Research On Low-cost Multi-antenna GNSS/INS Integration Attitude Determination

In recent years,low-cost GNSS has developed rapidly.The European Union Space Program predicts that its shipments will increase significantly in the next 10 years.China’s "Ministry of Industry and Information Technology" also issued relevant policies in 2022 to promote the high-quality development of the Beidou industry.Low-cost and high-precision navigation,attitude and positioning services will increasingly play an important role in various industries as the basis for further industry breakthroughs.Research on low-cost multi-antenna GNSS/INS integrated attitude determination systems is of great significance and value.At present,there are relatively few researches at home and abroad based on lowcost GNSS/INS integrated attitude determination.Most of the existing researches choose ideal test data sets,and the corresponding GNSS receiver and IMU hardware costs are difficult to popularize in the consumer market.In addition,there are many types of multi-antenna GNSS function models,immature ambiguity fixing methods,insufficient positioning accuracy,and insufficient research on combined attitudes,which lead to unclear understanding of its theoretical methods and improper use.These factors limit the integration of GNSS/INS applications in the consumer market.Aiming at overcoming the technical and theoretical difficulties in the application of low-cost multi-antenna GNSS/INS integration in the civilian consumer market,the main research work and contributions of this paper are as follows:(1)In view of the current problems of confusion of multi-antenna GNSS function models and unclear solutions,the optimization of multi-antenna GNSS function models is carried out.The model principle of the multi-antenna GNSS attitude determination model based on the vectorization method and the filter method under different parameterization methods is clarified,and the difference in coordinate system definition caused by the flexible layout of low-cost antennas is comprehensively considered.Conditional measured data are preferred to function models.The results show that the filtering model based on rotation vector parameters has the best solution,which provides key technical support for low-cost multi-antenna GNSS attitude determination.(2)Two improved constrained ambiguity fixing methods are proposed to address the difficulty of ambiguity fixing for low-cost multi-antenna GNSS in complex environments.Due to the different orientations of multi-antenna GNSS baselines and different observation conditions in complex environments,this paper proposes a CLAMBDA method based on attitude domain search,considering that there is only a single degree of freedom attitude angle when a fixed single baseline is calculated.Furthermore,the known nonlinear conditions are incorporated into the objective function in the form of linear approximation,and a CLAMBDA method based on ambiguity domain search is proposed.The measured data show that the new method is not sensitive to information such as the number of satellites,satellite geometry,and environmental multi-path,which significantly improves the ambiguity fixed success rate and the search efficiency.(3)A complete fusion positioning strategy based on low-cost GNSS RTK is demonstrated.The paper uses GNSS velocity measurement to increase the reliability of the state prediction model,and comprehensively proposes a method that combines the least squares carrier time differential velocity solution and Kalman filter Doppler velocity solution.The real data show that the RMS of velocity is 0.06m/s、0.05m/s、0.04m/s;the paper studies the preprocessing method with consumer-grade GNSS data,and carries out gross error and cycle slip detection of original observations in the prior test and posterior test stages of data processing;A consumer-grade ambiguity fixing method is proposed from three perspectives: partial fixing,ambiguity fixing judgment,and ambiguity constraint,and then a complete consumer-grade GNSS RTK processing strategy is proposed.The experimental results show that when positioning in an opensky environment,the fixed ambiguity rate exceeds 99%,and the horizontal and elevation dynamic positioning accuracy reaches centimeter-level;when positioning in a complex urban environment,the solution strategy proposed in this paper can better suppress error,effectively improve the fixed rate of ambiguity,and improve the usability of single-frequency RTK.(4)For the calibration of the multi-antenna GNSS/INS integrated attitude determination system,a complete comprehensive calibration strategy is proposed,and the characteristics of the rotation error are mainly studied.The coordinate system of the multi-antenna GNSS/INS integrated system is various and complex,and a large number of system errors need to be calibrated.The paper comprehensively considers the existing system error calibration and compensation methods,focuses on the rotation error compensation term between the GNSS antenna coordinate system and the INS body coordinate system,clarifies its error propagation mechanism.Experiments proves that the influence of this error on the attitude of the integrated system cannot be ignored,and can only be eliminated after calibration compensation.(5)The thesis studies the low-cost multi-antenna GNSS/INS integration method.The thesis clarifies the tight integration method of multi-antenna GNSS/INS,studies the multi-epoch CLAMBDA method based on the attitude domain,and verifies that its attitude accuracy is less than 0.5° in the horizontal direction and 0.65° in the heading direction through the real data.RTK positioning is then incorporated into the integrated system.The three comprehensive road conditions data show that under the integration of high-precision RTK algorithms,the horizontal angle accuracy is less than 0.35°,and the heading angle direction is less than 0.5°.(6)The thesis builds a low-cost multi-antenna GNSS/INS attitude solution platform.Based on the theoretical method of this paper,a multi-antenna GNSS/INS prototype hardware platform with independent intellectual property rights has been independently designed and developed.The overall cost is controlled within 1,000 yuan,and it has many advantages such as low system complexity,simplicity and ease of use,and high cost performance.It has high application and promotion prospects in the consumer market.To sum up,this thesis has conducted in-depth research on low-cost multi-antenna GNSS/INS integrated attitude determination technology,built a hardware platform,constructed a complete mathematical model,and proposed an ambiguity fixing method suitable for low-cost equipment.The proposed algorithm model is fully verified by the measured data.The research results of this paper will effectively promote the development of academic research and industrial applications of low-cost GNSS highprecision attitude determination technology in complex environments.