That looks like a useful module ... sine for one of the coils, cosine for the other, and simply multiply the cosine signal by the servo drive signal +1 goes one direction, -1 goes the other and anything in between is just slower ...
I have a company that manufactures audio amps, driver stages won't be a problem. Just got to do some testing of the resolvers and decide which version of the Mesa hard to order, I think these resolvers output 2 x the input voltage, so I probably need the HV version, but we'll see. This will be used on the 10GHz band, with about 400W from a travelling wave tube .... there are good Python modules for moon position data, 'skyfield' is the best of the bunch, I need roughly +- 1 degree precision, with just a position update every 30 seconds or so .. the move doesnt move that fast. A good resolver should easily be able to get within 0.5 degrees ... I'll let you know how it pans out. On Sun, 22 Jan 2023 at 00:57, gene heskett <ghesk...@shentel.net> wrote: > On 1/21/23 06:25, Robin Szemeti via Emc-users wrote: > > So, in a vaguely CNC related folly I have purchased a 2 axis military > dish > > mount for radio stuff (moonbounce, if you must know) > > > > My plan is to control it from EMC, with a Mesa anything io card and the > > resolver interface, I already have various Mesa cards under EMC, so thats > > not an issue and I have a spare 5i23 PCI card and the isolated IO > duaghter > > card, so with the resolver card I should be able to uses the resolvers, > and > > pick up the limit switches on the IO card. I can just use some Python > > script to work out the moon position and generate "G1 X285.4, Y23.8" or > > whatever MDI motion commands every 15 seconds or so to track the moon, > not > > a problem. > > > > Now, the question is driving the two phase AC servos. Generating vast > > quantities of 50 or 400Hz or whatever AC for the drives is simple > enough, I > > can just use a couple of large Class D amplifiers, no worries. Generating > > the AC low level signals to drive these .... basically, it needs a > constant > > 50Hz signal on one coil of a fixed level, and a variable level sine wave > on > > the other coil, at either +90 or -90 degrees depending on which way it > > needs to go. > > > > Is it possible to use HAL or something to generate the variable level > 50Hz > > servo drive signals and output them from the PWM outputs on the resolver > > card? > > > I've not used it in that context, but take a look at man 9 siggen. > There are several mux's available that could be used to switch motor > directions. Its main use is in 1 kilohertz loop stuff for linuxcnc, but > if you need finer time resolution, should be happy in a 3 to 5 kilohertz > threads Use a halmeter to see how much time the individual module takes. > > Hal can do a lot, look the logic choices over in /usr/share/man/man9 of > an linuxcnc install and let your imagination out to play w/o a > chaperone. You can use float vars at a 1 or even 4 kilohertz loop > thread, so updating a motor drive at 50HZ ought to be doable. > > For motor amps, take a look at class D audio amps, the 400 watt modules > are rather commonplace these days, running at ultrasonic carrier > frequencies. Use chokes to keep the carrier out of the motor wires, and > good single point(one bolt) grounds. > > Use mux's for analog switches. > > Using modern stepper drives that have current limits built in, you can > creep steppers along at .01 hz a second, and if you spend the sheckels > for the closed loop stepper/servo's suitably geared down, you ought to > be able to track the moons motion within an arcsecond in real time and > do it on 40 watts of power or less since they use the error to determine > how hard to drive the motor. The recovery time when it goes below the > horizon and has to pre-aim at the other horizon for when the moon comes > back in sight at next moonrise is a problem since the active times match > the dead times pretty closely. > > I've not paid that much attention but from satellite experience, you > likely need just a little azimuth, even for polar mounts, your latitude > above or below the equator determines that, and a large longitude. > > I have an old friend from back in the 70's that at that time was > building a 12 bay steerable 2 meter get up. 16 element yagi's in a > broadside array. But another job opening took me to NM from NE so I lost > track of him. Employment brought me to WV 38 years ago, and I'm now 21 > years retired, and still here. > > And tell us how you did it when it working. > > Cheers, Gene Heskett. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/> > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
