Frame in ardusub

[EliotBR (Eliot)]

@mnpmilan

What about the +ve and -ve sign?

@EliotBR

At the thruster level, the front of our thrusters is the more rounded side, where the cable comes in. ArduSub’s frame configurations are set up such that a thruster has positive contributions in the forwards direction of the thruster. Accordingly, if a thruster is pointing backwards relative to the vehicle then a “positive input” to that thruster will have a backwards effect on the vehicle motion, so the corresponding thrust factor (in the frame configuration) is negative.

As far as I can tell (just looking at the existing frame factors), the positive sign convention for the motor contribution factors is:

• Roll: right side down
• Pitch: nose up
• Yaw: nose to the right
• Throttle (vertical / heave): up
• Forward (surge): forward
• Lateral (sway): right

@mnpmilan

How are they calculated?

Aside from the posts I already directed you to:

@EliotBR

the thruster contribution factors are a tool, and are determined[/chosen] by the vehicle frame designer. They’re generally intended to be used to align thruster contributions with motion axes, so the autopilot has a nice abstraction for its control of the vehicle (e.g. the factors determine how autopilot tries to achieve commands/decisions to move in a particular way).

It is technically possible to do some extra things with the factors though, like if you have several vertical thrusters and they draw more power than you have available, then you could potentially reduce the magnitude of all the vertical and pitch/roll factors to restrict the vehicle’s vertical output.

@mnpmilan

… any clockwise or ccw roation direction?

I don’t believe there’s a specific convention here - the idea is just to have counter rotation between opposing pairs of thrusters (e.g. all the greens should have one propellor orientation and rotate a particular way to generate thrust in the desired direction, and all the blues should rotate the other way).