Message ID: 15971
Entry time: Sun Mar 28 14:16:25 2021
In reply to: 15957
Reply to this: 15973

Author:

Anchal

Type:

Summary

Category:

SUS

Subject:

MC3 new Input Matrix not providing stable loop

Rana asked us to write out here the new MC3 input matrix we have calculated along with the old one. The new matrix is not working out for us as it can't keep the suspension loops stable.

Matrices:

Old (Current) MC3 Input Matrix (C1:SUS-MC3_INMATRIX_ii_jj)

UL

UR

LR

LL

SD

POS

0.288

0.284

0.212

0.216

-0.406

PIT

2.658

0.041

-3.291

-0.674

-0.721

YAW

0.605

-2.714

0.014

3.332

0.666

SIDE

0.166

0.197

0.105

0.074

1

New MC3 Input Matrix (C1:SUS-MC3_INMATRIX_ii_jj)

UL

UR

LR

LL

SIDE

POS

0.144

0.182

0.124

0.086

0.586

PIT

2.328

0.059

-3.399

-1.13

-0.786

YAW

0.552

-2.591

0.263

3.406

0.768

SIDE

-0.287

-0.304

-0.282

-0.265

0.871

Note that the new matrix has been made so that the norm of each row is the same as the norm of the corresponding row in the old (current) input matrix.

Peak finding results:

Guess Values

Fittted Values

PIT Resonant Freq. (Hz)

0.771

0.771

YAW Resonant Freq. (Hz)

0.841

0.846

POS Resonant Freq. (Hz)

0.969

0.969

SIDE Resonant Freq. (Hz)

0.978

0.978

PIT Resonance Q

600

345

YAW Resonance Q

230

120

POS Resonance Q

200

436

SIDE Resonance Q

460

282

PIT Resonance Amplitude

500

750

YAW Resonance Amplitude

1500

3872

POS Resonance Amplitude

3800

363

SIDE Resonance Amplitude

170

282

Note: The highest peak on SIDE OSEM sensor free swinging data as well as the DOF basis data created using existing input matrix, comes at 0.978 Hz. Ideally, this should be 1 Hz and in MC1 and MC2, we see the resonance on SIDE DOF to show near 0.99 Hz. If you look closely, there is a small peak present near 1 Hz actually, but it is too small to be the SIDE DOF eigenfrequency. And if it is indeed that, then which of the other 4 peaks is not the DOF we are interested in?

On possiblity is that the POS eigenfrequency which is supposed to be around 0.97 Hz is split off in two peaks due to some sideways vibration and hence these peaks get strongly coupled to SIDE OSEM as well.

P.S. I think something is wrong and out limited experience is not enough to pinpoint it. I can show up more data or plots if required to understand this issue. Let us know what you all think.