In the use of piezoelectric actuators, it is a clear choice to use stack (or d<sub>33</sub> mode) architectures when very high force is required or benders (or d<sub>31</sub> mode) architectures when very high displacements are needed. However, the choice isn't as clear for applications that need simultaneously a moderate force and displacement. This paper presents one such application, INSTAR that is posed with this dilemma. INSTAR is a novel rifle system that has an inertially stabilized barrel via an active suspension based on piezoelectric actuation. While the frequency required for this application was low (~10Hz), the displacement (± 200 to 400 microns) and the force (22-45 N) are moderate. Two very different actuation approaches were developed, modeled, fabricated and experimentally validated within the INSTAR demonstration platform: 1) a d<sub>31</sub> approach based on the Recurve architecture with focus on generating higher forces than is common for d<sub>31</sub> actuators and 2) a d<sub>33</sub> approach based upon a compliant mechanism designed using topology optimization with focus on providing more amplified strain than is common for d<sub>33</sub> actuators. Both approaches were successful in meeting the INSTAR requirements, but each had its on advantages and disadvantages.
While good marksmanship is key to the effectiveness of the infantry mission, all soldiers experience a decrease in accuracy due to combat stress that generates detrimental physiological effects. INSTAR is a tactical rifle designed to address these effects by decoupling unwanted shooter-induced disturbances from the barrel via an active suspension system. The critical design driver for this active suspension was the "complete" actuation system (actuation, driving electronics and power supply). This paper presents an overview to the INSTAR architectural design along with the challenging actuation requirements. The architectural development and experimental performance characterization of the selected Recurve piezoceramic actuation system is discussed in detail along with the specialized driving electronics needed for power conservation. Range-of-motion experiments were conducted on a full-scale, 1 DOF INSTAR prototype, demonstrating the necessary actuation system control authority for a successful active suspension.