Robust, non-linear impedance control for robot manipulators

The work presented here is a practical, non-linear controller design methodology for robot manipulators that guarantees: 1) the robot end-point follows an input command vector "closely" when the robot is not constrained by the environment, and 2) the contact force is a function of the same input command vector (used in the unconstrained environment) when the robot is constrained by the environment. The controller is capable of "handling" both types (constrained and unconstrained) of maneuverings, and is robust to bounded uncertainties in robot dynamics. The controller does not need any hardware or software switch for transition between unconstrained and constrained maneuvering. In this design method, the structural compliancy of the manipulator has also been considered. A set of experiments were carried out to describe how this unified approach can develop electronic compliancy in a robot manipulator. The control architecture has been described by two different methods; frequency domain, and input/output time domain properties.25,26