Читать книгу Control Theory Applications for Dynamic Production Systems - Neil A. Duffie - Страница 36

The relationship between work in progress (WIP) and actual capacity shown in Figure 2.17 is another example of nonlinear behavior. When WIP w(t) is relatively low in a production work system such as that shown in Figure 2.15, production capacity may not be fully utilized and actual capacity can be less than full capacity because of the work content of individual orders and the timing of arriving orders. Conversely, when WIP is relatively high, work is nearly always waiting and the work system is nearly fully utilized. The actual capacity ra(t) of the work system therefore may depend on both its full capacity rf and the work in progress w (t).

Figure 2.17 Actual production capacity function and a piecewise linear approximation.

As shown in Figure 2.17, the actual capacity function can be approximated in a piecewise manner by two segments, delineated by a WIP transition point wt hours, where for w(t) ≥ wt

and for w(t) < wt