6 phase sinusoidal dc motor

[stellanhaglund]

Hi everyone, this is my first post here.

I recently watched a video about some robot company that had their bldc motors wound for sinusoidal commutation and used 6 phases and drained the current out of the unused coils they said.
That allowed them to get exact position control over the motor with great torque.

So basically the motor is not spinning its just turning to the desired positon by changing the electric angle of the sinusoidal waves, they didnt use any gearbox for the motors.

Ive been trying to find out how these motors could be wound and what torque they are talking about.
They call them pmsm but googling pmsm is a dead end because of the termonology mess for motors.

Does anyone here have any knowledge about this?
The closest i got is seeing some other video about field oriented control over an AC motor and how they where wound.
Would it be a bad idea try to rewind a small motor this way to test, or does anyone know where i can get one.

If rewinding is an option is there any additional info for the winding, all ive seen is a picture of a stator but that doesnt tell me everything i need to wind one myself.

Oh and i found the video i was talking about
https://youtu.be/SuQgBTlhRR8 At about 18 minutes in, and they come back to it a few minutes later again.

Any help would be great, thanks!

[stellanhaglund]

I just heard him say doesnt have to gear it down as much, i didnt hear that the first time.
So i guess its not exactly positioned by the motor alone there is a gearbox to.

Could it be FOC they use?

[rstofer]

Why not just contact the club and get in touch with the people who did the work?

If SD Robotics Club means San Diego Robotics Club, they have a web site and the contact info is on the home page:

http://sdroboticsclub.com/

[Circlotron]

I didn't watch much of the video, but if you wanted six phases you could have the motor wound with both a star and a delta winding. Drive both from the same 3-phase source. One winding will be offset either 30 or 60 degrees from the other, not sure which. Look up "12-pulse rectifier" for basic principle. But I can't see that a six phase setup would get you any advantages over three phase. Even two phase like a conventional stepper motor. Provided the motor's permanent magnet has uniform radial flux, any of these setups should have virtually infinite angular resolution.

[RandallMcRee]

The description sounds a lot like a direct drive motor.
e.g.

http://articles.adsabs.harvard.edu//full/2008SASS...27..123G/0000125.000.html

This is a detailed description of such a motor. They are also common for electric cars (sometimes called a pancake motor).

Another interesting link:
https://michaelnorcia.wordpress.com/motors/

I made a four phase version as a turntable motor. As another poster mentions there is not much difference between a properly constructed three, four or six phase motor. Any geometry is possible it's small matter of proper construction.

[moonquasar]

This copy is easier for me to hear.


To hold a position, the PMSM would simply apply a constant DC voltage to each of the coils. Am I understanding this right?