Output Saturated Error

I have a machine that has 2 different heads that can run independently. Lets call them Head 1 and Head 2 to have a reference point. I have a RMX150E with 2 I/O cards. I have 2 axis per Head. I have a valve for each axis for output, and 2 load cells as the input per axis. We have been running without any issues on both heads for years and now Head 2 we are getting “output saturated” error and shut down. Head 1 is working fine. The error is only on Axis 2, not on Axis 3. I recorded the voltage values being output from the Delta controller and, I never exceed 0.5 volts. I keep getting the output saturated each time I try to run it after some period of time running. It does not error out right away. This is not happening at the same amount of time on the head. Sometimes it starts and runs for 1-1/2 hours. Sometimes it starts and runs for 5 minutes. We have checked and even swapped out the valves and the cylinder. So we are back to the Deltra controller. I am looking for help with next step diagnostics as I am new to Delta and have a general understanding but very little on Programming and major diagnostics.

Cory,
It would be very helpful to get plots of the motion, which are very helpful to Delta tech support to help figure out the problem.
First, configure the plot to have a very long trending time. Get some plots of normal motion first by starting the trend before the motion, then stopping the trend after the motion completes. Then start a trend and just keep it running. When the problem happens, stop the trend and save the plot.
Here are some training videos to get you started: Videos. You will see that there are other webinar videos as well.

@Jacob_Paso , I ran the plot and this is what I got from it. It appears to see the pressure feedback but continues to send more voltage at it goes way to high then just drops like a rock. Thinking at this point it is the I/O card or the controller. feedback is appreciated.
E2_Radial_DelatPlot_Radial_Alarm.rmcplotx (3.5 MB)

In the plot, at time 7d 22h:18m:45.271s, the Control Output saturates. It appears that the axis halts in open loop or direct output, and the following decrease in the Control Output is the ramp down to zero, which is what normally happens when the axis halts. By the way, the ramp down to zero seems too slow because the Actual Force increases quite a bit during the ramp, which I assume is undesirable. You can shorten the ramp time by increasing the Open Loop Halt Ramp axis parameter.

I don’t understand why the Control Output is saturating to begin with. Typically, it would be because the error between the Target Force and Actual Force is too large, but it was not even as large as 15 msec earlier, at 45.204 sec, and the Control Output did not saturate then.

From what I see, there is no clear indication that this is a problem with the I/O module or controller. It seems like there must be more to the story. Are the gains being changed on the fly? Adding more detail to the plot could help, such as Status Bits, and the Proportional Term and Integral Term. It would also be helpful to see the RMCTools project.

I should also mention that the force feedback appears to be very noisy. It is noisy enough that it is of concern, whether or not it is a cause of this issue. I recommend reviewing the wiring.

-Jacob

@Jacob_Paso, I have attached a copy of the program. Written long ago and before me. This Axis is the radial pressure and the next one is axial pressure. With the actual force continuing to increase is why I was wondering that. The voltage keeps going up almost to 10 and then it goes to 0.

Why would it not adjust back down.

This is reading pressure applied against the radius of a cylinder spinning at high speeds. So we do see some variance in the feedback.

Feedback is appreciated.
MediumBOX_E_Rev2.rmcproj (90.5 KB)

OK, so the noise on the feedback is certainly understandable and expected.

The reason the Control Output does not quickly adjust back down after saturating (reaching 10V) is that the saturation caused the axis to halt, so the axis is not in closed-loop control anymore. At that point, the rate at which the Control Output ramps down is defined by the Open Loop Halt Ramp axis parameter, which I see is set to 100 V/s, which means it will take 0.1 seconds to ramp down to zero, which it did.

I just now noticed that in the plot, there are some samples missing right when this occurred, so it could very well be that the error between the Target Force and Actual Force was actually large enough to cause the output to saturate.

If you want the axis to not halt when the Control Output saturates, you can change the Output Saturated AutoStop to Status Only (Axis Parameters > Halts > Auto Stop Configuration), which means the axis will ignore the error. Then, if the Control Output Saturates, it will adjust back down just like you were expecting. However, you need to make sure that ignoring this error will not cause problems for the machine.

When making changes to axis parameters, make sure to download them to the controller, and update Flash.

Another option is instead of changing the AutoStop, you could add some Output Filter. This will smooth the Control Output and likely prevent some occurrences of saturation (but maybe not all). For the Output Filter, start with a large value, such as 100, then decrease it to apply more filtering.

If this is a new development, you will probably want to figure out why the Output Saturated error has started occurring. Could be mechanical wear in the system.

-Jacob