Fuzzy adaptive force control of robot manipulators

In this paper, it is proposed a two level hierarchical control strategy to achieve accurate force and end-point position tracking of a planar two-link rigid manipulator. The upper level, designated as the fuzzy position adjustment, is developed by synthesising several basic ideas from fuzzy control theory and self-organising control, and consists of a direct fuzzy controller and a learning mechanism, that observes the error in force and outputs the appropriate adjustment in position in order to following the desired force profile. At the lower level an adaptive controller is designed to tracking the adjusted reference position given by the upper level. This global control strategy demonstrates to cope with some uncertainties in stiffness of the environment and exact geometry shape. To validate the proposed control scheme, simulations results are presented in order to show a good performance on tracking force/position trajectories.