Bang-bang aspects of manual control in high-order systems

The tendency of many human operators to respond in a bang-bang fashion when controlling some high-order systems is investigated. A three-mode switch is compared with a linear control stick and shown to permit better manual control of some systems with more lag than double integration. In experiments requiring stabilization of a moving base flight simulator programmed as an unstable system (undamped inverted pendulum), operators use the linear control stick in a bang-bang fashion. In place of quasi-linear models for these situations, a simple on-off model for the human is suggested, and the switching lines and error trajectories in the phase plane are presented. The ability to control an unstable system with visual and motion cues is compared.