“…Control of second‐order nonholonomic systems, such as the planar underactuated vehicle considered in this paper, is quite challenging and significant, and has received increasing interest over more than two decades. In real engineering, second‐order nonholonomic systems may arise from several mechanical models, such as gravity‐assisted underactuated manipulators , planar rotational‐rotational‐rotational (RRR) manipulators (with the last joint un‐actuated) , planar prismatic‐prismatic‐rotational (PPR) manipulators (with the rotational joint un‐actuated) , rotational inverted pendulums , and underactuated surface ships . Second‐order nonholonomic constraints restrict the generalized accelerations and cannot be integrated to first‐order nonholonomic ones, rendering the techniques so far developed for first‐order nonholonomic systems non‐applicable.…”