Indoor Visible Light Positioning Based on CNN–MLP Multi-Feature Fusion under Random Receiver Tilt Conditions
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摘要: 针对室内可见光定位(VLP)系统中接收器姿态扰动会破坏接收光功率(RSS)与空间位置的对应关系,导致定位精度下降的问题,提出一种光电传感器(PD)阵列结合机器学习(ML)的特征融合定位方法。首先利用阵列中不同PD接收光功率的差异构建约束方程,采用高斯–牛顿迭代算法估计入射角余弦值。其次设计融合卷积神经网络(CNN)与多层感知机(MLP)的优化模型,实现对RSS与入射角余弦特征的联合建模,缓解了单一RSS在接收器随机扰动条件下位置映射关系不稳定的问题,增强系统对接收器姿态扰动的鲁棒性。最后引入拉丁超立方抽样(LHS)策略构建训练数据集,提升训练样本的空间代表性。仿真结果表明,在4 m×4 m×2.5 m的室内环境,平均定位误差约4.6 cm;即使接收器倾斜至55°时,平均误差仍在11.7 cm以内。与现有方法相比,定位精度提升约2.5 cm,均方根误差(RMSE)降低31.58%,实现了接收器在姿态发生扰动时的高精度室内三维定位。Abstract:
Objective Traditional visible light positioning (VLP) methods based on received signal strength (RSS) suffer from instability when the receiver experiences orientation perturbations, which disrupt the correspondence between optical power and spatial position, making reliable three-dimensional (3D) positioning difficult to achieve. Existing approaches typically rely on inertial measurement units (IMUs) to obtain orientation information; however, sensor fusion increases system complexity and hardware cost and introduces cumulative errors. To address these issues, this paper proposes a positioning method that fuses cosine-of-incidence-angle estimation based on a photodiode (PD) array with RSS information, enabling high-accuracy 3D indoor positioning under receiver orientation perturbations. Methods In the proposed fusion-based positioning method, a multi-PD array structure is first adopted, and a local coordinate system (LCS) is established at the array center. Constraint equations are then constructed based on the differences in received optical power among PDs in the array. A Gauss–Newton iterative algorithm is employed to estimate the incident light direction vector. By exploiting the orthogonal rotation invariance between the LCS and the global coordinate system (GCS), the cosine of the incident angle is estimated without the need for orientation sensors. Subsequently, a serial CNN–MLP fusion network is constructed, in which the estimated incident-angle cosine is introduced as an additional positioning feature on top of RSS-based localization. The network jointly models the RSS and incident-angle cosine information received by the PD array and maps them to 3D spatial coordinates. Finally, training samples are generated using Latin hypercube sampling (LHS) to uniformly sample spatial positions and orientation dimensions, thereby improving the representativeness of the training dataset. Results and Discussions Simulation experiments are conducted in a 4 m × 4 m × 2.5 m indoor environment. First, the effects of different numbers of PDs and tilt angles on the accuracy of incident-angle cosine estimation and spatial coverage are evaluated ( Fig. 6 ), and the cumulative distribution functions (CDFs) of positioning errors under different array configurations are compared (Fig. 7 ). The results show that a 3-PD array with a tilt angle of 40° achieves the best balance among cost, coverage, and positioning accuracy. Next, positioning performance under different receiver tilt angles is analyzed. When the tilt angle is small, more than 70% of positioning errors are below 5 cm; even when the receiver is tilted up to 55°, the average error remains within 11.7 cm (Fig. 8 ). Error component comparisons indicate that the error along the Z-axis is significantly smaller than those along the X and Y axes (Fig. 9 ). Further tests are conducted at a height of 0.0 m covered by the training data and at an unseen height of 0.6 m not included in the training set (Fig. 10 ). The results demonstrate that the proposed model does not exhibit strong dependence on a specific height plane and maintains stable 3D positioning performance at unseen heights. Finally, the proposed method is compared with related positioning schemes. It outperforms existing methods in terms of CDF convergence speed, RMSE, and standard deviation (Fig. 11 ), achieving an average error reduction of approximately 2.5 cm and an RMSE reduction of 31.58% compared with Ref. [12 ].Conclusions This paper estimates the cosine of the incident angle at the receiver by exploiting differences in the optical power received by different PDs in an array and introduces this cosine value as a joint positioning feature into conventional RSS-based localization, thereby alleviating the instability of position mapping caused by relying solely on RSS under random receiver perturbations. By further combining the spatial feature extraction capability of CNNs with the nonlinear modeling strength of MLPs, the proposed method effectively maps positioning features to 3D spatial coordinates. The approach reduces reliance on orientation sensors such as IMUs while overcoming the susceptibility of traditional geometric positioning methods to noise and high-dimensional nonlinear features. Under varying heights and receiver orientations, the proposed algorithm demonstrates significant advantages in both positioning accuracy and stability. -
表 1 仿真参数
参数 值 参数 值 参数 值 参数 值 参数 值 $ {P}_{\text{t},i} $/W 10 $ {\Phi }_{1/2} $/(°) 60 $ dA $/m2 0.01 B/(MHz) 10 T/(k) 290 A/cm² 1 $ {g}_{s}({\psi }_{i,j}) $/$ {T}_{s}({\psi }_{i,j}) $ 1 r/cm 2 $ {I}_{\text{bg}} $/μA 10 $ {R}_{f} $/$ \text{k}\Omega $ 100 $ {\psi }_{c} $ /(°) 75 $ \rho $ 0.6 k/(J/k) 1.38×10−23 $ {G}_{t} $/(A/V) 0.01 $ {g}_{m} $/(ms) 10 表 2 神经网络训练参数
参数 值 参数 值 参数 值 训练样本数 4000 ×60学习率调整策略 5 epoch×0.5 损失函数 MSE 数据集划分 70%/15%/15% 优化器 Adam 验证频率 0.2epoch 初始学习率 0.001 正则化系数 0.0001 - - 表 3 不同PD阵列设计的可见光定位性能评估
PD阵列 向量维度 均方根误差/m 平均误差/m 轮数 训练时间/min 3 24 0.052 0.046 47 20:05 4 32 0.047 0.043 45 19:01 5 40 0.046 0.041 44 18:40 6 48 0.044 0.038 43 18:12 -
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