PD8K-pendragon8000 said:
This is really bad news - I can only imagine the frustration and disappointment. But I expect you will soldier on and get this beat.
I was hoping that a member with experience tuning a powerful machine could help out - this is outside my experience. That said, here's some thoughts for the next go round that are just reasoned guesses:
A. Taming Axle-Breaking Power
I'm awestruck that you are able to apply enough power to break an axle and this is probably worth a separate discussion thread in its own right. Two things you might try are to set the block time to zero and to reduce the phase current to 2:1 or less. As mentioned recently, when doing a WOT getaway, the controller switches to an internal preset amp limit that is determined by board type for 'block time' seconds. It's generally so high as to be unlimited. The CA should limit this to MaxCurrent (or the throttle setting for Current Throttle), but there's no good reason to have the controller doing something unnecessary so the CA can try to undo it. Reducing the phase amps will reduce the torque immediately after getaway which may help hold your axle together.
B. Update to 3.0p6
You are running on B21 which is old and unsupported. I know this has been a struggle and you seem to have run through all the known options. You may have to resort to pulling the CA, taking it to another PC, and running it off a small battery to get it flashed.
Justin could better speak to this, but I don't believe there were any changes in the AGain/Current PI Controller logic between B21 and P6 that would materially affect the surging issues. The ramping settings were changed from a dimensionless 0-999 range to the newer Volt/sec scheme, but that should be a matter of interface not functionality.
C. Reduce Magnitude of PI Controller Correction
The PI controller (actually an 'I' controller) for current effectively applies ZERO/WOT to make any but the smallest corrections. As you know this can lead to extreme surging when there is significant overcorrection. Things tame down quite a bit when overcorrection is reduced and AGain approaches a good setting. Although there are no means to reduce the amount of throttle applied for a correction, you might use UpRate and DownRate to soften the correction application. This is sort of an unusual use, but it may help as the ramping logic prevents large changes in throttle. I think you were going in this direction, but here you might set this up and then resume normal tuning efforts with AGain. Once AGain is nearing a Good Setting, you might reduce the ramping and further fine tune AGain. Repeat to sneak up on workable final settings.
D. Alternate Power Reduction Technique
Another way to go after reducing the magnitude of the correction is to temporarily reduce MaxOut so the throttle cannot actually achieve WOT. The older V2 had a separate adjustment for this, but the effect is the same. Unlike increasing ramping, this leaves the speed of throttle change unaffected which may be more like your desired end result from an AGain tuning perspective, but may be more difficult to tune initially. Not sure about this one...
E. Tune AGain in Stages
It might be useful to dive off the 1 meter board before jumping off the 10 meter board. You might reduce MaxCurrent either directly or by 3-postion switch to get back to a less powerful bike. Tune this up (which we know is doable), then advance the current limit and fine tune AGain from the known 'nearby low-power' setting instead of going after it from the default. Even steps of one or two can make a big difference for small AGain, so you need to proceed slowly. With luck, increasing the current limit will only introduce minor surging and you will be able to tweak it out, etc.
Anyhow, just some musing about strategies that sound helpful but may not be effective in the end. It would be good to get some details on what eventually worked for you so some policy for powerful bikes could be added to the Guide.
Best of luck on The Quest.
