This 'chain' of sectional pieces is extended in a two part system:
1. Chain is 'unrolled' from outer ring
2. Verticality is maintained through a coordinated sensor/servo network
The chain is unrolled by rotating the outer ring around the hub drum using gimbal-like motors to actuate the unrolling action. Soft stop points are set up in the programming. The gimbal-like motors can work as inverted pendulum balancers once arm is at full extension, keeping the arm chain anchor point at the top of the outer ring. The sensor used for balancing is located in the arm chain anchor point on the outer ring and is activated only when the arm is fully extended.
Verticality of the arm chain is maintained through a gyro sensor in the 'head' of the bot. This runs an attitude correction servo in the linkage to maintain uprightness of the head link. Each successive section also contains a gyro sensor which is is activated when the chain section reaches an appropriate pitch, working with other servos to keep the chain section vertically aligned with the rest of the sections.