Knee bending in the wrong direction

daylanKifky

Hi,
This new version tries to recover your old calibration data and use it. This works well most of the time but there are certain situations in which a new calibration is needed.
You can try to use the current calibration, and if you have problems recalibrate.

By the way, the complete version 1.0.0 of the addon is already available at our downloads page. Install it as well in order to see the colors representing magnetic disturbances.
Upon startup you will see most sensors as red, that's because they need to gather a few samples of the current magnetic situation, since they perform a secondary "live" calibration while you use the suit. Just move them around until they become green.

The procedure for updating the notochord is correct 😃

AxonSpark

daylanKifky I tested out the default biped configuration with the current calibration and my results were stranger than usual, so I started re-calibrating my K-Ceptors today. However, I noticed that each time I calibrated a K-Ceptor it says that 0 samples were collected. Is this normal?

daylanKifky

Yes, that line dumps the samples collected with the old method. I just forgot to remove it 😅

A good way to tell a calibration was calculated correctly is look at the matrix. If it's numerically similar to an Identity matrix then it's probably OK. Of course this should be confirmed by testing the sensor with the testcube method.

An identity 3x3 matrix is:

| 1 0 0 |
| 0 1 0 |
| 0 0 1 |

so ones in the diagonal and zeroes for the rest.

As you can see the one from your screenshot is OK

AxonSpark

daylanKifky Here's my latest series of tests using the new software with the sensor fusion algorithm:

Since I was getting some pretty big issues with the arms and legs with the original calibration, I went ahead and re-calibrated the K-Ceptors and did more tests. I've probably mentioned this before, but I do my calibrations on top of a cardboard box on a wooden stool (in order to eliminate possible interference in case there are non visible metal pieces in the stool). Unfortunately, this didn't help.

What's odd to me is that despite doing these armature calibrations/tests in roughly the same place, which bones are registering magnetic disturbances tends to vary between tests, and based on the readings I took in the last tests aren't happening where I would expect them to at times. There also seems to be a fair amount of limb twisting happening in the tests with the new calibration.

I'm also unclear as to why certain bones started to change color when I would for instance, move my arms, as I wasn't getting closer to possible sources of magnetic disturbance.

I attempted to try and test the K-Ceptors individually today, but the add-on kept disconnecting them due to a divide by zero error that kept coming up.

As with my more recent tests this was the K-Ceptor configuration I was using:

Head: 2-1
Back: 1-1
Root: 0-1

L Shoulder: 0-4
L Forearm: 1-5
L Hand: 2-5

R Shoulder: 0-5
R Forearm: 1-4
R Hand: 2-4

L Upper Leg: 0-3
L Lower Leg: 1-3
L Foot: 2-3

R Upper Leg: 0-2
R Lower Leg: 1-2
R Foot: 2-2

Hope some of this info is useful.

daylanKifky

Hi!
It's also unclear to me why you are getting those red bones, particularly those in the upper arms.

I don't remember if we discussed this before, but have you ever tried calibrating and capturing without the enclosures? I remember you were using brass screws as I suggested at the beginning, and that you tested them with a magnet before using them. But since you are getting this systematic errors the only remaining part I can think of as causing troubles are those screws. You can try to use the temporary fixing technique I described here: https://forum.chordata.cc/d/98-build-log/28

For the "division by zero error" bug you can delete the Stats node until we have the time to fix it.

Let me know how it goes

AxonSpark

daylanKifky Hey, sorry it's been awhile. Between corporate work, some Blender VFX work, and volunteering during the lead up to the US election, I've been a bit busy.

I was looking through the post you linked to and had a question: Are you using nano tape to secure the K-Ceptor to the rigid foam? I ask because in researching nano tape, it seems like if I have to make any future mounting changes, trying to remove the tape might damage the PCB. Is there an alternative to this that you would suggest? TY!

daylanKifky

Hi!
We are not using actual nanotape, just regular two sided tape. It can be eventually detached without problems.
As a side note to others reading this: we are discussing quick fixes to test some aspects of the KCeptors, the tape would probably not be the best solution for permanent fixing

AxonSpark

daylanKifky

I re-mounted all of my K-Ceptors on foam using double-sided tape, and then put the foam pieces together with hot glue and attached self-adhesive velcro to the bottoms. Then, I re-calibrated them all, suited up for a full biped test, and...well...nuts:

At least the problems I'm having seem to be more consistent now. The knees are still bending incorrectly, and for some reason the Left Forearm, Right Upper Leg, and Right Hand don't seem to be too happy (nor are the joints on the left leg when I move it around). I'm not sure where to go from here. 😕

NakedRabbit

Hi, @AxonSpark, I'm the one who was using nanotape!

And yes, initially I used it to adhere the Kceptors right to the SKIN, because I was trying to keep everything as low profile as possible. That's when I discovered that any tension or torsion on the Kceptor PCB could cause it to get out of calibration! SO I made 3D printed cases for them. I do stick the Kceptors to these cases with the nanotape. I have not had any issues removing the tape, but I tend to do it slowly so I can wash the tape and reuse it.

And, since I made the cases, I've not had to remove the Kceptors, so it's not been an issue. The cases allow me to access the Kceptor for anything I need to without having to remove them. The current design uses elastic straps, like most people have been using, to hold the Kceptors to the body.

The nanotape has not, in my experience, been difficult to remove from the Kceptor, nor particularly adherent to any aspect of the PCB.

Hope this helps!

daylanKifky

Hi!
yes, as you said the knee problem is more consistent in this video.
The only thing I can think of trying would be to make the test outside, I assume these ones were done in your apartment, right?
It would also help if other users with working suits can confirm this problem is not occurring to them. So far I haven't seen anyone else with this particular issue.
Perhaps you could send us the sensors to test them here

ShiroSaki

in blender 2.9.2

QUATERNION Quaternion (WXYZ), No Gimbal Lock.
with the calib box downloaded from the site, the Chordata_node.cpp should edit the line 449 to

Quaternion q(the_quat.q0, the_quat.q2, -the_quat.q1, the_quat.q3);

I will open a pull-request later

daylanKifky

ShiroSaki
Hi!
Exactly which issue should be solved with this modification?

ShiroSaki

daylanKifky after I modified this, in my blender(2.9.2) all the ceptors worked correctly. before the modify, all the ceptor's x and y are not in the right position. when I lift up my arm, the module in blender will rotate. and when I rotate my arm, the module lift up the arm.

NGWORKS

daylanKifkyAccording to the test, the project does have the situation of X axis and Y axis interchange (that is, the rotation along X axis is settled as rotation along Y axis). I think this situation may be caused by the different properties of the coordinate system (the difference between the Blender coordinate system and the sensor coordinate system).

daylanKifky

ShiroSaki

It sounds strange to me. I still haven't tested it in blender 2.9.2, but it sounds unlikekly that they change the sign of one of the Quaternion components from one release to another.

Could you elaborate why you choose to negate the Y component of the Quaternion and why it was causing troubles before?

I will test it with a suit as soon as possible

ShiroSaki

daylanKifky
The calib box provided in the site https://chordata.cc/wp-content/uploads/2019/04/CalibrationBox.pdf
Seems not the same as https://wiki.chordata.cc/wiki/File:Magnetometer_calibration.gif)
Maybe this difference cause the bug?

ShiroSaki

daylanKifky After talking to @NGWORKS we found out that

is not using the same Coordinate System.
Maybe this is the true reason why the ceptor is bending to the wrong direction

Elediko

ShiroSaki but have you been able to fix with your build?...

ShiroSaki

Elediko after modify the line my blender works. you can make a try.

Elediko

ShiroSaki ok..
Do you experience any jittering?...like sensors moving in the viewport while they are idle in real-world..

You can show a video demonstrating while using the suit..🙂

ShiroSaki

Elediko https://www.bilibili.com/video/BV13K4y1T7R8/

daylanKifky

The translation between coordinates system is done when feeding the sensor data to the sensor fusion, as in Chordata_node.cpp:434

Elediko

ShiroSaki the sensors on the legs are misbehaving..daylanKifky if you look at the video..the sensors on the legs are not stable but the remaining part of the body is ok(almost zero drift)..why is it that way?...or is it because of the hardwares?...I saw in a post you wanted to adapt the new hardwares to DIY... should everybody continue with this build or wait for the adaptation of new hardwares..cause this seems to be very buggy..

I ordered my parts of hardwares few days ago...but not PCBs...

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