A four-DOF balanced neck mechanism for a humanoid head

Humanoid robots are a relatively new branch of robotics. They are designed to interact with humans and their surroundings, and they should work with tools that are designed for humans. If a humanoid robot should look like a human, it needs a moving head and neck. Current neck designs are heavy and noisy, or are unable to create fluent motions because they suffer from backlash.

The objective of the assignment was to design a neck mechanism for a humanoid head, that can be used for testing man-machine interaction with equipment like eyes, ears and LED arrays. The result should be a lightweight mechanism with four degrees of freedom that is able to mimic human behavior. Backlash should also be low and the mechanism should not make a notable gear whine.

The result is a three degree of freedom parallel mechanism with all three motors mounted on the base, each with a range of 60 degrees . A lightweight fourth motor is placed on top of the parallel mechanism to drive the panning motion with a range of 160 degrees. All DOFs are statically balanced to reduce motor loads in a static position with at least 80 percent. Cable drives are used instead of noisy, expensive, backlash introducing gearboxes. Other methods used for keeping the backlash low are preloading and exact constraint design. A head plate can be used to mount equipment like cameras and a thin head shell.