The Design And Realization Of Trajectory Tracking For Tractor Autonomous Driving Simulation System

With the increasing price of labor market in China, the application of agricultural machinery navigation can greatly reduce human input, improving the operational efficiency and the output of crops, so it is the trend to open the agricultural machinery automatic navigation.In fact, the study of unmanned vehicles has been carried out for a very long time at home and abroad, but put it in use in agricultural tractors, compared with the domestic and foreign technology, there is still a long time to catch up. Automatic navigation system is a control system installed on the tractor, suitable for all types of field work, such as ridging, seeding, harrowing, harvesting, auxiliary film activities. The tractor is composed of five parts, which are the transmission system, the walking system, the steering system, the braking system and the working device, and the automatic navigation system is also composed of five parts, which are location, path planning, navigation control, vehicle model and communication. The design and application of this system is based on the previous experience.In this paper, a simplified mechanical platform is built, and a hardware platform based on ARM7 is also set up. Then the paper introduces the theory of navigation, posture and satellite positioning, and gives the building process of the simplified kinematic model of the tractor.According to the existing nonlinear mathematical model, the discrete linearization is carried out, and three different controllers are designed based on the state equation,the approximate linearization theory, the model prediction algorithm and the linear quadratic regulator. Through software simulation, the control effect of these three kinds of controllers is compared, and the optimal LQR controller is selected. Then, the software platform of this system is built,according to the system needs and combining the global positioning technology, posture fusion technology, using C language as the development language in Keil Vision5 software environment, the design and development of the software system is completed under the embeddedμ C/OS-II real-time operating system. The realization of the drive of the sensor serial port, the function of the data analysis and the navigation control is studied.Subsequently, the design of the system is carried out on the field test, the test shows, when the speed of the system is 0.5m/s, the horizontal maximum error is about 40 cm, the minimum error is about 5cm, the average error is about 15vm; when the speed of the system is 1m/s,the horizontal maximum error is about 70 cm, the minimum error is about 10 cm, the average error is about 28 cm. Obviously, compared with the market mainstream products, its performance is still in the shade, But already has the function condition. In the end, the cause of the error is analyzed, and the improved method is put forward.