Development of piezoelectric bending actuators with embedded piezoelectric sensors for micromechanical flapping mechanisms

This paper presents the fabrication and the testing of piezoelectric unimorph actuators with embedded piezoelectric sensors which are meant to be used for the actuation of the Micromechanical Flying Insect (MFI). First the fabrication process of a piezoelectric bending actuator comprising a standard unimorph and a rigid extension is described together with the advantages of adding such an extension. Then the convenience of obtaining an embedded piezoelectric sensor by a simple and inexpensive variation of the fabrication process is pointed out. A model for the sensor embedded into a unimorph actuator with rigid extension is derived together with its flat response band limits. Calibration steps are also outlined which allow, despite residual parasitic actuator-sensor coupling, the use of the actuator with the embedded sensor for measuring position and inertial forces when external mechanical structures are driven. An experiment is carried out which validates the model for the actuator/sensor device under desired operating conditions. Preliminary application of the fabricated device to the MFI is also presented where the mechanical power fed into the wing is estimated.