0
TECHNICAL PAPERS

Independent Identification of Friction Characteristics for Parallel Manipulators

[+] Author and Article Information
Houssem Abdellatif1

 Hannover Center of Mechatronics, Appelstr. 11, D-30167 Hannover, Germanyabdellatif@mzh.uni-hannover.de

Martin Grotjahn, Bodo Heimann

 Hannover Center of Mechatronics, Appelstr. 11, D-30167 Hannover, Germany

1

Corresponding author.

J. Dyn. Sys., Meas., Control 129(3), 294-302 (Aug 28, 2006) (9 pages) doi:10.1115/1.2718242 History: Received September 02, 2005; Revised August 28, 2006

The compensation for friction or joint losses in robotic manipulators contributes to an important improvement of the control quality. Besides appropriate friction modeling, experimental identification of the model parameters is fundamental toward better control performance. Conventionally steady-state friction characteristics are investigated for mechanical systems in the first step. However, and due to the high kinematic coupling, such procedure is already complicated for complex multiple closed-loop mechanisms, like parallel manipulators. Actuation friction of such mechanisms becomes configuration dependent. This paper presents a methodology that deals with such challenge. The kinematic coupling is regarded in the friction model and therefore in the design of the experimental identification. With the proposed strategy, it is possible to identify the steady-state friction parameters independently from any knowledge about inertial or rigid-body dynamics. Friction models for sensorless passive joints can also be provided. Besides, the method is kept very practical, since there is no need for any additional hardware devices or interfaces than a standard industrial control. The suitability for the industrial field is proven by experimental application to PaLiDA that is a six degrees of freedom parallel manipulator equipped with linear directly driven actuators.

FIGURES IN THIS ARTICLE
<>
Copyright © 2007 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

General scheme of the kinematics for parallel manipulators

Grahic Jump Location
Figure 2

Calculated rigid-body forces for a typical motion with constant end-effector velocity

Grahic Jump Location
Figure 3

Used trajectories for the identification of local friction characteristics

Grahic Jump Location
Figure 4

For identification motion calculated active joint variables and passive joint variables. The validated data correspond to close area, so that averaging is admissible.

Grahic Jump Location
Figure 5

Distribution of configurations in workspace with related PTP trajectories, used for the identification of friction parameters

Grahic Jump Location
Figure 6

The PKM PaLiDA. Left panel: test bed at the Hannover industrial fair 2001. Right panel: CAD model.

Grahic Jump Location
Figure 7

Velocity-force characteristics for PaLiDA. (◻) Measured actuation forces, (-∙-) fitted local model, (∘) measured forces after compensation of centrifugal effects, and (- - -) fitted local model after compensation of centrifugal effects.

Grahic Jump Location
Figure 8

Configuration dependent force-velocity characteristics for single actuator. (∘) measured forces and (—) fitted local model. The x axis of all figures refers to the actuator velocity (m/s), y axis corresponds to the actuator force (N).

Grahic Jump Location
Figure 9

A strut of the PKM PaLiDA with the respective passive and active joints

Grahic Jump Location
Figure 10

Measured (thick line) versus calculated forces. Thin line: only rigid-body model, medium line: with additional friction forces.

Grahic Jump Location
Figure 11

Experimental results: improvement of control accuracy by friction compensation (thick line) compared to compensation of rigid-body dynamics only (middle line) and by using simple PID control (thin line)

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In