Decoupling identification and physical parameter estimation for serial two-link two-inertia system

Junji Oaki, Shuichi Adachi

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

This paper proposes a multivariable identification method for a SCARA-type planar two-link robot arm with elastic joints caused by reduction gears, which is treated as a serial two-link two-inertia system. The arm for the experimental verification is equipped with accelerometers that have the two roles described below. The proposed method consists of three steps. The first step is the rigid model parameter estimation by the least-squares method. The second step is the elastic model identification using a multi-input multi-output state space model technique, which enables the nonlinear interaction torques between two links to be decoupled. The torques, calculated using the accelerometer signals and the rigid model parameters, are employed as inputs for decoupling in the multi-input identification. The angular velocities of the links, calculated using the accelerometer signals and the motor encoder signals, are employed as outputs for improving accuracy in the multi-output identification. The decoupling method divides the serial two-link two-inertia system into two one-link two-inertia systems in this step. The third step is the physical parameter estimation of the onelink two-inertia systems. The physical parameters consist of motor inertias, link inertias, joint-friction coefficients and joint-spring coefficients. Furthermore fine tuning of the estimated physical parameters is carried out using closed-loop simulations with the nonlinear least-squares optimization. Experimental results using the two-link arm have shown the accuracy of the proposed identification method.

Original languageEnglish
JournalIEEJ Transactions on Industry Applications
Volume128
Issue number5
DOIs
Publication statusPublished - 2008
Externally publishedYes

Fingerprint

Parameter estimation
Identification (control systems)
Accelerometers
Torque
Angular velocity
Gears
Tuning
Robots
Friction

Keywords

  • Accelerometer
  • Elastic joint
  • Multivariable identification
  • Scara-type robot
  • Subspace identification method
  • Two-inertia resonant system

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Industrial and Manufacturing Engineering

Cite this

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title = "Decoupling identification and physical parameter estimation for serial two-link two-inertia system",
abstract = "This paper proposes a multivariable identification method for a SCARA-type planar two-link robot arm with elastic joints caused by reduction gears, which is treated as a serial two-link two-inertia system. The arm for the experimental verification is equipped with accelerometers that have the two roles described below. The proposed method consists of three steps. The first step is the rigid model parameter estimation by the least-squares method. The second step is the elastic model identification using a multi-input multi-output state space model technique, which enables the nonlinear interaction torques between two links to be decoupled. The torques, calculated using the accelerometer signals and the rigid model parameters, are employed as inputs for decoupling in the multi-input identification. The angular velocities of the links, calculated using the accelerometer signals and the motor encoder signals, are employed as outputs for improving accuracy in the multi-output identification. The decoupling method divides the serial two-link two-inertia system into two one-link two-inertia systems in this step. The third step is the physical parameter estimation of the onelink two-inertia systems. The physical parameters consist of motor inertias, link inertias, joint-friction coefficients and joint-spring coefficients. Furthermore fine tuning of the estimated physical parameters is carried out using closed-loop simulations with the nonlinear least-squares optimization. Experimental results using the two-link arm have shown the accuracy of the proposed identification method.",
keywords = "Accelerometer, Elastic joint, Multivariable identification, Scara-type robot, Subspace identification method, Two-inertia resonant system",
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AB - This paper proposes a multivariable identification method for a SCARA-type planar two-link robot arm with elastic joints caused by reduction gears, which is treated as a serial two-link two-inertia system. The arm for the experimental verification is equipped with accelerometers that have the two roles described below. The proposed method consists of three steps. The first step is the rigid model parameter estimation by the least-squares method. The second step is the elastic model identification using a multi-input multi-output state space model technique, which enables the nonlinear interaction torques between two links to be decoupled. The torques, calculated using the accelerometer signals and the rigid model parameters, are employed as inputs for decoupling in the multi-input identification. The angular velocities of the links, calculated using the accelerometer signals and the motor encoder signals, are employed as outputs for improving accuracy in the multi-output identification. The decoupling method divides the serial two-link two-inertia system into two one-link two-inertia systems in this step. The third step is the physical parameter estimation of the onelink two-inertia systems. The physical parameters consist of motor inertias, link inertias, joint-friction coefficients and joint-spring coefficients. Furthermore fine tuning of the estimated physical parameters is carried out using closed-loop simulations with the nonlinear least-squares optimization. Experimental results using the two-link arm have shown the accuracy of the proposed identification method.

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