Cycle Analyst Issues

[truly_bent]

Oy! (that's Jewish for Yo, which I'm pretty sure means Hello)

I had a Cycle Analyst (CA) issue on startup and couldn't find a related thread to tag onto. Thought maybe i'd start one.

My CA is a direct connect version (CA-DP rev 2.25) into a Lyen controller. What was happening was that the bike would accelerate for a second or two and then immediately cut out. When I disconnected the CA the bike would run normally. The CA will override a controller for any number of reasons and I had no idea why this was happening. I actually had to stick my nose into the manual.

The CA comes from the factory with default parameter values, of course, and one of those was "Set # Poles" (section 8.6 in the manual), which was set to 1. That couldn't be right. So, how many poles does a MP have? Anybody? I found that info here: http://tinyurl.com/c2bh9e5. Apparently it has 56, because when I plugged that info into the CA the bike ran as it should.

The good folks at ebikes.ca (http://www.ebikes.ca/drainbrain.shtml) suggested that I calibrate the Rshunt value (section 8.3 "Set Rshunt") for more accurate power reporting. Before I had to resort to actually figuring out how to do that, Edward Lyen supplied the shunt resistance as 1.333 milliohms.

So now we're running, calibrated, and ready for the next bug to strike. Can't wait to start playing around with those PI parameters...

[truly_bent]

Question to Bikemad: Do the MPs in fact have 56 poles?

The reason I ask is that my CA seems to be reporting a lower velocity than expected. The direct connect CA apparently picks up the hall effect pulses per rotation and factors in the diameter of the wheel (actually the circumference) to calculate the speed. I haven't measured the circumference of the Marathon Plus 26 x 1.75, but at 2100mm it can't be that far off.

That only leaves the pole count in question - or i'm getting old and 22kph feels a lot faster than it used too...

[Bikemad]

Answer from Bikemad: Yes, the MPs do have 56 poles:




Please note that there will only be 28 high/low pulses per revolution because there are 28 North Poles and 28 South Poles positioned alternately around the motor ring.
Try setting the value to 28 and it should hopefully read correctly, and the resultant 44kph should then feel just like it used to, but without all the tiresome pedalling!

Alan
 

[truly_bent]

Reply to Bikemad: Okay. I set the number of poles to 28 and all is hunky dory, thanks. Runs just as well and top speed on the flats is showing about 45 kph, which feels pretty bloody fast no matter how old you are.

I was trying to limit the top end to 32 kph, for the benefit of our local gendarmes. I set the Speed Limit in the CA and could tell it was trying to work, but there were wide oscillations - between 36 and 28. I guess i'll need to play with the PI parameters after all.

There's a lot of slop in the throttle as well...

[truly_bent]

A helpful gnome, named Justin, at ebikes.ca got back to me about the speed regulation hunting (oscillating) issue. Actually, he got back to me almost immediately. I just forgot to post it until now.

He agrees that the necessary parameters to play with are IntSGain and PSGain, but goes on to say:

The reality is that it's hard to achieve a good smooth speed control with a PI control algorithm. Once it settles it will be OK but whenever there are disturbances like changes in the grade or pedal effort that can start another small oscillation. A smoother but less stiff approach would be to just set MaxThrottle to a value that gives you around the desired top end cruising speed

I'm not sure how "smoother" can also be "less stiff", but I think the general idea is clear enough. I haven't implemented this suggestion because I ordered my (Lyen) controller with a 3 speed range option, which does pretty much the same thing. For the rest of you () changing the MaxThrottle parameter to a predetermined setting, before entering a suspected kill zone (radar perhaps?), could save legal hassles... maybe.