We’ve had a recurring issue with our Blueboat, which we thought was initially due to just really poor conditions with 30+ kt winds. If you can see from the image below (captured on a very calm day!), the Blueboat seems to squeeze two parallel lines of travel together, leaving larger gaps between every other survey line. It always looks like it’s not compensating enough to turn to the left (e.g. it always leaves the transect line to the left of direction of travel, rather than being over it).
Hi @Vincent -
I’m a bit confused - was the image taken in conditions with 30 knot winds, or a very calm day? Generally the unit should track the survey course perfectly, but if there are strong conditions it may not be able to overcome them.
Have you modified any of the default parameters, particularly around steering?
If you can share a .BIN autopilot log from one of the missions that exhibited the behavior, we can take a look!
No, the track above was in very calm seas, which is why I think it’s some sort of setting. No, we haven’t touched anything in the autopilot settings aside from the survey speeds.
The mission BIN files were too large to share (88mb), so here’s one with the Blueboat just on if you can look at autopilot parameters. 00000034.BIN (340 KB)
We ran a mission with more transect separation yesterday (2m) and the problem is still there but doesn’t scale (so still staying to the right of the transect travel, but not proportionally the same as with narrower transects).
This may get more well-informed responses in the general ArduPilot forum, as the developers there have had significantly more involvement with the mission planning and vehicle tuning parts of the ArduRover/ArduPilot codebase.
From personal experience with control systems, consistent offsets are often managed by an integral controller (error integrates over time, so small errors build up until corrected for), so perhaps the tuning is to blame (e.g. through an insufficient ATC_STR_RAT_I or PSC_VEL_I value, in the attitude and position controllers respectively, or saturation/limiting occurring due to the corresponding IMAX parameters).
That said, rather than adjusting those values independently it’s likely preferable to go through the Rover first drive documentation, as your issue may be caused by something else (e.g. steering trim, perhaps due to unbalanced vehicle drag / weight distribution or motor/propeller strength), and the controller tuning parameters are not independent of each other, so should generally be changed together via the recommended tuning processes.
It would be great if you’re able to follow up here with things you’ve tried that haven’t helped, and hopefully with the resulting solution so others can benefit from it too
Interesting, I hadn’t thought the payload would impact this sort of behaviour. Would you recommend doing this sort of rover first drive tuning every time a new payload is attached?
The payload is completely symmetrical, aside from the ping sounder. Since the sounder is on the starboard hull, it makes sense that it has a bit of ‘trouble’ turning to port. I’ll test this when the Blueboat comes back from the field and report back.
Hi @Vincent -
I too doubt that just the asymmetrical ping is causing the affect you’re seeing. Are there very strong water currents? Sharing a mission file, via weshare or similar, would let us investigate further. I didn’t see anything out of the usual in your autopilot parameters, they look to be the stock BlueBoat parameters?
The last mission we ran was in very calm conditions (no currents). I’ll see if I can dig up a mission file that has some more detail once I retrieve the blueboat from freight.
Yes, pretty much all stock settings, just some changes to survey speed.
