Tracking Contact Transitions During Force-Controlled Compliant Motion Using an Interacting Multiple Model Estimator

This work concerns both monitoring of contact transitions and estimation of the unknown first-order geometric parameters during force-controlled motions. The robotic system is required to move an object among a sequence of contact configurations with the environment, under partial knowledge of geometric parameters (positions and orientations) of the manipulated objects and of the environment itself. An example of a compliant motion task with multiple contacts is considered, that of moving a cube into a corner. It is shown that by describing the contact configurations with different models, and by using the multiple model approach it is possible: i) to detect effectively at each moment the current contact configuration and ii) to estimate accurately the unknown parameters. The reciprocity constraints between ideal reaction forces and velocities are used as measurement equations. An Interacting Multiple Model (IMM) estimator is implemented and its performance is evaluated based on experimental data.