A fuzzy logic force controller for a stepper motor robot

The authors describe a fuzzy logic force controller used to solve the robotic hard contact problem. This involves the control of force interactions between a stiff manipulator and an environment with very little compliance. It is demonstrated that this type of force control is well suited for a fuzzy logic controller. The controller was implemented on a MERLIN 6540 industrial robot. The design considerations that went into developing a joint-position force controller for a stepper motor robot are discussed, as well as the reasoning behind the selection of the fuzzy membership sets and rule base. Experimental force responses are presented for a step and sinusoid change in desired force when the MERLIN robot is in contact with a hard surface. Results of commanding the robot to maintain a constant force on a surface while following a trajectory tangent to the surface are described