Research On Multi-antenna GNSS/INS Integrated Navigation Algorithm

The core of the mobile measurement system is the GNSS/INS integrated navigation technology,which uses the features of GNSS navigation results with high precision and INS navigation results are not affected by external influences.It provides users with better position,speed and attitude information through different combinations.In recent years,mobile measurement system has developed rapidly,especially in the field of vehicle mobile measurement system.However,the traditional vehicle GNSS/INS measurement system usually carries a GNSS receiver.When the vehicle is in a linear motion for a long time,there will be a problem that the position information is not observable,especially the heading information will gradually diverge with time.It is more remarkable for low-level inertial navigation devices.The heading angle,pitch angle and roll angle can be provided directly from multiple GNSS antennas mounted on the carrier,leading to the direct observation of the attitude angle error in the integrated system.In addition,the relationship between the double-difference carrier phase observation vectors among the antennas and the carrier platform error angle can be established.Therefore,this paper focuses on the multi-antenna GNSS/INS loosely and tightly coupled navigation algorithm.The main research work is as follows:(1)The principle of relative positioning technology of GNSS is studied.The carrier phase interference principle is used to solve the baseline vector formed the different GNSS antennas of the rover.The heading angle,pitch angle and roll angle can be obtained by using the attitude transformation matrix by different descriptions of the baseline vector in the local navigation frame and the body frame.A simple and practical calibration method is proposed to compensate the installation angle error between the antenna coordinate system and the body frame.According to the measured data,the heading angle RMS reaches 0.32° when the baseline length is about 1 meters.(2)The mechanical arrangement of the local navigation frame and the earth-centered earth-fixed frame are introduced and the specific derivation formula of the INS error equation under two coordinate systems are given in detail.The standard Kalman filter is introduced,and the linearization of nonlinear Kalman filter and the discretization of linear Kalman filter are expounded according to the actual engineering application.(3)The multi-antenna GNSS/INS loosely coupled equation of state and measurement equations in the local navigational frame and the multi-antenna GNSS/INS tightly coupled state equation and measurement equation in the earth-centered earth-fixed frame are rigorously derived.The feasibility of multi-antenna GNSS/INS integrated navigation algorithm to improve heading angle accuracy is verified by measured data.The results obtained by high-precision inertial post-processing are used as reference values.The results obtained by post-processing data collected by high-precision inertial navigation are used as reference values.The results of single antenna loosely coupled and multi-antenna loosely coupled and the results of single antenna tightly coupled and multi-antenna tightly coupled are compared and analysed.The example results show that the multi-antenna coupled has a certain smoothing effect on the position and velocity.The improvement of the pitch angle and the roll angle is not significant,the heading angle improvement is most obvious.Among them,the multi-antenna loosely coupled RMS is improved by 65.15%and the multi-antenna tightly coupled RMS increased by 58.06%.