System Modelling and Bulk Modulus Estimation of an Electrohydrostatic Actuator

An electrohydrostatic actuator (EHA) is an emerging type of actuator typically used in the aerospace industry. EHAs are self-contained units comprised of their own pump, hydraulic circuit, and actuating cylinder. The main components of an EHA include a variable speed motor, an external gear pump, an accumulator, inner circuitry check valves, and a cylinder (or actuator). This article presents the system modelling of an EHA built for experimentation. The system has been built to study a variety of different faults (friction, leakage, and bulk modulus); and models were obtained mathematically, and through system identification. Furthermore, using these system models, this article studies the results of estimating the bulk modulus by implementing the extended Kalman filter (EKF) algorithm.