In some cases, it is necessary to guide a person in his movements inside or outside a building. In particular, aid with the navigation of blind persons in public places is becoming obligatory.
The technical problem can be solved outdoors through the use of GPS signals. Numerous navigation systems exist commercially, for equipping automobiles and also hikers. Inside a building it is no longer possible to use GPS signals. The current solutions are not satisfactory. Two types of solutions exist. The solutions of a first type are based on the use of location beacons. The other solutions are based on recognition of places.
As regards beacon systems, there exist solutions established by way of experiment in public places. These systems use location posts. By integrating a large number of reference beacons and by applying the known schemes based on trilateration, triangulation or schemes based on hyperbolas, it is possible to locate an object and thereafter propose a navigation. However, these schemes demand very significant complementary equipment for buildings and therefore give rise to installation and maintenance costs which penalize these systems. For example, a solution based on RFID beacons requires that posts be set up every five meters in the underground corridors and stations of the subway, this not being financially conceivable.
In the case of systems based on recognition of places, various solutions exist, and they arise for the most part from robotics. Some use inertial units. These units include sensors of accelerometer or gyrometer type. By data fusion between these sensors, it is possible to reproduce the three-dimensional orientation of the unit. However for inertial units intended for use by the “general public”, the measurements performed exhibit a significant temporal drift making absolute location impossible. Other solutions exist using vision. The location function can in these cases be ensured by the images from a camera through the use of techniques called SLAM, which stands for “Simultaneous Localization And Mapping”. However, all the vision-based schemes are currently rather unreliable and they are notably sensitive to variations in the scene captured, such as for example changes in brightness, displaced objects or else different angles of view. In addition, they require a large amount of calculation. Moreover, it is necessary to provide for the use of a camera worn by the person to be located and guided, this being detrimental to the discretion of the device. Finally, other solutions use a laser. A two-dimensional laser scanner makes it possible to measure according to an angle of about 180° the distance with respect to the obstacles. The image obtained is thereafter realigned with respect to the map of the building in which the object or the person to be located is situated. This realignment makes it possible to reposition this object in the scene. This principle, now commonly used in industry, is unsuitable for the present location application. Indeed, the presence of other people, considered by the laser to be obstacles, disturbs the measurement and prevents location. Moreover, laser scanner systems are not yet sufficiently miniaturized to be easily worn and they are not discreet. Moreover, their cost is high.
An article by Y. Tadokoro, S. Takuno and Y. Shinoda “Portable Traveling Navigation System for the Blind and its Application to Traveling Training System” Proceedings of the First Joint BMES/EMBS Conference, Advancing Technology October 1999, Atlanta, page 589, describes a portable navigation system comprising a computer with the planned path for a destination in the memory, movement sensors and an audible HMI. The computer calculates the distance traveled and the direction of movement and compares them with the planned path, and the HMI gives indications to the user. However the solution described in this publication does not make it possible to correct the drifts of the calculated path with respect to the real path.
A patent application WO 2005/080917 discloses a system for determining the path followed by a pedestrian. This system comprises three inertial sensors attached to a user. It requires a calibration for each user.