# A UWB-Driven Self-Actuated Projector Platform for Interactive Augmented Reality Applications
## 5 Experimental Design
### Stage 1: On the System's Interaction Accuracy, Interaction Time, and Workload  
Before starting the main session of Stage 1, each participant had training on using the hand-held input device and experience interacting with the projected screen's items from varying distances. In the beginning, the USAP platform holds back its position 2 m away opposite to Wall 1 (Figure 7(b)) while keeping the orientation that placed the projector perpendicular to the horizontal centerline of the same wall. The projected screen was created using Unity software to generate a 2D interactive image of 19 randomly placed circles with a 0.2 m diameter appear on the screen. Each participant was asked to use the input device to click the center of each circle precisely and quickly as much as possible, where visual feedback was given on the user's hand position in the form of a cursor on the projected screen. One circle stays on display until the participant clicks the input device's button then a new circle appears in a new location. Participants were asked to stand at different distances opposite to Wall 1. Firstly, they interacted from a close distance by choosing a location between the USAP platform and Wall 1; afterward, they stood behind or beside the USAP platform according to their preference to try the far distance interaction (Figure 8(a),b). The participants were free to choose between moving to face the popped-up circle or stretch their hand aside to reach the circle location in both interaction distances. Once the participant had enough experience using our system, we moved forward to the main session. In the main session, participants tried to reach the randomly popping-up circles and select them by clicking the hand-held input device's button. Half of the participants start to experience close distance interaction, where the rest of the participants start with far distance interaction. In each case, nineteen circles needed to be reached and selected. Figure 8: Experimental setup: (**a**) Two simulated walls; (**b**) the USAP platform projected onto the first simulated wall. Interaction accuracy was calculated when the participant pressed the input device's button to trigger the target circle. The Euclidian distance was measured by finding the distance between the cursor's tip and each target circle's center point positions using Unity engine to measure the interaction accuracy. The calculated Euclidian distance is converted from pixels scale to a meter scale representation using pixels per meter constants (9, 10). Interaction time was also considered as a criterion to evaluate system performance. The elapsed duration between the circle's appearance and the participant's selection was measured in seconds to calculate interaction time. Finally, the workload for both interaction distances was measured using the NASA-TLX index [51]; participants were asked to fill out the online survey's relevant workload parts immediately after they finished each interaction. Stage 2: Experience Screen Customization Function and Examine the Influence of UWB-Based Calibration on System Performance  
In this stage, customization of the projected screen was tested. Participants designated two diagonal points defining their demanded location and size of the projected screen. In response, the USAP platform moves to deliver the most appropriate display (Figure 10). Subsequently, the participants were asked to perform the same interaction task (to select 19 popped-up circles) as in the first stage. However, participants did this task one time and were free to choose the interaction distance according to their preference. To unify the test condition between the first and the second stages, the popped-up circles kept their 0.2 m diameter by updating their graphical size according to the USAP new position. In the first stage, we defined a pre-calibration measurement for the projection boundaries, as the USAP platform remained static for the entire duration of this stage.