Robot comprising arm unit of length variable structure

A robot comprising:

• a main printed circuit board;
• a controller electrically coupled to the main printed circuit board;
• at least one arm unit;
• and
• a variable length unit coupled to one section of the at least one arm unit,
• wherein the variable length unit further includes:
• a motor;
• a flexible printed circuit board coupled to the motor and the main printed circuit board;
• a first cam having at least one slit with a specific inclination in one area thereof;
• and
• a second cam, at least a portion of which is disposed in an interior of the first cam, and having at least one first boss that passes through the at least one slit of the first cam,
• wherein the first cam is rotated via the motor,
• wherein the second cam is linearly moved while the at least one first boss is slid in the at least one slit during a rotation of the first cam, and
• wherein a length of the at least one arm unit is changed according to a linear motion of the second cam.