liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
On Modeling and Control of Flexible Manipulators
Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Industrial robot manipulators are general-purpose machines used for industrial automation in order to increase productivity, flexibility, and quality. Other reasons for using industrial robots are cost saving, and elimination of heavy and health-hazardous work. Robot motion control is a key competence for robot manufacturers, and the current development is focused on increasing the robot performance, reducing the robot cost, improving safety, and introducing new functionalities. Therefore, there is a need to continuously improve the models and control methods in order to fulfil all conflicting requirements, such as increased performance for a robot with lower weight, and thus lower mechanical stiffness and more complicated vibration modes. One reason for this development of the robot mechanical structure is of course cost-reduction, but other benefits are lower power consumption, improved dexterity, safety issues, and low environmental impact.

This thesis deals with three different aspects of modeling and control of flexible, i.e., elastic, manipulators. For an accurate description of a modern industrial manipulator, the traditional flexible joint model, described in literature, is not sufficient. An improved model where the elasticity is described by a number of localized multidimensional spring-damper pairs is therefore proposed. This model is called the extended flexible joint model. This work describes identification, feedforward control, and feedback control, using this model.

The proposed identification method is a frequency-domain non-linear gray-box method, which is evaluated by the identification of a modern six-axes robot manipulator. The identified model gives a good description of the global behavior of this robot.

The inverse dynamics control problem is discussed, and a solution methodology is proposed. This methodology is based on a differential algebraic equation (DAE) formulation of the problem. Feedforward control of a two-axes manipulator is then studied using this DAE approach.

Finally, a benchmark problem for robust feedback control of a single-axis extended flexible joint model is presented and some proposed solutions are analyzed.

Place, publisher, year, edition, pages
Institutionen för systemteknik , 2007. , 146 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1336
Keyword [en]
System identification, multivariable systems, differential-algebraic equations, robots, manipulators, flexible structures, robustness, position control, nonlinear systems, closed-loop identification, frequency-response methods, industrial robots, robotics, control, feedforward, flexible arms
National Category
Control Engineering
Identifiers
URN: urn:nbn:se:liu:diva-10463ISBN: 978-91-85895-29-8 (print)OAI: oai:DiVA.org:liu-10463DiVA: diva2:17211
Presentation
2007-12-19, Visionen, Hus B, Campus Valla, Linköpings Universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-01-07 Created: 2008-01-07 Last updated: 2009-05-08
List of papers
1. Frequency-Domain Gray-Box Identification of Industrial Robots
Open this publication in new window or tab >>Frequency-Domain Gray-Box Identification of Industrial Robots
2008 (English)In: Proceedings of the 17th IFAC World Congress, 2008, 15372-15380 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper considers identification of unknown parameters in elastic dynamic models of industrial robots. Identifying such models is a challenging task since an industrial robot is a multivariable, nonlinear, resonant, and unstable system. Unknown parameters (mainly spring-damper pairs) in a physically parameterized nonlinear dynamic model are identified in the frequency domain, using estimates of the nonparametric frequency response function (FRF) in different robot configurations/positions. The nonlinear parametric robot model is linearized in the same positions and the optimal parameters are obtained by minimizing the discrepancy between the nonparametric FRFs and the parametric FRFs (the FRFs of the linearized parametric robot model). In order to accurately estimate the nonparametric FRFs, the experiments must be carefully designed. The selection of optimal robot configurations for the experiments is also part of the design. Different parameter estimators are compared and experimental results show the usefulness of the proposed identification procedure. The weighted logarithmic least squares estimator achieves the best result and the identified model gives a good global description of the dynamics in the frequency range of interest.

Keyword
System identification, Multivariable systems, Nonlinear systems, closed-loop identification, frequency response methods
National Category
Engineering and Technology Control Engineering
Identifiers
urn:nbn:se:liu:diva-12711 (URN)10.3182/20080706-5-KR-1001.02600 (DOI)978-3-902661-00-5 (ISBN)
Conference
17th IFAC World Congress, Seoul, South Korea, July, 2008
Available from: 2007-10-30 Created: 2007-10-30 Last updated: 2013-02-23
2. A DAE Approach to Feedforward Control of Flexible Manipulators
Open this publication in new window or tab >>A DAE Approach to Feedforward Control of Flexible Manipulators
2007 (English)In: Proceedings of the 2007 IEEE International Conference on Robotics and Automation, IEEE , 2007, 3439-3444 p.Conference paper, Published paper (Refereed)
Abstract [en]

This work investigates feedforward control of elastic robot structures. A general serial link elastic robot model which can describe a modern industrial robot in a realistic way is presented. The feedforward control problem is discussed and a solution method for the inverse dynamics problem is proposed. This method involves solving a differential algebraic equation (DAE). A simulation example for an elastic two axis planar robot is also included and shows promising results.

Place, publisher, year, edition, pages
IEEE, 2007
Keyword
Differential algebraic equations, Feedforward, Flexible manipulators, Industrial robots, Inverse problems
National Category
Engineering and Technology Control Engineering
Identifiers
urn:nbn:se:liu:diva-12853 (URN)10.1109/ROBOT.2007.364004 (DOI)1-4244-0602-1 (ISBN)1-4244-0601-3 (ISBN)
Conference
2007 IEEE International Conference on Robotics and Automation, Roma, Italy, April, 2007
Available from: 2008-01-07 Created: 2008-01-07 Last updated: 2013-12-04
3. A Benchmark Problem for Robust Feedback Control of a Flexible ManipulatorA benchmark problem for robust feedback control of a flexible manipulator
Open this publication in new window or tab >>A Benchmark Problem for Robust Feedback Control of a Flexible ManipulatorA benchmark problem for robust feedback control of a flexible manipulator
2007 (English)Report (Other (popular science, discussion, etc.))
Abstract [en]

A benchmark problem for robust feedback control of a flexible manipulator is presented. The system to be controlled is a four-mass system subject to input saturation, nonlinear gear elasticity, model uncertainties, and load disturbances affecting both the motor and the arm. The system should be controlled by a discrete-time controller that optimizes performance for given robustness requirements. Four suggested solutions are presented, and even though the solutions are based on different design methods, they give comparable results.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2007. 12 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2820
Keyword
Robots, manipulators, flexible structures, robustness, position control
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-12854 (URN)LiTH-ISY-R-2820 (ISRN)
Available from: 2008-01-07 Created: 2008-01-07 Last updated: 2014-10-08Bibliographically approved

Open Access in DiVA

cover(50 kB)59 downloads
File information
File name COVER01.pdfFile size 50 kBChecksum MD5
b3c526e5a242ed1d22876c3684b61dde8bb3c03ce48a7016a1dd15b319269fb6eaafde78
Type coverMimetype application/pdf
fulltext(2129 kB)6487 downloads
File information
File name FULLTEXT01.pdfFile size 2129 kBChecksum MD5
3dddf64881f63998931c0cdac9d354cb2ec152d1e552dd6aa88442213621949e0ff0b93b
Type fulltextMimetype application/pdf

Authority records BETA

Moberg, Stig

Search in DiVA

By author/editor
Moberg, Stig
By organisation
Automatic ControlThe Institute of Technology
Control Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 6487 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1151 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf