An Intelligent Indirect-Hybrid Force/Position Controller for Smooth and Accurate Tracking of Unknown Contours

A force-controlled portrait drawing robot

“…The robot is mounted with a 6-axis Force/Torque sensor at its wrist. To draw an edge on the whiteboard plane with roughly known board's position and orientation, we can use an unknown contour-tracing approach as given in [8] and [9]. But these approaches can draw in two dimensional world only.…”

“…In order to align the drawing pen with the net force vector, the above transformations were performed in the reverse order. Also, using a single set of force values, the complete alignment was not performed; rather incremental orientation corrections were made using fully active sensing as described in [8]. Finally, when the pen is aligned with the net force vector, there is only the force component in z-axis and the other force components are negligible in magnitude.…”

“…After the pen is oriented properly, it can be moved either tangentially or using prediction (as given in [8]) over the drawing surface.…”

Robotic polishing of pilger-die

“…For this, the die was placed one over the other ( Figure 2) and the robot tries to move the polishing tool to and fro over the groove-surface while applying a constant force of 10 N. The robot is given a start point and then it moves over the unknown die contour. For this, the contour tracking approaches for unknown contours as discussed in [7] can be used. The tool needs to be oriented tangential to the surface.…”

“…This is known as the Hybrid Position/Force Control (called Indirect Hybrid Position/Force Control in case of an Industrial Robot since the force commands are also converted to the position commands as can be seen in Figure 8). The orientation control of the tool can be done either from the force values read [7] or considering the die surface circular and providing the center of the die initially as an input to the polishing program. This approach had several drawbacks viz.…”