No abstract

The modulation of the rocket thrust is required for many practical applications regarding certain missions to be performed by the missile. An existing thrust controller with two modes of operation has been studied and analyzed. To upgrade the controller to acquire a continuous gradual thrust modulation, an Electro-Hydraulic Servo-Pressure Controller (EHSPC) has been integrated with the system after making necessary adaptation of the current design. The valve parameters: controlled pressure, input pressure, pilot pressure variations, and input controlling current have been investigated and compared for the two systems using MATLAB SIMULINK program. It was possible to acquire a new system capable of performing a continuous thrust modulation while keeping the other characteristics of the system before modification. KEY WORDSLiquid Propellant Rocket Engine, Thrust Controller, Electro-Hydraulic Servo-valve, and Thrust Modulation.

ThA papek deals with the modelling and 'imitation o6 an aikckait Longitudinal control zyztem including a hyd4omechanicat boortek. A bond gkaph model ob the boorte4 .ins developed. the equation's dezckibing the boo4te4 ake deduced Pcom the bond gkaph taking into con-'side/cation the bazic nontineakitiez. The motion ob aikcka6t iz kepkezented by a tkan46ek 6unction dezckibing itz behavioult du/Ling the .shoat pekiod longitudinal owittation4. The validity (3 ,6 the deduced model the boortek « 4tudied by the compalaton ob calculated tkanzient kezponze o6 boo4te4 with cokkezponding expekimentat kezuttz. The ebiect o6 some conztkuctionat and operational pakametekz on the dynamic behaviouk c(6 the hyditautic boo4te4 and al4c4qt td Atudied by the exptoitation o6 the deduced model.

The control system of a helicopter, including a hydraulic servoactuator, HSA, and an autopilot is investigated. The dynamic behavior of HSA is studied theoretically and experimentally. A nonlinear mathematical model and a computer simulation program are developed for the HSA and validated by comparing experimental and theoretical results. A second order transfer function for the HSA is also deduced by using the simulation program. A mathematical model for the hovering helicopter is developed and used to deduce the. helicopter transfer function. The helicopter is found to be unstable in hovering, it could be stabilized either through the pilot action or by using an autopilot. An autopilot is designed to assure the system stability. The transient response of the helicopter equipped with the HSA and the proposed auto pilot is investigated. The effect of some operational parameters on the, HSA and helicopter dynamics is studied theoretically. The results showed that the autopilot insures the required helicopter. stability and reduces substantially the effect of certain. HSA defects, such as the increase in internal leakage.

Using bond graph, a model is developed for two-way pressure compensated flow Control valves with pressure balancing stage perior to the throttling section. The model, which carries the physical and mathematical structures of the valve, is in a ready form to be interconnected to models of other components to get the bond graph for a global system incorporating the valve. • Equations governing the valve dynamic behaviour are obtained from the bond graph in the form of assignment statements. Simulation is realized on digital computer to investigate the valve transient response to step load-pressure variation, when the valve is used in a hydraulic circuit of a meter-in mode: of speed control. Results showed that at low values of resistance of the passage connecting the load to the spring chamber of compensator, the response is of high initial load flow overshoot that decreases rapidly to the ste4dy ptate value. At higher resistances, initial overshoot is reduced and the response is slower and of oscillatory nature.