Design of a Humanoid Robot Eye

This chapter addresses the design of a robot eye featuring the mechanics and motion characteristics of a human one. In particular the goal is to provide guidelines for the implementation of a tendon driven robot capable to emulate saccadic motions. In the first part of this chapter the physiological and mechanical characteristics of the eyeplant1 in humans and primates will be reviewed. Then, the fundamental motion strategies used by humans during saccadic motions will be discussed, and the mathematical formulation of the relevant Listing’s Law and Half-Angle Rule, which specify the geometric and kinematic characteristics of ocular saccadic motions, will be introduced. From this standpoint a simple model of the eye-plant will be described. In particular it will be shown that this model is a good candidate for the implementation of Listing’s Law on a purely mechanical basis, as many physiologists believe to happen in humans. Therefore, the proposed eye-plant model can be used as a reference for the implementation of a robot emulating the actual mechanics and actuation characteristics of the human eye. The second part of this chapter will focus on the description of a first prototype of fully embedded robot eye designed following the guidelines provided by the eye-plant model. Many eye-head robots have been proposed in the past few years, and several of these systems have been designed to support and rotate one or more cameras about independent or coupled pan-tilt axes. However, little attention has been paid to emulate the actual mechanics of the eye, although theoretical investigations in the area of modeling and control of human-like eye movements have been presented in the literature (Lockwood et al., 1999; Polpitiya & Ghosh, 2002; Polpitiya & Ghosh, 2003; Polpitiya et al., 2004). Recent works have focused on the design of embedded mechatronic robot eye systems (Gu et al., 2000; Albers et al., 2003; Pongas et al., 2004). In (Gu et al., 2000), a prosthetic implantable robot eye concept has been proposed, featuring a single degree-of-freedom. Pongas et al., (Pongas et al., 2004) have developed a mechanism which actuates a CMOS micro-camera embedded in a spherical support. The system has a single degree-of-freedom, and the spherical shape of the eye is a purely aesthetical detail; however, the mechatronic approach adopted has addressed many important engineering issues and led to a very