## 4 Results
### Maintenance Task Use-Case Efficiency Validation  
A maintenance task of an electronic board was chosen as a use-case for testing the MANTRA system. Electronic boards are low-power devices that have generally fairly low temperature levels, in which the highest temperature points can be easily located. Specifically, the electronic board selected was a VDS EURO230 MZ control board. This small control board can control two motors of up to 550 W each and is powered by a 220 V alternating current. An output load (typically the motors) was simulated using a Vishay 330 \(\Omega\) high-power variable resistor. The setup used is shown in Figure 10. \begin{table}
\begin{tabular}{c c c} \hline \hline
**PHASE** & **PARTS** & **TIME (s)** \\ \hline \multirow{3}{*}{Initial detector and pose estimation} & Option 1: & LINEMOD & 0.069 \\ \cline{2-3}  & Option 2: & YOLOV4 & 0.036 \\ \cline{2-3}  & LINEYOLO & LINEMOD & 0.035 \\ \cline{2-3}  & Parallel ICP & & 0.051 \\ \hline
6 DOF pose tracking & [PERSON] et al. method (2017) & & 0.023 \\ \hline IRT Fusion & IRT to RGB-D Registration & & 0.012 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Average time (in seconds) of the main methods used in the AR module. Five usual non-destructive faults suffered by these kinds of electronic boards were chosen and simulated. Specifically, the electronic board could be in any of the following conditions:  
1. Reference state: This is the case where the electronic board works correctly. In this state, the board is programmed to complete the electromechanical process in 5 s by pressing the operation button. 2. Blown fuse: This consists of the detection and replacement of one or more fuses on the board. To simulate this failure, a blown fuse was installed. 3. Bad input connections: This occurs when a wire has come loose from the power input terminals or has burned out and does not conduct electricity. 4. Relay malfunction: Relays control the activation of the outputs. If the mechanism is not making full contact or is stressed due to higher inrush current, carbon build-up can happen, due to excessive electrical arcing. This could lead to blockage, such that they cannot open or close the circuit. 5. Bad contact in load outputs: This occurs when the wires have come loose from the output terminals and are not making good contact. This failure, which can lead to more severe failures and even lead to breakage of the device, consists of the appearance of bad contacts in the load connections where the different drives are powered. 6. Overload/underload in the board drive: This fault occurs when the current to be supplied to the actuators is not as expected, which may be due to the interference of some type of external factor on the drive itself, which requires a higher power demand. The task to be carried out by the users was to correctly diagnose the electronic board state and, in case of failure, to repair it. To perform this task, the participants were divided into three groups, depending on the system used to address this task:  
1. Manual (_M_): This is the standard procedure, in which they have a manual, the equipment specification sheets, and an electrical diagram. 2. MANTRA with AR (_AR_): They used the MANTRA system, but without the thermal camera. 3. MANTRA with AR and IRT (_AR+IRT_): They used the full MANTRA system. The objective of this use-case was to check whether the AR system (with or without IRT) improved the usual procedure carried out for the maintenance and repair of electrical circuits. To do so, the diagnosis time and repair time were analyzed for each of the users, usability questionnaires were carried out with SUS Test [62], and cognitive load was assessed with NASA-TLX test [63]. The NASA TLX questionnaire is a multidimensional assessment test that collects the cost of cognitive load that users incur when using a system. It uses six factors that are relevant in the subjective experience of workload, using a post-hoc Likert scale questionnaire.