imu
I am using the I2Cdev library which configures the MPU-6050 to use it's DMP and generate a quaternion output on it's FIFO. The problem is that when that quaternion number is converted to yaw, pitch and roll angles, the pitch and roll angles are limited to +-90 degrees (this constraint comes from the inverse trigonometric functions used in the equations).
What equations should be used to convert the quaternion number in euler's angles that give full information on the sensor's orientation.
I have never worked with this component before.
First off, you may or may not realize, but it is impossible to measure exact position with the gyro & accelerometer, but only change in position. The gyroscope will give you orientation, but if you are not moving, or moving with negligible acceleration, the 3-axis accelerometers in your MPU-6150 will not give any signal.
I would suggest to look at the datasheet. Which I found here:
http://www.invensense.com/mems/gyro/documents/PS-MPU-6100A.pdf
By the looks of it the device will use an I²C Bus which you will have to use to communicate between the two embedded devices.
Hope it helps
The MPU 6050 pegs at either end of the range (you can see the red series flat lining):
I assume the 9050 does the same, though haven't tested it. We use the 6050 in production.
Best Answer
Before I answer, it should be noted that there are some benefits to using quaternions:
That being said, I would consult the Representing Attitude article from Stanford University.
To summarize, equation 452 states that:
$$ \begin{bmatrix} \psi \\ \theta \\ \phi \end{bmatrix} = \begin{bmatrix} Y \\ P \\ R \end{bmatrix} = \begin{bmatrix} \mathrm{atan2}\left( -2q_1q_2 + 2q_0q_3,\; q_0^2 + q_1^2 - q_3^2 - q_2^2 \right) \\ \mathrm{asin}\left( 2q_1q_3 + 2q_0q_2 \right) \\ \mathrm{atan2}\left( -2q_2q_3 + 2q_0q_1,\; q_3^2 - q_2^2 - q_1^2 + q_0^2 \right) \end{bmatrix} $$
Wikipedia has a good explanation of atan2, if you need it.