Basically, at no load, a servo amplifier has a characteristic relationship between the voltage in and the velocity. If the relationship is (close to) linear, then FF1 will give an approximately correct speed even before specifying P, I, D.
On an inch machine, if you set the OUTPUT_SCALE so that a PID output (PWM/DAC input) of 1.0 makes the axis move at 1.0 inch/second, then the correct value for FF1 is 1. More generally, the value of FF1 should be the PID output (PWM/DAC input) that gives a speed of 1.0 inch/second. FF2 is "like" FF1 but for acceleration instead of velocity. However, I don't know of a simple rule of thumb for setting FF2. Instead, I used halscope to look at the error during G1 moves and tweaked it until the errors in the accel/decel phase were minimized. In the case of my own system, the magnitude of FF2 is about 1% of FF1. Jeff ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
