# Calculating the quaternion increments in geometry_msgs/Transform

I control the end effector of a robot with the following message:

```
geometry_msgs/Transform tf_incr
```

which contains:

```
geometry_msgs/Vector3 translation
geometry_msgs/Quaternion rotation
```

I need to sent the increments for transition and rotation. Calculation of transition increment is straight forward, but I have difficulties to calculate the increments of rotation. Need to mention that I have the current orientation of the robot as a matrix (let's say T0). if I want change the orientation slightly to T1, how can I calculate the increment in either quaternion or matrix representation?

Your system does not make sense. What does your message represent? Why does it have two items in an array?

There are two arms. I edited the question to avoid confusion. The position and orientation of the robot are controled by this message. The inputs are increments of transition and rotation.

What is tf_incr relative to?