Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Industrial Education and Technology

First Advisor

William D. Wolansky


This research was aimed to develop and simulate the mathematical model for the control of an axial piston pump using a flapper-nozzle valve. It was assumed that all the state variables are defined as the perturbations in the physical quantities; therefore, linearized relations were used. These linearized relations were combined to form the state-variable representation of the model;The model was then simulated to investigate the control characteristics of the proposed system. The responses of a stand alone flapper-nozzle valve were evaluated first. Excellent agreement between the experimental data and theoretical data of output pressure rise of the valve was found;The open-loop system performance of the axial piston pump and flapper-nozzle valve combination was unstable. To enhance the stability of the system, an optimal control design was applied. It was found that the computed results of the nonaugmented optimal design lack robustness for improving the existing control system. Thus the augmented optimal control method was used to enhance the system performances;Time responses of the augmented optimal control system were evaluated. It was observed that the increase of input current had little effect on the system responses. Doubling the discharge flow rate also doubled the overshoot. Whereas increasing the discharge volume tended to slow down the system responses. Finally, the increase of the rotational speed of the pump shaft produced a higher overshoot and a slower response of the system;The performances of the control of an axial piston pump using a flapper-nozzle valve as a controller were compared to the performances of using a four-way hydraulic valve, a single-stage electrohydraulic servovalve, and a two-stage electrohydraulic servovalve as controllers. It was concluded that the system of a flapper-nozzle valve and an axial piston pump combination was superior to other combinations in terms of the balance between pressure-time response and maximum pressure overshoot.



Digital Repository @ Iowa State University,

Copyright Owner

Shir-Tau Tsai



Proquest ID


File Format


File Size

89 pages