Initial experiments on the end-point control of a 2-DOF long-reach elastic manipulator

To support the study of dynamics and control for long-reach, space-based manipulators, an experimental planar manipulator has been developed. The arm has a 15 ft reach with flexible links at the shoulder and elbow joints. The arm's equations of motion are derived with the aid of TREETOPS, a multibody dynamics analysis program. The resulting model is validated against experimental data. To serve as a base line for future work, two classically designed controllers have been implemented. One relies on sensors collocated with the joint actuators, while the other uses an end-point sensor measuring Cartesian displacements. Comparison of the controllers' experimental closed-loop responses demonstrate the performance improvements achievable using end-point position feedback; most notable is the more than two fold increase in control bandwidth. Experimental and simulation results also demonstrate the end-point controller's improved `Cartesian impedance.'