Ji-Seong Jang

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

A method of accurate position control with a pneumatic cylinder driving apparatus

In this paper, a method of accurate position control using a pneumatic cylinder driving apparatus is presented. To overcome the effect of friction force and transmission line, low friction type cylinder applied externally pressurized air bearing structure is used and two control valves attached both side of the cylinder directly. To compensate nonlinear characteristics of control valves, linearized control input derived from the relation between control input and effective area of control valve, and dither signal are applied to the valve. The controller applied to the pneumatic cylinder driving apparatus is composed of a state feedback controller and a disturbance observer. Experimental results show that the effectiveness of the proposed method and position control error of 5 μm accuracy could be obtained easily.

Study on the Measurement Method of Leakage Flow-rate for Pneumatic Driving Apparatus

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there was no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measured by the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing steel wool into it. Therefore, wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic apparatus. The effectiveness of the proposed method is proved by experimental results