Robotic Assembly of Rounded Parts With and Without Threads

This letter addresses the assembly of rounded parts with and without threads, which is considered as the backbone of several types of assembly, and proposes novel human-inspired strategies for the hole-in-peg and nut-in-screw assemblies. These strategies employ force/torque (F/T) measurements provided by a F/T sensor and consist of two phases, namely adjustment and alignment. The proposed solution is based on quasi-static models and on the concept of attractive region in environment, and it is implemented using active force control on a velocity-controlled manipulator to avoid damages in the manipulator or in the environment. The experiments using mechanical parts with narrow tolerances show a high success rate and performance, where relatively large position and orientation errors are dynamically eliminated.