Predictive Control

Abstract

The exact nature of the multiloop control system governing gross eye tracking is still largely unknown although two principal types of movement have long been distinguished [15]. The saccadic jump movement is characterized by its high velocity, the inability to control this velocity consciously, pauses of at least 100 msec between successive saccades, and possible absence of (foveal) vision during the saccadic movement. The magnitude and direction of the saccade is generally such as to correct for position error [70, 73]. Smooth pursuit movements, on the other hand, are slow (less than 20 deg/sec), seem to be continuous, are not produced consciously, occur only when the eye is tracking a smoothly moving target, and appear to keep the target image, with respect to the retina, stabilized rather than fixated [48, 74]. These two movements are integrated in any tracking task, as illustrated in Fig. 1. The important points to note are initial time delay, occurrence of saccades to correct any appreciable error, and smooth pursuit movements locking onto the target.