Time Delay Measurement In A Real-Time Simulation Environment

Real-time, man-in-the-loop simulators are important tools for operator training as well as human performance research. Simulator implementation using digital computers offers many important advantages, such as flexibility, reliability, and noise immunity, but may also cause problems. One of the most significant and troublesome artifacts of digital computer simulation is the presence of time delays in the operator/vehicle control loop. These computational delays have been shown to destabilize the system, resulting in poorer control of the simulated vehicle. They may also contribute to an increased likelihood of \u27\u27simulator sickness\u27\u27 in human operators. It is desirable to be able to quantify time delays in a given simulator to determine the extent of the problem and to allow for compensation of the system such that delay effects on operator performance and well-being are minimized. The research presented in this article involved the measurement of simulator time delay using two different methods: a time-domain approach involving the detection of a response to a simulated step control input, and a frequency-domain approach involving the measurement of phase shift from a simulated sinusoidal input. These delay measurement and compensation techniques were applied to a low-cost, real-time interactive automobile driving simulator The investigations using both measurement techniques revealed that a substantial time delay was present in the system. The delay values determined by each method were the same within a reasonable margin of experimental error Finally, the steady-state method of delay measurement was used to verify the operation of three delay compensation filters added to the simulator