Geometrical optimization of an ultrasonic tactile plate

The Tactile plate consists of piezoceramics glued on a copper-beryllium resonator. Its purpose is to create programmable tactile sensations, which give the illusion of finely textured surfaces. The illusion originates from the variable friction between a finger and the vibrating resonator, caused by the squeeze film effect. In order to obtain a maximal deflection of the plate for a minimal supply voltage, an optimization is carried out of the length, thickness, and width of both the resonator and the ceramics. Constraints are realistic geometrical dimensions, a resonance frequency of at least 25 kHz, and a low supply voltage. The plate is modelled by both an analytical and a numerical model. The maximal dynamical deflection per volt was achieved with thin piezoceramics (0.5 mm) at the minimal frequency of 25 kHz. A high deflection can be obtained in a wide range of the resonator length. With increasing length, the optimal resonator thickness increases too. The plate width seems to have little influence. Experiments are carried out on two plates with different geometry.