Finite degree-of-freedom models for animal vibrissae

The reception of vibrations is a special sense of touch, important for many insects and vertebrata. The latter realize this reception by means of hair-shaped vibrissae. Disregarding different types of such sensors we set up a principal mechanical model to describe their modes of operation (passive and active vibrissae). Biologically, the oscillating excitations are transmitted to receptor cells which adjust their sensitivity in such a way that, despite a permanent excitation, the receptor system tends to its rest position. Consequently, the model system has to allow for stabilizing control while nevertheless being able to detect superimposed solitary excitations. The controller has to be adaptive in view of both the randomness of the external signals to be suppressed and the uncertainty of the system data. The paper presents a mechanical model and an improved adaptive control strategy that avoids identification but renders the system sensitive in the above mentioned sense.