基于UWB-IMU的设施园艺移动平台组合定位方法

    Combined positioning method for a mobile platform in facility horticulture based on UWB-IMU

    • 摘要: 为解决设施场景下遮挡严重所致的电驱移动平台定位精度低、稳定性差的问题,该研究设计了基于超宽带(ultra wide band,UWB)和惯性测量单元(inertial measurement unit,IMU)的组合定位方法,并提出基于卡尔曼滤波的自适应抗差组合定位算法(adaptive robust combination positioning algorithm,ARCPA)。首先,针对单传感器定位误差大的问题,搭建基于UWB与IMU两种传感器的组合定位系统;其次,为精准检测UWB数据的非视距误差,设计差分距离非视距误差检测滑动窗口;最后,为抑制卡尔曼滤波中的量测噪声,采用余弦重启函数实时调整渐消因子,并引入位置精度因子权值修正抗差因子。为验证所提定位方法的有效性,搭建设施园艺电驱移动平台和实时定位系统,并进行仿真与实车定位试验。试验结果表明,采用所提UWB-IMU组合定位方法的均方根误差为6.63 cm,比单传感器的定位精度提高了81.92%,相比于经典卡尔曼滤波、无迹卡尔曼滤波、扩展卡尔曼滤波、粒子滤波与自适应抗差卡尔曼滤波算法,所提ARCPA算法定位精度分别提高50.15%、74.63%、60.01%、60.88%、28.34%。研究结果可为设施园艺环境下的定位导航提供理论依据和实施方案。

       

      Abstract: Protected horticulture is required for the high positioning accuracy and stability of mobile platforms. However, the electric drive mobile platforms can be often confined to object obstruction under the natural scenes. In this study, a high-precision positioning system was designed using an ultra-wide band (UWB) and inertial measurement unit (IMU). Additionally, an adaptive robust combination positioning algorithm (ARCPA) with Kalman filtering was developed to effectively improve positioning accuracy and stability. Firstly, a multi-sensor integrated positioning was constructed to combine UWB and IMU. Secondly, a differential distance-based sliding window was introduced to precisely detect nonline of sight (NLOS) errors in the positioning data of UWB. Thirdly, a cosine restart function was used to dynamically adjust the fading factor in real time, in order to reduce the interference of noise fluctuations in Kalman filtering. The accuracy and robustness of the filter were enhanced after optimization. Finally, a position dilution of precision (PDOP) weighted robust factor was incorporated to improve the resilience of the positioning system against noise and model disturbances under-protected horticulture scenes. An electric drive mobile platform and real-time positioning were constructed to verify the effectiveness of the integrated system. Then the simulation and real experiments of vehicle positioning were conducted in the typical protected horticulture. The experimental results demonstrate that the root-mean-square errors before and after UWB ranging correction under line-of-sight condition were 119.0 and 49.0 cm, respectively, and the ranging accuracy was improved by 58.8% after correction. The positioning error of the integrated positioning was only 6.63 cm, which was 81.92% higher than that of the single sensor (36.68 cm). The maximum error of positioning accuracy was also reduced by 88.89%. Therefore, this integrated positioning significantly reduced the impact of NLOS and geometric error on the positioning accuracy of the electric drive mobile platform for protected horticulture. Moreover, the root-mean-square error and the maximum positioning error of ARCPA were 17.70 and 44.44 cm, respectively. Furthermore, the accuracy of the improved system increased by 50.15%, 74.63%, 60.01%, 60.88%, and 28.34%, respectively, compared with the Kalman filtering, unscented Kalman filtering, extended Kalman filtering, particle filtering, and adaptive robust Kalman filtering. Correspondingly, the maximum positioning error was then reduced by 66.83%, 73.67%, 69.07%, 71.2%, and 50.50%, respectively. The integrated positioning significantly improved the robustness of the electric drive mobile platform for protected horticulture. The finding can also provide a specific theoretical basis and plan for the positioning and navigation in a protected horticulture environment.

       

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