Comparison of Piezoelectric, Magnetostrictive, and Electrostrictive Hybrid Hydraulic Actuators

Abstract

In recent years, active material driven actuators have been widely researched for potential applications in the fields of aerospace, automotive, and civil engineering. While most of these active materials, such as piezoelectric, magnetostrictive, and electrostrictive materials, have high force and bandwidth capabilities, they are limited in stroke. In combination with hydraulic systems, the field-dependent motion of these materials can be amplified to produce high force, high stroke actuators. In a hybrid hydraulic pump, the motion of an active material is used to pressurize a hydraulic fluid. Since the properties of active materials vary greatly in terms of free strain and block force, there is a need to identify the optimum active material for a particular application. This study compares four active materials, Lead—Zirconate—Titanate (PZT), Lead—Magnesium—Niobate (PMN), Terfenol-D and Galfenol, as the drivers of a hybrid hydraulic actuation system. The performance of each of these active materials has been evaluated in the same hydraulic actuator through systematic testing of the actuator while maintaining the same length and volume for each active material. In each case, the active material has a length of around 54 mm and a cross-sectional area of 25 mm2. Commonly used metrics such as output power and electromechanical efficiency are used for comparison. Of the four materials tested in this study, PMN presented the largest free strain (2000 με), while Galfenol presented the least (300 με). The highest no-load velocity is also exhibited by the PMN-based actuator (270 mm/s). The maximum output power obtained is 2.5 W for both PMN and Terfenol-D-based actuators while the highest electromechanical efficiency obtained is 7% for the PMN-based actuator.