2.5.2. Steepest Ascent Test Design

To screen the optimal parameter range of the significant factors in the phloem and xylem, Design-Expert software was used to conduct the steepest ascent test. During the simulation, based on the results of the Plackett–Burman test, the values of the nonsignificant factors were taken from the physical test values, and the values of the remaining factors were taken from the median values of the Plackett–Burman experimental levels. The significant factors were gradually increased according to the selected step size. The relative error between the measured results and the simulated stacking angle was analyzed until the minimum range of the upper and lower relative errors was selected as the basis for the response surface test value.
