Study of the Dynamic Properties of the Miniature Electro-Hydrostatic Actuator

The electro-hydrostatic actuator (EHA) is a new type of high-performance servo actuator that originated in the field of aerospace, and it is gradually becoming a common basic component for various types of large equipment. A miniature EHA, mainly composed of a micro two-dimensional (2D) piston pump and a brushless DC motor, is designed in this article by simplifying the system structure. This paper analyzes the structure and working principle of this EHA and establishes the mathematical models of the brushless DC motor, micro two-dimensional pump, and hydraulic cylinder. Field-oriented control (FOC) is used to drive the brushless DC motor, and the models of the controller are established in Simulink. Furthermore, the models of the mechanical and hydraulic systems of the miniature EHA are established in AMESim. In addition to this, a prototype of this miniature EHA was fabricated in this paper and an experimental platform was built for experiments. In the joint simulation environment, the rise time of the EHA system at 6000 r/min is 0.158 s and the frequency response amplitude attenuation to -3 dB has a bandwidth of 20 Hz. On the other hand, the constructed miniature EHA prototype was dynamically characterized to obtain a rise time of 0.242 s at 6000 r/min and a bandwidth of 13 Hz. In this paper, the feasibility of the design scheme of the miniature EHA system is verified, and its excellent dynamic properties are verified with simulation and experiment.