Design of A Tangible Prototype for Displaying Hapticons

In recent years, haptic feedback has been widely used in various devices, including mobile phone, PDA, game controllers, and medical instruments. Current researches of haptic feedbacks could be divided into 2 main groups. The first group of researches consists of developing a detailed, near realistic haptic feedback, which is usually targeted for medical applications or virtual reality. The other group consists of developing a simple yet low-cost haptic display for interactivity or game support purposes. In the later group, although reasonably cost-effective, its haptic sensation has not fully utilizes human physiological abilities, especially in terms of sensing the physical properties of the materials. Furthermore, recent development of haptic technology suggests a new method of displaying haptic sensation using surface actuation technology. Using this method, any complex artificial haptic stimuli could be generated, thus enabling full utilization of mechanoreceptor capabilities. We consider that the application of haptic feedback and its design will be more important in the future. This paper proposes a preliminary guideline of designing hapticon, i.e.: a kind of haptic feedback that is mainly used to convey emotions. We started to build the model by conducting a physical and psychological classification and analysis on touch perception. Psychological test is done using Semantic Differential Method and 13 Japanese Onomatopoeia were selected as adjectives. Using multivariate statistical analysis, we classified the psychological touch properties into 3 main parameters, i.e.: roughness, softness, and stickiness and conducted confirmatory analysis with the physical properties. Statistical tests confirmed the correlation between physiological and physical properties, i.e.: roughness with Standard Mean Surface Difference (SMD) expressed in urn; softness with material compliance, expressed in ㎛/gf; stickiness with coefficient of friction (MIU), a dimensionless constant. Using this psychological-physical correlation, we suggested a possible relation with the physiological properties. Physiological mechanoreceptor consists on main receptors, i.e.: Meissner’s corpuscle (FA Ⅰ), Merkel corpuscle (SA Ⅰ), and Pacinian corpuscle (FA Ⅱ) that reacts independently to specific selective stimulation ranges. We have conducted preliminary physiological experiments using 3 different artificial selective stimuli designed at different frequencies, i.e.: 30 ㎐, 5 ㎐, and 200 ㎐. This paper further suggests that each frequency could elicit unique perceived sensation that differs from one another. Finally, we developed the hapticon design that based on selective stimulation ranges. In designing hapticons, we proposed 2 kinds of parameters, i.e.: related perceived sensations and haptic dynamics. We used 3 frequencies mentioned above as the main variable and performed superposition and envelope in order to form haptic dynamics. Furthermore, by using the same principles, we consider that the proposed preliminary guideline could be applied on any kinds of vibrotactile actuator or frequency modulation based haptic display devices.