Message ID: 16005
Entry time: Wed Apr 7 17:38:51 2021
In reply to: 16001
Reply to this: 16007

Author:

Anchal

Type:

Update

Category:

SUS

Subject:

Trying to uncouple only PIT and YAW first

To test if our method is working at all, we went for the simpler case of just uncoupling PIT and YAW. This is also because the sensor used for these two degrees of freedom is similar (the MC Trans WFS).

We saw a successful decrease in cross-coupling between PIT and YAW over the first 50 iterations that we tried. Here are some results:

Final output matrix:

Output matrix for uncoupling PIT and YAW from eachother

PIT

YAW

COILS

1.01858

1.16820

UL

0.98107

-0.79706

UR

-0.98107

0.79706

LL

-1.01858

-1.16820

LR

Plots:

Attachment 1 shows distance of sensing matrix from identity as iterations go.

Attachment 2 shows the off-diagonal elements of sensing matrix as the iterations increase.

It is worth noting that PIT -> YAW coupling was the main element that was reduced successfully while the YAW -> PIT was reducing but much more slowly.

Most of the remaining cross coupling in the end was from YAW -> PIT.

Attachment 3 shows first 10 oscillations in the time series data during excitation of some of the iterations.

Attachment 4 shows the cross spectral density of the sensed data during excitation with each other. This has been normalized by reference PSD data (taken with no excitation) of the sensed DOFs involved in the CSD calculation.

Attachment 5 shows the TF estimate made by normalizing CSD data column wise by the diagonal elements. The excitation frequency point in these plots become the Sensing matrix in the calculation.

One can notice how the PIT -> YAW element is going down in these plots.

Even though we are using only the real value of the sensing matrix, the imaginary values are also going down.

Next, tried uncoupling POS and PIT:

Next, we tried to uncouple POS and PIT. We expect them to be more coupled than with YAW.

At the time of writing this post, 15 iterations of this attempt have been completed and it is not looking good .

The distance of the sensing matrix from identity is growing at an accelerated rate.

The POS output matrix column seems to be trying to go towards the negative of PIT output matrix column! Why? We don't know.

We have seen in the past that once POS transforms into PIT or YAW, it just makes the output matrix worse as no feedback actually goes into the POS column. Eventually, the IMC will cease to remain locked.

So, I'm cancelling this attempt for now. Will consider more alternatives later.