Decoupling identification with closed-loop-controlled elements for two-link arm with elastic joints

Junji Oaki, Shuichi Adachi

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)


The purpose of our study is to build a precise model by applying the technique of system identification for the model-based control of a nonlinear robot arm, taking jointelasticity into consideration. We previously proposed a systematic identification method, called "decoupling identification", for a "SCARA-type" planar two-link robot arm with elastic joints caused by the Harmonic-drive reduction gears. The proposed method serves as an extension of the conventional rigid-joint-model-based identification. The robot arm is treated as a serial two-link two-inertia system with nonlinearity. The decoupling identification method using linkaccelerometer signals enables the serial two-link two-inertia system to be divided into two linear one-link two-inertia systems. The MATLAB's commands for state-space model estimation are utilized in the proposed method. Physical parameters such as motor inertias, link inertias, jointfriction coefficients and joint-spring coefficients are estimated through the identified one-link two-inertia systems. This paper describes an accuracy evaluation of the identification method through experimental results using the two-link arm with "closed-loop-controlled elements". The results show the method is applicable to a "PUMA-type" vertical robot arm under gravity.

Original languageEnglish
Pages (from-to)675-680
Number of pages6
JournalIFAC Proceedings Volumes (IFAC-PapersOnline)
Issue number16
Publication statusPublished - 2009
Event9th IFAC Symposium on Robot Control, SYROCO 2009 - Gifu, Japan
Duration: 2009 Sept 92009 Sept 12


  • Closed-loop identification
  • Frequency response
  • Mechanical resonance
  • Multivariable systems
  • Nonlinear optimization
  • Nonlinear systems
  • Robot arms

ASJC Scopus subject areas

  • Control and Systems Engineering


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