Objectives of the user tests

Through several workplace studies and tests of different I/O modalities at the operators working environment the requirements for the envisioned application were elicited. One key element for the whole development process is the end user and its needs. Another key element is the benefit that should emerge out of the introduction of wearable systems in industrial working environments. By conducting interviews with several maintainers and by observing those while working requirements were identified for the application and its functionalities as well as crucial prerequisites for the introduction of innovative wearable systems.

The application development and test process followed this approach (see Figure above):

Workplace Study and User Requirements: The team conducting the interviews consisted of a person responsible for the UI (User Interface) implementation tool used by application developers, the application developer himself, and the scientific support that took also the lead in organizing the development. After having arranged the elicitation of general requirements and working conditions of the maintenance operators, the whole team analyzed and interpreted the collected information and formulated the overall application goal and its func-tionalities. This analysis led to unique requirements for the wearable application besides requirements concerning, e.g., the morphology and functionalities of equipment that are not in the focus of this paper but are limited in any case to the availability of Commercial of the Shelf (COTS) Components. As a result of the interviews the main constraints of the end users directed to a wearable application can be described as follows:

• Every development (application) must have a benefit for the user. This could be a process improvement e.g. saving of time or reduction of complexity (reduce the number of persons involved in the task).
• The end user stated that the use of wearable equipment is very (only) interesting for the support of complex maintenance procedures that have an inherent danger of confusion e.g. confusing very similar but different parts.

These constraints/requirements are obviously very high level and need to be interpreted with the perspective of an end user. Even when creating a picture of wearable computing during the workplace-studies in the operators’ mind it is the task of the development team to transfer high level requirements into innovative and useful innovations or experiments which lead to valid and reliable results.

Building the Application Mock-Up: Starting from the point of knowing the users needs and the overall goal mentioned above, the team started developing the application. Due to the nature of the used implementation tool for wearable systems, work started concurrently. I.e. the application developer designed a mock-up with the implementation tool, not knowing how the content will look like in detail, while the scientific part collected the content and the information needed for the real application. The first mock-up showed only the structure of the envisioned system. Because of the iterative approach that was chosen, several mock-ups were developed and with each iteration of the mock-up the range regarding functions and content increased. Accompanied by reviews of the application done by the whole team corrective decisions were taken.

Performing Usability Tests and Experiments: As the result of usability tests of input and output modalities, technical requirements emerged. Specifically customized interfaces were tested for input modalities: speech, hand mouse and data glove (gesture device). As output modalities plain text, image (photo), video and audio were tested. Input and output tests were performed with ten maintenance operators through a mock-up that was created with an implementation tool for wearable systems.

User Feedback and Requirements: The final application of the first iteration was implemented by using the data glove (gesture device) and the speech navigation as input modality. The team came to this decision basing on the results of the usability tests that showed that the data glove outperformed compared to the speech navigation and performed nearly equal as the hand mouse (as a traditional input device). Speech was also chosen because interviews of the usability tests showed a significant interest of the subjects in such an innovative technology. Although operators were best with the hand mouse, they felt reluctant using the device for interaction with a wearable computer. Operators argued that holding the mouse device in hand is unpractical and uncomfortable during real work in aeronautic maintenance environments. Instead, they preferred using the data glove even though they performed worse with it. The output modalities were also chosen after evaluating the results of the usability tests. Results showed that the fastest and most exact modality in respect to correctness was the image output. A combination of the reproduced maintenance manual (text output) and images as well as technical drawings (taken out of the maintenance manual) were selected as output modality (Figure below).