alian Summer Research Program 2005
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Kim Butcher
University of Buffalo
Aerospace and Mechanical Engineering
Port Jefferson, New York
Topic: Modeling of an Electro-Hydraulic Actuator by System Identification Method
Mentor: Wu Zhigang
Abstract
An electro-hydraulic servo actuator is being used in the laboratory to induce vibrations in a model structure. The purpose of this research is to model the actuator as a second-order system, despite the fact that the system poses many nonlinearities. This study used the “n4sid” command in Matlab to create a state-space model, and then a transfer function, that would accurately represent the open-loop actuator system. It was tested using a variety of input functions, over a variety of frequencies and amplitudes, and found to be largely satisfactory, despite some discrepancies at higher frequencies. Matlab’s Simulink then used to model a closed-loop system, incorporating the generated transfer function and a simulated PID servo. The purpose of this work was to eventually create a PID servo and incorporate it into the laboratory’s system. The PID servo’s parameters were estimated using a method of parameter optimization checks. The end results of this research were (a) a transfer function that can simulate the electro-hydraulic servo actuator in the laboratory and (b) parameters that can simulate a PID servo that will be added to the actuator system. These results can be used to better control the actuator system, in the hopes of more accurately simulating ice forces.