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Research Papers

Dynamic Parameter Identification of Overactuated Parallel Robots

[+] Author and Article Information
Sébastien Briot

Institut de Recherche en Communications
et Cybernétique de Nantes (IRCCyN),
UMR CNRS 6597,
Nantes 44321, France
e-mail: Sebastien.Briot@irccyn.ec-nantes.fr

Sébastien Krut

Laboratoire d'Informatique,
de Robotique et de Microélectronique
de Montpellier (LIRMM),
UMR CNRS 5506,
Montpellier 34095, France
e-mail: sebastien.krut@lirmm.fr

Maxime Gautier

Institut de Recherche en Communications
et Cybernétique de Nantes (IRCCyN),
Université de Nantes, UMR CNRS 6597,
Nantes 44321, France
e-mail: Maxime.Gautier@irccyn.ec-nantes.fr

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received June 2, 2014; final manuscript received June 12, 2015; published online August 3, 2015. Assoc. Editor: Srinivasa M. Salapaka.

J. Dyn. Sys., Meas., Control 137(11), 111002 (Aug 03, 2015) (13 pages) Paper No: DS-14-1237; doi: 10.1115/1.4030867 History: Received June 02, 2014

Offline robot dynamic identification methods are based on the use of the inverse dynamic identification model (IDIM), which calculates the joint forces/torques (estimated as the product of the known control signal (the input reference of the motor current loop) with the joint drive gains) that are linear in relation to the dynamic parameters, and on the use of the linear least squares technique to calculate the parameters (IDIM-LS technique). However, as actuation-redundant parallel robots are overactuated, their IDIM has an infinity of solution for the force/torque prediction, depending on the value of the desired overconstraint that is a priori unknown in the identification process. As a result, the IDIM cannot be used as it is for such a class of parallel robots. This paper proposes a procedure for the dynamic parameter identification of actuation-redundant parallel robots. The procedure takes advantage of two possible modified formulations for the IDIM of actuation-redundant robots that can be used for identification purpose. The modified IDIM formulations project some or all input torques/forces onto the robot bodies, thus leading to a unique solution of the model that can then be used in the identification process. A systematic and straightforward way to compute these modified IDIM is presented. The identification of the inertial parameters of a planar parallel robot with actuation redundancy, the DualV, is then carried out using these modified IDIM. Experimental results show the validity of the methods.

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References

Figures

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Fig. 1

A 1DOF robot with actuation redundancy

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Fig. 2

A general parallel robot (gray circles denote actuated joints): (a) Kinematic chain (Ci,j is the joint j of the leg k, and mk is the total number of joints for the leg k) and (b) virtual tree structure

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Fig. 3

The DualV: (a) prototype of DualV robot and (b) kinematic description of DualV in a configuration where base frame x0Oy0 coincides with platform frame xpPyp

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Fig. 4

The controller for the DualV

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Fig. 5

Values of Γ1, estimated from input torques using the relation JpinvTτ from Eq. (30) (red lines) and calculated using identified parameters χ∧ from the relation IDMχ (blue lines) with the payload of 5.37 kg

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Fig. 6

Values of Γ2, estimated from input torques using the relation τ1:3-Jτ4Tτ4 from Eq. (36) (red lines) and calculated using identified parameters χ∧ from the relation IDMχ (blue lines) with the payload of 5.37 kg

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Fig. 7

The two trajectories used for the cross-validations: (a) trajectory 1 and (b) trajectory 2

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Fig. 8

Measured (red lines) and estimated (blue lines) input torques rebuilt using the identified parameters of case 1 on trajectory 1

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Fig. 9

Measured (red lines) and estimated (blue lines) input torques rebuilt using the identified parameters of case 1 on trajectory 2

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