Offset and noise in hall sensor value

3 years 9 months ago #29532654 by bigBadger
Hello,
We have 8 3kW BLDCs, each driven by an MBL1660 driving a mecanum wheeled robot. While driving all wheels in speed control mode (while the wheels are off the ground), if we view the plot of the speeds of the motors as reported by the hall sensors, we see that 3 of the motors are going slower than the others. Measuring them with a tachometer indicates that in reality all the motors are going at the same speed, as does encoder feedback. Two of them are much noisier than the third. Is this just something that happens with hall sensors, or should we be concerned about it? I have attached a screen shot of the plot in question.
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3 years 9 months ago #29532655 by blake
If all of your motors are the same then you should be roughly the same speed on all of them. What is the difference in speed that you are seeing between the motors? Are you using the exact same configuration file for all 8 motor controllers?

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3 years 9 months ago #29532656 by bigBadger
Hi Blake,
Same configuration script, same parameters. Same physical setup (gearing, wheel, encoder, etc).

Hall sensors says 3 drives are 20% slower than the others, but a tachometer says all 8 wheels are within 4% of each other.

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3 years 9 months ago #29532657 by blake
Please send me the configuration file and microbasic script that you are using at This email address is being protected from spambots. You need JavaScript enabled to view it..

Which version of firmware is running on all of your controllers? This will show in the bottom right corner of Roborun+ when you have the controller connected.

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3 years 9 months ago #29532658 by bigBadger
Hi Blake,
I've emailed you the requested files. I think you might have seen them before, as I think my colleagues on this project have mentioned phoning you. The firmware version is v1.7 MBL1XXX, from 10/13/2016 on all drives.

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