Sensors for motor control

[annirak]

I'm putting together a motor controller sensing front-end for a digital motor controller. The motor controller itself is extremely general purpose. I'm expecting that the front-ends will need to be tooled to the type of motor being used.

I admit I'm a bit of a newbie to motor control. I've sortof been tossed in head-first.

I'm looking for second opinions on what would be good to include on the sensing front-ends.

So far, what I have is this:
Common to all motors:
1x 6-channel simultaneous sampling ADC with differential inputs
2x Comparators for sine/cosine shaft encoder
2x inputs for quadrature shaft encoder
2x SCAs for hall effect sensors
1x RDC (Resolver-Digital Convertor)

DC motors:
2x Attenuator preamp for ADC (Bus Voltage & Back EMF)
1x preamp for ADC (Current)

AC motors:
3x Attenuator preamp (phase voltage)
3x preamp (phase current)

I'm not sure what's needed for steppers and DC brushless motors.

I'd appreciate any feedback and/or suggestions.

 

[nbucska]

There is no such thing as "GENERAL PURPOSE" anything.
There are at least 1000 different screwdrivers on the market

The closer you get to the "GP" the closer the cost
and design/manuf. time approximates the infinity...

To a helpful answer we need AT LEAST:
Motor HP or torque vs speed , speed range, acceleration min/max. Any special requirenments?

What do you want to control ( speed, acceleration, position, torque, )?

How do you want to set/program the controlled variable(s)
( e.g. manually continuous/discrete steps/fixed OR by
computer using intelligent program or fixed profile)






<nbucska@pcperipherals DOT com> subj: eng-tips

 

[annirak]

You're quite correct, there's no such thing as "general purpose," however, there certainly is such a thing as a modular system. Which is what I'm working with.

I'm not looking at a general purpose controller, I'm looking at a somewhat general purpose sensor block.

Are there any differences between what's required for speed, acceleration and position control on the sensor side of things? I'd think that the only differences between those parameters would be the firmware of the controller. I'm looking to control torque and as many others as possible, but it seems to me that they should look the same in hardware.

The signal sources that I know of on motors are:
phase voltage, phase current, PFC (power factor capcitor) voltage, PFC current, back-emf, position/speed. Where position/speed can come from a resolver or any shaft encoder. Hall effect sensors also play a role, but I admit I'm none too sure where.

Are resolvers common? I hadn't heard of them until very recently.

 

[IRstuff]

Resolvers are older than most of the other sensors, since they existed prior to the advent of cheap silicon integrated circuits. A resolver is modulated with a AC sine signal and generates an amplitude difference as function of offset angle.


TTFN