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NCAL Lab Test - 31st July 2019
PEM tests
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0900
Entered lab, lights on.
Plugged in Beckoff PC and attempted to power on via DC power suppy. Turns out the wall plug socket as tripped so this was reset. 
DC power supply works and Beckhoff motor controller, Beckoff PC and monitor are powered on.

     Chan 2 A: 0.32 +/-0.01 amps
     Chan 2 V: 24.4 volts
     Chan 1 A: 0.39 amps
     Chan 1 V: 24.4 volts

Re-assebled the NCAL and bolted everything up tight. Applied dog clamps to the base plate and installed the accelerometer. Moreover, the accelerometer Krishna as supplied was affixed. The rotary encoder is not attached.

Loaded up TwinCat via Visual Studio 13 and logged into the Beckhoff motor controller. I was getting no rpm readout on the motor controller display therefore I swapped the ethernet cable on the back of the Beckhoff PC to the X103 port. I now have rpm counts. Then logged into a session on the PC and started up Visual Studio 17 that contains the handles the IOC.

NOTE: I am using an older version of the TwinCAT code (the version Krishna delivered) since this is the method I am most familiar with to control the NCAL as well as the newest version of the code has not been extensively tested yet. 

Checked the motor control drive setting in te DRIVE MANAGER in the EtherCat software to make sure the velocity filter settings are correct.

    Low pass time constant T1: 15.00 ms
    Gain KP: 0.030 Nm/(rad/s)
    
0930
TEST 1  :   Setting the motor at 104 counts (~1Hz) for ~ 60 seconds to verify the set up works. 
RESULT 1:   For some reason, I am unable to start the scope to show the traces of velocity, torque and current. Other than that, the motor spins and holds constant velocity.

0933
TEST 2  :   Selected 500 counts (~5Hz) and verify the motor can spin up without issues.
RESULT 2:   Motor spins up with no issues and is holding constant velocity. Small hum coming from te motor. No visual vibrations from the NCAL unit. If one puts their hand on the table, a slight vibration can be felt. 

0950
TEST 3  :   Verify the NCAL can spin down. Selected 0 counts.
RESULT 3:   Motor spinds down smoothly with no issues.

1030
Left the lab, PC off

1230
Entered lab.

Wheeled in a spectrum analyser. Got batteries for the accelerometer

When trying to power the spectrum analyser, we tripped the wall socket (Serial Number: ). fter resetting the wall socket, tediosly, we tried each plug one by one on the wall and did not trip the wall. We found that using the we could apply no more than 3 plugs to the wall before it tripped. It did not matter if we used a power extension or directly into wall. 

To get around this issue, we used a extension from anther wall socket (Series Number: ) in combination with the wall socket in this combination:

Socket A :  Spectrum Analyser, DC power supply, Oscilloscope, PC Monitor
Socket B :  Beckhoff motor controller

When using the power stip, we found we could only use 3 slots as plugging in a 4th plug would trip the wall socket. 

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Filiberto Clara showed Matthew Bell and myself how to use the spectrum analyser for taking Transfer Functions. The details are below.

To select te file to read or write from:
->From the main menu
    ->Select folder (second button)
    ->Select the file name (first button)
        -> Use scroll wheel to browse files in the folder and press enter to select

To read data from a floopy disk:
->Disk
    ->Recall Disk
     
To write data to the floppy disk:
->Disk
    ->'Print Screen' button
    -> Change the display to save with 'Active Display' button.


To change the frequency settings swept signal for the Transfer Fumction:
->Freq
    ->Stop
    ->Start

NEVER REMOVE THE FLOPPY DISK WHILE THE GREEN LIGHT IS FLASHING BECAUSE DATA IS STILL BEING READ?WRITTEN TO THE FLOPPY.

*********************************************************************

Powered the magetometer and the accelerometer connected them to the oscilloscope. 

1330
TEST 4  :   Verify the NCAL can spin to ~10Hz and test the accelerometer and magnetometer
RESULT 4:   We are able to spin the NCAL up to ~10Hz by requesting 1043 counts on the PC. Once the NCAL had reached 10Hz, we noticed the orange comms cable shaking and the table the NCAL is bolted to is shaking more than normal, to the point where the table and the contents upon it are visably shaking. This is not normal because when the NCAL was spun at ~30Hz 3 weeks ago, this motion was not observed. 

At the time of TEST 4, we had the magnetometer and the accelerometer hooked up to the oscilloscope and we could see no signals other than the nominal sensor noise. 


1430
Matt packed up the PEM equuipment and exited the lab since. Commensing wobble hunt. My initial concerns are (as thoughts :

1) Bearing play
2) Damaged NCAL flywheel
3) Damaged NCAL back plate
4) Misaligned motor on the NCAL shaft
5) Bent NCAL shaft
6) Bolts not tightened correctly upon reassemble this morning
7) Addition of Krishna accelerometer unbalanced the NCAL

1500
In order of how I investiaged.

7) Addition of Krishna accelerometer unbalanced the NCAL
I removed the accelerometer and ran the NCAL at ~10Hz. It is still wobbling

4) Misaligned motor on the NCAL shaft
I removed the motor and reattached it, paying very, very close attention to the level (using a spirit level). Tightened everything down hand tight. Ran the NCAL to 10Hz and the wobbling is still present. 

2+3)Damaged NCAL flywheel and Damaged NCAL back plate
Dis-assembled the NCAL such that the NCAL side covers are off and the NCAL is resting on the side covers. Spun the NCAL by hand and observed the side and top profiles of the NCAL flywheel and back plate. Both items shown a slight deviation as they rotate. In particular, the back plate shows signs of uneven thickness in addition a slight (<lmm) misalignment with the main flywheel. 

Loosening the scews that hold the back plate to the flywheel, I pass alcohol wipes between the mating surfaces to remove any particulates. 

Removing each 13-20 3/8 cap screws one by one, then with Isopropanol and a wire brush, I clean the internal threads in the flywheel and replace each screw. One of these cap screws now no longer wants to thread back into the flywheel. Upon further testing, I had 1 of 2 suspicions:

a) It is a metric M5 screw
b) It is a bad quality imperial 10-32 3/8 cap screw

I consulted with Chandra and Rick and the overall conclusion was that it is a bad 10-32. This is because:
1) After 1 1/2 turns with the offending screw would 'bind' (increase resistance) when tested in other 10-32 holes in the NCAL and when testing in a screw pitch gauge.
2) When putting the offending screw into the metric M5 screw pitch gauge, it would fit but would wobble (strike one for metric theory)
3) When comparing the threads of the offending screw to a 10-32 tap and other 10-32 screws, the threads match (strike two for metric theory).
4) There are no marking on the top of the head of the screw as this is typical of metric screws (strike three for metric theory).

What I suspect is that a longer 10-32 has been cut down to the required size (I think 3-8) and has not been done properly. I am going to order more 10-32 3/8 screws and replace the bad one. In addition I have already cleaned up the threads with a wire brush as Isopropanol.I have also clean the mating surfaces of the NCAL and the back plate with alcohol wipes and cleaned the threads of the remaining good screws.

The problem of the wobble still remains.

I try using different screws to check the internal threads are not damaged (cross threaded, stripped etc) however, all the other cap screws fit with no issues. Testing the offending capp screw in other cap screw holes, this screw will not go. 

1830
Powered off all equipment and exit lab. Lights off.