Addendum to "A new minimum-time control law for a one-mode model of a flexible slewing structure"

In a previous article by Barbieri et al. (ibid., vol.38, p.142-6 (1993)) a set of five conditions were given to characterize the switching hypersurface of the minimum-time, single-axis controller for an undamped, one-mode model of a flexible slewing structure. The purpose of this paper is to show that the five conditions have been found to be reducible to three. This oversight is repaired, and a new plot of the three conditions in a two-dimensional plane is isolated to easily identify the switching strategy in real-time.