De-Rotating vectors using Quaternions
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I have a set of acceleration values along the x, y, z directions (sensor body frame). The sensor tilted and changed orientation many times during operation. Using the gyroscope, magnetometer and accelerometer, I was able to fuse and extract the Roll, Pitch and Yaw angles all in quaternion format ( cal it Q). 

Now, to derotate the acceleration values into global X, Y, Z positions. Do I just simply 
1. convert the acceleration values into quaternion by setting the scalar part to 0 (call it Acc)
2. Multiply the acceleration quaternion as follows : Qtranspose * Acc * Q??

Or is my conclusion wrong? how do we derotate the values?

thanks