Study on a Piezohydraulic Motor for Maximal Energy Efficiency

Abstract

A piezohydraulic linear motor driven by a piezostack diaphragm pump is presented and studied. The diaphragm of pump chamber consists of a membrane and rigid disk, instead of a single piston or membrane. An analytical model is established to evaluate piezohydraulic motor performance in terms of velocity, pushing force, mechanical energy conversion efficiency (MEE), and electromechanical energy conversion efficiency (EMEE). The involved effect factors of motor performance are radius ratio (rigid-disk radius to chamber radius), area ratio (pump-chamber area to cylinder-piston area), force ratio (external load to blocked force of piezostack), and step ratio (cylinder-piston stroke to free displacement of piezostack). Analytical results show that there are optimal structural parameters (radius ratio and area ratio) for property parameters (force ratio, step ratio, MEE, and EMEE) to obtain maximal values. Considering the achievable peak MEE and EMEE, the design method was introduced for different purpose of applications. A piezohydraulic motor was fabricated and tested to examine the influence of radius ratio on performance of the piezohydraulic motor. The experimental results show that both the motor velocity and driving force can be enhanced with optimizing radius ratio.