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Subject: Re: Recommendations for EPICS Based Data Acquisition System
From: Matt Rippa <mrippa@gemini.edu>
To: Mark Rivers <rivers@cars.uchicago.edu>
Cc: Rolando Rogers <rrogers@gemini.edu>, Talk EPICS Tech <tech-talk@aps.anl.gov>
Date: Thu, 7 Dec 2017 12:29:30 -1000
Hi all, 

Thanks for the replies.

Here's more info:


Can you describe a bit more the specifications and how it operates?

- How many inputs at 5 kHz?
 
​Attached​ is a cut sheet. There's 38 analog and 14 TTL inputs.
 

- How much calculation to determine the outputs?

We have two core processing tasks for mirror position and vibration control.
This results in a total of 5, 3x3 matrix vector multiplies per cycle. This is to
transform for linear sensor space to AZ/EL tip tilt coordinates.

The legacy DSP's are TI-TMS320.


- How many outputs to be written, and at what rate?

​All the stepper motor control is implemented with TTL lines.​ So a 20 Hz stepper clock
is realized by skipping sufficient 200 us cycles to generate the clock.
Again, the IO cut sheet shows this as 35 outputs. But only the motors are using the sample rate.

 
- Is this just for feedback control, or do you need to log the inputs and if so at what rate?

​I'm keen on logging ​inputs up to the sample rate in an engineering mode if it's easy to do.
This would be very useful for tuning the system. At a minimum I'd want to log the inputs at
1 kHz. The closed loop bandwidth of the system is about 100 Hz.

​I have a wealth of information if you're interested to understand this better.


​-Matt​

 


Mark



________________________________
From: tech-talk-bounces@aps.anl.gov <tech-talk-bounces@aps.anl.gov> on behalf of Matt Rippa <mrippa@gemini.edu>
Sent: Wednesday, December 6, 2017 2:54 PM
To: Talk EPICS Tech
Cc: Rolando Rogers
Subject: Recommendations for EPICS Based Data Acquisition System

Aloha,

I'm looking for your recommendations on the latest data acquisition
hardware, compatible with EPICS.

Our Secondary Mirror system at Gemini has a 1 meter diameter,
55 kg mass. There's 3 degrees of freedom and a 5 kHz control loop.
The system was designed in the 90's by Lockheed Martin, based on
a DOS PC with an ISA backplane (PICMG 1.0) and a DSP data
acquisition board with 16 bit ADC's and DAC's. The DOS PC interfaces
with an EPICS IOC via Reflected Memory.

In 2010 I did a conceptual redesign based on a Hytec Blade 9010 using
IP cards and an Intel CPU running RTEMS. Today it seems FPGA's are
a popular choice for data acquisition. Perhaps a Xylinx zynq solution?
Would anyone still consider VME?

I have no requirement for 5 kHz EPICS control.  Although that's intriguing.

Thanks for your time.

-Matt

Attachment: CEM_IO_Requirements.pdf
Description: Adobe PDF document


Replies:
Re: Recommendations for EPICS Based Data Acquisition System Mark Rivers
Re: Recommendations for EPICS Based Data Acquisition System Peter Milne
References:
Recommendations for EPICS Based Data Acquisition System Matt Rippa
Re: Recommendations for EPICS Based Data Acquisition System Mark Rivers

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