Kenneth Lerman wrote: > Steve, > > The problem with a filter is that it introduces a delay. So a two-tap filter > would introduce a delay of at least one servo cycle. Is that better or worse > than just halving the servo cycle? Could feedforward compensate for that? No, if you set up the order of the processes correctly in the script that installs the hal components, there is actually NOT a total delay of all frequency components. You would set it up so that the servo thread reads the encoders, then does the PID, then the filter, then the selected servo output. This is in the addf commands in ..../configs/univpwm/univpwm_load.hal, for instance.
The filter takes the current input times a coefficient, then adds several previous samples times their coefficients. Depending on how much each sample is weighted, there would be more delay on the lower frequency components with a low-pass filter. I'll have to see how this works. Since it is filtering the command OUTPUT of the PID, it shouldn't increase error that much, IF you can make the loop stable. I'll have to think about the notch filter vs. low-pass filter thing. Maybe I really want a notch filter at 1/2 the sample rate. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
