Abstract— This paper investigates the robustness of underconstrained cable-driven robots to external disturbance wrenches (force/moment combinations). Two cases are considered: impulsive disturbance wrenches and static (constant) disturbance wrenches. In the analysis of these cases a mapping to an intermediate space is introduced, which allows a restatement of Gauss’ Principle of Least Constraint in a simpler form. Two measures are developed: the impulsive disturbance robustness measure and the static disturbance robustness measure. It is then shown that these two measures can be expressed as a single disturbance robustness measure, R. This single measure enables underconstrained cable robots to be designed for maximum robustness to both impulsive and static disturbances.