An experimental study of adaptive force/position control algorithms for an industrial robot

This work presents the results of an experimental study of force/position control algorithms for an industrial robot with open control architecture, equipped with a wrist force sensor. The robot's end effector is in contact with a compliant surface of unknown stiffness. Two types of control schemes are considered which respectively achieve regulation and tracking of position on the contact surface and force along the direction normal to the surface. The desired position is scaled along the constrained direction so as to fulfill the force control objective; adaptive mechanisms are designed for the two schemes to compute the scaling factor, which depends on the unknown stiffness coefficient of the environment. A number of case studies are developed throughout the paper to illustrate the effectiveness of the force/position control algorithms under nonideal conditions.