A Rationale for Human Operator Pulsive Control Behavior

When performing tracking tasks which involve demanding controlled elements such as those with K/s2 dynamics, the human operator often develops discrete or pulsvie control outputs. Although such pulsive control behavior has been linked to the necessity for low-frequency lead equalization on the part of the human operator, no satisfactory model-based explanation of pulsive behavior has been offered to date. A dual-loop model of the human operator is discussed, the dominant adaptive feature of which is the explicit appearance of an internal model of the manipulator-controlled element dynamics in an inner feedback loop. Using this model, a rationale for pulsive control behavior is offered which is based upon the assumption that the human attempts to reduce the computational burden associated with time integration of sensory inputs. It is shown that such time integration is a natural consequence of having an internal representation of the K/s2 -controlled element dynamics in the dual-loop model. A digital simulation is discussed in which a modified form of the dual-loop model is shown to be capable of producing pulsive control behavior qualitively comparable to that obtained in experiment. d e ed J k K Ke