ABSTRACT
Electro-hydraulic system technology is employed in many modern control systems
including aircrafts and missile flight control systems. These systems used to position
the control surfaces of the flying vehicles with high controllability and accurate action.
Pilot or autopilot commands are translated into electrical position commands to the
electro-hydraulic control system (EHCS). This study is based upon the development
of a detailed nonlinear mathematical model of the EHCS and a computer simulation
program using MATLAB/SIMULINK package. The EHCS mainly consists of two
systems; main and secondary with two separate active hydraulic power supply
systems, used to supply the EHCS with the required power. The studied EHCS
incorporates two electro-hydraulic servo-valves and a smart design of built-in direct
operated directional control valves, controlled by electrical solenoids. The EHCS is
designed with smart capability to over-ride the possible problems of failure in the
hydraulic power supply systems or in the servo-valves. The transient response is
obtained by the simulation program using the solver of ode23s (stiff/Mod.
Rosenbrock) method. A comparison between the dynamic responses of the EHCS is
presented in different modes of failure. The simulation results show that this EHCS is
capable to provide a continued safe flight even when experiencing a certain
component failure or a combination of failures.