Omni Thruster configurations

I have been looking at the current OMNI frame classes and from what I can tell they are essentially just rover layouts and are more like theoretically ideal setups rather than what is possible. the reason I bring it up is that I have had some debates recently about how to apply omni frame control to real world boats.

these 3 frames can be easily modified to fit most existing ships and boats with bow or stern thrusters using some slightly different layouts

Omni 3A would represent most standard omni capable boats that are out there, something like a twin screw tug, 2 propellers and a bow thruster, the reason it would work as an omni is even through the bow thruster is really far forward and applies a lot of yawing force, it can still push the boat to the side as long as the main motors can counteract the yaw, it will move slowly and use a lot of power to do it but it will be possible. I added the rudder to show how it can also help divert some flow from the propellers to help with translating, twin rudders would work better but a single one will still help.

The omni 3 plus layout is basically a single screw boat with bow and stern thrusters. this is configured as a Omniplus with the 4th motor not used, since 4 and 2 just mirror each other it makes motor 4 redundant.

OmnPlus advanced is the omni plus configuration, but we have replaced motors 2 and 4 with left and right motor output. This gives the advantage of having much more yaw authority since you have both left and right motors doing yaw along with the thrusters. this makes sideways movement far more accurate, as your not relying just on small thrusters to control yaw and propel the boat sideways.

these 3 extra layouts can be done with current code as is the only issue I ran into was with prearm checks because it’s using 2 steering methods at the same time for omniplus A plus the lack of motor 4 for omni3plus.

1 Like

The problem is, last I heard loiter is not possible yet with these omni configurations. A combination of differential steering and ackerman could probably be used. Steering rate tuning may be tricky though.

acro works at the moment, it will hold position and orientation in that mode, loiter just works as normal.

Hello Geofrancis
I’m looking at building a 5x4 meter platform with “dynamic positioning”. I’m envisioning a Trimaran configuration (Composite Center hull and additional inflatable hulls on either side). I like your OmniPlus A setup. I could put a bow and stern thruster in the center hull, and a main thruster on each side.
have you been able to do any real testing?

The only reason I would recommend the omni +A is if you have really weak bow and stern thrusters, so the propulsion motors will help with yaw control.

Copy that. We like the trimaran setup as this should allow for fairly good travel speeds for when the platform needs to get from A to B.
Have to tried around with ArduSub? ArduSub allows for custom setups:
http://www.ardusub.com/developers/developers.html#making-a-custom-configuration
I wonder how the ArduSub firmware allows you to hold position…
I also just saw your other posts. Wow, that is an impressive Build!

I tried posting the following on the ArduSub Forum and they more or less sent me back to Ardurover :wink:

Maybe we I can get some more ideas?

Hello. We have been building USVs (skid steering setup) for the last couple of years and optimizing them for good position holding (loitering in ArduRover). We have very good precision but are dependent on wind direction, as the vehicle always points against the wind (and or a combination with Current when available).
We are now venturing into a dynamic positioning project. More concretely we want to build a larger platform (5m x 4m) for scientific purposes. This platform must be able to hold position and any direction.

We are thinking of a trimaran setup , with both a bow and stern thruster and a main motor on either side. The idea being that we should have fairly efficient position holding and also cruising capabilities.
What is the current status in the Arduboat software? Is any kind of Positioning with a given heading (with an OmniPlus A configuration) possible?
We’ll be happy to put in some legwork and testing…

Thanks!
platform_config.pdf (263.2 KB)

I believe it currently works in acro mode but not auto mode.