A comparison of Filippov sliding vector fields in codimension 2

We consider several possibilities on how to select a Filippov sliding vector field on a codimension 2 singularity surface ΣΣ, intersection of two codimension 1 surfaces. We discuss and compare several, old and new, approaches, under the assumption that ΣΣ is nodally attractive. Of specific interest is the selection of a smoothly varying Filippov sliding vector field. As a result of our analysis and experiments, the best candidates of the many possibilities explored are those based on the so-called barycentric coordinates. In the present context, one of these possibilities appear to be new.