Human control strategies in pursuit tracking with a disturbance input

Human operators can manipulate an integrator plant and manually track a single sine wave very well with almost unity amplitude ratio and zero phase lag as long as the frequency of the sine wave is not too high. However, the pattern of responses across single sine signals of different frequencies does not resemble the pattern of response across random appearing sum-of-sines signals for moderate to high frequencies. There is a significantly larger phase lag in tracking a sum-of-sines than tracking a single sine wave for moderate to high frequencies. This phenomenon suggests that humans utilize different control strategies for predictable tasks than for unpredictable tasks. In this paper we designed experiments and methodologies to identify non-parametric feedback and feedforward controllers in human operators for manual tracking with an explicit display of the sinusoidal reference signals and a disturbance input. Our results show that the feedback controller resembles McRuer's “crossover model”, and the feedforward controller attempts to invert the system dynamics that the human operator is manipulating if the reference signal is predictable.