| Agriculture belongs to the Chinese largest industry,whose importance is selfevident.70% of China's cultivated land belongs to hilly areas,and the degree of agricultural mechanization in hilly areas is still very low.The terrain in the hilly area is complex and the roads are winding and narrow.Therefore,traditional tractor operations in hilly areas face many problems,such as low safety,poor operation quality,difficult movement,and so on.To reduce the labor intensity of farmers,improve the level of agricultural mechanization in hilly areas,and ensure the operation safety of tractors in hilly areas and the quality of crop production,it is imperative to develop novel types of tractors with features of the stable body and flexible operation.Body leveling is crucial to the hilly mountain tractor,which can provide a solid technical guarantee for the safety and stability of the tractor when operating in hilly areas.Therefore,a complete set of body leveling systems suitable for the work requirements of the hilly mountain tractor is developed in the study.Furthermore,the body leveling mechanism and its control system are also studied in depth.The main research work and related findings are as follows.1.Based on the whole machine parameter requirements of the hilly mountain tractor,the body leveling mechanism of the hilly mountain tractor is studied,and the overall scheme of the body leveling control system is determined.The front-drive axle and rear-drive axle with the functions of body leveling,four-wheel drive,and fourwheel steering are designed.The load-sensitive body leveling hydraulic system and various functional valves are developed.Relying on the index requirements of the whole machine,the body leveling mechanism and body leveling hydraulic system,auto-leveling controller and manual leveling controller,and other key components are selected,and the body leveling control system is developed.2.The simulation model and kinematics analysis of the body leveling mechanism are established.The kinematics characteristics of the attitude self-adjusting steering drive axle during four-wheel steering,body leveling,and power transmission at the same time are studied.The problems of four-wheel steering,body leveling,matching coordination,and motion interference between transmission and drive of the hilly mountainous tractor are solved.The characteristics of the body leveling hydraulic system are studied,the functions of the load sensing hydraulic system are verified,and the appropriate throttling parameters of the hydraulic system are selected.3.The four-point leveling principle is used to level the tractor body in hilly and mountainous areas,and the body leveling motion equation is given.A multi-sensor fusion detection method for tractor body attitude in hilly and mountainous areas is proposed.By compiling an appropriate filtering program,on the premise of not affecting the response speed of body leveling,the problem of sensor signal offset caused by engine vibration of hilly and mountainous tractors under heavy load is solved,which lays a reliable signal foundation for the rapid decision-making of the control system.4.Aiming at several typical working conditions of tractors in hilly and mountainous areas,different body leveling control strategies are proposed.Based on different control strategies,two body leveling control algorithms are developed,which correspond to high-speed response leveling and high-precision leveling respectively.The hydro mechatronics co-simulation model of the hilly mountain tractor was established.,and two control algorithms are used for analysis.The results show that the high-speed position control algorithm can respond to the road changes faster,and the high-precision position control algorithm has higher body leveling control accuracy.5.Considering the use requirements and actual working conditions of the hilly mountain tractor,the user interface of body leveling control,control instruction and CAN bus communication protocol of the tractor was developed and designed.Based on the communication protocol,control instructions,and body leveling control algorithm,the tractor body attitude control software was developed for the body leveling controller.6.To test the performance of the body leveling control system and verify the actual control effect of the body leveling control algorithm,the bench test and the prototype test of the body leveling control were carried out respectively.The performance of the electrohydraulic control system for body leveling was verified by a bench test.The results show that the velocity error and displacement errors are 0.55% and 0.02%respectively.The whole machine test tested the ability of the machine body leveling control algorithm to identify operating conditions and its machine body leveling control accuracy under road conditions,farming conditions,and movement conditions.The test results show that the body leveling control system works well under different working conditions,and the accuracy of the hydro mechatronics co-simulation was verified through the analysis of the hydro mechatronics co-simulation and the comparison of the body attitude in the test process. |
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