Position Error

Position errors stop motion when the axis isn't in the expected location within some tolerance.

Causes

A position error fault could be thrown by either the Servo drive or the Controller the difference between the actual position of a motor and the commanded position exceeds the limit threshold or trigger value. There are many potential causes for a difference between these values:

Issue

Type

The Position error limit trigger threshold is set too low

configuration issue

The axis hits an obstruction preventing it from following the command position

mechanical issue

The axis is commanded to move at impossible accelerations or speeds

software issue

The axis has instability causing it to oscillate

tuning issue

Motor is could be wired incorrectly

electrical issue

Controller Based v.s Drive Based Position Error

A position error can be raised by the controller or drive firmware. Usually one of them would have a tighter limit so that would be the one that always triggers.

  • Controller Based position error

If the controller throws the fault it shows up in Rapidsetup as a position error limit and the Position Error box will be red on the Limits and Actions Tab:

  • Drive Based position error

    If the servo drive throws the fault, then it will show up in RapidSetup as an Amp fault (439 following error) and the AMP FAULT box in the limits and Actions tab will be red.

Solutions

The most common cause of position error is a too tightly configured position error in the controller. You can loosen the tolerance using: ErrorLimitTriggerValueSet()