Getting started with MPU6050- use of quarternions w-components?

Hi all,

I'm trying to wrap my head around the quarternions returned by MPU6050's DMP processor. Specifically, I'm wondering what the w-Component of the quarternion is used for. If the quarternion is the device's orientation in Space, w should in my understanding indicate the rotation around that axis- which is most likely not an axis that the device rotates on.

Am I completely mistaken or ist the quarternion just used as it's a suitable data structure for further processing and the w-value is neglegible?

Cheers,
Andi

Read manual and basics of accelerometer once :slight_smile:

Cheers,
Rdr

Wow, this is increadibly helpful :confused:

I believe I've meanwhile found out (no, not from the datasheet), that the quarternion does not indicate the devices orientation in space relatively to some reference system (which would void the need for the w component), but instead describes the rotation (=w) around a vector in a reference system (x,y,z) to reach it's current orientation.

The current orientation itself is what the Euler angles describe?

Sorry :slight_smile:

As of my knowledge, MPU 6050 gives accelerations in x-,y- and z- directions and the angular velocities :slight_smile: from gyro (wx,wy,wz). Correct me if I am wrong.

Cheers,
Rdr.

rdrprsdm:
Sorry :slight_smile:

As of my knowledge, MPU 6050 gives accelerations in x-,y- and z- directions and the angular velocities :slight_smile: from gyro (wx,wy,wz). Correct me if I am wrong.

This is true, but again only part of the story- unless I'm mistaken. If you look here i2cdevlib/MPU6050_6Axis_MotionApps20.h at master · jrowberg/i2cdevlib · GitHub you'll see that in DMP modes you get:

/* ================================================================================================ *
 | Default MotionApps v2.0 42-byte FIFO packet structure:                                           |
 |                                                                                                  |
 | [QUAT W][      ][QUAT X][      ][QUAT Y][      ][QUAT Z][      ][GYRO X][      ][GYRO Y][      ] |
 |   0   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  |
 |                                                                                                  |
 | [GYRO Z][      ][ACC X ][      ][ACC Y ][      ][ACC Z ][      ][      ]                         |
 |  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41                          |
 * ================================================================================================ */

3 axis gyro and acceleration, plus the 4 components quartenion- and that's what I was asking about.

I dont know . Sorry man! I too wanted to know what values does accelerometer gives exactly (units of the acceleration and angular velocity).

Cheers,
Rdr