Different modeling technologies of hydraulic load simulator for thrust vector control actuator

Abstract

Hydraulic simulators are extremely important in the flight control actuator system's verification process. Flexible nozzle has a number of specifics, comparing to other flight controls, because the load cannot be described, classically, by the hinge moment. Additionally, classical hydraulic simulator, in which the cylinder simulates the load, is not sufficient for performing a complete simulation of the real load. Building a mechanical pendulum, to which a hydraulic cylinder acts, and that rests on two elastic supports, enables simulation of additional phenomena that exist in flexible nozzle, but not in other control surfaces. Force from impulse that exists in reality, and which is impossible to be generated by standard hydraulic simulator, can be realized through the pendulum. This paper demonstrates that a simulator can be designed through modelling of the elastic load using bond graph, without a precise elaboration of direction of forces in elastic structure, just by observing, on energy level, the input of force in flexible structure over the point in which actuator force acts. Simulator with hydraulic cylinder is convenient to be used when there is a need for considering the risk of self-oscillation of flexible joint and nozzle, i.e. for defining the so-called notch filter. Then, the hydraulic cylinder of load simulator can generate the oscillation, frequency and amplitude that match this dynamic case of flexible nozzle actuator's load that is being reduced to its piston rod, without a risk of damaging the flexible structure that exists in the construction of a simulator with pendulum.