  This paper investigates the stability properties and performance of
super-twisting sliding-mode control loops subject to periodic perturbations.
Although there exist conditions on the control gains that guarantee finite-time
stability of the closed-loop system, such conditions are often too restrictive
from a practical standpoint, especially in relation to actuator limitations and
induced chatter. Using regularisation and averaging theory, it is proven that
under milder conditions for the control gains, the trajectories of the
periodically perturbed closed-loop system converge to a stable limit cycle of
the same period containing the origin. Additionally, guidelines for selecting
the controller gains are provided based on bounds of the closed-loop system
states. Finally, the theoretical findings are validated through simulations.
