An analysis has been conducted on the flapper-nozzle stage of a two-stage electrohydraulic controller that has been specifically designed to be a stable, stand-alone dynamic system. Calculations performed on equilibrium control pressures, stage gain, and frequency response characteristics agree with values obtained experimentally to within close limits. The analysis applies generally to a flapper-nozzle combination using any set of dimensions convenient for the designer. Flow-pressure equations and flapper dynamic properties have also been given to enable the designer to obtain full design characteristics.
Optimal control theory is applied to the design of a pressure regulator for an axial piston pump and single-stage electrohydraulic valve combination. The control valve has been modeled and an optimal control law has been formulated. The time response curves due to a step input inflow rate and in current input to the servovalve have been obtained for the open loop and for the optimal control system. Comparison of the results has been made with previous work in which the supply valve to the swashplate actuators was not modeled. It is shown that controlled system modeling of the servovalve significantly improves system performance in terms of response frequency and pressure peaks.
A previous analysis into the dynamic behavior of the flapper-nozzle component of the electrohydraulic servovalve was performed after linearization of the equations relating to control piston flow (Lin and Akers, 1989a). This paper reports results for first-stage gain and for dynamic behavior when linearization has not been performed. Good agreement has been achieved between results calculated from the nonlinear theory presented and experimental results.
Values of pressure caused by entrapment beneath a valve plate have been calculated. The technique used consists of the solution of the dynamical equation of motion in the piston control volume. Instantaneous and average values of torque have also been deduced from the pressure distribution. Plots have been constructed showing the effect of swashplate angle, pump angular rotation, discharge pressure, and entrapment angle upon instantaneous pressure, torque, and average torque for a typical axial piston pump.
This work presents a study of the applicability of optimal control theory to the design of a pressure regulator by use of an axial piston pump with a two-stage electrohydraulic servovalve. The control valve has been modeled and an optimal control law has been formulated. The time response curves due to a step input in flow rate to the pump have been obtained for the open loop and the for the optimal control system. An examination of the results has shown that the performance, in terms of pressure peaks and frequency during recovery to the flow disturbance, is significantly improved over that obtained when a single-stage valve is used.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.