It is known that the most stressful bounded (time maximum) disturbance for
stabilized linear systems is of bang-bang type. This bang-bang disturbance
can often he implemented with a switch set of current states for second-ord
er systems. The isochrones, as the level sets, determine the value of the d
isturbance index in a state space setting. In this note, we suggest an effi
cient way to construct the time maximum disturbance from the information of
isochronal wave front using it in a model predictive scheme. This overcome
s the shortcomings of the original switch set which are constructed through
time backward computation and only available for first and second-order sy
stems. Simulation results show how the isochrones evolve and can be utilize
d in synthesizing the time maximum disturbance for linear systems of second
and then higher order. For third-order systems, the associated L-infinity-
gain of the time maximizing disturbance is found.