On Tuesday 15 March 2016 12:16:50 Kirk Wallace wrote: > On 03/15/2016 12:28 AM, Gene Heskett wrote: > > ... snip > > > What type of interface Kirk? > > A Pico Sys +10 V analog output. I keep thinking it's PWM but it's not. > It uses a DAC. > > > I intend to use a pwmgen, which would update its analog equ at the > > servo rate, normally at 1 KHz. If thats a problem, coming out from > > zero radius where the first 1/8 would be a pretty large & fast > > slowdown, I think I would look at it as a windup in the PID caused > > by the 2500 rev limit, and would try to apply the usual suspects > > fixes for a windup condition. I've had symptoms of that show up in > > my testing speed changes while looking for the best pid response, > > and had to reduce the IGain if the speed chnage commands were too > > close together in time. > > ... snip > > I don't recall running my speed commands though a PID. CSS has a > maximum RPM setting which I had to turn down to about 800 RPM to avoid > errors before getting the dynamic braking working. A simple MDI or > g-code command from 2500 RPM to 300 worked fine and at the VFD's decel > setting. I'm guessing that a step from 2500 RPM to 300 RPM is handled > differently from having CSS go from a small radius to a large one. My > guess was that the difference was the constant stream of speed > commands, but the output stream is constant all of the time anyway, > which shoots holes in my guess. The VFD may have a noise filter on the > analog input that makes the difference.
I hadn't thought of that but it could be a possibility. Not using a PID... That says you don't have an encoder on it either I guess. I only have one machine without an encoder, the toy mill with its 200 watt motor, but its motor controller is still very stiff. I enhance the stop with a resistor to dump the motor into, so stop times are in the 1-1.5 second range, but starts, even to max of 2500, are well below 1 second. And no encoder, just the back emf. I blew so many fuses because I had no clue the motor was working that hard so I cobbled up an ammeter which usually gives me enough warning to save the fuse. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785231&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
