After a recent power cycle, the y-axis referencing was lost for the 1000 kg crane. The position readout was also incorrect, somewhere on the order of > 30,000 mm. On 2024-11-29, A. Newsome re-referenced the y-axis. The position readout correctly reset to zero, and both +y and -y motion is functioning correctly, but the y-axis position readout on the HMI constantly displays 0 and does not change. To be investigated.

Update 2024-12-02:

After going online with the PLC, it was determined that the reason for the display of 0 as the position is that the two values used for calibration of the +y and -y limits were actually the same, meaning the scaling factor (the difference between these two values) was 0, which resulted in the displayed value being 0. The root cause of this is that the encoder was not functioning correctly so its value was not changing when the crane moved and it was stuck at one value. Upon investigation of the encoder input card, the red "ERR" light was on. This indicates the encoder signals are not properly reaching the input card. Once this was discovered, it was remembered that this happened in July 2024 as well (no e-log was written). In July, the root cause was identified as being a loose encoder signal wire in a junction box. Junction box CJB1-BC, located on the bridge crane near its disconnects, was opened and investigated. Upon checking each wire, it was determined that the red wire seemed not to be making full contact. The wire was removed and re-inserted, and the "ERR" indicator on the encoder card turned off. The crane's +y and -y limits were re-referenced. The crane is functioning normally after re-referencing. (Note: if something like this happens again, during the re-referencing process, the displayed value on the HMI will be incorrect.. this is because the PLC's scaling factor is not fully adjusted until both +y and -y limits are reached. The actual encoder measurement taken at those limits is used for the scaling factor. This is not an ideal way to program the system, but this is how it works with all ARIEL hot cell subsystems. So incorrectly displayed values can be ignored, in general, until full referencing is completed).