Adaptive force/position control of robot manipulators with bounded inputs

In various automated industrial, medical, or service applications using robotic systems it is required to regulate both robot movement and contact force. In order to address this control problem, this paper presents a force/position control structure that has two characteristics that are very relevant in robot-environment interaction tasks. First, the structure of the controller is based on the use of generalized saturation functions, and this makes it possible to ensure that the robot actuators operate within a safe region without exceeding their torque limits. On the other hand, an adaptable term is included within the structure that allows to compensate for parametric uncertainty related to gravitational forces and the stiffness of the environment on which the robot operates. The validity and correct performance of the proposed control structure is based on a rigorous stability analysis, as well as numerical simulations using a three-degree-of-freedom robot manipulator.