A Cable-Driven Robotic Eye for Understanding Eye-Movement Control

We propose a design for a bio-inspired robotic eye, with 6 independently controlled muscles, that is suitable for studying the emergence of human saccadic eye movements char-acteristics. Understanding how characteristics like the restriction of eye orientations to a 2D manifold, straight saccadic trajecto-ries, and saturating relationship between saccade amplitude and its peak velocity come about in a highly nonlinear system with non-commutativity of rotations is not trivial. Although earlier studies have addressed some of these problems, none have so far considered the full 3D complexity of ocular kinematics and dynamics. Our design contains a spherical eye actuated by six motor-driven cables with realistic pulling directions to mimic the six extraocular muscles. The coupling between the eyeball and eye socket has been designed to specify a damped rotational system, which is key to understanding the signals involved in the control of artificial and biological eyes. We present the mechanical design of the robotic system and a simulation model based on it. The system has a large range of movement and its dynamical responses to step inputs are shown, thus illustrating its ability to perform a wide range of eye movements with the appropriate characteristics.