week 4 summary Bo Pang
Pedestrian Tracking with Shoe-Mounted Inertial Sensors
This paper introduces a shoe-mounted 3D-tracking system called NavShoe system developed by Eric Foxlin and folks in InterSense. NavShoe is built based on inertial sensing technology. The advantage of this system is that it provides relative precise position and orientation tracking without any infrastructure installation. The system is also very convenient because it is small and wireless.
Using inertial sensing alone cannot provide good tracking result because of inertial sensors cannot maintain accuracy for a long time, even 10 seconds. The main concept of NavShoe is how to circumvent the drift problem. They found that when a person walks, his feet can be considered alternating between a stationary stance phase and a moving stride phase. In this system, when the stance phase is detected by the software zero-velocity updates(ZUPTs) will be applied as pseudomeasurements into the Extened Kalman Filter to correct some error caused by drift. However, because only ZUPT cannot solve the problem caused by heading drift, it also cannot work well in long-term navigation. The author gives 3 different ways to solve the heading drift problem: using higher-performance gyro, using a magnetic compass or using GPS or other external aiding technologies.
Then this paper gives a lot of details about how they implement this NavShoe system. The author also talk about how do they model the Geomagnetic because there are magnetic declination and magnetic deviation need to be considered. In the result section, both indoor and outdoor experiment result are given, which indicate the NavShoe system can get accuracy of approximately 0.3 percent of distance traveled without GPS. The altitude accuracy is higher. Then the author discussed how this system cans integration with GPS as well as any other position-aiding approaches.
Overall, I think this system is very cool because it can also work well in indoor environment. Considering that many people may get lost in some shopping mall or other build with complex structure, this system can give them navigation inside the build which I think is very useful.
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