The design and evaluation of a new controller for a multi-finger tactual (kinesthetic and cutaneous) display, the TACTUATOR, is discussed. A crucial performance requirement is that the relative amplitude of spectral components be preserved in terms of perceived intensity as judged by human users. In this article, we present a two degree-of-freedom controller consisting of a feedback controller and a pre-filter, and its digital implementation. The overall system was evaluated with frequency-response function measurements and with human psychophysical experiments. The measurement results confirm that the steady-state frequency response closely follows the design specifications. The psychophysical results indicate a deviation in the model of the human detection threshold curve at frequencies below 30 Hz. Future work will compensate for this deviation by reshaping the pre-filter. Our work demonstrates the validity of designing controllers that take into account not only the electromechanical properties of the hardware, but the sensory characteristics of the human user.

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