On 01/01/2014 10:27 AM, Ed wrote: > I am working on a mill with a Pico Systems setup and am having troubles > with the tuning. > > Wells-Index 3 axis mill, similar to a Bridgeport, formerly using Gecko 320's > > Pico Systems UPC PWM controller > > 3 Ea. PWM DC servo amps set at 10 Amps > > Original nominal 90 Volt supply > > With the P set to 100 I set to 0 and D set to 0 the axis will hold > against turning the screw in one direction very well but the other > direction faults out very easily. > > Changing the current limit resistors did not make an appreciable difference. > > Setting P to a higher value does help some but using any D sets it into > oscillation. Many other settings have been tried but it has been mostly > a blind change and try thing. You need to tell us a lot more about the system. Are the encoders directly on the motors, or somewhere else in the system? What is the encoder resolution? Are the motors direct-drive, or coupled by belts? > It will jog at about 10 IPM then faults when stopping. > > The difference in torque in the different directions is what has me baffled. > If you are not using the velocity estimation mode, it is HIGHLY recommended. it uses a feature of the newer boards (since early 2013) to use time between encoder counts to more accurately measure velocity). In the sample configs, there is univpwm (without velocity) and univpwmv (with velocity estimation). It is easier to tune the servo response with the velocity estimation.
The current limit feature depends on 5 milli-Ohm resistors in the servo amp. So, it is very sensitive to the resistance of the traces on the board. Resistors on the board were set to try to balance the variation, but it is not perfect. But, you should not be getting into the current limit under normal conditions, only during hard acceleration. You might want to step back and test your motors for performance. Your machine should move smoothly on one Amp of motor current. If it doesn't, the cause should be found. What is the current rating of your motors? Is that continuous or peak? Do the motors produce something close to rated torque at rated current? If not, the magnets are cooked, which is not all that rare. What value are the current set resistors you are using on the servo amps? Jon ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
