Blips in closed loop speed control (SDC2130)

9 years 4 weeks ago #29525937 by kmuecke
In closed loop speed control, every 4-5 seconds or so (speed independent), I get a blip in the motor speed and power applied to the motors. The blip is a decrease in speed in power.


This appears to be related to the integral component of the PID control. When I set the integral gain to 0 and just use the proportional term, there is no blip. I don\'t know if there is some kind of reset on the integral every few seconds, but it is creating a jerk every four-five seconds.

I have the latest firmware (8-24-11), but have noticed this behavior in a 3-11-11 and july firmware.
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9 years 4 weeks ago #29525941 by roboteq
We have had a similar problem reported by another customer. So we know there must be an issue somewhere. Unfortunately, we have not been able to replicate the problem in our lab. So troubleshooting is very difficult.

Please provide as much info as possible on your setup (encoder PPR/CPR, motor type, voltage, load or no load, ...)

Disable the pulse capture on the PulseIn1, PulseIn2 and PulseIn5. If these are enable, the MCU will be processing the encoder pulses as if they were radio signals and waste time.

Also, try changing the value of the Integrator Limit, in the PID configuration.

Report if the two suggestions above make any difference.

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9 years 4 weeks ago #29525945 by roboteq
Send your configuration profile to This email address is being protected from spambots. You need JavaScript enabled to view it.

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9 years 4 weeks ago #29525947 by kmuecke
Pulse capture was already disabled. Changing the integrator limit had no affect.

38 poles per turn or 76 pulses per revolution.
24V
Tried both loaded and unloaded.

Motor spec:
www.superdroidrobots.com/product_info/IG52GM-04.gif
43:1 gear ratio

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9 years 3 weeks ago #29525963 by roboteq
We ordered the same motor. If the problem can be replicated, it will be fixed.

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8 years 11 months ago #29526057 by kjy423
I am having the same problem. Any additional info on this problem?

I have latest firmware as well. As mentioned, setting the integral gain to 0 seems to be the only way to get rid of the blip. I am using two motors in tank steering mode 1, closed loop speed control. Encoders are 360 CPR (US Digital S4) and run just below 10kHz at full speed. The blip seems to happen regardless of motor speed. (new 24V, 200W brushed DC)

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8 years 11 months ago #29526059 by roboteq
We tested with a motor identical to this of another user reporting the problem.

We did notice something that looks like what is described except that it is not as hard a blip as what has been reported. The blip here cannot be heard but it can be felt as a very soft jerk when holding the motor.

We have not been able to track the problem here. It is not entirely certain that what we see is the same as what you and other users have reported.

Could you please do the following for us:
- capture a log showing Motor Power, Motor Command, Speed RPM, Loop Error. Click off the status, digital & analog in, digital out, pulse input so that the chart captures with more time resolution
- record a video with sound that would allow us to see and hear the blip and compare to what we have here.
- send both to This email address is being protected from spambots. You need JavaScript enabled to view it.

Thanks

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8 years 8 months ago #29526321 by Bblocher
I\'m also getting blips in output on my ax1500. I\'ve been debugging this for weeks. I\'m using an open loop. From my micro controller I\'ve tried seriel and PWM IO. I\'ve also tried a futaba rc setup but I see the same blips in output. The timing is very random and each motor has it happen randomly as well. Sometimes one, or the other, or both. This is seen as a quick burst or drop in requested power. The only way I\'ve been able to see consisted power output is using seriel with watchdog disabled, the issue a single speed command and not alter the speed again. I\'m trying to use this on balancing scooter so the output must change frequently to maintain balance.

Any thoughts?

Brian

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8 years 8 months ago #29526339 by roboteq
The AX1500 is a totally different design and no such blips have been reported before. If they occur it would be a problem unrelated to the SDC2130 problem discussed on this thread.

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