Vibration rendering on a thin plate with actuator array at the periphery

Abstract

Vibrations are rendered on the display panel of a mobile electronic device to transfer a tactile sensation to users. Because important electronic components are usually positioned in the central part of the devices, the only practical choice for actuator location is the periphery of the panel although the periphery is not the advantageous position for the excitation. As the basic principle to generate a rendered vibration pattern, two methods to determine the contributions of modes, viz., eigenfunction superposition or traveling wave control method, are implemented individually. The purpose is to generate a pattern of vibration amplitudes that can be felt by fingertip in the hot zone but not in the cold zone, which is outside the hot zone. General inverse methods are applied to obtain the actuator weightings for achieving the target pattern. Proper weighting for both amplitude and phase for each actuator in the array is determined by the relationship between modes or velocity responses and input signals of actuators. Two methods are implemented individually on the display panel of a commercial tablet computer using an array of moving-coil actuators, and the responses on the panel are measured. Performance index referred to as success ratio for evaluating satisfaction of target field constraints is proposed considering the different thresholds of vibration sensation. Reasonable fulfillment of achieving the target vibration pattern is observed experimentally. The success ratio is more than 86% by using the eigenfunction superposition, and more than 97% by using the traveling wave control for rendering 2 x 2 and 3 x 3 section.