Orthogonal experimental design is another design method to study multi-factors and multi-levels. It selects some representative points from the comprehensive experiment according to orthogonality, and these representative points have the characteristics of "uniform dispersion and uniform comparability". Orthogonal experimental design is the main method of partial factor design. This is an efficient, rapid and economical experimental design method. Kenichi Taguchi, a famous Japanese statistician, lists the horizontal combinations selected by orthogonal experiments in a table, which is called orthogonal table. For example, to do an experiment with three factors and three levels, according to the requirements of comprehensive experiments, experiments with cubic =27 combinations must be carried out, and the number of repetitions of each combination has not been considered. If the experiments are arranged according to the orthogonal table of L9(3)3, only 9 experiments are needed, and 18 experiments are carried out according to the orthogonal table of L13) 7, which obviously greatly reduces the workload. Therefore, orthogonal experimental design has been widely used in many fields. (Khan, I can't type the correct expression here. Anyway, everyone who studies this knows the specific writing. ) orthogonal table is a set of regular design tables, where l is the code of orthogonal table, n is the number of experiments, t is the horizontal number, and c is the number of columns, that is, the number of factors that can be arranged at most. For example, L9(34) means that 9 experiments are needed, and at most 4 factors can be observed, each of which is at level 3. Orthogonal tables can also have different levels in each column. We call it a mixed orthogonal table, such as L8(4×24). In the five columns of this table, 1 is level 4, and 4 columns are level 2. According to the data structure of the orthogonal table, the orthogonal table is a table with n rows and c columns, where the j column consists of numbers 1, 2, ... SJ, and these numbers all appear N/S times. For example, in the table 1 1, the number of digits in the second column is 3, and S=3, that is, 1, 2.