Passive Force/Velocity Field Control for contour tracking of constrained robots

Passive Force Velocity Field Control (PFVFC) renders tracking along tangent of the contour, with low normal velocity regime, which is of particular interest for constrained tasks. Despite the evident advantageous characteristics of PFVFC, the original pioneering approach by Li&Horowitz has shown limitation for implementation. In this paper, a simpler yet faster and robust PFVFC is proposed for exponential contour force-velocity-position tracking. A regressor-free second order sliding mode is presented to produce an invariant error manifold for all time and for any initial condition. In this way, the robot velocity is immersed all time in the Passive Force-Velocity Field (PFVF), which is based on a fuzzy aggregation of orthogonal decomposition of the holonomic constraint that models the contour. In contrast to the original approach, our scheme does neither require the virtual fly wheel subsystem nor robot dynamic model nor derivative of the field. In this sense we argue our approach stands for a novel PFVFC, not a betterment nor extension of the Li&Horowitz one. Simulations for 2D and 3D robots are presented and discussed, which show the feasibility and viability of the proposed approach.