Abstract-Indoor navigation technology is needed to support seamless mobility for the visually impaired. This paper describes the construction and evaluation of an inertial dead reckoning navigation system that provides real-time auditory guidance along mapped routes. Inertial dead reckoning is a navigation technique coupling step counting together with heading estimation to compute changes in position at each step. The research described here outlines the development and evaluation of a novel navigation system that utilizes information from the mapped route to limit the problematic error accumulation inherent in traditional dead reckoning approaches. The prototype system consists of a wireless inertial sensor unit, placed at the users' hip, which streams readings to a smartphone processing a navigation algorithm. Pilot human trials were conducted assessing system efficacy by studying route-following performance with blind and sighted subjects using the navigation system with real-time guidance, versus offline verbal directions. A wide assortment of technologies has been proposed to develop indoor navigation systems for the blind and vision impaired. Proximity-based and triangulation systems have been successfully demonstrated [1] and employed. Despite the technical success of these technologies, broad adoption has been limited due to their significant infrastructure and maintenance costs (for review, see Giudice and Legge, 2008 [2]). The approach explored in this research seeks to solve this infrastructure cost problem by utilizing only body-worn inertial sensors, MEMS accelerometers and gyros, combined with a smartphone processing a navigation algorithm. The approach described here is one component of an ongoing project that will ultimately fuse several complementary indoor navigation technologies together. In recent publications, the authors have described and demonstrated another component of this project utilizing magnetic sensing of indoor magnetic anomalies to localize the traveler along an indoor route [3] [4]. To optimize each navigation component, a complete indoor navigation solution has been constructed and tested using only the current technology under development. This approach has provided our team with frequent opportunities to demonstrate our technology and user interface with potential users. Indoor navigation technology is needed to support seamless mobility for the visually impaired. Most people who are blind or have low vision can navigate outdoors using a cane, guide dog or their own low vision as an aid, but indoor navigation in large or unfamiliar buildings can be very challenging. To be done accurately, it requires reading signs, room numbers, building maps, and/or identifying landmarks, tasks which are difficult or impossible for a person with low vision. A significant problem in indoor navigation for the visually impaired relates to orientation information: knowing current position in the building and updating changing position/heading with movement. The biggest challenge to low-vision navigation is not mobility information, awareness and avoidance of obstructions to the path of travel, or in executing routes, but with spatial updating, spatial inference and cognitive map development [5] . The navigator technology described here is based on a pedestrian dead reckoning (PDR) approach. PDR algorithms combine step detection with heading estimation to compute changes in position. Body worn accelerometers are sensitive to the characteristic motions involved with walking and this data can be processed to detect steps. Step detection is coupled with an individual's measured gait length to provide an estimate of the distance traveled with each step. Sophisticated PDR approaches include algorithms to estimate the change in gait length as an individual modifies their stride. Heading is typically measured by magnetometers sensing the Earth's field, or gyroscopes which sense angular velocity. When combined with the accelerometer's measurement of the gravity down vector, the components of the magnetic field or angular velocity in the horizontal plane provide an estimation of heading. Given a known starting point and a measured gait length, PDR can provide a users' approximate real-time position without relying on external infrastructure. This approach, however, suffers from error accumulation. Small errors in gait length and heading slowly accumulate and eventually overwhelm the position estimate. Dead reckoning is typically paired with localization technologies that do not suffer from error accumulation, such as GPS, to avoid this problem. The approach developed here uses the trajectory of the planned route to supply additional information to the navigator algorithms, enabling the problem of error accumulation to be controlled. A planned route is composed of straight-line segments and expected heading changes. PDR is used within straight-line segments to update the distance along the segment. Error accumulation is controlled by comparing sensed turns to map features.
Trying to solve this problem, Riehle et al. REF proposed to use the trajectory of a planned route to provide additional information to reduce the error accumulation problem.
Indoor inertial waypoint navigation for the blind
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
Computer Science Medicine