  The paper shows sufficiency conditions for stability of continuous periodic
orbits under phase uncertainty. Phase based uncertainty is a trait of bipedal
walking robots, where the desired trajectories are parameterized by a
monotonous function. This monotonous function, called the phase variable, is
often affected by intermittent perturbations due to noisy sensors. We will
mainly focus on continuous periodic orbits obtained via parameterized
trajectories, and then analyze their stability properties under a noisy phase
estimation. In other words, our focus is on examples where phase variables are
difficult to compute, and therefore are imperfect. We will show that stable
periodic orbits subject to phase based uncertainty are input to state stable.
