Edge-following with a PUMA 560 manipulator using VAL-II

The ability to follow a curved edge with controlled contact force using a robot manipulator is useful in many tasks. An edge-following system using a PUMA 560 manipulator with unmodified Unimation controller and VAL-II language, wrist force sensor, and accomodation force control is described and modeled. The model is fourth order and is conditionally stable. The system is analyzed using this model, and the results compared with experimental data. Agreement is good considering the simplicity of the model. With commanded normal force of 6.67 N and following velocity of 20 mm/s we obtained RMS force errors of 1.03 N when following a straight edge and 2.72 N when following a curved "bump" of 40 mm radius of curvature.