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Development of Pressure Observer to Measure Cylinder Length of Harbor-Construction Robot

항만공사용 로봇의 실린더 길이 측정을 위한 압력 옵서버 개발

  • Kim, Chi-Hyo (Dept. of Control and Instrumentation Eng., Changwon Nat'l Univ.) ;
  • Park, Kun-Woo (Dept. of Control and Instrumentation Eng., Changwon Nat'l Univ.) ;
  • Kim, Tae-Sung (Dept. of Control and Instrumentation Eng., Changwon Nat'l Univ.) ;
  • Lee, Min-Ki (Rotos Co., Ltd.)
  • 김치효 (창원대학교 메카트로닉스공학부) ;
  • 박근우 (창원대학교 메카트로닉스공학부) ;
  • 김태성 (창원대학교 메카트로닉스공학부) ;
  • 이민기 ((주)로토스)
  • Received : 2010.09.04
  • Accepted : 2011.01.10
  • Published : 2011.03.01

Abstract

In this study, we develop a pressure observer to measure the cylinder length of a harbor-construction robot. For the robot control, sensors are required to measure the length of a hydraulic cylinder. The cylinder-position sensor is relatively expensive when the operating environment prohibits external approaches for the measurement of the cylinder position. LVDT or linear scales are usually mounted on the outside of the cylinder, which causes poor durability on a construction site. We use a pressure sensor to indirectly estimate the length of the cylinder. The pressure sensor is mounted inside a hydraulic valve box so that it is protected by the box and easy to waterproof for an underwater robot. By treating oil as a compressible fluid, we derive the nonlinear pressure dynamics as a function of the cylinder position, velocity, and pressure. The recursive least squares (RLS) algorithm is applied to identify the dynamic parameters, and the pressure observer estimates the cylinder position through the pressure acting on the head and the rod of the hydraulic cylinder. The position accuracy is relatively low, but it is acceptable for a construction robot that handles large armor stones.

본 논문은 항만공사용 로봇의 실린더 길이 측정을 위한 압력 옵서버 개발이다. 로봇의 유압 실린더 제어를 위해 변위 센서가 필요하며 일반적으로 LVDT, 리니어 스케일 등이 사용된다. 이러한 센서는 실린더 외부몸통에 장착되므로 건설현장과 같은 열악한 환경에서 사용할 경우 내구성이 좋지 못하다. 본 논문에서는 압력센서를 이용하여 간접적으로 실린더 길이를 측정한다. 압력센서는 유압 밸브박스 내부에 장착되어 외부충격으로부터 보호되며 방수가 용이하다. 오일을 압축성 매개체로 간주하여 실린더의 위치와 속도 함수인 동적압력 방정식을 유도하고 RLS를 이용하여 실린더가 전진, 후진 리미트에 도달할 때마다 파라미터를 갱신한다.

Keywords

References

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