Astro 3220 at low speed?

[joec]

I am starting to investigate the idea of building a power wheelchair with a pair of Astroflight 3220s, with seven turns on 48 volts, geared for just under 7 mph top speed (75 amp phase current limit, 4600 RPM top speed). I have a couple of questions.

First, have people had success adding sensors to these? I would want to drive these with a Roboteq HBL2350, and it needs sensors. I did search, but didn't immediately come up with a good example of a successful sensor mod.

Second, how is the cogging? Does it seem reasonable to hope for smooth control accelerating from 0 to 200 RPM?

Third, am I correct in figuring a 37,000 electrical RPM for this motor?

Any other comments are welcome. Also, if anybody out there accidentally has too much money, you're welcome to buy parts for me too.

 

[crossbreak]

Third, am I correct in figuring a 37,000 electrical RPM for this motor?

That seems right for me. Sadly I haven't added any halls to such a motor yet. You could also fit opitcal sensores, this seems easier for me, but also has disadvantages like their sensitivity to sunlight. Make sure your timing is (nearl) perfect before you start testing, and start with very low currents to save your equipment in case your assumes were wrong. Owning a stock sensored motor would be great for you, just to learn how to play around with the controller software. That's what I'm going to start with either.

Good luck and tell us of your efforts!

Update: 200 rpm at the wheels seem to be too much for a wheelchair!? You will need a big gearbox 4500/200=22.5 reduction ratio. So you will need at least a 3-stage reduction. Or you try what I do in the RC-Hubmotor thread.

Best regards!

 

[joec]

The wheelchair has ten inch wheels, and it's used specifically for a sport played on an indoor basketball court- that's why ~200 RPM is about right 8)

I presently have a couple of examples of two-stage 20:1 reductions for existing chairs, so I'm pretty confident that this can be made to work. It might be a little heavier than bike guys would tolerate, but it's OK because we'd be saving a solid five pounds on a 3220 compared to the old brushed motors that we use now.