Sensorless bldc motor control

[cglenn]

I'm interested in using computer hard drive spindle motors in a small robotics application. I figure that the motors are mass produced(cheap), reliable and readily available, but controlling them is the hard part. Does anybody have any experience doing this kind of thing and do you have any suggestions for methods or hardware?

 

[IRstuff]

HD motors are only intended to run at a single speed.

TTFN

 

[Clyde38]

As IRstuff has stated, the spindle motors used in disk drives are intended to accelerate a mainly inertial load in a short amount of time and continue as a velocity servo. The motors could conceivably be used in a robotic (very small robot) application. Sensorless should not be a concern, because you will have to provide some sort of shaft position feedback for position/speed servo control. Although the motors are mass produced ie. relatively inexpensive, they have been designed in to the drive and you may find difficulty in getting them on your own. And if you do, they will probably consist of a part set rather than a complet motor. Their are several "small motor" companies that provide quality products at a reasonable (in quantity) price.

 

[cglenn]

I'm cool with that.

 

[cglenn]

Mostly I just salvage the motors off of old hard drives. Most of them use the exact same motor irregardless of hard drive manufacturer. I want to use the motor in a small robotic vacuum, so constant speed = not a problem.

 

[Clyde38]

When you say "old" hard drives, I think of a spindle motor that used to be refered to as a "motor in the hub". If the motor has a base plate that attaches to the drive housing and a rotating portion that is has the outside diameter of the disk(s) inside diamter, some of them have hall feedback. However, sensorless drive schemes are abundent. Try a search for "sensorless drive" and see. Also, try

http://www.irf.com/technical-info/refdesigns/irmcs2031.pdf

for grins.

 

[IRstuff]

A vacuum requires a high torque, high horsepower motor, neither of which is a hallmark of a disk drive motor.

TTFN