Performance Modeling and Efficiency Analysis for a Piezohydraulic Pump with Active Valves

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.