  Scalable safety verification of continuous state dynamic systems has been
demonstrated through both reachability and viability analyses using parametric
set representations; however, these two analyses are not interchangable in
practice for such parametric representations. In this paper we consider
viability analysis for discrete time affine dynamic systems with adversarial
inputs. Given a set of state and input constraints, and treating the inputs in
best-case and/or worst-case fashion, we construct invariant, viable and
discriminating sets, which must therefore under-approximate the invariant,
viable and discriminating kernels respectively. The sets are constructed by
scaling zonotopes represented in center-generator form. The scale factors are
found through efficient convex optimizations. The results are demonstrated on
two toy examples and a six dimensional nonlinear longitudinal model of a
quadrotor.
