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Topic-icon Torque mode control sbl1360

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3 years 1 month ago #29532517 by MJSmith
Hi,

I'm currently trying to control a 48V 10amp brushless DC motor operating in torque mode, with a hall sensor for closed loop feedback, using the sbl 1360 controller. I've set the gain at the recommended default of P=0, I=1, D=0. At this setting the motor doesn't run smoothly especially as the load is increased. I'ved tried manually adjusting the gain and can't get any smoother operation. I noticed in monitoring the motor current that is was fluctuating up to 50% in both directions from the set motor command amps. Attached is a spreadsheet showing the fluctuations at different loads with a set current of 1 amp. Could these fluctuations be the cause of the jerky motor motion? If so what can be done to reduce or eliminate these fluctuations? My amps limit is set to 5 amps. I've tried changing this to higher and lower values and still had the same result so I'm not convinced it's a resolution issue.

The desired application of this motor is to keep paper tensioned in a roller web system by controlling the torque of the 2 paper rolls

File Attachment:

File Name: MotorCurre...Time.zip
File Size:29 KB
Attachments:

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3 years 1 month ago #29532521 by blake
Replied by blake on topic Torque mode control sbl1360
The SBL1360 measures battery current and then calculates motor current. Because of this there are some limitations when it comes to torque control just using the controllers current sensors. For lower duty cycle like you are using we recommend an external current sensor. This is detailed on page 138 of our User Manual.

To provide more insight I would need to see more data than just the Motor amps vs time. Please send your configuration file along with a log of the following:

Battery Volts
Motor Command
Motor Power
Motor Amps
Battery Amps

You can send to This email address is being protected from spambots. You need JavaScript enabled to view it. if you'd rather not post it here on the forum.

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3 years 1 month ago #29532536 by MJSmith
Replied by MJSmith on topic Torque mode control sbl1360

File Attachment:

File Name: ConfigLog.zip
File Size:4 KB


As it's a brushless motor an external current sensor wouldn't be possible. Open reading page 138 I can see now that it is probably a resolution problem as the motor will in practice generally operate between 2-3 Amps and the maximum resolution is only 500mA. Is it possible that new firmware will be released that will increase this resolution? Or will it remain only reliable in torque mode at above 50% or so of the rated current?

I've attached the configuration file as well as the requested log running at a 2 amp current command as this is closer to how it would need to operate. If there's anything to do with the configuration that may help that would be appreciated. If not is there another controller you could recommend with a higher resolution in torque mode?

Thanks
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3 years 1 month ago #29532538 by blake
Replied by blake on topic Torque mode control sbl1360
There are some techniques that can be used to reduce electrical noise on page 30 of our user manual. Other than this you may try again to tune the PID as you may be able to get some smoother operation. The integral gain will be the most important in torque mode and will always have the highest value.

Other than that there isn't much else that can be done about the resolution with the SBL1360. Since your max current is set at 5A that means you'll have a 10% resolution.

Our FBL2360 motor controller actually measures motor current.

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3 years 1 month ago #29532542 by MJSmith
Replied by MJSmith on topic Torque mode control sbl1360
Ok great thanks for the advice and quick responses. I'll check out the FBL2360 as well

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