Control.com - Nerds in Control

As rule all drives have ability to create simulated encoder output from a main motor feedback. Drive producers are doing the feature in different ways which are depended from a type of a main encoder. One way does a hardware simulation output of a main motor encoder only if this encoder is incremental. Another one does a software simulation when a encoder is sin/cos, Hiperface or EnDat.

The case of hardware simulation is clear for me due to a small delay time about nanoseconds. The case of software simulation is complicated due a big delay time for the process about 250 us or 125 um which is depended from a drive maker.It seems to be large value when a position loop of an upper controller works on 2.25 kHz isn'it?

How do you do your applications with upper motion controller and drives in this case? Do you use a feedback signal with software simulation and don't notice a delay time or perhaps you use encoder signal splitter for drive and conroller or instead of you mount second encoder in a motor?

Thank you for your help

This seems to be one of those that depends on the application.

in most cases I would try to get the encoder signals directly if possible, just to eliminate the update loop worries.

If your application can use using single ended encoder signals, you may be able to "split" the encoder by using one with a differential output by feeding A,B,Index to one place and A-, B- Index- to another.

You of course have to make sure you don't build in any ground loops and make sure that the single ended wiring will be adequate for noise immunity.

The other thing to keep in mind is that the signals will be 180 Electrical Degrees out of phase. Not such a big deal with a velocity loop, but could create potential issues with a strict positioning application.

Jim Miller
Application Engineer
Quantum Devices Inc.
www.quantumdev.com
(608) 924-3000

Resolver must be added to your list of position sensors also.

At first I don't think delay for simulated encoder outputs will be in (ms) - even internal DSP is fast enough. I work with such module from Control Techniques for resolver without problem.

Second if you want overcome possible problem in any case use controller with build-in amp (Elmo, ACS). For brushless motor you may use Hall commutation (middle performance) or servo amp with two analog inputs for sinusoidal commutation (high performance).

leonid.lega@gmail.com