On Sunday 15 July 2012 20:51:58 andy pugh did opine: > On 15 July 2012 22:14, Gene Heskett <[email protected]> wrote: > > Sure there is Jon. Timestamp the last 4 edges so you can develop an > > average speed over the total time period of those 4 stamps. > > That's quite a lot like putting a lowpass on the velocity output. > I tried that too Andy, but the 'gain' had to be cranked into the .001 range to get a value that only had the last 5% in it, and at that gain, the settling time was many seconds. The basic problem there is that the last value clocked in is 50% weighted. If the whole thing was a shift register that read out in parallel, so an instant value variation if the gain was .25, would only contribute 25%, with the old value shifted out to null. That would absorb a lot of the digital noise by averaging the mechanics out over 4 edges, and would settle fast enough to be usable. The lowpass does not. But here is a thought. The lowpass can be 'loaded', then allowed to drift as needed, if we can figure out when to enable the load pin. The $64 question, that.
> I know you want a more satisfactory solution, and so would I after > spending so long making the encoder so perfect, but pragmatically a > filter will probably work. By the time you think you can see it might be helping, the lag getting through it is playing tiddly-winks with stability, overshoots and oscillation then become the order of the day. Or at least that was my experience when I was trying to make the first few disks I made actually work. > I actually get a whole lot of dither from my lathe encoder, and I have > never really figured out why. I just assume it isn't a great encoder. Mine, on my 100mhz dual trace, might have 2% dither & a half degree quadrature error right now. There is no way that I can see that would multiply that small a wibble into a + - 40% velocity error on a servo- thread run to the next servo-thread run basis. Do you still have the ebay sellers name that had those extra long setscrews to make these dual diameter bolts from? I swear that I saw some at Lowes in that aisle with all the drawers of odd parts, but tonight the longest they had in 5/16-18 allen set screws was 1/2". That obviously won't fly. I also darned near had to swim home, Just as I hit the Brushy Fork road traffic light on 33 headed back west toward Weston, somebody opened up a big, long zipper in the bottom of the overcast & slightly noisy sky. 2 miles later I am down to about 35 mph on a 70 mph road, 4 way flashers running, and hydroplaning intermittently in a 99 GMC pickup truck that says it weighs 7200 lbs on the door post, it was 4" deep in the ruts of the worn blacktop. I didn't get back up to 50 mph & shut the 4 ways off for about 9 miles. I also passed several other vehicles whose drivers had the sense god gave a goose and had pulled over to let it go by. It has settled some now, but the telly is still yipping about more of the same & warning us about flash floods. But while I can see the river from here, I'm also 50 feet above its banks & safe. This is West Virginia after all. I used to have a friend that farmed south of town 5 miles or so, whose land was pretty steep & he claimed he could farm both sides of some of it. I think he must have had more than 400 acres, all folded up to fit in 160 surveyed acres from my deer hunting on it years ago. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Suddenly, Professor Liebowitz realizes he has come to the seminar without his duck ... ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
