Troubleshooting position control faults
Position control fault can occur due to several reasons. This page gives tips how to troubleshoot the reason of the fault.
Using fault status information[edit | edit source]
Method for finding the root cause of the fault: check Fault location from Granity Testing tab (scroll down the page to find Fault location numbers). This indicates the fault that occurred first of all faults, and is likely the reason causing rest of the faults as well.
Some most typical reasons that may happen:
- Insufficient torque on motor: motor will lag behind if it is not allowed to produce enough torque to overcome load resistance (see scope examples below). Solutions: decrease acceleration/velocity rates or increase motor current limits to get more torque.
- Undervoltage fault: HV DC bus power supply dropped voltage under the load and caused drive to fault stop
- Tracking error occurred: too tight tracking error tolerance (see Position tracking error thresholdFPT) and Servo motor tuning guide
Using Granity scope[edit | edit source]
One of most effective ways to find reason for fault is to use scope capture in Granity. In this example, we capture signals revealing fault reason in example cases:
- Choose Capture on fault as trigger
- Choose quite low sample rate, such as 500 Hz
- Choose channels Torque achieved, Torque setpoint, HV bus voltage and Tracking error
- Untick Continuously repeating capture
- Start capture
- Perform the operation that causes the fault
If you can't reproduce the fault while Granity is connected, you may use the offline capture feature.
|The method above is most effective with latest firmware version and Granity version that support offline capture and capture trigger delay. In older versions Capture on fault records data only after the fault, which may not provide very useful information, while the new version records also events before the fault.
If your drive firmware and Granity supports trigger delay, there will be [TBT] Capture before trigger event spinbox in the Testing page.