The output y is obtained by applying a factor in the interval [0,1] to the maximum output u_max (the ceiling). It effectively calculates a smooth minimum with regard to the inputs u and u_max:
The following graph shows the results for u_max = 1.0
and k ∈ {10,5,3,2}
:
When the intended output u
is a small fraction of the maximum output u_max
(ceiling) the actual output y
will be equal to the intended output. As u
approaches the ceiling the limitations will have a gradual effect so that less than the intended output is returned. Eventually the output will be identical to the maximum value.
u : u_max
is used as input to the smooth minimum; John Sterman [3, pp. 711-713] uses the ratio u_max : u
instead.