A short story of the robot MAC-EYE
Usually robots are bulky mechanical structures using geared mechanisms used to transmit motion from motors to the various links (the actual mobile parts). This approach works well for industrial robots where high load capabilities are required and bulky and massive devices are appropriate or reasonable.
On the other hand, when it is requested to scale down the size of the robots the “classical” mechanical approach become critical. Furthermore, modern robots are equipped with sensors thus making smaller devices poses challenging engineering and technical problems.
In the context of advanced and humanoids robotics many eye-head robots have been designed in the past few years, but little attention has been paid to emulate the actual mechanics of the eye.
The story of the robot eye called MACEYE (MAC-Lab Eye) starts from this point.
We are interested in developing a robot eye which could have characteristics similar to those of a human one, to be embedded in a humanoid robot system. In particular, we have the goal of building a robot eye with size and motion capabilities equivalent to those of a real eye.
The inspiration for the design obviously came from the study of the anatomy of the eye in humans and primates. Therefore, we decided to use cables as tendons to actuate the system (i.e. to rotate the eye) and to design a particular structure to support the eye ball . The human eye is driven by six extra-ocular muscle-tendons (EOMs), our prototype uses only four tendons (equivalent to the four rectii muscles ), however these are sufficient to generate motions similar to the typical saccadic movements (i.e. sudden changes of the fixation direction of the eye) observed in animals and humans. The eye also embeds a video camera that in the next future will be used to provide feedback to drive the eye motion.
Eye movements seem to obey to basic laws, whose role for the vision and perception in animals, and implications for the development of intelligent robot and machines are still to be fully understood.
Eye movements have been studied since the mid of the 19 th century. However, only during the past 20 years quantitative mathematical models have been proposed, and validated by experiments and clinical test.
Saccadic movements are a very important class of eye motions. During saccades the eye orientation is determined by a basic principle known as Listing's Law , which establishes the amount of eye torsion for each direction of fixation. Listing's Law has been experimentally verified on humans and primates, and also found to be valid during other types of eye movements such as smooth pursuit .
The key problem addressed in our design has been that of designing a robot eye which could generate motions compatible with Listing's Law .