# A UWB-Driven Self-Actuated Projector Platform for Interactive Augmented Reality Applications
## 5 Experimental Design  
### Demographic Information and Procedure  
Sixteen participants were recruited to perform this experiment. Participants' age ranged between 25 and 38 years old (\(M\) = 28.75; \(SD\) = 3.29; Gender: Male = 11; Female = 5). All were postgraduate students with diverse technical backgrounds (engineering, bio-medical, physics, etc.) and nationalities. Participants did not report any mobility problems (e.g., problems using their hands), and all of them used their right hand for performing the interaction. Our system would be used mainly for interactive demonstrations or education purposes and supposed to be used by the trained people. Therefore, testing our system with different population groups was not essential. Each participant was compensated for an hour of their time with a gift that cost on average $10.  
An experiment of four stages was designed to evaluate our system performance. In the first stage, interaction accuracy, interaction time, and the user's workload were tested while varying the user's relative interactive distance with the projected screen. In the second stage, we tested the projected screen's customization function and the interaction performance in the presence of UWB-based calibration under the same criteria as in the first stage. The USAP navigation accuracy, navigation time, and the difference between the user's desired designated screen and the actual projected screen were reported as well. In the third stage, we evaluated the hand-held input device performance by testing its swiping accuracy in different directions and measuring the user's workload performing this task. In the fourth stage, participants were asked to evaluate our system's overall experience using a system usability scale. Participants were instructed to take a five-minute break during the transition between experimental stages while the experimenter setup the software and hardware needed for the next stage.  
To reduce the learning effect, we designed a counterbalanced within-group experiment by making participants undergo the four stages and shuffling the order of the first  
Figure 7: Data flow inside the central server for an interactive space.  
stage's sub-parts (interacting from close and far distances). Before starting the first stage, participants provided their personal information by answering preliminary questions through a pre-designed online survey using the Survey Monkey platform. They were then asked to read an explanation describing the general use of our system, UWB tracking technology, the various hardware components (e.g., the USAP platform and the hand-held input device), and mainly what they will be asked to perform during the experiment.  
The experiment was conducted in a controlled laboratory environment, where six UWB anchors were installed in an 8 \(\times\) 7 m\({}^{2}\) room, as illustrated in Figure 4. The tracking accuracy given by the UWB sensor's manufacturer was \(+/-0.1\) m laterally and about \(+/-0.2\) m vertically, where we set the position information update rate to 20 Hz. Most of the time, the tracking accuracy values were lower than the upper accuracy limits provided by the UWB sensor's manufacturer. Our laboratory walls are not suitable for directly projecting images, so we installed two projector screens in the form of an L-shape to simulate two walls with a size of 2.5 \(\times\) 2.1 m\({}^{2}\) for each (Figure 7(a)). The USAP platform was positioned at different distances from the simulated walls (Figure 7(b)).