How to calculate angular kinematics from quaternions?

Hi everybody!

I'm new with quaternions so I'm having trouble with them! So, I have 4 IMU sensors which gives me quaternion information; IMUs are positioned like this, with the correspondent frames

So I'll have only this informations:

• trunk quaternion
• upperarm quatrernion
• wrist quaternion
• hand quaternion

Now, I have to find the angular kinematic, i.e.flexion/extention of elbow, shoulder and wrist, ab/adduction of shoulder and pronosupination of wrist.

The referance frame is that one on the trunk.

How can I manage this?

Thanks so muck in advance!!