One of the least desirable schemes for a linear electro-hydraulic motion control actuator is having a low backup structure stiffness coupled with a high flow gain of the spool valve. It has been demonstrated that this condition causes instability in the form of high frequency oscillations. This thesis examines how actuator parameters can be varied to add stability when a low backup structure stiffness and high flow gain are mandatory design criteria. The stability of the system is examined by developing the system characteristic equation and analyzing its poles in the complex frequency domain. In the complex frequency domain, the parameters are varied to determine when stability begins and ends for a given qualitative range of a specific variable. Taylor's Theorem is used to expand the region around an unstable root to yield a sensitivity function for assessing parameter values that cause system instability. Combining the sensitivity equations for each parameter renders a function for predicting the instability of the system as various parameters are modified. The extent to which variable parameters aid or inhibit stability are discussed, as well as recommendations on the applicability of the parameters changes.

Library of Congress Subject Headings

Actuators--Design and construction; Hydraulic servomechanisms--Design and construction; Stability

Publication Date


Document Type


Department, Program, or Center

Mechanical Engineering (KGCOE)


Kempski, Mark

Advisor/Committee Member

Torok, Josef

Advisor/Committee Member

Ghoneim, Hany


Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: TJ223.A25 S76 1999


RIT – Main Campus