Smartphone hard key locations need to be ergonomically determined to improve grip stability and operational efficiency for users' convenience. The present study proposed an ergonomic design process that determines smartphone hard key locations by statistically analyzing the preferred hard key control areas of users with various hand sizes based on users' preferred grip postures and hard key control areas. The proposed design process analyzes the characteristics of product design, user, task, and use context, the types of preferred grip posture, the preference distribution of grip posture, and the preference distribution of hard-key area, and then recommends the locations of hard keys by considering the preference distribution of hard-key area and design constraints. The proposed design process was applied to a smartphone with a 5-inch screen, resulting in 77-96 mm from the bottom of the device for a volume key to 20 mm on the left side and 88-97 mm for a power key to 10 mm on the right side. The proposed design process for the determination of smartphone hard-key locations would be of use to determine the locations of various portable product interfaces.
Keywords: Grip posture; Hard-key location; Physical user interface; Preference distribution; Smartphone.
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