| China is an agricultural country.Agriculture is the cornerstone of the national economy and an important guarantee for social stability.The development of agriculture is directly related to the national economy and people's livelihood.In order to promote more efficient agricultural production,the government has continuously introduced support policies to promote the comprehensive integration of information technology and agriculture to strengthen the construction of agricultural machinery information.For the farm working environment,the working platform based on the navigation sensor autonomous mobile robot has the advantages of high work efficiency,low labor cost,strong carrying capacity,accurate positioning and strong expansion,and has been applied in small scale in agricultural production.The autonomous mobile operation capability of the carrier in the farm environment depends largely on the positioning accuracy of the navigation system.In this thesis,mobile robot positioning is used as the entry point,and inertial navigation system(INS)is used to compensate for the navigation problem when the GPS signal is disturbed and invalid.GPS positioning error does not diverge with time to correct inertial navigation data.The GPS/INS combined navigation mode is used to build the mobile robot navigation system.Through theoretical analysis and experimental verification,relevant research work has been carried out on the positioning error.The related research work are as follows.(1)For the application scenario of the mobile robot,a four-wheel mobile robot platform with a suspension damping mechanism was selected.The platform is based on the STM32 embedded processor and uses differential drive to control carrier motion.Experiments are carried out under different road conditions to verify that the carrier is superior to the four-wheel mobile robot without independent suspension structure in shock absorption and impact resistance.The research shows that the selected mobile robot can reduce the measurement error caused by the body shake when equipped with the inertial measurement unit.(2)The mobile robot in this thesis adopts the GPS/INS integrated navigation method,which makes up for the deficiency in the single navigation mode by using the complementary redundancy relationship between GPS and inertial navigation.By analyzing the error source of the system,the error model was established,and the loosely integrated combined navigation mode was selected.The information outputted by the sub-navigation system was combined and corrected,and the state equation and measurement equation of the dynamic characteristics of the integrated navigation system were established.According to the nonlinear characteristics of the system model,extended Kalman filter was used as the information fusion method.By adding error information such as error noise,the motion trajectory of the carrier was simulated.According to the simulation results,the performance of the combined navigation mode was better than that of the single navigation mode.(3)Based on MEMS technology,the inertial measurement unit,GPS receiver and embedded chip were selected to form the hardware platform of the integrated navigation system.Based on the C language framework,the data acquisition and processing,navigation algorithm solution and monitoring interface design were combined to form a combined navigation system software platform;the navigation platform of mobile robot was successfully built.For the built mobile robot,function testing experiments were carried out in outdoor environment,including static calibration experiments and dynamic map building experiments.By collecting coordinate information on the path,navigation electronic map was generated to realize autonomous navigation of mobile robot in outdoor environment.The experimental results shows that the mobile robot can move according to the preset path in the electronic map,and the combined navigation mode has higher positioning accuracy in practical applications.In this thesis,the autonomous navigation design and navigation error analysis of mobile robots in outdoor environment are taken as the research content.To meet the needs of positioning,navigation and experiment in outdoor environment,the mobile robot prototype and integrated navigation system was completed.The results of combined navigation experiments show that the navigation system has higher positioning accuracy and expands the operation range and ability of mobile robot in outdoor environment.The data processing and solving algorithms in the navigation system will constitute the key technology for the chassis control of mobile robots. |
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