Development of holistic tactile display device and effect of contact area in thermal feedback

Abstract

This thesis proposes a tactile display device providing both pin-array type tactile feedback and thermal feedback. The pin-array type tactile display is composed of a 6x5 pin-array that is actuated by 30 piezoelectric bimorphs. Micro shape and vibrotactile feedback can be generated by the device, and various planar patterns can be displayed such as Braille cell patterns. The thermal feedback device is composed of a thin film resistance temperature detector(RTD), a Peltier thermoelectric heat pump and a water cooling jacket. Two experimental tests using simulated thermal cues were conducted. As humans can discriminate among different materials by perceiving temperature variation when they touch a real object’s surface, a thermal contact model between the material and fingertip is proposed to simulate the virtual touch of materials. To test the suitability of the proposed model, a comparison experiment between the simulated thermal cues was conducted. The simulated thermal cues are able to be distinguished with a similar rate to those of the real thermal cues. Furthermore, an identification test among the simulated thermal cues was conducted with a change in the number of fingertips contacting the material. Increasing the number of fingertips shows an increasing proportion of correct identifications. With this result, evidence for the possibility of the spatial summation of cold among fingertips in same hand was found. Based on the previous experimental results, thermal spatial processes need to be investigated to know perceptual characteristics of thermal sensing for fingertips. Two more experiments were conducted using a thermal display that simulates thermal cues associated with making contact with different materials. In the first experiment, participants indicated which of two simulated materials presented to the index fingertip was cooler. The results indicated that participants were unable to resolve the two areas of thermal stimulation despite consid...