Peter C. Wallace wrote: > > > Velocity feed forward is especially important with straight PWM ampilifiers > as > it allows the system to approximate current control, that is, make the drive > torque independent of motor back EMF. It also has one advantage over current > control systems in that the inherent damping factor is higher (the amplifier > has a low output impedance) > > One way to allow higher damping (and hence higher P) is to raise the servo > sample rate. For small or high performance motors, 1KHz is _way_ too slow, > the > zero-order hold effect (because the velocity calculation from the previous > cycle is applied over the current cycle) introduces a very unwanted delay in > the D part of the feedback loop. This delay is inversely proportional to > sample rate. I have been wondering about this. Of course, increasing the sampling rate makes the quantization problem worse, but each glitch lasts for a shorter time. My general feeling was that with these small motors hitched to heavy machinery, the bandwidth of the iron is pretty low compared to even the 1 KHz rate. But, it certainly is worth investigating. Some of the PWM users are running on really slow computer hardware and the rate can't be raised a whole lot. Others are using faster computers, and 10 KHz is not unreasonable to try.
I will have to do some experiments and see what happens. 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-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
