Ill-yeong Lee

Feedback Linearization Control of a Hydraulic Servo System

This paper suggests a hydraulic servo system with a linear controller using feedback linearization. Feedback linearization technique is applied to overcome the non-linearities of the system. The authors pay attention to simpler realization of the controller for the object system and prepare a controller with an additional compensator to recover the response time due to using the reduced order model. The control object consists of a hydraulic servo-valve, a servo-cylinder with an inertia load. The control performances of the control system with the newly suggested controllers and a conventional controller (designed based on a system model linearized around a specific operation point) are compared, and the excellency of the controllers proposed in this study is confirmed

Effects of Major Design Parameters on Three-Stage Electro-Hydraulic Servovalve Performance

This paper presents the solution to overcome the lack of knowledge in design parameters on the three-stage electro-hydraulic servovalve that has not been clearly investigated by other studies. At first, various physical parameters of servovalve are measured, then a physical modeling for the three-stage electro-hydraulic servovalve is developed based on the full mathematical model of servovalve. MATLAB/Simulink is used to develop a simulation model. Then, the acquired Simulink model is verified by comparing the simulation result with the experimental result (Moog Inc.). Finally, various suspected parameters affecting on the performance of main valve in the three-stage electrohydraulic servovalve are analyzed in detail.

High-Bandwidth Tracking Control of Electric Hydrostatic Actuator (EHA) Using an Input Shaping Filter

The purpose of this study is to achieve high-precision and high-bandwidth reference tracking control for an electric hydrostatic actuator (EHA). First, the pole placement method and the zero placement method were used to design a reference input tracking controller consisting of a PI-D controller and a feed-forward controller for the EHA-driven system. The feed-forward controller exhibited a high gain symptom in the frequency response as the actuation frequency of the system increased. An input shaping filter (ISF) with the style of a lag compensator was incorporated into the control system to suppress the increase in the control gain in the high-frequency range. The effectiveness of the proposed control system was evaluated by conducting experiments. The results indicate that the application of the proposed control system, including the ISF, can greatly improve the reference tracking control performance of the EHA-driven system. In addition, the proposed control system using the ISF is stable with a sufficient margin for a broad frequency range.