UWB/INS Combined Indoor Positioning Method Based on ISRUKF

Ultra-wide band(UWB)positioning technology is a highly competitive technology in the field of indoor positioning; however, its low accuracy and poor stability in the indoor non-line-of-sight(NLOS)environment makes it difficult to meet the high indoor positioning accuracy requirements. Combining UWB positioning technology and inertial navigation system(INS)can reduce the impact of the NLOS environment on UWB positioning; therefore, a UWB/INS combined indoor positioning method based on improved square root unscented Kalman filter(ISRUKF)is proposed in this study. The positioning information of the positioning target was first output through the INS when the UWB/INS fusion positioning system was in operation; however, the single INS results contain very large errors. Then, to initially eliminate the INS cumulative errors, an INS optimized framework consisting of zero velocity update(ZUPT), zero angular rate update(ZARU), and heuristic drift reduction(HDR) was utilized. Finally, based on ISRUKF, the UWB and INS positioning information was deeply fused in a tightly coupled manner, and the fusion positioning results were obtained. Using the standard square root unscented Kalman filter(SRUKF), the ISRUKF added UWB pseudo-range information smoothing, UWB pseudo-range information outlier correction, and state covariance matrix update strategy. A series of experiments were completed in the indoor NLOS environment. The experimental results showed that the proposed method could compensate UWB positioning technology accuracy loss in the NLOS environment and further eliminate the INS cumulative errors. In addition, the ISRUKF improves the positioning accuracy by 9.48% and 4.59%, compared to the EKF and SRUKF, respectively, and it has a better filtering effect and robustness. © 2022, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.