Analysis and control of a water hydraulic manipulator for iter divertor remote maintenance

L. Zhai, T. Virvalo, J. Mattila, Hannu Saarinen

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

This paper focuses on the analysis and control of a water hydraulic manipulator, which is specific for the International Thermonuclear Experimental Reactor (ITER) cassettes' (each weighing 10 tonnes) maintenance tasks. The manipulator comprises a closed-chain main body and an open-chain end-effector. Following a systematic way of analyzing differential kinematics and vibration modes, it is revealed that from a control point of view the manipulator faces two main restrictions. The first one is that the closed-chain structure degrades tracking performances, rising from kinematic coupling. Secondly, as the end-effector drives a very high inertial load instead of a gravitational load, small actuators are used, resulting in low system natural frequency and damping. To solve the first issue, a kinematic model-based decoupling controller is designed. Moreover, to improve the steady-state accuracy in spite of low frequency and damping, acceleration feedback is adopted, achieving higher damping and position loop gains. Experimental results show that decoupling controller brings five times smaller tracking errors, while acceleration feedback controller reaches three times better accuracies than proportional controller. This study also confirms that in spite of using commercially available water hydraulic components, the achieved positioning accuracies and dynamic behavior are competitive with oil hydraulics.
Original languageEnglish
Pages (from-to)47-59
Number of pages11
JournalInternational Journal of Fluid Power
Volume11
Issue number1
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

Fingerprint

hydraulics
maintenance
Manipulators
manipulators
controllers
Hydraulics
end effectors
Controllers
Kinematics
kinematics
Damping
damping
End effectors
decoupling
water
Water
Feedback
Experimental reactors
Weighing
positioning

Keywords

  • coupling
  • hydraulic manipulator
  • ITER
  • kinematic model-based decoupling
  • vibration mode analysis
  • divertor
  • ITER divertor
  • JET divertor
  • fusion reactors
  • decoupling vibrations

Cite this

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title = "Analysis and control of a water hydraulic manipulator for iter divertor remote maintenance",
abstract = "This paper focuses on the analysis and control of a water hydraulic manipulator, which is specific for the International Thermonuclear Experimental Reactor (ITER) cassettes' (each weighing 10 tonnes) maintenance tasks. The manipulator comprises a closed-chain main body and an open-chain end-effector. Following a systematic way of analyzing differential kinematics and vibration modes, it is revealed that from a control point of view the manipulator faces two main restrictions. The first one is that the closed-chain structure degrades tracking performances, rising from kinematic coupling. Secondly, as the end-effector drives a very high inertial load instead of a gravitational load, small actuators are used, resulting in low system natural frequency and damping. To solve the first issue, a kinematic model-based decoupling controller is designed. Moreover, to improve the steady-state accuracy in spite of low frequency and damping, acceleration feedback is adopted, achieving higher damping and position loop gains. Experimental results show that decoupling controller brings five times smaller tracking errors, while acceleration feedback controller reaches three times better accuracies than proportional controller. This study also confirms that in spite of using commercially available water hydraulic components, the achieved positioning accuracies and dynamic behavior are competitive with oil hydraulics.",
keywords = "coupling, hydraulic manipulator, ITER, kinematic model-based decoupling, vibration mode analysis, divertor, ITER divertor, JET divertor, fusion reactors, decoupling vibrations",
author = "L. Zhai and T. Virvalo and J. Mattila and Hannu Saarinen",
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Analysis and control of a water hydraulic manipulator for iter divertor remote maintenance. / Zhai, L.; Virvalo, T.; Mattila, J.; Saarinen, Hannu.

In: International Journal of Fluid Power, Vol. 11, No. 1, 2010, p. 47-59.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Analysis and control of a water hydraulic manipulator for iter divertor remote maintenance

AU - Zhai, L.

AU - Virvalo, T.

AU - Mattila, J.

AU - Saarinen, Hannu

PY - 2010

Y1 - 2010

N2 - This paper focuses on the analysis and control of a water hydraulic manipulator, which is specific for the International Thermonuclear Experimental Reactor (ITER) cassettes' (each weighing 10 tonnes) maintenance tasks. The manipulator comprises a closed-chain main body and an open-chain end-effector. Following a systematic way of analyzing differential kinematics and vibration modes, it is revealed that from a control point of view the manipulator faces two main restrictions. The first one is that the closed-chain structure degrades tracking performances, rising from kinematic coupling. Secondly, as the end-effector drives a very high inertial load instead of a gravitational load, small actuators are used, resulting in low system natural frequency and damping. To solve the first issue, a kinematic model-based decoupling controller is designed. Moreover, to improve the steady-state accuracy in spite of low frequency and damping, acceleration feedback is adopted, achieving higher damping and position loop gains. Experimental results show that decoupling controller brings five times smaller tracking errors, while acceleration feedback controller reaches three times better accuracies than proportional controller. This study also confirms that in spite of using commercially available water hydraulic components, the achieved positioning accuracies and dynamic behavior are competitive with oil hydraulics.

AB - This paper focuses on the analysis and control of a water hydraulic manipulator, which is specific for the International Thermonuclear Experimental Reactor (ITER) cassettes' (each weighing 10 tonnes) maintenance tasks. The manipulator comprises a closed-chain main body and an open-chain end-effector. Following a systematic way of analyzing differential kinematics and vibration modes, it is revealed that from a control point of view the manipulator faces two main restrictions. The first one is that the closed-chain structure degrades tracking performances, rising from kinematic coupling. Secondly, as the end-effector drives a very high inertial load instead of a gravitational load, small actuators are used, resulting in low system natural frequency and damping. To solve the first issue, a kinematic model-based decoupling controller is designed. Moreover, to improve the steady-state accuracy in spite of low frequency and damping, acceleration feedback is adopted, achieving higher damping and position loop gains. Experimental results show that decoupling controller brings five times smaller tracking errors, while acceleration feedback controller reaches three times better accuracies than proportional controller. This study also confirms that in spite of using commercially available water hydraulic components, the achieved positioning accuracies and dynamic behavior are competitive with oil hydraulics.

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KW - ITER divertor

KW - JET divertor

KW - fusion reactors

KW - decoupling vibrations

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