Research On The Navigation Of Forest Firefighters Based On GNSS And INS Integration

A large number of smoke is produced in the process of forest fire spreading.The firefighters inhale smoke for a long time when carrying out the task of forest fire fighting,which will seriously threaten the personal safety.According to monitoring of firefighters' location information and the organization of effective rescue in real-time,the loss of firefighters can be reduced.At present,satellite navigation and inertial navigation are widely used in the field of forest fire fighting.However,the global navigation satellite system(GNSS)is vulnerable to the influence of tree occlusion in forest environment,and it has lost the positioning ability.In addition,the inertial navigation system(INS)has accumulated errors for a long time,which cannot provide accurate navigation.In view of their complementary characteristics,INS and GNSS are combined in our work to improve the navigation accuracy and meet the positioning needs of firefighters.Firstly,the basic theory of pedestrian inertial navigation is described in our work in detail.The foot movement characteristics of pedestrians models are established,and the attitude and position algorithm of pedestrians is deduced.In order to suppress the accumulated error caused by sensor drift,the zero-velocity update method is applied to the inertial navigation system.The zero-velocity detection method based on the generalized likelihood ratio test and the zero-velocity correction algorithm based on Kalman filter and particle filter is designed.In view of the shortcomings of particle filter,the zero-velocity update accuracy is improved by adaptively adjusting the threshold value of particle filter.At the same time,the magnetometer is easy to be interfered by ferromagnetic materials in the process of search and rescue.At present,the existing methods have the phenomenon of false detection for the weak magnetic interference,which affecting the subsequent heading correction.Therefore,a magnetic field interference detection algorithm based on the generalized likelihood ratio is proposed in our work.In addition,an improved Kalman filter is designed to improve the accuracy and reliability of positioning by suppressing the magnetic field interference.Secondly,aiming at the problem of GNSS signal loss and INS error divergence,the integrated navigation system of GNSS and INS is designed in loose coupling form.By fusing the output information of GNSS and INS through Kalman filter,the error model of sensor and navigation parameters is established and deduced.GNSS is used as observation feedback to INS,so as to restrain INS drift.Finally,a set of navigation and positioning device for forest fire fighters is designed,and several groups of experiments are carried out.The device is worn on the firefighters to collect relevant information.Moreover,the field static experiments,straight-line walking experiments and closed track experiments are carried out in the forest area.Compared with single INS system and single GNSS system,the position accuracy of the integrated navigation system is significantly improved,and the superiority of integrated navigation algorithm is verified.