On 12/10/2012 5:10 AM, andy pugh wrote: > On 10 December 2012 04:10, Jon Elson <[email protected]> wrote: > >> I have a $13K box (Schlumberger dynamic signal analyzer) that is >> supposed to acquire the data for Bode plots. I tried to use it on my >> home-made analog servo amplifiers. I cut the servo loop and >> added a 100 Ohm resistor, and connected the drive/sense >> terminals across that. It excited the system with a sine wave, and at >> the lowest frequencies, I could see the table rock a small amount. >> But, the data I got made no sense at all, and may not have been >> repeatable, either. > Is a sine-wave the correct input signal? > When I spent my working day creating frequency response curves we > typically used white-noise excitation. > I assume that Jon is saying that it excited the system with a swept sine wave. We used to use that to measure the system response of aircraft wings when I worked at Grumman. Response to an impulse (step) and to white noise (well, actually pink noise) are other ways of measuring system response.
One problem I've always had with the PID controller is that the classic controller views the problem as one of controlling a system so as to maintain a setpoint in the presence of variations in the system being controlled. So, in our context, it might control a spindle speed in the presence of variations of load. Our problem is generally different, though. We are changing the *setpoint* and trying to get the system response to match the setpoint. Regarding comments Jon has made about 'I', some systems I've worked on had something called "wind up limiting". The idea was to limit the amount of integral that could be added to the system. Regards, Ken ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
