ROBAS - Advanced Robot Assembly (1995-1998)

The Robotics Group of the University of Patras is interested in the following three tasks:

  • Development of a Knowledge-based System for the generation of assembly strategies.
  • Simulation of robot cells for assembly of a valve produced by Zita Ltd.
  • Development of a Hybrid Force/Position Controller for the implementation of assembly strategies.

Knowledge Based System

  • The knowledge-based system accepts as input IGES files where the parts are containing geometrical data for the parts to be assembled.
  • The parts are classified according to their Geometric Features.
  • The parts for each assembly task are classified as either moving or stationary.
  • The C-Frames is defined on the moving part.
  • The artificial constraints of each assembly subtask are formulated according to the contact case between the moving and the stationary part.

A special algorithm for the identification of the contact case is developed. This algorithm inputs the signal from the force sensor. In addition, a fuzzy decision system has been developed in order to reason about the feasibility of the assembly with respect to the tolerances between the two parts and the robot repeatability error.


Simulation of Robot Cells

In GRASP program, two robot cells for the assembly of the Zita's valve are simulated. In the first cell, one robot is used. In the second cell two robots are used which are working in parallel.




Force Control Part of the Hybrid Control

A new force control law is developed. It is based both on an extension of the Sliding mode and of the Adaptive Estimation theory. The main feedback for the implementation of this law is the force sensor signal. In this law the uncertainties of the environment and of the robot parameters are considered. The adaptively is used for the reduction of the bounds of the uncertainty and of the estimation of the real parameters of the model, while the stability of the sliding model control law is taken into consideration.

Partners:
  • UWCC: University of Cardiff  (G.B.)
  • UP: University of Patras (Gr)
  • TUB: Technical University of Budapest (Hu)
  • UR: University of Rousse (Bu)
  • Zita Ltd. (Bu)
Research Group:
  • N.  Aspragathos
  • A. Dentsoras
  • C.J. Tsaprounis