Rotary axes and direction of rotation

The figure below shows the positive rotation directions of rotary axes. The base is a right-handed Cartesian coordinate system.

Rotation is referred to as positive if it is counter-clockwise when viewed in the direction of the arrowhead of the coordinate system axis. If the rotary axis rotates around the X axis, it is referred to as the "A axis"; when it rotates around the Y axis, it is referred to as the "B axis" and so on. If not separately stated, these rotation directions are used in kinematic transformations involving rotary axes.