Optimal control location for the customer-oriented design of smart phones

Recently, the smart phone has become a representative device in information communication. The smart phone generally adopts a full touch-screen panel that reflects the growing need for improved multimedia access. In the interest of customer-oriented design, HCI features such as controllability and a menu structure have to be properly considered. Among the numerous factors that have an effect on the controllability when using smart phones, the effects of the phone size, user’s hand length and control location are investigated in this paper. Moreover, an effort was made to determine the changes in the user preference according to the control location. A series of experiments were conducted, in which preference scores were measured. It was found that the product width and thickness have significant effects on the user preference. Specifically, the effect of the product width is greater than that of thickness. However, the optimal control location varies little regardless of phone size and hand length. A desirable phone size was defined for the customer-oriented development of smart phones. Iso-preference contour plots in the form of a rotated ellipse were derived by the Support Vector Regression (SVR) method while the difference in sensitivity was assessed with respect to the meridian (horizontal and vertical directions). The concept of the preferable control zone was developed by linking the critical points in four directions despite the difference in the angle of rotation. In addition, the situation where the product is concurrently controlled by both hands was investigated. The results of the study are expected to aid in defining the size of handheld information communication devices such as smart phones and PDAs. It is also expected that the optimal control location and proposed contours can guide the designer to optimally layout various functions of the menu on the display.