## 2 Methodology
### Proposed Tracking Strategy
The iterative process begins for each of the points of the trajectory (\(k~{}=~{}1,\ldots,n\)). The first step is the movement from point (\(\beta_{k}\), \(\gamma_{k}\)) to (\(\beta_{k+1}\), \(\gamma_{k+1}\)). The mixed tracking error (\(\varepsilon_{m,k}\)) is calculated by comparison of the real-time position (\(B_{k+1,tr}\), \(\gamma_{k+1,tr}\)), measured by the solar pointing sensor, with the desired position as defined in Equation (2). The acceptance angle of the photovoltaic technology defines the maximum admissible tracking error \(\varepsilon_{max}\), and the tracking error \(\varepsilon_{m,k}\) is minimized by the selected control strategy for the tracking action. To ensure that the positioning is less than the maximum error, the selected control strategy will seek to minimize the error until it meets the condition, and the tracker stops the movement action while maintaining the achieved position (\(\beta_{k+1}\), \(\gamma_{k+1}\)). In that position, a reference power value of the photovoltaic system \(P_{pv,ref}\) is measured and stored as a reference for decision-making. The system will remain in position (\(\beta_{k+1}\), \(\gamma_{k+1}\)) as long as the power generated in real-time (\(P_{pv,tr}\)) is similar or greater than or very close to the

Figure 3: Scheme of the solar path, including the azimuth and elevation angles. reference value. This condition allows the reduction of the number of points to be tracked without affecting energy productivity and reducing the wear on the axis mechanisms. Otherwise, the insolation (\(I_{tot,rt}\)) is measured in real-time, compared with the estimated value of the insolation vector at the \(k+1\) step (\(I_{tot,k+1}\)) if the values are similar or greater, the robotic system maintains the position \((\beta_{k+1},\gamma_{k+1})\), implying that the day continues sunny with possible PV-damage or partly cloudy, sending alarm and recording data for future analysis and failure prediction. If it is much less, it implies the sky was cloudy, the PV technology is dirty or has some possible damage. Then, the data are saved for future analysis. The period that the tracker does not perform the movement action due to fulfilling the two criteria (\(P_{pv}\) and \(I_{tot}\)) represents a reduction in energy consumption and wear of the mechanisms. Consequently, the time instant of the day (\(t_{S,rt}\)) is compared with the time of day vector \(t_{S}\) to define the new value of position \(k\), and the tracker moves to the defined \(k\)-point of the trajectory for the next iteration. Simultaneously, with the recorded values and based on Equation (1), an energy balance calculation is carried out for the period \(\tau\), which is defined from the initialization of the movement from \(k\)-point until the taken decision of the new \(k\)-point to track. Lastly, a comparison is made between the energy generated and the energy consumed based on the consumption constraint factor, allowing the definition of the energy productivity of the energy harvesting system considering the tracking action and monitoring process. These actions are performed until the \(k\)-point of the trajectory is equal to the defined \(n\)-point, then the tracker moves to the home position, represented by \(\beta_{1}\) and \(\gamma_{1}\), to be ready to continue tracking the next day. In addition, the data obtained during the day are saved for future analysis, and the monitoring and tracking processes are stopped. Finally, with the saved data, future strategies must be defined to improve the overall performance, identifying cases in which consumption increases or decreases, and analyzing the times in which the tracker mechanisms remain active to estimate the lifetime. ## 3 Case Study

The tracking strategy was experimentally validated through testing in an integrated system to verify the functionality of the decision-making process and to calculate the improvement of the lifetime by comparing the proposed algorithm with a conventional one under identical environmental conditions.