Piezoelectric actuation is an expanding field that makes use of piezoelectric materials that have high power density as actuators. These actuation systems have the potential higher power density than the traditional servo motor technology. However, due to tiny strain of the piezoelectric materials, displacement amplification mechanism should be incorporated into design for most commercial applications. Piezohydraulic actuation provides an ideal amplification that can achieve any combination of stroke and force, which is superior than most other amplification technologies. The concept of piezohydraulic actuation takes advantage of the high force capabilities that piezoceramics have and combines it with the operation at high frequencies, in order to achieve the hydraulic actuation of a system under a specified stroke and force. In this research, a compact piezohydraulic pump with active valves has been developed, tested and characterized. Furthermore, theoretical models are developed based on different levels of approximation of the hydraulic fluid. The first model, which assumes an incompressible and inviscid fluid, provides us views of the basic features of piezohydraulic actuation. The second model which takes into account the viscosity of the fluid and the third model which takes into account both viscosity and compressibility of the fluid are then presented. Then, their simulation results are compared with experimental data, which shows the compressibility of the fluid is important to system performance. At last, a power and efficiency analysis based on experimental results is presented. / Master of Science

The purpose of this study was to create a proof-of-concept piezoelectric actuator system capable of meeting the performance requirements necessary for actuation of a trailing edge flap for a helicopter main rotor blade. Due to extremely small displacements produced by piezoelectric actuators, their output is amplified several times in order to produce the required displacement for this device. The amplification is accomplished in two stages. The first stage, mechanical amplification, uses differential length lever arms to increase the piezoelectric actuator output. The second stage, hydraulic amplification, is coupled to the first stage and uses differential area pistons to further amplify the output of the mechanical amplifier. The actuation systems force and displacement output is characterized based on frequency.