Take a look at the motion steps of a brachiation in Figure 1.
The following tree represents the main function and the subfunctions that have to be fulfilled (see figure 2).
To achieve the open/close gripper function and the rotation between two arms function,
we need at least three servomotors were required. Two of them were used for open/close gripper function and the last one was used for rotating two arms.
Also, we need at least two sensors were required to signalize when the gripper had to be opened or to be closed at a particularly state (more information see Electronics section).