Experiments and simulations for the study of temperature effects on the performances of a fly-by-wire hydraulic actuator

The paper deals with the study of the temperature effects on the performances of fly-by-wire hydraulic actuators. The activity is developed via both experiments and simulations, using a primary flight actuator of a modern fly-by-wire jet trainer as reference hardware. A dedicated experimental set-up is arranged, by integrating a thermal chamber with a real-time actuator control system developed in the MATLAB-Simulink-xPC Target environment, and an extensive test campaign is performed on the actuator in environmental control conditions. In particular, both the static and the dynamic performances are concerned, characterizing the valve threshold, the valve motor gain, the open-loop, and closed-loop frequency responses. The tests are performed at ambient, extreme hot (71 C), cold (-20 C), and extreme cold (-40 C) temperatures. Experimental results are reported and discussed, providing a physical interpretation of temperature sensitivity effects. Concerning the simulation studies, they started from a detailed model of the actuator dynamics, previously developed and validated by the author at ambient temperature. The model is adapted for taking into account the temperature effects, and an experimental validation is obtained at servovalve level. The influence of temperature at actuator level is predicted by simulation, highlighting and discussing the expected closed-loop control concerns.