Demonstration of optimizing piezoelectric polarization in the design of a flextensional actuator

Much effort has gone into amplifying the displacements of actuators built around piezoelectric materials (PZTs). Some researchers have used topology optimization to design compliant mechanisms that best magnify either the geometric or mechanical advantage of piezoelectric wafers or “stack” actuators. PZTs are generally poled through the “thin” direction, so actuation by an electric field in that direction only induces eigenstrains normal to the free edges. Some researchers have shown advantages of “shear mode” actuation, and material scientists have demonstrated the ability to pole a PZT in an arbitrary direction. This work attempts to justify the inclusion of the PZT polarization vector as a design variable in the design of a flextensional actuator. We present two examples based on the “cymbal” actuator: one using a simplified model to justify off-angle polarization and another using the polarization vector as a design variable to optimize the topology of a compliant mechanism.