stubborn following error

[henradrie]

Hi Everybody,

I'm working with a PCI-7344 and I keep getting following errors for one of the axes. I've checked almost everything I can think of. No matter what I do it moves in the right direction but won't stop at the desired position. It keeps going until the controller kills it due to following error. 

I've switched axes to make sure that one isn't defective. Made sure there are no loose connections and that everything is hooked up correctly. 

When I give the system a command to move positive it moves positive which means that the encoder and command wires are hooked up correctly. It's also the same configuration as the other working axis. It has the exact same motors and encoders wired up exactly the same way. This is also how I know the encoder resolution is set up correctly. 

The motor has enough torque to move the system.

The only thing I can think of is improperly set PID parameters. I've tried everything but can't seem to find a combination that works. Autotune sometimes works but also produces following errors. Sometimes autotune will set some parameters but the axis won't respond to any commands from MAX.

Anybody have any ideas on how to fix this issue?

[Daniel.Parrott]

Could you provide the specific following errors you get? Is an error number included?

It would also be helpful if you can include any screenshots of how you have the PID gains configured along with a screenshot of the code you're using whenever you get the error.

And just to clarify, the other axis you have setup has the exact same configuration and code but you're still seeing the errors come up? 

[henradrie]

I'm using NI max with motion assistant so there is no labview code.

I give the command to move 500 steps. When it reaches 500 steps it just keeps going without slowing down. Once it reaches 1000 overshoot steps motion assistant kills it and gives an error.

Yes the other axis has the same wiring and mechanical configuration but errors still come up

[Daniel.Parrott]

Are you using one of the UMI breakout boards?

One thing to check and make sure is working is the encoder. You can disable the drive and motor, then go to the Advanced tab in the Motion Assistant. You should be able to see encoder readings there and can spin your motor manually to make sure this is updating correctly. 

One other thing you could do is copy the Axis configurations that are working by going to NI MAX, selecting this Axis and selecting 'Save to All Axis'. 

[henradrie]

Figured it out. The error was caused by the encoder and actuator being set in different directions. The actuator would move the motor and the encoder would register opposite the movement. This caused a following error that would get larger till the software killed the motor. 

I followed this procedure. http://digital.ni.com/public.nsf/allkb/D2F1EF10A39A549B86256DB20081C879

Only instead of reversing the encoders I swapped the power wires for the motor. It was a simple brushed DC motor.