The X-rudder has many advantages over the cruciform rudder. One of them is that it can still well control the vehicle even when some rudder blades fail. According to the rudder angle conversion theory of X-rudder and cruciform rudder; this paper proposes some direction angle control schemes; proposes a fault-tolerant control method and conducts a semi-physical simulation. The result shows that when rudder blade fails; the direction angle that we want to achieve finally stabilizes at the value we want.


The ocean is the origin of life; and the exploration to the ocean is endless. However; the ocean climate is relatively harsh and the underwater world is mysterious and unpredictable. So advanced underwater navigation equipment is a premise for the development of marine resources. For the personal safety of scientific researchers; underwater unmanned vehicles (UUV) have incomparable advantages over human operated vehicles. Scholars from all over the world have done a lot of research on the UUV. The motion control of the vehicle includes power control and attitude control. The power control relies on the propeller; and the attitude control depends on the control surface to change torque. The control surface generally refers to the rudder; and it includes two parts: the stabilizer and the rudder blade. Due to many advantages of the X-rudder with four rudder blades arranged in an X shape; it has been a research focus in recent years. Whether compared with traditional cross rudder or separate cruciform rudder; X-rudder has obvious advantages; which are mainly reflected in the following aspects:

1. Due to its special layout; the area of the rudder blade can be increased under the premise that it is not too wide horizontally and vertically does not exceed the baseline; thereby improving the rudder efficiency. Some scholars have justified the X-rudder's efficiency is over the cruciform rudder's (Han; et al (2017)).

2. Because it can control the direction and depth through four rudders instead of two or three rudders of the cruciform rudder; the relative rudder blade area is increased.

3. The motion of the vehicle can still be well controlled when single or double rudders are damaged.

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