PID loop sounds great. Roll will typically seek 0 when steering is neutral.
But for good maneuvering setting the desired value is critical.
- For a catamaran it’s likely you’ll want to stay close to 0 during turns regardless of speed so thats an easy one.
- But for a monohull, the amount of roll in a turn usually depends on what ‘feels’ comfortable or safe when on a boat. Too flat and you feel like you’re being thrown out of boat, and too steep and the boat can spin out.
The roll affects the g forces experienced, as well as the turn radius and how much speed can be carried through the turn. It also affects how much throttle you need to complete the turn. So, for a racing boat, this would be really handy to optimize, and it will be different for each boat depending on type and number of props, and the ‘V’ of the hullform.
It would be nice to make the desired roll a function of both steering and throttle inputs:
- Steerage because that will indicate how sharp a turn is being executed
- Throttle because the desired roll angle in a turn also decreases with increased speed.
Regarding pitch… well the boat will usually pitch up a lot initially as it gets onto the plane, and then once there it will settle down. Ideally this is a function of speed, but for now if you could manually set the target (to say, 2-4 degrees bow up) that would be just fine. Bear in mind that the trim tabs can only create a bow down moment. So if the boats center of mass is too far forward, then it may not even reach these pitch values and the trim tabs wont do anything. (In his case the pilot can simply adjust the CoM further aft to increase the natural pitch of the boat at speed).
Lastly, I guess you could mix the two so that the roll outputs are simply added to the pitch outputs, and those mixed values are what the servos execute…?