# A UWB-Driven Self-Actuated Projector Platform for Interactive Augmented Reality Applications
## 5 Experimental Design
### Stage 3: On the Evaluation of the Hand-Held Input Device Interaction Features  
In Stage 3, we evaluated other interactive features of the hand-held input device. As discussed before, the input device was equipped with a UWB tag to track the user's hand movements and a push-button to trigger the selection. In the first and second stages, we used the input device to select the popped-up circles and evaluate various interaction performance aspects. In addition, our customized device could also perform a mid-air drag-and-drop task for a target item (Section 7.4), and it enables the user to perform basic UWB-based mid-air swiping gestures (Section 4.3) for a particular interaction purpose. Drag and drop interaction shares the same mechanism as the normal triggering task in the first and second stages. However, the swiping gestures interaction has a different implementation technique; therefore, we need to evaluate this interaction channel's performance.  
Figure 10: Customizing the projected screen and resuming the interaction: (**a**) The user enters the first point, (**b**) the user enters the second point, (**c**) the USAP moves to customize the projected screen, and (**d**) the user resumes interaction.  
Participants started the third stage learning how to perform swipe gestures in four directions (right, left, up, and down) using the input device. Corresponding to their swipe gestures, they could perceive the motion of a stream of numbered blocks designed by the Unity engine (Figure 11a). The numbered blocks shifted right or left when a participant swipe their hands right or left, respectively. The participant could delete the central block up or down by swiping up or down.  
After participants feel familiar with using our device to perform swiping gesture-related interactions, we move forward to the evaluation part. In this stage, we measured the swipe gestures detection accuracy by counting missed or wrong swipes. Missed swipe means that the participant made a swipe gesture in a specific direction, but it does not reflect any movement in the numbered blocks stream. The wrong swipe refers to an uncorrelated movement in the numbered stream (e.g., the participant performs a right swipe action, and the numbered stream shifts left). Also, we check the workload amount when doing UWB-based mid-air swiping tasks. To assess the interaction performance, the experimenter asked each participant to perform four tasks using the input device (Figure 11b-e):  
* Bring the block with the number 5 to the screen's center by swiping right.
* Bring the block with the number 9 to the screen's center by swiping left.
* Bring the block with the number 7 to the screen's center by swiping right and then delete it by swiping up.
* Bring the block with the number 2 to the screen's center by swiping left and then delete it by swiping down.  
Eighteen swipe gestures are the total number of swipes each participant supposed to do when following the previous four steps without encountering any problem. The experimenter monitored each participant's performance and asked them to report any wrong or missed swipe to calculate the swipe gestures interaction accuracy. Both missed and wrong swipes represent an unwanted performance of UWB-based swipe gesture detection.  
Additionally, participants were asked to assess their workload when performing swipe tasks through the online survey and answer a 10-point Likert scale questioner to understand how they think about the importance of adding these swipe gestures interactive features.