Re: Torque control in BLDC motor

As someone else said, this is not the right group, but you might get lucky -
the MPC5xx chips are often used for motor control.

If everything is running properly (you're switching steps at the right
place, and that sort of thing), then the torque is directly related to the
current.  Some current is "lost" to heating, and to generating or reducing
magnetic fields, but the rest is then directly proportional to the torque.
So what you want to do is control your current.

However, there is no way to control the speed and the torque independantly,
since the speed is directly dependant on the torque.  It's easier if you
think about the linear equivalents (at least, I find it easier) - torque is
the equivalent of force.  In asking to control the speed and the torque
independantly, you are asking to control a speed and a force independantly.
If you are pushing something along a path, and start pushing harder (all
other things, like friction, being equal), you go faster.

Does that help?

David


> Hello:
>
> I'm doing a torque control project in a BLDC motor. At the moment, I'm
> testing diferent power stages with MC33035P and after I shall do the
> specific torque control.
> I want help to assist with the motor force independently of the speed.
> My first strategy is do a test to the motor and find torque,speed and
> current curves.
> I have thought use T=K1*i(t)-K2*w(t), in a Look up table, where my input
is
> torque needed assist at the maximum speed possible of motor. The output is
> the current, and with this, the voltage and the duty cycle necessary to
get
> this current(torque).
> What think about this?? Is it correct??
>
> Thank you and sorry for my english.
>
>
>
> Best Regards.
>
>
>
> Igor
>
>
> [Non-text portions of this message have been removed]
>
>
>
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