First, for each opening, we calculate the coordinates ðx; y; zÞ of
the point where the forklift picks up or deposits an item on the opening Oijkt (Fig. 11).
Analogous to what we did in Section 3.1, here we provide a mathematical finite sequence to calculate the picking point of an opening Oijkt , denoted as OPijkt 1⁄4 ðXPijkt ; YPijkt ; ZPijkt Þ where