Piezoelectric actuators with on-board sensing for micro-robotic applications

We present a piezoelectric actuator design with integrated position sensing for millimeter scale mobile robotics. Actuators are fabricated using the smart composite microstructure fabrication process which consists of laser micromachining and composite lamination. Electrically isolated strain-sensing regions of the piezoelectric material undergo identical motion as the actuation layers and thus directly sense tip deflection through the piezoelectric effect. We present the design considerations of strain-sensing piezoelectric actuators which can be made over a wide range of sizes and in both unimorph and bimorph configurations. These actuators demonstrate a linear relationship between the piezo sensor voltage output and the actuator tip to tip displacement when actuated over input bias voltages ranging between 25 and 200 V and frequencies from 10 to 250 Hz. We demonstrate the applicability of strain sensing actuators for microrobotic flying robots through wing-collision and wing-degradation experiments. Actuators enabled successful detection of instantaneous wing collisions when flapping near an obstacle. Furthermore, wing degradation through loss of wing area resulted in increased wing amplitudes which were observed in the sensor. Coincident actuation and sensing within microrobots represents a meaningful step towards closed loop control capabilities of microrobots using on-board sensors. (paper)