# Intelligent Office Lighting Control Using Natural Light and a GA-BP Neural Network-Based System
## 4 Simulation  
### Lighting Environment Simulation  
In this section, the performance of the proposed lighting control system is validated through simulations conducted on the DIAlux and MATLAB platforms. A randomly \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Lamps Test** & **L1** & **L2** & **L3** & **L4** & **L5** & **L6** \\ \hline F1 (lx) & 546 & 399 & 336 & 352 & 339 & 326 \\ F2 (lx) & 314 & 465 & 324 & 259 & 273 & 262 \\ F3 (lx) & 196 & 261 & 422 & 190 & 206 & 222 \\ F4 (lx) & 364 & 350 & 336 & 552 & 407 & 342 \\ F5 (lx) & 261 & 277 & 265 & 313 & 462 & 320 \\ F6 (lx) & 183 & 201 & 220 & 188 & 251 & 407 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Illuminance components of work plane in daytime mode. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test** & **F1** & **F2** & **F3** \\ \hline Point & 484 & 572 & 514 \\ \hline  & F4 & F5 & F6 \\ \cline{2-4}  & 476 & 574 & 511 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Test point illuminance on work plane at 8 o’clock at night on 15 July 2023.  
selected date of 15 July 2023, at 12:00, was used for validation, assuming a sunny sky on that day. Under these conditions, the office lighting environment is influenced by natural light, as detailed below. As shown in Figure 6, if the shading mode is turned off, the average natural light illuminance of work planes is 1090 lx, with the work plane illuminance near the window exceeding 1500 lx. While this level of natural light is adequate for meeting the office's lighting requirements, it also raises concerns about potential natural glare. Additionally, the illuminance uniformity of the office in this scenario is only 0.35, which falls short of the required standards for office illuminance uniformity. To address these issues, both the natural light and the operation of the blinds must be considered. The above \(\alpha\) and \(\gamma\) are inputted into the GA-BP prediction model, resulting in an optimal angle of 37.5\({}^{\circ}\) for the blinds. After implementing this shading adjustment, the office lighting environment is re-simulated using DIAlux software, and the resulting conditions are outlined below. As shown in Figure 7, the implementation of blinds significantly reduces illuminance, improving the illumination uniformity to 0.60. However, the average illuminance of the work plane is measured at only 274 lx, which does not meet the lighting standards for the office environment. Consequently, some areas of the work plane still fall short of the required illuminance levels. To address this, artificial lighting supplementation is necessary in order to fulfill the illumination demands and enhance the uniformity further. To evaluate the performance of the control system, the DIAlux software is employed to generate numerical values. The evaluation is based on the dimming factors (K) derived from previous calculations. These dimming factors are applied to the LED luminaires by multiplying each factor by the total luminous flux (\(\Phi\) = 4000 lm) to obtain the adjusted luminous flux for each LED luminaire. The subsequent step involves verifying whether the simulated lighting environment achieves the target illuminance values of 500 lx for occupied work planes and 300 lx for unoccupied work planes while maintaining an office illuminance uniformity of at least 0.7. Additionally, it is necessary to confirm that the six work planes meet the specified illuminance targets, with the work plane height set at 0.75 m.  
Figure 6: 15 June 2023 at 12:00, sunny day, no blinds, indoor 0.75 m space natural illumination. In the daytime mode, the mathematical model calculates the dimming coefficient K = [0, 0.40, 0.97, 0, 0.46, 0], resulting in the following luminous flux outputs for each luminaire: [0, 1600, 3880, 0, 1840, 0] lm. Figure 8 illustrates that the illuminance levels at work planes F1 and F6 are 453 lx and 340 lx, respectively, while the illuminance at the other occupied work planes exceeds 500 lx.