Active Vibration Control of Flexible Robots Using Virtual Spring-damper Systems

  • Authors:

  • Werner Bernzen

  • Affiliations:

  • University of Duisburg, Faculty of Mechanical Engineering, Department of Measurement and Control, D-47048 Duisburg, Germany/ e-mail: Email: bernzen@uni-duisburg.de

  • Venue:
  • Journal of Intelligent and Robotic Systems
  • Year:
  • 1999

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Abstract

When using robots for heavy loads and huge operating ranges, elasticdeformations of the links have to be taken into account during modeling andcontroller design. Whereas for conventional rigid multilink industrialrobots modeling can schematically be done by standard techniques, it is amassive problem to obtain an accurate analytic model for multilink flexiblerobots. But an accurate analytic model is essential for most moderncontroller design techniques, and modeling errors can lead to instability ofthe controlled system due to spillover since the eigenvalues of the systemare only slightly damped. A new approach to active damping control forflexible robots is presented in this paper where the actuators act likevirtual spring-damper-systems. As the spring-damper-element is a passiveenergy dissipative device, it will never destabilize the system and thus thecontrol concept will be very insensitive to modeling errors. Basically, thetwo parameters, spring stiffness and damping constant of this system, arearbitrary and model independent. To satisfy performance requirements theyare adjusted using knowledge of the system model. The more it is known aboutthe system model, the better these parameters may be adjusted. The new inputof the controlled system is a virtual variation of the spring base. Thepaper illustrates this technique with the help of a simple and easy to modelone link flexible robot which is also available as a real laboratory testbed.