ENGINEERING SUMMARY REPORT ON A HYDROFOIL AUTOPILOT SYSTEM DESIGN STUDY PROGRAM

摘要

Preceding work on an automatic control system for the 110-ton craft has been reported in Reference 1 and has demonstrated satisfactory performance of the longitudinal system design. A potential hazard was uncovered in the course of the lateral control system design, however, in the form of a divergent instability for the case of large differential strut submergence and it was the purpose of the work reported herein to analyze this problem in greater detail and, having established a lateral control system design, to demonstrate overall performance of the craft in three-dimensional simulation.nSince the differential strut submergence stability problem is not unique in principle to the 110-ton craft, a brief analysis of the conditions that might lead to such instability was compared for the 110-ton craft and the Navy 5-ton experimental hydrofoil craft "Sea Legs". Sea Legs was chosen for this comparison because this craft has been operating in seas commensurate with its size for many months with only a roll angle-aileron loop without manifesting the stability problems that are predicted by the present analysis for the 110-ton craft. Mathematical details of this comparison may be found in Appendix C with the results (Figure 2-1) showing that differential strut immersion must be rela¬tively more extreme (and so the likelihood accordingly) for Sea Legs than for the 110-ton craft before stability problems- are encoun¬tered. Conversely, this phenomenon is more probable on larger craft (like the 300-ton craft) than it is on the 110-ton craft.