Encoder vs resolver

Zer0,

This is what I know: Resolvers are used to translate angular position of its shaft to Sin and Cos voltages. These output voltages comes from the sin and cos windings in the resolver that have fixed transformation ratios with its reference winding. Resolution and accuracy are usually high with resolvers.

So, it depends on your application whether it is do-able or not. You might need complex circuits to be able to emulate resolvers with encoders and still not match the resolution and accuracy.

LLH B. Picket (MSC)

gr8 handle btw, just swih

It also depends on the skill & experience of whoever is trying to do it...

Hi!
Well i asked because i had made mainetenance in some servo industrial servos, for change their bearing and i need act on the resolvers, so i must be carefull to mark the position on the shaft and on estator too. So i though if one day something happens on the resolver and we most change for a new one. How can i find the right position for the new resolver on the servo shaft and the estator??, because if will not be well mounted we will had sveral problems for the machine.
So have anyone the knowledge or idea if its possible for a field techician execute this job or most delivery the servo to the manufacture?
thanks for the replays!!

Best regards
Zer0.

What does this have to do with Keil tools??

You normally design a system with a calibration feature, so the machine can start and then rotate an axis or move an arm or whatever until a sensor detects a known state. Then it is enough for the mechanic to remember to initiate a calibrate cycle - unless they are automatic on each power-up. Having two position sensors means that you may even teach the software the resolution of the sensors, i.e. how many ticks or similar there is between two reference positions.

Work on autocalibration normally pays off quickly in less support costs and possibly also lower maintainance costs and safer operation.

Hi!
At first i'm gratefull for your attentions;
At moment it is not possible to answer to your questions because i must wait for the momemt for an preventive programeted maintenance in one machine. But i will pay attention and as soon as possible i try post the measures.
I have resolvers that in the place of the shaft is a hall and so the rotational part is mounted directly on the motor shaft.
When you mean powered the resolver you meaning feed the resolver by the motor drive? I ask, because in his condition the motor is blocked on the position until he receives order to start, and if i try move the shaft he motor spins untill get is position again, this could be a dangerous task.Exist an alternatif way to take this task foward?
When i had to interview in one servo i use a temporary mark for dismount a resolver for change the servo bearings, and for now i have been sucessed.

best regards
Zer0

Hi zero,

The reference winding for most resolvers (like size 11) usually has operating voltage that can be any value between 5 and 26 V rms. Frequency usually is between 1KHz to 10KHz. Some can be as low as 400 Hz, these low frequency units are usually used in aircraft application.

In a typical resolver, if you measure with a DVM the output of either the cos or sin winding while you rotate the shaft one complete revolution starting from a reading of close to zero Vrms, you will observe that the reading will increase then decrease close to zero, then increase and decrease again back to close to zero. If you plot, this voltage versus shaft angular rotation, the plot will be two half sines. One of the half sine should be opposite the other half about the zero volt axis in the plot giving you a complete cycle. Resolver manufacturers use various measuring equipment better than a DVM. see www.naii.com/.../viewProduct.aspx

For the above example, one electrical cycle occurs in one mechanical rotation. This resolver is said to have a 'speed' of 1X. So, a 2X 'speed' resolver will have two electrical cycles in one mechanical rotation, etc.

Wishing you well with your project.

LLH B. Picket (MSc)