Sunday, November 4, 2007

It's Alive!

Well, almost alive. Very, very slow. See this movie:

I spent the day yesterday disassembling the clutch & flywheel. Nothing was obviously wrong - I tweaked the tightness of the hub adapter set screws - and the hideous sound the motor makes was there even without the flywheel mounted. So, I reassembled it all, making sure all the bolts were torqued according to specs, and got back to tweaking DMOC parameters

The following are what I have tweaked so far

EEXMaxAccelPower = 43000 (was ~73000)
EE2NoRegenBat 100 (was 300)
EE2NoAccelBat 127 (was 360)
EEXNoIgnSwitch = 1 (was 0)

I set EE2NoRegenBat down so low because the regen was coming on all the time (as evidenced by the brake lights coming on). EEXMaxAccelPower had no perceptible affect. And nothing happened until I set EEXNoIgnSwitch to 1 (tells the DMOC it does not need an external "ignition switch" signal) and EE2NoAccelBat to 127 (it thought my batteries were way too low to run).

I suspect there is much tuning ahead of me. As usual, Azure Dynamics has been very helpful. I sent off a complete dump of parameters along with 30 seconds of data capture; we'll see what recommendations they have for tuning.


Dave said...

For what it's worth, the fundamental frequency of your "grinding noise" appears to be 2400Hz (assuming that video was encoded 1:1). The noise drops a bit in pitch as things get under load -- and there also appears to be a third harmonic resonating through the car's frame. Is your AC motor controller providing power at some multiple of 2300Hz? It should be WAY lower than that at motor startup (2Hz or so to get things spinnig). Perhaps the controller is somehow going "open loop" with your motor?

Dave said...

I meant some multiple of _2400Hz_. The pitch seemed to be dropping to around 2300Hz under load.

Ross Cunniff said...

Thanks for the analysis - yes, the video is 1:1. This is the same noise as Tim observes - you can hear it about 4:20 into this video - Tim thinks it's due to the 10KHz PWM the controller uses to drive the AC (perhaps it's actually 9600Hz aliasing to 2400Hz thru the video).

TimK said...

Hi Ross,

Congratulations on getting things moving! I had the same problem as you with moving just a few inches per second at full throttle. My problem was that the ground on the encoder signals wasn't getting back to the controller. I don't have the pinout with me, but check all the connections (and perhaps put a scope on them) for the position feedback cable going into the DMOC. If any of the encoder signals are bad, the controller thinks the motor is stalled and only applies a tiny bit of torque. Cheers!