Mixed prototyping with configurable physical archetype for usability evaluation of product interfaces

Mixed prototyping (MP) is an emerging approach for usability testing, thanks to its multimodal environment, which is able to involve sight, hearing and touch thus improving the ability to analyze the inter-relationships between the physical form and the behavior of the industrial products. This paper presents a method to perform usability tests in a mixed reality (MR) environment for analyzing human performance in target acquisition tasks while interacting with household appliances. The proposed method is based on the use of different kinds of digital and physical prototypes and, moreover, it introduces an experimental physical archetype for mixed prototyping that contributes to increase the efficiency of the usability evaluation process. Through this archetype the design of a user interface can be easily changed by the adoption of plug-and-play moving components (knobs and buttons) that allow to model in a few seconds any kind of control panel for washing machines, thus reducing the prototyping costs and enlarging the variety of MR interfaces that can be evaluated. The paper proposes also a validation of the use of the physical archetype through a case study in which three different control panel alternatives have been evaluated in a competitive usability study. The competitive testing allows to gather user behaviors with a broad range of design options before the development of a new control panel refined through iterative design. Experimental results show that the proposed method based on the physical archetype can be an effective support to improve the usability of the product interface.