VARIABLE STRUCTURE STATE OBSERVER FOR FLEXIBLE JOINT ROBOTS

Abdel Badie Sharkawy - Anton Vitko - Ladislav Jurišica

   In the control of flexible joint robots (FJR), all state variables are usually assumed to be known. The description of the complete dynamic model requires four state variables for each joint: position and speed of the motor rotor (in front of the gearbox) and position and speed of the link (behind the gearbox). Setting four speed and position sensors in each joint appears difficult if not impossible. One method how to overcome this difficulty is to construct an observer which provides the estimate of a part of the state variables. The goal of this paper is to present an observer that requires neither exact knowledge of the robot parameters nor its non-linearity. Only average values of the robot dynamics are needed in deriving both the controller and the observer. The control scheme belongs to the category of variable structure systems (VSS). Simulation results show superiority of the proposed method.

Keywords: robot control, variable structure systems (VSS), flexible joint robots (FJR), robustness

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