Open-Loop Experiments for Modeling the Human Eye Movement System

Open-loop experiments were used to develop a linear model for a physiological system. The specific system studied was the eye movement system; however, the technique presented may be applied generally to other physical systems. Human smooth-pursuit eye movements were measured in response to sinusoidal, step, ramp, and step-ramp target motions in the normal closed-loop condition and in the open-loop condition. The human responses were compared to the outputs of four models, and the best match was provided by the K/(τs + 1) model. Simulation results suggested that in the open-loop condition, the human often changed control strategy, for example by turning off the saccadic system and making no position-correcting saccades, in spite of large positional errors.