Modeling and control of a hydraulically actuated flexible robot link of variable length

Through research in and production of radioactive materials the Department of Energy (DOE) has been generating toxic waste that was commonly stored in large, underground storage tanks. Long-reach manipulators (LRMs) will be used to remove waste from the tanks. LRMs exhibit flexible behavior and present control problems that are different from those seen with conventional manipulators. Because of the large payload requirement for removing tank waste, LRMs will use hydraulic rather than electric actuators. To explore the behavior of LRMs the Flexible Beam Test Bed (FBTB) was constructed at Pacific Northwest Laboratory (PNL). This thesis describes research performed on a simulation of the PNL FBTB at Oak Ridge National Laboratory (ORNL). The simulation includes dynamic properties of the FBTB, a PD controller with robust notch filter for control of the base actuator, and a model of the hydraulic actuator. The beam was rotated by the base actuator while being either held at a fixed length or varied in length. For each of these tests the controller was tuned for two different configurations. The results of the simulation experiments are presented in plots of actuator position versus time and actuator torque versus time. Rise time, settling time, and overshoot were calculated for each move. These performance characteristics were used to find the best control scheme for a given beam configuration.