Figure 4.

Four solutions of Filippov system (6) which starts from different initial values, where the sliding region Σ_S is shaded and crossing region Σ is unshaded. The solutions switch their directions at T = C_T = 500, and orbits slide along the shaded region which corresponds to mechanical sticking. The parameter values are given in Table 1 with η_RT = 0.8 and η_{P I} = 0.