**2.2 Measurement of welding speed, welding angles, and orbital angle**

Other variables that must be measured to control robotic welding processes are those that characterize the relative movement and position between the piece and torch. These variables can be obtained from the position control system of the robot, but many times an initial or absolute reference is necessary.

The relative movement between the piece and torch is defined by the *welding speed*. Sometimes, the torch is coupled to the robot manipulator and moves while the piece is fixed. Other systems fixed the torch and move the piece. More complex robotic systems move the torch and piece. In all cases, it is important to consider the relative speed between the torch and the piece to obtain the welding speed. This speed can be calculated using the torch and the piece speed obtained from the robotic system. On plane welding, the speed can be expressed in longitude per time unit, such as *mm=s*.

In orbital welding, the *orbital angle* is used to indicate the torch position in the polar coordinate system with the origin on the pipe axis. This measurement is very important because the welding conditions can be different for each orbital position. Its value must be obtained from the robotic system too. In this case, it is possible to express the welding speed using orbital angle per time unit, such as *<sup>o</sup>=s*.

<sup>2</sup> The information bits are sent one by one through a communication channel.

### *Online Measurements in Welding Processes DOI: http://dx.doi.org/10.5772/intechopen.91771*

The *forehand angle* or *attack angle* is the torch angle side view relative to the base metal surface, which is the angle in direction of torch travel. The *work angle* is defined by the torch angle end view relative to the base metal surface as shown in **Figure 3**. These angles can be fixed before starting the welding and staying constant or can be controlled by the robotic system. In the second case, the angles can be calculated or obtained from the robotic system also.
