Can anybody suggest a good one?
Can anybody suggest a good one?
For their use in old time systems, Rad Lab Series Vol.21.
If you need to connect between a synchro and a resolver, use a Scott-T transformer. :-)
-- Virg Wall, P.E.
I have that. And most of the other books don't seem to be much newer!
An expensive transformer seems to be a silly way to do a little trig. Adding another multiply to an ARM program costs ... calculates furiously ... $0.00.
I'm contemplating designing an LVDT/synchro/resolver simulator. The sensible way seems to be to digitize the excitation voltage and make the various winding voltages with DACs, and do all the rest in a uP or FPGA.
I think some of the chip manufacturers have resolver to digital converters, they may have useful documentation or app. notes. I have some brushless servo motors with resolver feedback, I'm hoping to use someday in a CNC project.
Old Analog Devices books. They used to have a "Synchro/Resolver Handbook" iirc.
-- Dr Philip C D Hobbs Principal
You might check Analog Devices. I seem to recall they had a fair bit of literature on the subject in the late 70's (how much of this has survived is the issue).
We used to use them (made our own) in some avionics (?) kit back then (AD was across the street :> ). I doubt I have kept any of the literature that I had (at least, not on *those* sorts of things! :> ) from that era.
Ha ha ha ha ha he he he he he ho ho ho ho ho aaaaaaaaaaaaaaaaagh!
(I'm not making fun of you here, that's hysterical laughter).
Call Renco Encoders and see if you can sweet-talk them out of a copy of "Feedback Devices in Motion Control Systems", by Robert M. Setbacken.
Then call Moog Components -- wade through the Moog website and find the guys that sell the precision industrial and aerospace encoders. Sweet talk them, too.
Be aware that all the electronics whizzes who worked on encoders have died of old age -- it's all mechanical engineers; they know bearings, they know winding machines, and they know how to test things, but when you start asking questions about impedance vs. frequency and other seemingly obvious things the best you'll get is a friendly shrug.
They're variable transformers. They're really inefficient. Their impedance is pretty close to the wiring resistance plus the inductance times radian frequency (no surprise there). They work over an astonishingly large frequency range, although they are traditionally only specified at the frequency that the first customer wanted to use. The drive amplitude is specified in voltage, although if you read between the lines they're limiting the I^2R losses in the primary. Try to ask the guys who design them these days and at best you'll get a friendly shrug...
You can order them specified for other frequencies, or sizes, for "some" NRE. "Some" is relative, and Moog is an aerospace company...
How tightly are you gonna simulate the resolvers? Just behavioral?1st-order with inductances and winding resistance? Parallel capacitance? Electrical nonlinear effects? Spatial nonlinear effects? Are you gonna simulate multi-speed resolvers?
There's probably a market for a general-purpose resolver simulator, and possibly even more so for a general-purpose resolver _meter_ (I recall looking and not finding one, at a time that one was desperately needed).
But there's lots of metrology issues to overcome if you want the meter or simulator to exceed the accuracy that you can get from a resolver -- the really good ones work down to arc seconds, which is "don't breath" territory if you want to check out the physical system.
-- Tim Wescott Control system and signal processing consulting
"John Larkin" ha scritto nel messaggio news: firstname.lastname@example.org...
There seems to be some stuff from, say, 1955 or so. I don't suppose much has changed.
Seems that way. A lot of the books and lit seem cartoonish.
My gadget is going to be transformers, adcs, dacs, and an FPGA. Whatever I can do with that. I'll be generating low-power signals into an electronics box that thinks it's connected to an LVDT or a synchro. It's representing mechanical positions of things like flaps or bits of engines, so it doesn't need arc-second accuracy. Stuff like multi-speed would be easy.
The meters are around.
I'll have to get one if I go ahead with this project. I already have a couple of those old 6-dial variable-ratio transformer boxes, the ppm-accurate things that last forever... left over from an LVDT project.16 bit electronics should work. There are lots of affordable sub-MHz 16-bit ADCs and DACs around nowadays.
I was thinking a bit about this recently-- it would have been handy to have an LVDT simulator at the time. In particular, how to generate a simulated output that has a variable phase with respect to the externally supplied input. Thinking maybe a Hilbert tranform in an FPGA..
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" email@example.com Info for manufacturers: http://www.trexon.com
The basic LVDT or synchro simulation doesn't need phase shift, just amplitude scaling. In real life, there are some phase shifts in the signals, from inductive and capacitive effects, but they are usually minor. I'm leaning towards overkill on the FPGA so that we could have enough resources to do stuff like phase shifts. Maybe a customer would want us to simulate some phase shifts, to sim cabling capacitance or something.
Since we could measure an external excitation frequency, a simple delay line (RAM based fifo) or some integrators+summers could do the phase shifting. But things like Hilberts aren't hard if the signal frequency is low.
You didn't get it, did you? :-)
-- Virg Wall, P.E.
Hop over to DDC Corporationand navigate down to Pick up a copy of their "Synchro/Resolver Conversion Handbook." DDC are the go-to guys for a cubic butt-ton of Navy synchros and S/D & D/S converters and the handbook contains quite a lot of good general info.
There's also a NEETS training module on synchro/servo/resolvers over at
-- Rich Webb Norfolk, VA
I stumbled across pdfgeni.com, a pdf search engine, and found this page...
which includes a bunch of the DDC stuff.
I am presuming that you have the wit to digitize ratiometrically between the excitation and the output(s). Then the fancy transformers are unnecessary.
And all the decent books i knew of were Military tech training manuals from the 1970s and earlier. It is not that complex but it has some twists.
Multispeed easy?? Not going to happen. Do you know how to elecromechanically zero a multispeed synchro?
I can see where you think you can break into a lucrative, but niche, market. I worked on synchro/ digital and digital/synchro converters in the 1970s (tech days, but i did learn them right).
I have not the wit to understand what you're talking about. The real point being, do you?
I don't have to break into a market. A pretty big aerospace company is asking me to do this to replace a board that they designed themselves and don't want to/can't make any more.
A lot of big aerospace companies and national labs used to design their own electronics. Sometimes it was good, but often not. The trend is now towards outsourcing, for several reasons.
I meant this in jest, referring to methods as old as the reference.
The Scott-Tee was used to convert from three synchro windings to two resolver windings. No trig was involved, just a two phase/three phase conversion, which the power types used when two phase power was around.
For use in a synchro/resolver system/simulation the "expensive transformer" can be replaced by two op-amps and a hand full of resistors. The resistors replace the ~86% tap on one transformer.
They never were.
Virg Wall, P.E.
My apologies, Virg, Larkin is a bit like Al Gore :-) ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et |
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