Three degrees-of-freedom joint for spatial hyper-redundant robots

We present a new mechanical design for a compact three degrees-of-freedom joint mechanism. This joint design is ideal for use in robotic devices, especially hyper-redundant or snake-like robots. This joint exhibits an unprecedented range of motion: the origin of a coordinate frame attached to the output link of the joint can move on a spherical cone whose apex angle is 120° and this coordinate frame can be rotated around an axis passing through its origin and the center of the sphere. Moreover, the joint is optimized for strength, compactness and accuracy. These characteristics are verified by exploring the magnitude of the wrenches and errors that the joint can produce in its effective workspace. Finally, we present a mechatronic integration of four of our joints to construct a 12 degrees-of-freedom spatial hyper-redundant robot.