Stepper motors usually make noise, because they step, and the
electronics also step. So the point was to make steps without
stepping. This means making every movement smooth.
Using microstepping helps a lot, but I went further.
I use dither stepping, where microstepping and digital
signal processing are combined directly with cybernetics
to give smooth silent movement to the motor.
In the beginning I used microstepper controllers, but they have
been replaced with H-bridges driving the stepper motors
directly. They are controlled by an Atmel microcontroller which
in the background runs my interrupt based driver routine. It
uses negative positional feedback with smooth bessel filters
implemented as coupled differential equations.
RhytmsMy silent motor drive was also used in the electro mechanical rhythm box BlinkWheel by Koka Nikoladze. It was featured on the Discovery Channel.