A rotary actuator driven by piezoelectric bimorphs has been developed for various smart structure applications. A rotary (roller) clutch rectifies bimorph oscillation into rotational motion to convert electrical to mechanical power. While prototype actuators perform well, they were designed with just engineering intuition. Here, a mathematical model of the actuator is developed. Using empirical data collected from a prototype actuator and a roller clutch, the mathematical model was tuned so that it predicted accurately the performance of the prototype. The model was then used to perform parameter studies and optimize the design of the actuator. The model predicts that performance can be significantly increased by making slight modifications to the prototype. Work to verify these predictions of the mathematical model is underway.