Characterization of an inchworm prototype motor

Abstract A new driving principle for an active joint intended for, e.g., a microrobot, has been evaluated. Piezoelectric bimorphs are used as actuator elements, and quasistatic positioning in combination with an inchworm type of repetition produces the rotation. The performance of a macroscopic prototype has been investigated and compared with an analytical model and with finite-element analysis. The agreement between the model and the prototype is good, and it is believed that the characteristics of a microsized active joint can be estimated from the analytical model. The difference in size between the prototype and the proposed micromotor is a factor of 100. A micromotor is expected to have a very high torque-to-volume ratio (3 kN m −2 ). Its power and speed limits are believed to be sufficient for an operational micromotor. Other characteristics that make it well suited for microrobotics are: no gliding contact causing wear, simple design and locked rotor when the voltage is turned off. A possible fabrication process, microassembly, is demonstrated. A bimorph microelement has been successfully bonded to a support on a substrate and the expected behaviour has been verified.