This paper presents feedback control laws for pursuing and catching a fly ball by taking Chapman's hypothesis into the closed-loop system connecting perceptions and actions. Through the analysis of the closed-loop system, we make it clear that the hypothetical trajectory Chapman showed is a special dynamic solution of the closed-loop system. Moreover, using a motion-analyzing technique over a finite time, it is shown that the proposed feedback control laws make it possible to generate a pursuing trajectory automatically that a fly ball can be caught in the right place and at the right time. It is also shown that the pursuing trajectory gets closer to the one Chapman showed as a feedback gain increases. In addition, we compare the proposed feedback control laws with Proportional Navigation (PN) which is the most common navigation technique for tracking a moving target, and demonstrate that the proposed control laws perform better than PN.

The SPD (Structured Programming Diagram) is a documentation technology used to design well structured programs. With SPD, designers can easily express functional structure, control structure, and physical layout of a program on one sheet of paper. Its straightforward expression appeals to both document writers and readers. SPD concept and conventions are introduced in this paper. SPD usage is then explained with a program design example. Other documentation technologies used in coordination with SPD are briefly touched upon. Finally, SPD reputation and evolution in the last ten years are reviewed.