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Abstract

In the design of a high fidelity simulator environment, knowledge about motion perception thresholds is essential. Thresholds are generally measured in a passive experimental setup, in which subjects do not actively influence their motion profile. In this paper, a method for analytical identification of motion perception thresholds in active control tasks is proposed. The effect of vestibular motion on thresholds was analyzed and a comparison to conventional passive threshold measurements was made. The threshold identification method was based on a multi-channel pilot model extended with a nonlinear absolute threshold element. Maximum likelihood parameter estimation, combining a Genetic Algorithm and an unconstrained Gauss-Newton algorithm optimization, was applied. A theoretical study indicated that there is an upper limit to the vestibular motion amplitude to allow accurate threshold identification. Two experiments were performed in the SIMONA Research Simulator to test the application of the method. A passive experiment to measure the sensory pitch threshold and an active control task to identify the active pitch threshold. In the active experiment, the vestibular motion amplitude was varied and two types of control tasks were used. For the disturbance-rejection task, the pitch threshold was only identifiable for high motion amplitude levels. The target-tracking task allowed identification of the threshold for medium and high amplitude levels. Neither of the tasks allowed threshold identification with low levels of motion amplitude. The pitch thresholds obtained from the active and passive experiment were in the same order of magnitude.