Expansion device and movable body

An expansion device, comprising:

• a main body;
• and
• a limb portion attached to the main body, wherein the limb portion includes:
• a main link connected to the main body via a specific joint;
• an end link at a front end of the limb portion;
• at least one intermediate link between the main link and the end link;
• a first limb joint;
• a second limb joint, wherein
• the first limb joint is between the end link and the at least one intermediate link,
• the second limb joint is between the at least one intermediate link and the main link
• the first limb joint and the second limb joint connect the main link and the end link,
• the first limb joint is rotatable in a first direction, and
• the second limb joint is rotatable in a second direction opposite to the first direction;
• a first connection point on an end side of the end link, wherein the end side corresponds to a side of the end link opposite to the first limb joint;
• a first guide at a midpoint position of the at least one intermediate link;
• a second guide at a midpoint position of the main link;
• a second connection point at a center position of the specific joint;
• and
• a linear member that includes a first end and a second end, wherein
• the first end and the second end of the linear member couple the main body to the end link,
• the first end of the linear member is associated with the first connection point,
• the second end of the linear member is associated with the second connection point,
• the linear member passes through the first guide of the at least one intermediate link and the second guide of the main link, and
• the first end and the second end of the linear member are retractable to at least one of the end link or the main body.