If you are just counting the number of rotations per minute or second I don't think you are going to get what you want.
You really need to be able to detect a phase change so you need to know the generator rotor position - at least a lot more accurate than one phase rotation at 60hz. The error you are seeing is 1/60 of a second which is the minimum error you can see. Your current system will probably hunt between an error of zero and 1. You need finer resolution. A second is really quite a long time in this situation. A hall effect device watching holes fly by on a pulley should work or watching gear teeth. A coarse encoder would also work. What are you using for your reference timebase as the speed setpoint for the generator?? How accurate do you want this generator to run? Do you want to be able to switch it in on out from a grid connection? Dave On 2/3/2011 9:32 PM, Jon Elson wrote: > Don Stanley wrote: > >> Hi All; >> I am attempting to configure EMC2 10.04.06 to control RPM >> on a 60 HZ AC generator. >> >> The basic approach is: >> -Set the steps per inch to the number of AC cycles per day. >> -Monitor the AC frequency into phase A of a HAL encoder. >> -Feed the encoder output into the axis and PID feedback. >> -Feed the axis motor-pos-cmd to stepgen position-cmd. >> -Feed the stepgen out through the paraport to a stepper motor driver. >> >> This seems to work in general but there are two problems I >> have not been able to pin down. >> 1- The PID error is a sawtooth shape causing the throttle >> stepper motor to quiver at 60 HZ. >> A HAL Scope image is available at >> http://imagebin.org/135986 >> >> >> > The sawtooth appears to be happening at 16.6 ms, which is one 60 Hz cycle. > Perhaps that is significant. What is the velocity coming out of the > encoder counter > component? Does it waver at all? If all these calculations are > performed in arithmetic > scaled to days, you may be looking at the limits of binary precision. I > notice your > sawtooth is fluctuating by much less than 1 millionth of a unit, roughly > 2 x 10 ^ -7. > > Jon > > ------------------------------------------------------------------------------ > The modern datacenter depends on network connectivity to access resources > and provide services. The best practices for maximizing a physical server's > connectivity to a physical network are well understood - see how these > rules translate into the virtual world? > http://p.sf.net/sfu/oracle-sfdevnlfb > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ The modern datacenter depends on network connectivity to access resources and provide services. The best practices for maximizing a physical server's connectivity to a physical network are well understood - see how these rules translate into the virtual world? http://p.sf.net/sfu/oracle-sfdevnlfb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
