What is the difference between a Hyperface Encoder and a Absolute Encoder

Coachman

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Sep 2006
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What is the difference between a Hyperface Encoder and an
absolute encoder. I am thinking of changing our Lenze motors to
SEW , but keeping the drives for right now. I do not see anywhere
that SEW using a Hyperface encoder. Is Hyperface a trade name that
Stegmann uses.

Thanks in advance,
 
Yes, Hyperface is Stegmann's version of high speed serial interface for encoders. It is similar in concept to Heidenhain's EnDat. These encoders typically also have multi-cycle per revolution differential sine and cosine channels along with the two data lines.

Absolute encoders can have any of a number of interface types, including but not limited to discrete digital, SSI or any of the popular fieldbusses. I don't personally know of any drive manufacturers that us any of these, although it wouldn't surprise me if SSI was used by someone.

Keith
 
kamenges said:
although it wouldn't surprise me if SSI was used by someone.
Many of our customers us SSI. I like SSI because it allows one to mix and match linear and rotary feedback types. MDT rods can have SSI interfaces. Single and multiturn encoders can have SSI interfaces. The hiperface and Endat are glorified and resolver like interfaces where there are many sinewave cycles per revolution to increase resolution. My customers haven't pushed for hiperface or Endat interfaces but SSI must make up about 1/3 of the interfaces we sell.

BTW, SSI and hiperface are absolute interfaces.
 
I had intended that the 'someone' in my post would be limited to drive manufacturers. But I wasn't particularly clear on that point.

I guess it surprises me a little that more of the drive people don't use SSI. I suppose they figure that the position derived for the SSI transmission would come from the same physical signal they are looking at anyway (sine and cosine outputs from a photodetector) so why not eliminate the middleman. I can't imagine an SSI interface costs all that much.

Keith
 
One difference between feedback for hydraulic systems and feedback for servo motors is that there needs to be some timing set up between the feedback and rotor position for the electrical servo motor. This is so that the drive knows hwo to commutate the motor properly.

Some encoders have something called "Halls" tracks for this. Others use absolute encoders or resolvers. Many drives will have a command for figuring out this timing where you initate the command and then manually move the motor shaft.

You should make sure you know how your drives are expectign to get the informaiton they need to commutate the motor. If the drives don't have a way to adjust the phasing of the signals, you have to make sure the timing in the new motors is what the drives are expecting.
 
thanks ndzied..

because m wondering why should there be a need for sin/cos encoders. while there are already absolute or incremental encoders? and i noticed that most new elevators are using heidenhain sin/cos encoders... why don't they use ordinary encoders?
 
danieluy said:
why don't they use ordinary encoders?
Because some applications require high resolution feed back. I tell my customers to get the highest resolution feed back they can.
If you had to compute the speed of a motor every millisecond and you needed 0.5 rev per second resolution would you use a 1000 count per revolution encoder or a 10000 count per revolution encoder? Do the math.
 
To expand a little on Peter's post, there is a point in line count where it becomes physically impractical to make the encoder disk grating any finer. I think BEI, for example, stops at about 5000 lines in their size 35 encoders. Anything above that is interpolated from the sine and cosine grating interference signals anyway and the square wave pulses are generated by an ASIC from that interpolation. For high resolution applications why not move the interpolation to the receiver? Both EnDat and Hyperface can be interpolated to well in excess of 1,000,000 counts per revolution.

Also, as the PPR of the encoder increases the pulse frequency at a given speed also increases. Unless you are extremely careful there is a point where the pulse edges start to degrade to the point that they are unreadable, due largely to cable capacitance. The SIN/COS interface is somewhat immune to this. You have the possibility of phase shift affecting the absolute position by some amount due to the same physical effect. But ultimately no position information will be lost.

Keith
 
A servo drive typically interpolates each sin wave to a resolution 8192. So on a small hiperface feedback with 128 "pulses" you have a resolution of 1048576. Since your velocity feedback comes from the derivative of your position feedback, the higher the resolution, the better the performance of your velocity loop.
The sin/cos feedbacks are better for determining a bad feedback signal than an old school square wave.
Hiperface and endat feedbacks have memory to store motor data and commutation offsets.
 

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