Hun Yi - a spherical pointing and measuring instrument invented in Ancient China

Abstract

Hun Yi is an armillary sphere invented in ancient China. The Hun Yi is essentially a spherical pointing mechanism, which was built with equatorial mounting of sighting tube, an invention to usher the modern world of astronomical instruments. This paper reviews the Hun Yi from perspective of mechanism design. Its history of development and kinematic structure are briefly introduced. The working principle is interpreted by kinematics, along with its workspace analysis and error analysis. Reconstruction work with 3D printing technology is described. Moreover, the range of pointing and its error are analyzed to reveal the hiding technical information about Hun Yi that is not available in literature.