ABSTRACT
To exploit the complementary strengths of WiFi positioning, pedestrian dead reckoning (PDR), and landmarks, we propose a novel fusion approach based on an extended Kalman filter (EKF). For WiFi positioning, unlike previous fusion approaches setting measurement noise parameters empirically, we deploy a kernel density estimation-based model to adaptively measure the related measurement noise statistics. Furthermore, a trusted area of WiFi positioning defined by fusion results of previous step and WiFi signal outlier detection are exploited to reduce computational cost and improve WiFi positioning accuracy. For PDR, we integrate a gyroscope, an accelerometer, and a magnetometer to determine the user heading based on another EKF model. To reduce accumulation error of PDR and enable continuous indoor positioning, not only the positioning results but also the heading estimations are recalibrated by indoor landmarks. Experimental results in a realistic indoor environment show that the proposed fusion approach achieves substantial positioning accuracy improvement than individual positioning approaches including PDR and WiFi positioning.
ABSTRACT
This paper proposes a novel heading estimation approach for indoor pedestrian navigation using the built-in inertial sensors on a smartphone. Unlike previous approaches constraining the carrying position of a smartphone on the user's body, our approach gives the user a larger freedom by implementing automatic recognition of the device carrying position and subsequent selection of an optimal strategy for heading estimation. We firstly predetermine the motion state by a decision tree using an accelerometer and a barometer. Then, to enable accurate and computational lightweight carrying position recognition, we combine a position classifier with a novel position transition detection algorithm, which may also be used to avoid the confusion between position transition and user turn during pedestrian walking. For a device placed in the trouser pockets or held in a swinging hand, the heading estimation is achieved by deploying a principal component analysis (PCA)-based approach. For a device held in the hand or against the ear during a phone call, user heading is directly estimated by adding the yaw angle of the device to the related heading offset. Experimental results show that our approach can automatically detect carrying positions with high accuracy, and outperforms previous heading estimation approaches in terms of accuracy and applicability.
ABSTRACT
Heading estimation is a central problem for indoor pedestrian navigation using the pervasively available smartphone. For smartphones placed in a pocket, one of the most popular device positions, the essential challenges in heading estimation are the changing device coordinate system and the severe indoor magnetic perturbations. To address these challenges, we propose a novel heading estimation approach based on a rotation matrix and principal component analysis (PCA). Firstly, through a related rotation matrix, we project the acceleration signals into a reference coordinate system (RCS), where a more accurate estimation of the horizontal plane of the acceleration signal is obtained. Then, we utilize PCA over the horizontal plane of acceleration signals for local walking direction extraction. Finally, in order to translate the local walking direction into the global one, we develop a calibration process without requiring noisy compass readings. Besides, a turn detection algorithm is proposed to improve the heading estimation accuracy. Experimental results show that our approach outperforms the traditional uDirect and PCA-based approaches in terms of accuracy and feasibility.
ABSTRACT
OBJECTIVE: To observe the effect of transcutaneous acupoint electrical stimulation (TAES) of Zusanli (ST 36) on gastrointestinal activities in organophosphorus pesticide poisoning (OPP) patients undergoing emergency treatment so as to explore its action in scavenging gastrointestinal toxicant. METHODS: A total of 116 OPP patients were randomly divided into control group and TAES group (n=58 in each group) according to the simple random sampling method. All the patients received comprehensive treatment including gastric lavage, catharsis, oral administration of atropine Pralidoxime Chloride, Omeprazole, etc. For patients of the TAES group, TAES stimulation (30 Hz/60 Hz, 15-20 mA) was applied to bilateral Zusanli (ST 36) for 30 min, 3 times a day till black stool was discharged. The vomiting times after catharsis, the time of the first defecation and black stool discharge, the dosage of atropine and the length of patient stay in hospital were recorded. RESULTS: Of the two 58 cases of OPP patients in the control and TAES groups, 11 (18.9%) and 3 (5.2%) underwent vomiting after catharsis, being significantly lower in the TAES group (P<0.05). Compared with the control group, the time of first defecation and black stool discharge, the dosage of the administrated atropine and the time of hospitalization were significantly lower in the TAES group (P<0.05). CONCLUSION: TAES of ST 36 may lower incidence of emesis, enhance the cathartic effect, promote gastrointestinal poison discharge, reduce total atropine dosage and shorten the hospitalization time in OPP patients, favoring the patient's rehabilitation.
