On Friday 13 December 2013 13:50:44 Marius Alksnys did opine: > 6 axis articulated robot. Its 5th and 6th joint motion is transferred > from servo motor to the end by belts. Controlling 1-5 joints is trivial, > but 6th one has to be offset by 5th position. > > This means you have to rotate both 5th and 6th motors equally to move > only 5th joint. > > ( BTW, this is the reason why I started to think that there could be > three different objects / levels in linuxcnc: motor - joint - axis ) > > There are resolvers on the motors and I use 7i49 card to read them. > > I am using genserkins for world mode and an offset component for > offsetting 6th motor position and feedback signals in relation from 5th > motor position signal. And it works correctly, except for homing, but I > can't figure out how it _normally_ works. > > My homing uses resolver index. The problem is that I get following > errors even when MIN_FERROR is 60 degrees. And I see that resolver > position feedback signal makes a step when homing.
Yikes. I know little to zip about resolvers, only that if its lying to you, I would call it a resolver problem and would be all over the maker asking for a solution from them until it was proven that it was indeed my setup generating the error. I'd move one of them that is doing this to a stepper just laying on the table, and log what it says for at least a turn going both ways when the stepper is driven in full step mode, one step at a time, where it generally will rest at very close to 1.8 degrees per step. Probably closer than .05 degrees per step from ideal. If there is a repeat error cycle every 4 steps, thats the motor itself, so use the average of the last 4 steps which should remove that error, but anything else has to be a funkity resolver. IMO of course. Over 200 steps, a full revolution of the motor, it has to be 1.8 degrees per step for most steppers. > I do see that big steps happen in resolver feedback signals, when they > approach index. But the same is with normal joints. > > Any ideas how to solve this? See above as a "I have got the tools" way to isolate resolver error to the resolver. > I know I could do this in kins, but I would like to be able to use > standard genserkins. > > > > Some lines from my config (joint / motor components and signals are > numbered from 0): > > .hal file: > ----------------------------------------------------------- > loadrt offset names=offset-j56 > > addf offset-j56.update-feedback servo-thread > addf offset-j56.update-output servo-thread > > net mot.4.pos-cmd joint.4.motor-pos-cmd => pid.4.command > offset-j56.offset > > net mot.4.index-enable pid.4.index-enable > net mot.4.index-enable joint.4.index-enable <=> > [HM2](BRD)resolver.04.index-enable > > net mot.5.pos-cmd offset-j56.out => pid.5.command > net mot.5.pos-fb => offset-j56.fb-in pid.5.feedback > [HM2](BRD)resolver.05.position > net jnt.5.pos-cmd joint.5.motor-pos-cmd => offset-j56.in > net jnt.5.pos-fb offset-j56.fb-out joint.5.motor-pos-fb > > net mot.5.index-enable pid.5.index-enable > net mot.5.index-enable joint.5.index-enable <=> > [HM2](BRD)resolver.05.index-enable > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> * Knghtbrd notes he has mashed potatoes for brains tonight <Valkyrie> yum, can I have some? <Knghtbrd> um ... * Knghtbrd hides from Valkyrie A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
