a phase measurement instrument for making adjustments to the servo system. The servo worked just as the mathematical model based on Laplace-domain analysis predicted, since the servo bandwidth was under 200 Hz. A mode- switched servo design was employed using a tachometer-stabilized system that could be mode-switched to change the feedback characteristics of the servo loop. Modeling used a time-domain continuation approach using initial conditions in the Laplacian representation. Another simulation model used state-space methods.

Finally, I developed a 6809-based servo simulator, controller, and analog I/O multiplexing for production testing of servo controllers, and made proposals for phase-locked loop velocity regulation. Most of the hardware was built up and checked out by me personally. The servo controller typeset the most demanding jobs with a positioning accuracy of 1 micron, at higher speed than the previous system.

Earlier, as a C programmer in a UNIX environment, I worked on character generation algorithms for phototypesetters and conversion of vector- outline characters to a form suitable for an interactive computer graphics terminal, the spectacular Berthold Magic System. My software contribution included character representation recoding and smart character fill routines and produced handsome output on a printer, spinning out character sets as a batch system that converted alphabet after alphabet from vector-outline form to run-length-encoded form without human intervention.

Dr. Peter Krumhauer came up with some novel and ingenious methods for applying the theory of cubic splines to character generation, and I wrote programs for applying the spline theory to the generation of large multipage images. Using spline theory to generate characters had already occurred to myself and other design engineers, but Peter had brilliantly rediscovered some things that are hard to prove, and carried them further forwards than ever with ingenious refinements and experiments on the achievable density of the representations and compaction on his PC. I proposed implementing the difference equations generating the splines with a 68000 and actually building something, but our principal results were magnified graphical images that proved the utility of the method. The differnce engine approach to generating polynomials solely by additions of differences led to fast algorithms for character generation from very compact data sets. Flawless characters the size of billboards could be produced.

Perhaps the most entertaining days I had at that time were the ones in which I investigated the way polynomial spline characters can be transformed to produce various distortions, such as barrel projections, pincushion distortion, and other special effects.

The video memory planes and character scaling hardware in the pipeline character processor were redone by me for The FOX series of typesetters as standard Multibus cards.

(Charles River Data Systems: UNOS, UNIX Version 7, Berkeley UNIX with the CSHELL, also the Bourne Shell, digital video design, servo system design and simulation, analog design, microprocessor system design, and computer graphics.)