Ultra-wideband shearer positioning technology based on calibration compensation and VBUKF smoothing

The precise positioning of the shearer has been a bottleneck that needs to be addressed urgently for many years, and it is the key to realize the intelligent and unmanned mining of the underground shearer. In view of the issue of the low positioning accuracy of the shearer, it is proposed to install the Ultra-Wideband (UWB) base station at the end of the fully-mechanized mining face. As the shearer runs to the end, the UWB positioning system provides the reference for the calibration of the inertial navigation. In order to obtain higher localization accuracy for UWB positioning system, the influence of base station position error, scale factor error and deviation on positioning accuracy is considered, and a calibration strategy is proposed which can independently calculate these parameters to calibrate and compensate the position error of the base station. The non-line-of-sight (NLOS) bias varies due to the impact of NLOS environment, with the consideration of the uncertainty and time-variant measurement noise, and the variational Bayesian unscented Kalman filter (VBUKF) is proposed to smooth the NLOS measurement distance to reduce the effect of the NLOS error and ameliorate distance estimation accuracy. On the basis of calibration compensation and VBCKF smoothing, the Caffery localization (CL) approach is utilized to determine the coordinates of the target node. To further improve the positioning accuracy, Gaussian-Newton localization algorithm (GN) is employed to optimize the results of the CL result, and the effectiveness of the proposed method is verified by dynamic and static experiments using UWB positioning system.The experimental results show that the VBUKFsmoothing can efficiently reduce the NLOS error, and the GN algorithm is able to further improve the positioning accuracy. The positioning errors on the X-axis, Y-axis, and Z-axis are significantly diminished after calibration and VBUKF smoothing. The average fixed error of CL and CL-GN method is decreased from 0.347 m, 0.250 m to 0.239 m, 0.109 m, respectively, and the corresponding average positioning accuracy is improved by 31.1% and 56.4% respectively. Simultaneously, the dynamic motion trajectory is closer to the real trajectory, which certifies that the proposed approach is capable of improving the positioning of UWB system and providing theoretical guidance for underground positioning technology, but this scheme requires to be certified by further actual environmental verification.