On Tue, Mar 2, 2010 at 6:24 AM, Dave <[email protected]> wrote: > At first glance I would say that you are getting too aggressive with the > gain. Back Pgain off to 8 and dial in some D to kill the oscillations. >
Dave > Thanks for the advice. I did some more experiments with a Pgain of 1 to 7. I'll add in the Dgain after I figure out what the proper Pgain should be. I attached a link to the image of the halscope traces. I had to change the error scale to make the error traces fit on the screen. The old traces from the previous message had an error scale of 10m/div, these new traces have an error scale of 100m/div so 10x more error scale. I also redid a Pgain of 8 with the new scale to give a sense of scale compared to the older set of halscope traces. http://i.imgur.com/G4NXl.png I'm not quite sure how to interpret what is happening though. It looks like the lower the Pgain, like at Pgain = 1, the larger the error, but the smoother the error and smoother the ouput of the pid loop. The higher the Pgain the less error appears, but the error and output of the pid bounce around a lot and get real fuzzy from small oscillations. For setting an initial P is it generally better to have the larger but smoother error values and dial it in using the other PID adjustments, or is it generally better to have the smaller error but rougher error and output lines? > > On 3/1/2010 10:10 PM, Flying Electron Inc wrote: > > Hi all, > > > > Hoping some people that have tuned their servos with EMC2 might be able > to > > share some of their insights that they learned during their tuning with > me. > > I built a pick and place machine with a servo on the X axis and I > started > > running tests to tune the PID loop for the servo. Right now, I have > > everything set to zero, a deadband set to 0.00001 and I am adjusting the > > Pgain to find the optimal Pgain before I start varying the other > parameters. > > > > The test I am using is to start from a standstill at X=0, move to X = 8 > > inches with an acceleration of 25in/sec^2 and a maximum velocity of > 9in/sec, > > come to a full stop and wait for 0.5 seconds, then reverse back to X=0 > with > > the same acceleration profile. > > > > I tried different Pgain values of 4, 8, 10, 12, 13, and 14 to see what > the > > error looked like. at Pgain of 16 the machine began oscillating badly. > > I've attached a link to an image of the screenshots i took from hal > scope > > for the different Pgains that I tried. To my inexperienced eye, it looks > > like Pgain 12 is the best, but I'm not sure if the error graphs are even > > supposed to look like this. > > > > http://i.imgur.com/hefCf.png > > > > If anyone can tell me if these error graphs look normal or not, I'd > > appreciate it! > > > > Thanks > > > > Lawrence > > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
