Analysis and experimental validation of a sensor-based event-driven controller

We present an event-driven servo controller that is based on an (extremely) low resolution encoder. The control value is updated at each moment that an encoder pulse is detected, yielding zero measurement error. However, as the time between two control updates is varying now, conventional controller design methods do not apply as they normally assume a constant sample time. To deal with this problem, the controller design is performed by transforming the system equations from the time domain to the position (spatial) domain, in which the encoder pulses, and therefore the controller triggering, are equidistant. In this way, the control problem is rewritten as a synchronous problem for a non-linear plant. A gain scheduled controller is designed and analyzed in the spatial domain. This event-driven controller is experimentally validated on a prototype printer where a 1 pulse per revolution encoder is used to accurately control the motion of images through the printer.