A degenerate planar piecewise linear differential system with three zones

In (Euzebio et al., 2016 [10]; Chen and Tang, 2020 [8]), the bifurcation diagram and all global phase portraits of a degenerate planar piecewise linear differential system <(x)over dot> = F(x) - y, <(y)over dot>= g(x) - alpha with three zones were given completely for the non-extreme case. In this paper we deal with the system for the extreme case and find new nonlinear phenomena of bifurcation for this planar piecewise linear system, i.e., a generalized degenerate Hopf bifurcation occurs for points at infinity. Moreover, the bifurcation diagram and all global phase portraits in the Poincare disc are obtained, presenting scabbard bifurcation curves, grazing bifurcation curves for limit cycles, generalized supercritical (or subcritical) Hopf bifurcation curve for points at infinity, generalized degenerate Hopf bifurcation value for points at infinity and double limit cycle bifurcation curve. (C) 2021 Elsevier Inc. All rights reserved.