INS/GPS/EM-LOG Integrated Navigation System Technology

As people's requirements for navigation accuracy become higher and higher,it is difficult for individual navigation systems to meet navigation accuracy requirements.Therefore,using integrated navigation system technology to improve navigation accuracy is an effective way.This paper is to study the INS/GPS/EM-LOG integrated navigation system technology.Firstly,based on the principle of strapdown inertial navigation system(SINS),this paper establishes the SINS error model.Subsequently,the basic principle of GPS and its error source are analyzed.Based on this,the state equation and measurement equation of INS/GPS tightly coupled integrated navigation system are given.A satellite selection algorithm and an algorithm based on ephemeris to calculate satellite position and velocity are designed.Based on the above,the simulation study of INS/GPS tightly coupled integrated navigation system is completed.This simulation proves that the precision of tightly coupled navigation system is much better than the single SINS,and its reliability is better than INS/GPS loosely coupled navigation system.Because GPS requires the support of external information,it is difficult to obtain GPS signals under underwater conditions or strong interference conditions.Considering that the electromagnetic log is an autonomous navigation device and has many advantages such as strong anti-interference ability,the electromagnetic log is used to assist the inertial navigation system in the case of difficulty in obtaining GPS signals.However,the electromagnetic log is a relative log,and it will bring ocean current velocity error,which will affect the accuracy of the navigation system.So this paper proposed a method to eliminate the influence of ocean current through making the electromagnetic log different the output value of the electromagnetic log at two sampling moments with short interval,thereby improving the accuracy of navigation information.A state-delayed Kalman filter is designed,and the speed increment obtained by the differential output of the electromagnetic log and the speed increment calculated by the inertial navigation system are introduced into the state-delayed Kalman filter.This filtering technique is used to optimally estimate and compensate the navigation parameters.Simulation and experimental verification of the INS/EM-LOG integrated navigation system are completed.Compared with the external velocity level damping scheme and the conventional Kalman filtering scheme,superiority of the Kalman filtering method with delay state is proved.