Capteurs et algorithmes pour la localisation autonome en mode pédestre

The challenge of knowing one's position in a precise and reliable way, at any time, with and without reception of satellite signals, represents an area fairly explored for the navigation of vehicles. To widen this service to the pedestrians requires a different approach that adapts to the dynamics, to the speed and especially to the total freedom of movement of the people. The traditional approach implements a triad of accelerometers and gyroscopes, which signals are integrated to obtain the relative displacement. This concept is unfortunately not judicious for a low-cost system. The principal reason is that the speed of displacement of a person is lost in the sensor noise level. In order to take into account all these specificities, an occurential approach was developed, based upon a subset of sensors as well as physiological and biomechanical parameters of the walk. This research is divided into three main directions. The first area of interest consists in the determination of the physiological parameters necessary to quantify the speed of walk and the step length. While the agitation of the accelerometer signals is a good speedometer, the frequency of the steps improves the robustness of the models. The influence of the gender added to the great human diversity imply the normalisation of the various relations deduced. Many tests carried out under conditions of everyday life reveal that the variation of the stride length, especially with the slope, strongly depends on the physical training of the person as well as on the duration of the climb or descent. Characteristic pattern were identified to differentiate between the forward, backward and lateral movements. The various suggested models were then favourably tested with some blind people, whose walking rhythm strongly varies according to the degree of confidence they have towards the course. The second part directly relates to the multiple technologies integrated to build an autonomous three-dimensional Pedestrian Navigation Module (PNM). The knowledge of the terrestrial magnetic field and its orientation makes it possible to determine the azimuth of displacement of a person. The use of a gyroscope improves the reliability of the system and facilitates the detection of magnetic disturbances. More stable in the short term than the compass, it is therefore the optimal complement under such circumstances. The altimetric information is obtained by barometric measurements which, according to the required precision, can be differential. The implementation of a GPS receiver allows the absolute positioning simultaneously to the calibration of the different sensor parameters and physiological models. The third part describes the integration of the models and measurements as well as the characteristics and treatments specific to pedestrian navigation. An initialisation phase is presented to individualize the parameters of the walk and adapt them from the general model. Hence, thanks to the compass-gyroscope integration together with the detection of any movement, this allows an optimal determination and filtering of the azimuth that has little or no temporal degradation. The consideration of several phenomena specific to the displacements of the humans brings artificial intelligence in pedestrian navigation. The coupling of the various sources of measurements, the influence of their precision on the computed position as well as their implication on the PNM reliability are described and illustrated. More than 550 km covered in various circumstances by 31 people allowed to validate the presented approach while fixing its limits

Improvement of walking speed prediction by accelerometry and altimetry, validated by satellite positioning

Activity monitors based on accelerometry are used to predict the speed and energy cost of walking at 0% slope, but not at other inclinations. Parallel measurements of body accelerations and altitude variation were studied to determine whether walking speed prediction could be improved. Fourteen subjects walked twice along a 1.3km circuit with substantial slope variations (−17% to +17%). The parameters recorded were body acceleration using a uni-axial accelerometer, altitude variation using differential barometry, and walking speed using satellite positioning (DGPS). Linear regressions were calculated between acceleration and walking speed, and between acceleration/altitude and walking speed. These predictive models, calculated using the data from the first circuit run, were used to predict speed during the second circuit. Finally the predicted velocity was compared with the measured one. The result was that acceleration alone failed to predict speed (meanr=0.4). Adding altitude variation improved the prediction (meanr=0.7). With regard to the altitude/acceleration-speed relationship, substantial inter-individual variation was found. It is concluded that accelerometry, combined with altitude measurement, can assess position variations of humans provided inter-individual variation is taken into account. It is also confirmed that DGPS can be used for outdoor walking speed measurements, opening up new perspectives in the field of biomechanic

Structural And Vibrational Studies on Isomers of Antiviral Ribavirin Drug in Gas and Aqueous Environmental by Using The SQM Approach

Five stable isomers of antiviral ribavirin agent were theoretically determined in gas and aqueous solution by using the hybrid B3LYP/6-31G* method. Here, the solvent effects were studied with the self consistent reaction field (SCRF) methodology employing the polarized continuum (PCM) and the universal solvation model (SM). Structural, electronic and topological properties were reported for all isomers while the vibrational analyses were performed only for those two polymorphic structures experimentally observed in the solid phase by X-ray diffraction. Calculations have evidenced that C2 correspond to the polymorphic V1 structure while C5 to the polymorphic V2 structure. The high dipole moment values predicted for C2 and C5 in both media could probably explain their presences in the solid. Experimental available IR and Raman spectra of ribavirin in the solid state and normal internal coordinates were employed together with the scaled quantum mechanical force field (SQMFF) approach to perform the complete vibrational assignments in both media. Here, the 81 vibration modes expected for C2 and C5 in both media were completely assigned. The frontier orbitals studies reveal that C5 is the less reactive in both media. Here, the gap value observed for C5 is in agreement with the value recently reported for ribavirin by using B3LYP/6-311++G** calculations

In Step with INS Navigation for the Blind, Tracking Emergency Crews

As demand increases for positioning rescue crews, military users, and individuals with special needs, miniaturized low-power inertial measurement units (IMUs) coupled with GPS receivers and other sensors can provide accurate position in both indoor and outdoor situations

An Alternative Approach to Vision Techniques - Pedestrian Navigation System based on Digital Magnetic Compass and Gyroscope Integration

Over the last few years, research had been conducted on how to develop basic mobility aid for visually impaired and blind people using vision and image processing techniques. However, our research at Geodetic Engineering Laboratory has taken a different view to this problem