The Nonlinear Accuracy Model of Electro-Hydrostatic Actuator

The electro-hydrostatic actuator (EHA) is a kind of power-by-wire (PBW) actuator. In this paper, a typical architecture of EHA is described and the block diagram model of EHA is established directly from the mathematic equations without transfer functions, which is a nonlinear accuracy model. The influence of refeeding circuit on the EHA system is discussed based on the comparison with conventional linear model. A gain-variable PID controller is introduced to this model to compensate the friction.

I. Introduction

The demand for conventional hydraulic actuation is gradually decreasing due to its limitations such as: low energy efficiency, leakage, noise, low maintainability. The Power-By-Wire (PBW) technology is becoming an attractive direction of future airborne actuation system. A PBW flight control system would simplify the secondary power generation, eliminate the need for a central hydraulic power supply, and replace the hydraulic pipes by electric power cables. As a result, the reliability, survivability, efficiency and maintainability of the aircraft would be greatly improved.