**3.1. System dynamics**

Some basics lessons come from a brief analysis of the uncontrolled system dynamics. The open loop plant equations are potentially unstable (at least persistently oscillatory) with respect to only the bow rudder, while the relationship can be stable with respect to the stern rudder alone. *Can be stable* is exaggerated to emphasize the presence of pole-zero cancelation, which is an unwise practice (especially in this instance with both poles and zeros at the origin on the stability boundary) unless the estimates for the constants in the system equations are very well known. The analysis of the dynamics also revealed the bow rudder was least relativelyeffective at maneuvering alone when compared to the stern rudder, however the bow rudder does enhance vehicle maneuverability when used together with the stern rudder as a "scissored-pair" where the sign of the maneuver angle is opposite for each rudder. This "scissored-pair" constraint simplified the MIMO control design, allowing the design engineer to treat the system as a SISO design, since one rudder's deflection become a dependent variable constrained to the other rudder's deflection.
