# A Real-Time BLE/PDR Integrated System by Using an Improved Robust Filter for Indoor Position
## 6 Conclusions  
In this paper, we concentrated on the real-time BLE/PDR integrated System and fusion method. For BLE real-time fingerprint, we found that the position error of BLE is not only with the signal fluctuation but also with the scanned number of BLE APs. If the scanned  
Figure 16: The trajectory of four methods in 331 test site.  
number is too few, there will easily be gross errors. Next, we introduced the method of commonly used attitude methods and an improved Mahony complementary filter is proposed to estimate the heading angle under different motion states. Finally, a robust filter model was proposed to fusion the BLE/PDR methods because of the gross error in the BLE method. We conducted an experiment to validate the efficiency of the proposed method in the true position scenario. The mean position accuracy obtained by the robust filter was 0.844 m and RMSE was 0.745. The experiment showed that the proposed method has better performance in positioning accuracy and stability. The experimental scenario in this paper is surrounded by glass in the center, which has serious multi-path effects for the fingerprint positioning method and can easily cause coarse errors. The classic Kalman filter or Extended Kalman filter is not effective for coarse difference suppression. The proposed method can detect gross errors at different granularities and suppress them. The fusion methods based on the KNN and EKF are suitable for the high-real-time requirements of the positioning applications, keeping a balance between computational efficiency and position accuracy. The estimation of the heading angle is more stable based on the people's motion states. However, the effect of different pedestrian motion states on hybrid positioning was not analyzed in detail. In addition to the detection and suppression of coarse differences in the observation noise matrix, some modifications of the state transition matrix will be made based on the people's motion states. How the variance matrix of process noise adaptively changes according to the people's motion states will be investigated in-depth in future work. Combined with other positioning methods such as map matching, landmarks matching for multi-mode fusion positioning will be considered too.  
Conceptualization, S.X.; Formal analysis, S.X. and M.S. ([PERSON]); Funding acquisition, Y.W.; Methodology, S.X.; Project administration, Y.W.; Data curation, H.C. and M.S. ([PERSON]); Writing-original draft preparation, S.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key Research and Development Program of China under grant number 2016 YFB0502102.  
Not application.  
Not applicable.  
The experiment uses an internal data set and the data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest. The funding sponsors had no role in the design of the study; in the writing of the manuscript; and in the decision to publish the results.  
Received signal strength indicator  
The east coordinate in the pedestrian dead reckoning at time \(k\)  
The north coordinate in the pedestrian dead reckoning at time \(k\)  
The step length at time \(k\)  
The heading angle  
The pitch angle  
The roll angle  
Refer to the rotation matrix from the carrier system to the carrier coordinate system  
The ith item of the quaternion vector  
Refer to the error correction in the Runger-Kutta method  
The proportional control parameters in the proportional-integral method  
The integral control parameters in the proportional-integral method  
Refer to the gyroscope data in Section 3.3