# 3D Force vector rotation

1. Jan 9, 2008

### IMK

Hello
How do I manipulate (rotate) one 3D force vector so they are relative (in the same plane) as another 3D force vector please.

First I have is a static reference vector SF that is the accelerometer stationary at some orientation. Next I rotate the accelerometer around one or more axis and take another set of stationary measurements that are the SI vector.

What I want to do is to apply some function (rotation?) to the SI vector that will produce a new vector N that it is in alignment and proportional with the SF vector.

Thus:
N = SF ? SI
N = SF
Where SF is a static vector, SI is the current vector, N is a new vector

As you will see below I have included some sample accelerometer x,y,z axis data for SF and SI vector where
___________
/x*x+y*y+z*z = Eg

I have tried a very simple 2D axis subtraction method with only the Y and Z axis and this works well, but I have no idea how to do it for 3D can someone help please.

NB The accelerometer axis output value is the sine of the force on the axis.