Behavioral Control Characteristics of Performance under Feedback Delay

As part of a larger research project dealing with technological change, the U.S. Bureau of Mines has initiated a study of the nature and sources of variability in human performance during teleoperation. One important source of performance degradation during remote work is delay in sensory feedback from the remote site to the operator during task execution, caused by such factors as transmission and signal processing lags or inertia/momentum properties of large equipment. To investigate the properties of the behavioral control system under delayed feedback conditions, the Bureau has implemented a pursuit tracking task during which delay is imposed as a continuously varying sinusoidal forcing function. Using 11 subjects, the dynamic characteristics of tracking performance were assessed across a range of variable delay frequencies. Specifically, sinusoidal variations in visual feedback delay between 0 and 400 msec were imposed during a tracking task at frequencies between .05 and 2 Hz. The results show that RMS error, gain (fundamental FFT peak for the cursor signal/fundamental FFT peak for the target signal), and phase (phase angle difference between the target signal and the cursor signal) of the tracking control system are independent of variable feedback delay imposed across a forty-fold range of frequencies. One important implication of these findings is that operators may have limited ability to adapt to feedback delay conditions that may be present during teleoperation of large mobile mining equipment.