Baby AUV

(This page adds some supplementary information to the Beacon article.)

Baby AUV is a low cost 2-DoF, micro AUV with some novel features. Without fins or sway thrusters, Baby AUV has to synthesise yaw:

Baby AUV coarse heading control

The moving mass actuator shifts the battery fore-and-aft to change balance and therefore pitch. The manoeuvre begins with the mass to the rear. Running the thruster slowly backwards generates a counter torque which is used to rotate the AUV about the vertical. At the appropriate moment, the thruster is shut off and battery is shifted again to pitch the AUV horizontal. At this point forward thrust is commanded and the AUV surges with a new heading.

Once the manoeuvre is complete, the AUV's heading can be trimmed:

Baby AUV fine heading trim

In the above video, the AUV has been programmed to maintain a heading pointing directly to the viewer's left. The AUV is free to pivot at the nose, like a tethered blimp. The single bladed propeller normally causes the AUV to wiggle left and right. By modulating the torque to the propeller, the wiggle can be exaggerated in one direction and diminished in the other, as required to trim the heading. The "single-bladedness" of the propeller is not relevant to the coarse heading twirl, only in fine heading trim.

An untethered demonstration of heading trim via prop walk is forthcoming.

Note: In the videos, the thruster is seen to be mounted off centre; this is due to internal space constraints and is not germane to the effects described.