Tom wrote: > Peter C. Wallace <p...@...> writes: > > snip... >> Also (connecting some dots here) if you are using HostMot2, D term > crunchyness >> should be much improved when EMCs PID loop is modified to be able to use the >> drivers Velocity output (which uses DeltaCounts/DeltaTime velocity >> estimation). This should allow larger D terms without instabilities >> >>> > snip... >> Peter Wallace >> Mesa Electronics >> > > Peter, > Are you saying that if I upgrade to Hostmot2, there is a Velocity output hal > pin that is not available to me using Hostmot? Would this require > modifications > to the motion.hal file in order to modify the PID loop? > Could you connect a few more dots for me here?
The hostmot2 encoder driver has a good velocity estimator, with the value available on the .velocity-fb pin. I believe (though i dont know for sure) that the older hostmot (aka m5i20) driver does *not* export encoder velocity, so with that driver velocity has to be estimated using additional HAL components (like ddt), which won't give as good a result. However... The current PID implementation in EMC2 does its own velocity estimation (controlled via the feedforward gain), and can not accept velocity information from outside itself. There are other reasons you might want good velocity feedback from your encoders, but better PID control is not yet one of them. Maybe in 2.4 ;-) -- Sebastian Kuzminsky ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
