On Wed, Aug 7, 2013 at 12:16 AM, Don Stanley <dstanley1...@gmail.com> wrote: > Most stepper controllers have idle torque. > Some will have full torque at idle (stopped). > Most modern stepper controllers will have a selectable > idle torque and some will wait a few seconds > before switching from run torque to idle torque.
You missed Stephen's point---yes, there's a holding current going through the stepper coils, but in the middle of the step the torque is zero. In other words, the stepper motor holds the position by having local maxima of holding torque at half step ahead and after the desired position. There's no closed loop like in a servo, where you can increase the precision by increasing the resolver resolution and/or the gain. Don't get me wrong---I actually like steppers, because they are simple and reliable, and accurate enough if engineered properly by matching their inherent accuracy to the desired movement precision. It's just that we have to understand their limitations. ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
