2-D contact detection and localization using proprioceptive information

This paper employs proprioceptive information (joint angles and torques) to estimate properties of the contact between a planar robot and an unknown object without specifically requiring strategic manipulator motions. The algorithm presented tackles this task in two stages; a contact localization analysis is followed by a force domain contact detection analysis. In the former, the Cartesian endpoint velocities are used for each link to obtain an estimate of the location of a hypothetical contact point on the link surface. A second observer, based on the displacement between two consecutive postures of the manipulator, provides an estimate of the error associated with this location. This data is fused over time by tracking the contact location using a linear observer and results in a hypothetical contact location, an associated uncertainty region, and a surface normal estimate. The detection phase uses torque domain evidence and the location estimates to verify the existence of each of the contacts. This process allows the detection of one contact per link and provides estimates of contact location, velocity, surface normal, and contact force