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


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.


Armor Stone;Harbor Construction;Parallel-Typed Robot;Pressure Sensor;Pressure Observer


Supported by : 창원대학교


  1. Kim, T. S., Kim, C. H., Park, K. and Lee, M. K., 2004, "Development of Sensorless Hydraulic Servo System for Underwater Harbor Construction,” Proceedings of the KSME 2004 Fall Annual Meeting, pp. 708-713.
  2. Watton, J., 1990, "Digital Compensator Design for Electrohydraulic Single-Rod Cylinder Position Control Systems," J. Dyn. Syst. Meas. Contr., Trans. ASME, Vol. 11, No. 3, pp. 403-409.
  3. Moreau, T. J. and McFayden, A. W., 1998, "Magnetostrictive Linear Displacement Transducer Utilizing Axial Strain Pulses," U.S. Patent 5,717 330.
  4. Fraden, J., 2004, "Handbook of Modern Sensors-Physics, Designs and Applications(3rd Edition)," Springer-Verlag.
  5. Francis, J. H., 1996, "New Position Sensors for Fluid Power and Other Control Applications," Sensors, pp. 80-85.
  6. Conrad, F. and Jensen, C. J. D., 1987, "Design of Hydraulic Force Control Systems with State Estimate Feedback," IFA C 10th Treennial World Congress, Munich, FRG, Vol. 1, pp. 307-312.
  7. Merritt, H. E., 1967, "Hydraulic Control Systems," Johnwiley & Sons, Inc.
  8. Vossoughi, G. and Donath, M., 1995, "Dynamic Feedback Linearization for Electro hydraulically Actuated Control Systems," Transactions of the ASME, Vol. 117, pp. 468-477.
  9. Toivonen, L. and Morsky, J., 1995, "Digital Multirate Algorithms for Measurement of Voltage, Current, Power and Flicker," IEEE Transactions on Power Delivery, Vol. 10, No. 1, pp. 116-126.
  10. Zanganeh, K. E. and Angeles, J., 1995, "Real-Time Direct Kinematics of General Six- Degree of Freedom Parallel Manipulators with Minimum-Sensor Data," J. of Robotic Systems, Vol. 12, No. 12, pp. 833-844.