In real control systems, the realization of an instantaneous switching of the control parameter is not always feasible. In
order to mimic the delayed response of a pneumatic control system, in the numerical simulations we applied a continuous
approximation of the switching laws (35). For that purpose let us first introduce a discrete time representation. We consider
the time period ½0; T represented by a set of time instants ftjgj ¼ 0;1;…;n where t0 ¼ 0, tn ¼ T, and tjþ1 tj ¼ Δt for all j. We
assume that the initial control for the coupler a is given by u
aðt0Þ ¼ umin, and the time needed to switch the control value is
equal to DT (referred later as the delay time). Under these assumptions, for the coupler a we will use the following piecewise
linear control: