The objective of this research is to develop a defense/offense decision-making controller for a billiard robot by using Fuzzy and Extension theory. The main purpose is to make the billiard robot possess the imitation ability of how human beings do the defense/offense decision-making in a block ball game. The offense cushion shot means to pocket the object ball. After hitting the table rail, the defense strategy is developed by four conditions which are the distance between the cue ball and the object ball, distance between the object ball and the corresponding pocket, the angles between the cue ball, the object ball and the corresponding pocket, and the information of the block ball. In addition to the four parameters, it must be considered whether the cue ball or the object ball contacts the rail of the table after the cue ball strikes the object ball. Finally, the billiard robot will execute the hitting command to let the cue ball strike the object ball and make an offense or defense shot in the experiments.
