Preliminary Study of End-Effector Compliance for Reducing Insertion Force in Automated Fluid Coupling for Trains

Robotic assembly of mating parts (peg-in-hole (PiH)) inevitably encounters misalignments. Although passive end-effector compliance is key to successful alignment during the assembly, the literature does not propose many solutions for large misalignments, which is relevant to applications such as compliance of a robot end-effector for train fluid servicing. The results from physical experiments indicate insertion forces that are too large for practical applications, even with small misalignments. This preliminary study applies a hybrid approach combining physical experiments and simulation modelling for large motion PiH coupling with end-effector compliance. This provides a platform for investigating insertion force during misaligned coupling. The simulation model contains configurable parameters for robot compliance and PiH friction which are informed by the physical experiment results. The many robot compliances are lumped as two torsional springs on the pitch and yaw motion axis of the robot arm model. The simulation model is then calibrated using the physical results without having to conduct further intensive physical experiments. The calibrated model represents the physical measurements to a satisfactory degree, however its performance can still be improved.