Three small, low cost piezo-hydraulic pumps have been developed. The pumps deliver up to 600 psi of blocked pressure and 338 cc/min of free flow, while the smallest weighs less than 90 grams. The pumps utilize cofired multilayer piezoelectric actuators for low drive voltages and low cost. The properties of these pumps make them suitable for distributed actuation systems where pump, control valve and hydraulic actuator are located at the point of actuation, minimizing the system weight and length of hydraulic tubing.
A phase field model based on the work of Hu and Chen has been computationally implemented. The approach uses a minimization of global free energy to simulate the evolution of domain structures through the time dependent Ginzburg-Landau equation. The work focuses on the assumptions made when setting up the free energy function and the effect of these assumptions on the behavior of the model. Polarization is used as the independent variable. A fourth order polynomial is used to create four energy minima that represent the tetragonal phase in the two-dimension simulations. Linear superposition is used to modify the energy to account for the effects of sterss, electric field, and polarization gradients. This approach neglects field concentrations associated with material anisotropy and local geometric features. Considerable work will be required to incorporate these effects.