Biblio

The Inertial Navigation System(INS) and Doppler Velocity Logs(DVL) which are used frequently on autonomous underwater vehicles can be fused under different types of integration architectures. These architectures differ in terms of algorithm requirements and complexity. DVL may experience acoustic beam losses during operation due to environmental factors and abilities of the sensor. In these situations, radial velocity information cannot be received from lost acoustic beam. In this paper, the performances of INS and DVL integration under tightly and loosely coupled architectures are comparatively presented with simulations. In the tightly coupled approach, navigation filter is updated with solely available beam measurements by using sequential measurement update method, and the sensitivity of this method is investigated for acoustic beam losses.

Military reconnaissance in 1999 has paved the way to establish its own, self-reliant and indigenous navigation system. The strategic necessity has been accomplished in 2013 by launching seven satellites in Geo-orbit and underlying Network control center in Bangalore and a new NavIC control center at Lucknow, later in 2016. ISTRAC is one of the premier and amenable center to track the Indian as well as external network satellite launch vehicle and provide house-keeping and inertial navigation (INC) data to launch control center in real time and to project team in off-line. Over the ISTRAC Launch network, Simple Network Management Protocol (SNMP) was disabled due to security and bandwidth reasons. The cons of SNMP comprise security risks that are normal trait whenever applied as an open standard. There is "security through obscurity" linked with any slight-used communications standard in SNMP. Detailed messages are being sent between devices, not just miniature pre-set codes. These cons in the SNMP are found in majority applications and more bandwidth seizure is another contention. Due to the above pros and cones in SNMP in form of open source, available network monitoring system (NMS) could not be employed for link monitoring and immediate decision making in ISTRAC network. The situation has made requisitions to evolve an in-house network monitoring system (NMS). It was evolved for real-time network monitoring as well as communication link performance explication. The evolved system has the feature of Internet control message protocol (ICMP) based link monitoring, 24/7 monitoring of all the nodes, GUI based real-time link status, Summary and individual link statistics on the GUI. It also identifies total downtime and generates summary reports. It does identification for out of order or looped packets, Email and SMS alert to Prime and Redundant system which one is down and repeat alert if the link is failed for more than 30 minutes. It has easy file based configuration and no application restart required. Generation of daily and monthly link status, offline link analysis plot of any day, less consumption of system resources are add-on features. It is fully secured in-house development, calculates total data flow over a network and co-relate data vs link percentage.

Misalignment angles estimation of strapdown inertial navigation system (INS) using global positioning system (GPS) data is highly affected by measurement noises, especially with noises displaying time varying statistical properties. Hence, adaptive filtering approach is recommended for the purpose of improving the accuracy of in-motion alignment. In this paper, a simplified form of Celso's adaptive stochastic filtering is derived and applied to estimate both the INS error states and measurement noise statistics. To detect and bound the influence of outliers in INS/GPS integration, outlier detection based on jerk tracking model is also proposed. The accuracy and validity of the proposed algorithm is tested through ground based navigation experiments.