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Experimental study on a nonlinear observer application for a very flexible parallel robot


A flexible robot in lambda configuration has been modeled and built in hardware. This flexible robot includes some passive joints and flexible bodies and is an underactuated system. In order to control a very flexible underactuated system, using all states of the modeled nonlinear system is advantageous. Since there is no direct measurement of the end-effector positions and all modeled system states available, a nonlinear observer to estimate the states, the rigid motion of the passive joints and the elastic deformation of the flexible bodies, is designed based on the high gain observer method and experimentally tested on the lambda robot. Using the observed results from the nonlinear observer, the model of the robot used for control is improved so that the end-effector tracking error is drastically decreased. Based on the improved model, an updated nonlinear observer is redesigned and implemented on the lambda robot. The experimental results show that the end-effector positions and the states can be estimated with high accuracy in real-time even for the highly flexible parallel robot.

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This research was partially supported by the German Research Foundation, within the Cluster of Excellence in Simulation Technology SimTech at the University of Stuttgart. The authors appreciate these discussions.

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Correspondence to Fatemeh Ansarieshlaghi.

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Ansarieshlaghi, F., Eberhard, P. Experimental study on a nonlinear observer application for a very flexible parallel robot. Int. J. Dynam. Control 7, 1046–1055 (2019).

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  • Flexible parallel robot
  • Nonlinear observer
  • Multibody dynamics
  • State estimation