Data recording issues: raster rate and signal availability.

[chilehed]

I've got a Grin eZee front CA3 kit and am playing with the ramp rates. I tried to use the Phaserunner Suite to record motor input voltage, motor current, and wheel RPM/ vehicle speed with a really slow throttle ramp rate to try to find out how much current it takes to get through lash, but the raster rate is slow (~1/3 second average) and inconsistent (varies from 0.017 to 0.52 seconds over a 34 second trace). The motor RPM and vehicle speed values go to zero once I release the throttle even though the wheel is still spinning, and it looks like motor input voltage and current can’t be plotted.

Is there a way to record these signals at a consistent 10 Hz , and get actual wheel speed?

Thanks.

 

[amberwolf]

Is the problem with the PRSuite logging the data, or is it with the data being sent over serial to the computer running PRS?

You can use various terminal programs to log serial data directly from a port, if it's the former, then process the data later (don't know if the PRsuite can support that; might require some other processing application).


If it's the serial data itself...then is it a problem with the data being sent from the PR being insufficiently often? Or is it an issue with the quality of the connection causing dropouts or data corruption?

The latter can be usually corrected with a shorter cable or a better-shielded one, but sometimes requires lowering the data transmision rate (baud rate), which won't let you do what you're after most likely.

The former might be corrected if the PR has a data update rate (like the Cycle Analyst does) setting. This is not in the main PRSuite settings, but there is an advanced section where you can list and update other parameters that are not in the UI. I don't know hte meanings of all of them, but I have screenshots/etc in this thread Phaserunner startup issues (v6 and v1, each running an Ultramotor) in case you recognize the proper setting.

Regarding wheel speed, your best bet is to use an external wheelsensor (not the motor halls) and for precision at low speed, use as many magnets on the wheel spokes as you can. (or attach them to the hub's surface, etc).

 

[chilehed]

Is the problem with the PRSuite logging the data, or is it with the data being sent over serial to the computer running PRS?

You can use various terminal programs to log serial data directly from a port, if it's the former, then process the data later (don't know if the PRsuite can support that; might require some other processing application).


If it's the serial data itself...then is it a problem with the data being sent from the PR being insufficiently often? Or is it an issue with the quality of the connection causing dropouts or data corruption?

The latter can be usually corrected with a shorter cable or a better-shielded one, but sometimes requires lowering the data transmision rate (baud rate), which won't let you do what you're after most likely.

The former might be corrected if the PR has a data update rate (like the Cycle Analyst does) setting. This is not in the main PRSuite settings, but there is an advanced section where you can list and update other parameters that are not in the UI. I don't know hte meanings of all of them, but I have screenshots/etc in this thread Phaserunner startup issues (v6 and v1, each running an Ultramotor) in case you recognize the proper setting.

Regarding wheel speed, your best bet is to use an external wheelsensor (not the motor halls) and for precision at low speed, use as many magnets on the wheel spokes as you can. (or attach them to the hub's surface, etc).

I don't know, I don't really know much about communications stuff. I'm using the cable that Grin supplied. I did find a thread that suggested using PuTTY to get the data from the CA3 instead, so I downloaded the program and gave it a try. I did a bunch of throttle tip-ins with ramp rate set to 0.2 V/sec and it looked like current could get as high as 3.5 amps before RPM started increasing (usually at ~1.4 volts). Not sure what the raster rate ended up being, but with ten or fifteen tip-ins I figure that's a reasonable place to start. If I was doing serious development I might want more, but I ain't.

Thanks for the help. After I play around with the ramp rates some more I might make a post about what I'm thinking and why.

 

[amberwolf]

Whenever you've got more questions, post and we can try to help.