Model-Free Adaptive On-Off Step Controller for Piezoelectric Micro-Robots

An adaptive, model-free on-off controller is described for situations in which a desired step response is to be repeated many times, but there is incomplete information available about the system dynamics. The controller adapts a set of on-off switching transition times as a function of certain objective measurements defined by the designer. While the controller does not utilize any model of the system to perform this adaptation, the effects of the adaptation on known plants can be analyzed to find a range of systems for which the on-off switching times will result meeting desired objectives. This analysis is applied to lightly-damped 2^nd-order systems representative of micro-robotic leg joints driven by piezoelectric actuators, and used to identify on-off switching frequencies, sensing frequencies, and adaptation parameters that converge for many plants. This can produce a controller with good robustness to system variation and relatively low switching and sampling frequencies, which can keep power consumption of for piezoelectric servo control very low.