Receiver-Tilt-Robust RSS-Based VLP System Using a Normal Orthogonal Three-PD (NO3PD) Positioning Scheme

In received signal strength (RSS)-based visible light positioning (VLP) systems, receiver tilt directly affects the measured RSS and introduces bias into positioning estimates. To mitigate this issue, a normal orthogonal three-PD (NO3PD) structure is proposed to receive the positioning signal, where three PDs are arranged with mutually perpendicular normals. Theoretically, using the root- mean-square (RMS) of the RSS values from the NO3PD receiver for positioning eliminates the influence of tilt. To further reduce the complexity of the RSS extraction method, a cross-correlation-computed RSS (cccRSS) extraction method is proposed. To validate the robustness of the proposed NO3PD-based scheme against receiver tilt, we compare it with a single-PD-based scheme through simulations and experiments. Simulation results show that in a 100 cm × 100 cm × 160 cm space with the receiver tilt angle ranging from 0° to 15°, the NO3PD-based scheme achieves a maximum average positioning error of 2.91 cm with a range of 0.39 cm, while the single-PD-based scheme achieves 4.17 cm and 1.78 cm, respectively. Experimental results in a similarly sized space, with the receiver tilt angle ranging from 0° to 13.1°, show that the NO3PD-based scheme attains a maximum average positioning error of 4.67 cm and a range of 0.98 cm, compared to 6.78 cm and 3.37 cm for the single-PD scheme. To assess the time performance of cccRSS extraction method, we implement the method on a microcontroller unit (MCU) and compare it with a fast Fourier transform (FFT)-based method, showing that it consumes only 6.4 % of the computation time of the latter. Furthermore, at a receiver speed of 35 cm/s without tilt, real-time positioning using the NO3PD-based scheme achieves an average positioning error of 3.93 cm, which is consistent with the previous error. Overall, the proposed NO3PD-based scheme exhibits smaller error ranges under tilt variation and achieves centimeter-level real-time positioning, demonstrating its superior tilt robustness and real-time capability.