Output feedback sliding mode control for a planar flexible manipulator

This paper describes the design and analysis of an Output Feedback Sliding Mode Control (OFSMC) architecture for flexible manipulators. The results of this study include the analytical development and experimental verification. The hardware system investigated included, (1) a modular flexible one-and two-link planar manipulators with conventional strain gages strategically located on each link for strain sensing, (2) DC servo motors and incremental encoders for each degree-of-freedom used for rigid motion slewing, and (3) a MATLAB/SIMULINK/ dSPACE system for real-time control and data acquisition. A nonlinear observer based on the dynamic model was used to determine system states for the model-based portion of the control law for the flexible single-link. Cubic spline reference trajectories were used to slew the manipulator. A numerical simulation model was matched with the physical parameters with the experimental response to a reference input trajectory. A nonlinear optimization algorithm was used for the two-link setup to determine optimal gains from the calibrated dynamic model. The OFSMC was able to produce a rest-to-rest, residual vibration-free, large angle maneuvers. These OFSMC designs were verified on the Sandia National Laboratories flexible manipulator testbed. These results show reductions in both residual vibration and settling time