11/06/08 1

E+ Source Target PrototypeUpdate and Data to date

• Status

• Torque transducer / motor control data

• Accelerometers

11/06/08 2

Current Status• Local guarding frame has been built

• Awaiting confirmation of sheet thickness

• Still stuck at 60 rpm

• Initial work by Chris Nelson (RAL) agrees with Lisle Hagler (LLBL) rotordynamic and thermal stress analysis

• We have spoken to Jim Rochford (RAL) about magnetic modeling simulations in Opera/Electra: we may be able to do this in-house very soon!

• 4 thermal cameras operational

• PC seems to be able to cope with picoscope, torque software and CTscope simultaneously

• Accelerometer hardware trip completed

11/06/08 3

Motor Control

Torque Transducer (T12)

11/06/08 4

Encoder and requested rpm (y) time (x) CT motor control feedback data

Encoder ( 0 – 655320) : shown divided by 1000 on plot

Wheel continues spinning after motor switched off

RPM

ENCODER

POSITION

11/06/08 5

Torque and rpm (T12)

Speed shows oscilliatory behaviour

60 rpm seems to be peak speed, not even average

Speed tails off after motor switched off

TORQUE

Nm

RPM

11/06/08 6

Blue – requested rpm, Red – rpm from torque transducer, Green – encoder, Black – torque (Nm)

11/06/08 7

Torque drives speed change (matched but slightly ahead in time)

Tosc = 1 sec @ 60 rpm = 1 rev per sec ( x-scale = milliseconds )

Speed and Torque overlaid only for shape comparison purposes (not same scales)

TORQUE

SPEED

11/06/08 8

Rpm (calc) and encoder (ct)

Rpm calculated from encoder position change and time

Oscilliatory behaviour seen before not very clear

11/06/08 9

Blue – calculated rpm from encoder, Red – rpm from torque transducer

Difficult to convincingly show agreement, too few data points from encoder

11/06/08 10

• Speed = 30 rpm

• Oscilliatory structure far less clear

• Not obviously 2Hz as expected

• Speed well short of 30 rpm

• Too slow for torque transducer?

• Calibration?RPM

11/06/08 11

• Torque @ 30 rpm

• Highly oscilliatory

• Behaviour after motor switch off not the same as 60 rpm

11/06/08 12

Torque @ 30 rpm

3 seconds of data = 1 ½ revolutions

Spokes(5) are equally spaced but large troughs(6) are

too far apart in time to be spoke edges either

Unsure of cause :- ball bearings in bearing housing / motor, no. coils / windings / magnets ?

11/06/08 13

Accelerometers

One accelerometer on table (control) and one on bearing housing

11/06/08 14

Motor off: background noise

This is a static plot but frequent fluctuations seen on short time scales, all frequencies

Something loud at 450Hz? Air con? 100 Hz? (see next plot)

Red: on table in personnel area

Blue: on bearing in machine area

11/06/08 15

Motor on at 0 rpm: rumbles

rumble seen @ 420 Hz + 525 Hz ?

trough at 200Hz likely a short-term fluctuation

11/06/08 16

Motor at 60 rpm

Entire spectrum gets louder

Very difficult to pick out any particular

enhanced frequencies ( i.e. Hz ~ rpm )

11/06/08 17

• HBM measurement training day

• Torque transducer is just a set of strain gauges on a shaft

• The twist alters the resistance which is measured by wheatstone bridges

• To achieve the highest levels of accuracy, temperature and initial stresses must be considered

Makes solid metal rig seem like a wobbly structure!

11/06/08 18

Summary

• Progress is being slowed up by safety considerations

• Most DAQ is in place and data taking is happening

• As always there are a few teething problems and unexpected results

• Proprietary software is largely black-box plug-and-play… Easy to set-up but difficult to cater for specific requirements of the experiment