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Topic: how to stop BLDC motor always in same position (Read 397 times) previous topic - next topic

surukukoo

Hello.

Currently designing a table top mixer where i have used BLDC motor-NEMA 24 volt dc., 400 W with hall sensor (from Robokits- india- model-RMCS 1041) controlled by driver- (robokits-RMCS 3001).
I need to stop the motor's spindle at exact position, irrespective of duration of rotation.
CAn't afford servo motor due to budget constrains.

Ant suggestions/advise, please.
Thank you
S.Sureshkumar0091934224679



jremington

#1
Aug 23, 2019, 05:24 pm Last Edit: Aug 23, 2019, 05:24 pm by jremington
So you plan to make a servo rather than buy one?

Paul_KD7HB

Hello.

Currently designing a table top mixer where i have used BLDC motor-NEMA 24 volt dc., 400 W with hall sensor (from Robokits- india- model-RMCS 1041) controlled by driver- (robokits-RMCS 3001).
I need to stop the motor's spindle at exact position, irrespective of duration of rotation.
CAn't afford servo motor due to budget constrains.

Ant suggestions/advise, please.
Thank you
S.Sureshkumar0091934224679



Will the motor still be under power when it becomes time to stop? The reason I ask is, if the motor is not under power, you can use a solenoid to shove a breaking pad against the motor shaft to stop it's movement.

Paul

TomGeorge

Hi,
Welcome to the forum.


Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html


Is this your motor and controller?
https://robokits.co.in/automation-control-cnc/brushless-motor-drives/nema17-52w-brushless-dc-motor-with-rmcs-3001-rs485-modbus-drive


Can you tell us your electronics, programming, arduino, hardware experience?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

MarkT

Hello.

Currently designing a table top mixer where i have used BLDC motor-NEMA 24 volt dc., 400 W with hall sensor (from Robokits- india- model-RMCS 1041) controlled by driver- (robokits-RMCS 3001).
I need to stop the motor's spindle at exact position, irrespective of duration of rotation.
CAn't afford servo motor due to budget constrains.
Then you need to add an absolute encoder and implement position control. Could you clarify the meaning of "exact position" in sensible units please...  Use numbers, not adjectives.
Quote
Ant suggestions/advise, please.
Thank you
S.Sureshkumar0091934224679



[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

surukukoo

Hi ,

I will try to give more details here:-

- motor-" https://robokits.co.in/motors/brushless-motor/nema24-brushless-dc-motor-with-hall-low-noise-24v-400w-3000rpm"

- Driver-" Rhino Industrial Brushless DC Motor Driver 250W with RS485 Modbus Compatible 15 to 48V 20A (RMCS-3001

- Both these items are from - "https://robokits.co.in"

- Though the motor specifies that it has hall sensor, some issue and it does not stop at exact location.

- The reason  for stopping at exact position is that  - the motor drives a syringe like female portion that carries the powder and after certain rotation, it should come and stop exactly below the piston portion, so that the piston is actuated and enters the syringe to displace the powder.

- If needed, power can be constantly provided to motor.

- prefer no mechanical arresting of motor, and rather electronic topping is preferred.
-

MarkT

You keep using the word "exact", which has no meaning.  "Within 1 degree" or "Within 20 minutes of arc" are
phrases that have meaning.

Knowing the precision required allows a suitable encoder to be chosen.

Unfortunately that motor appears to be single-shaft, not dual-shaft, which makes fitting an encoder
really tricky.  Dual shaft motors, or one's with a built-in encoder, are the ones to chose for position
control.

Any reason a stepper motor not used?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

MarkT

#7
Aug 26, 2019, 02:48 pm Last Edit: Aug 26, 2019, 02:50 pm by MarkT
BTW seen this?  https://robokits.co.in/automation-control-cnc/hybrid-servo-motor-drive/hybrid-servo-set-33kg-cm-w-t-80v-7amp-drive-rs485-modbus-comm.?cPath=2_137&

Its a servo motor setup cheaper than the motor+driver you quote...  Admittedly lower speed
as its a repurposed stepper, but worth considering.

What are your torque and speed requirements ?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

ballscrewbob

 surukukoo please dont use the "REPORT TO MODERATOR" to reply to a post.

Bob.

His reply below.

"exact position - any position the motor stops, it should start from that position always. So- if the spindle is 90 degree , it should stop at 90 degree. a male and female component has to match after rotation."
It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

ballscrewbob

It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

MarkT

Nothing in the real world is "exact", you need to explain what tolerance you are looking for.  Does
"exactly 90 degrees" to you mean 89.9 -- 90.1 degrees, 89.99 .. 90.01 degrees, 88 -- 92 degrees or what?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

surukukoo

When I say "exact" :-

- Imagine the motor is kept in horizontal position on ta table, ie- the spindle is parallel to the table top.
And a line drawn from the center of the spindle to edge of the circumference of spindle , perpendicular to the table top. After rotation the line should be in this orientation. The tolerance can be 1 degree (+/-).


- Torgue of the motor is about- 1.2 N-M, and required rpm is 2000-3000.

- Servo motor is the best solution , but due to product selling cost constraints this option has been omitted.

- The motor (NEMA 24) is equipped with hall sensor. Please refer- "https://robokits.co.in/motors/brushless-motor/nema24-brushless-dc-motor-with-hall-low-noise-24v-400w-3000rpm".

-


TomGeorge

#12
Aug 27, 2019, 12:16 pm Last Edit: Aug 27, 2019, 12:17 pm by TomGeorge
When I say "exact" :-

- Imagine the motor is kept in horizontal position on ta table, ie- the spindle is parallel to the table top.
And a line drawn from the center of the spindle to edge of the circumference of spindle , perpendicular to the table top. After rotation the line should be in this orientation. The tolerance can be 1 degree (+/-).


- Torgue of the motor is about- 1.2 N-M, and required rpm is 2000-3000.

- Servo motor is the best solution , but due to product selling cost constraints this option has been omitted.

- The motor (NEMA 24) is equipped with hall sensor. Please refer- "https://robokits.co.in/motors/brushless-motor/nema24-brushless-dc-motor-with-hall-low-noise-24v-400w-3000rpm".
How are you going to stop it?
What is the mass of the rotating part?

Shouldn't this part of the design should have been worked out before costing?

Is this a one off device for a factory process, or is it going got into production as a machine in its own right?
Can you please draw a diagram of what you are talking about.

If you have  the expertise to begin this project, you should be able to produce a concept drawing.
Can you tell us your electronics, programming, arduino, hardware experience?

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

MarkT

#13
Aug 27, 2019, 12:38 pm Last Edit: Aug 27, 2019, 12:41 pm by MarkT
When I say "exact" :-

- Imagine the motor is kept in horizontal position on ta table, ie- the spindle is parallel to the table top.
And a line drawn from the center of the spindle to edge of the circumference of spindle , perpendicular to the table top. After rotation the line should be in this orientation. The tolerance can be 1 degree (+/-).
So not exact at all, but a precision of +/- 1 degree.  This means a 400 step encoder is enough.
Quote
- Torgue of the motor is about- 1.2 N-M, and required rpm is 2000-3000.
That's too fast for a stepper style servomotor like the one I referred to, alas...
Quote
- Servo motor is the best solution , but due to product selling cost constraints this option has been omitted.
So you need to create a servo motor using encoder, PID loop and motor driver
Quote
- The motor (NEMA 24) is equipped with hall sensor. Please refer- "https://robokits.co.in/motors/brushless-motor/nema24-brushless-dc-motor-with-hall-low-noise-24v-400w-3000rpm".
Which is of no use to you, its for the driver to commutate the thing.  An 8-pole motor will have 24 commutation
steps per rotation, ie every 15 degrees.

Due to your speed requirement and angular resolution, the encoder steps will max out at 20kHz for a 400 step encoder, ie 50┬Ás max for encoder processing, so a well designed ISR is needed to handle that.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

surukukoo

For Tom,


how are you stopping?-
Current design is to activate a solenoid that will engage with a notch in the rotating disc which is part of the motor spindle. Due to possibility of mechanical failure, omitted this option.

Mas of the rotating part is about- 200 to 250 gram only.

Costing- The product is under development and prototype stage.

The product is meant for pharmaceutical industry and will be manufactured and sold as a mixer.

I do have the complete engineering drawing and the product is working in full aspect , except for the stopping issue.



For MarkT

I am also using PLC from delta- DVP14SS211R and Delta HMI-TP04G/AS2.

 I am a layman in electronics, but can inform my engineer to come into this forum.

 Could you suggest a suitable ISR for the purpose?? if required, I can share the electronic components in details.


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