The below is exactly true. The problem is that PID is widely used and PID is only "reactive" it can only deal with what has already happened and the time lag is the source of oscillations. In the past, PID was the only control option because we had limited computing power. People are starting to use MPC for motion control now. MPC is predictive and can account for "spring back", backlash and the time it will take to decelerate. But it does require modern compute power. If you google, you find many papers on MPC applied to milling machines starting in about 2010.
Eventually, this will filter down to the open-source DIY hobby community. If you have ever seen a machine running with this kind of controller it is visible even just looking at it by eye, the machine looks "alive" and moves more like a human or a dog rather than a robot. It is hard to describe but it comes from "knowing" what is about to happen and taking the future half-second or so into account. The control will take action to prevent oscillation or spring because it is predictive, not reactive. This is in use now for some years, it's not speculative. The problem is the complexity. It requires some advanced math and the computer has to be able to run thousands or likely millions of simulations of the entire machine per second. This is maybe why we don't see research on this done in the 1990s or 2000s. It is a good use for a 6-core Intel i9 CPU On Sun, May 2, 2021 at 7:22 AM Gene Heskett <ghesk...@shentel.net> wrote: > > That is the unmentioned in polite company problem associated with glass > scales as even resolvers aren't completely instant. The rssolution of it > might include a higher frequency than 1 kilohertz for the servo loop. > Stepgen based feedback doesn't have that lag. They report the position > they've sent to the motors, no lag other than the quantization of the 1 > kilohertz servo loop. -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
