Actuation Development and Evaluation for INSTAR - Inertially Stabilized Rifle

In the use of piezoelectric actuators, it is a clear choice to use stack (or d₃₃ mode) architectures when very high force is required or bender (or d₃₁ mode) architectures when very high displacements are needed. However, the choice isn't as clear for applications that need simultaneously moderate to high force and displacement. This paper presents one such application, INSTAR, which 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 d₃₁ approach based on the Recurve architecture with focus on generating higher forces than is common for d₃₁ actuators and 2) a d₃₃ approach based upon a compliant mechanism designed using topology optimization with focus on providing more amplified strain than is common for d₃₃ actuators. Both approaches were successful in meeting the INSTAR requirements, but each had its own advantages and disadvantages.