Anders Wallin wrote: >>I couldn't find your serial number in my data base, so I don't >>know what version of it you have. The earliest models had a > > > you sent these to me in late December 2006. > Can you tell which rev. I have based on the date? > Yes, Rev D started in Feb, 2006, so your amps are also Rev. D, with the proper action on braking. So, that isn't the problem. All these amps DO have an asymmetry when on the current limit, due to variations in the .005 Ohm current sense resistors and the traces on the board. I select other components to try to compensate for that on each batch of boards. If you are at the current limit (the motors tend to "sing" in that mode) you either need to trun up the limit or back off the acceleration. Current limiting of the amplifiers breaks the closed-loop operation, and should be avoided. it is a safety feature for the amps and motors.
I should add I am not sure you ARE hitting the current limit, and one way to check is to slightly increase the acceleration. If the error becomes vastly larger, then you are on the current limit. > > I will have to check the current limit. I know the PWM signal is not > maxing out, but as the inductance of the motor keeps changing the DAC > output is not a good indication of current. > The DAC output looks trapezoidal, so I just assumed there are no > problems during accel/decel, but you are right - the current limit might > be setting in... The PWM would be expected to go to ~95% when the amp is in current limit, as it is no longer responding to the command. The "DAC" output is much more proportional to output voltage than current, and so is nearly an analogue of velocity. So, it doesn't sound like current limit. Other's comments about integral windup sound very relevant. I use I very cautiously, as it can have a number of side effects like this. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
