Motor Encoder emulation

When does your homework have to be handed in?

Deep

Hello Deep,
    no, it is not my homework. I am not a specialist in the encoders, I
write control programs for the IGBT inverters. Normally there is an
encoder on the machine, and this signal is used in the speed control
loop. But in this case there is no encoder provided and I want to
simulate this for test purposes. I would have to sit here and think
about the algorithm for a week or so, or maybe there is somebody, who
did this before and I can save my time for the control program tests.

Greetings,
Pawl_s

I've done it from a DSP56F805. I approached it several ways, then came
upon a really solid way. The timers in this DSP are about the best
I've ever seen for useful modes. Here are some comments from my
program. (I'd include the program but it is Forth and specific to this
processors, so just the comments might give you the idea.)

Using four timers could create perfect form waves, to 25ns anyway
One timer is needed to do prescaling to bring the quadrature down to
reasonable rates, say milliseconds. Then another timer is set to count
how
many of these ticks pass per phase. Two other timers count this
output.
These two timers have repetitive counts to 2, and are set off by one
count.
They toggle their outputs each time out.

Thanks for help. I don't want to do this in the DSP, because I use it to
control the Inverter and calculate a lot of other things in a bigger
project with the interrupt frequency up to 80kHz (I should do it up to
100kHz but it seems that my code is to much for the DSP). That is why I
want to send the signal out of the DSP to the external encoder emulator
made with FPGA or something. Your idea could also be implemented in the
DSP I think, I will try this.

Greetings,
pawl_s

The nice thing about my method of using timers is there is no
interrupt overhead, or software overhead necessary at all to have a
continuous stream of quadrature at a given frequency. Only when you
want a freqency change is there any processor overhead to change the
prescaler or middle timer.

If you want to put something external to your TMS, our TiniPod(TM) is
very small, costs less than $100, has the DSP56F803, and could do
quadrature generation, and still have most of its capacity left over
for other tasks. I can provide my software with it. (Several pages,
but most of it comments and explanation of how the timers work.

--
Randy M. Dumse
www.newmicros.com
Caution: Objects in mirror are more confused than they appear