Positioning of Unknown Flexible Payloads for Robotic Arms Using a Wrist-Mounted Force/Torque Sensor

The problem of control design for robotic arms manipulating unknown flexible payloads is considered in this paper. A novel scheme utilizing a force/torque sensor at the wrist of the manipulator is utilized. This choice of sensor is adequate to glean information about payload vibrations without outfitting the payload with sensors and offers the additional advantage of furnishing a minimum phase system, thus simplifying the control design. A controller utilizing wrist torque feedback from the sensor is designed as a function of the system parameters. An adaptive scheme for on-line identification of these parameters and adaptation of controller parameters is discussed. The proposed scheme is generic in regard to the nature of the flexible payload, as is shown through simulation studies. The scheme is implemented on a single-link manipulator carrying an unknown flexible payload. Simulation and experimental results validate the fact that the adaptive control maintains a robust performance for high speed slewing and varying payloads.