Zhang Wenyu, Zhang Zhigang, Zhang Fan, Ding Fan, Hu Lian, Luo Xiwen. Cooperative autonomous operation strategy and experiment of the rice harvester together with a rice-transporting vehicle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(15): 1-9. DOI: 10.11975/j.issn.1002-6819.2022.15.001
    Citation: Zhang Wenyu, Zhang Zhigang, Zhang Fan, Ding Fan, Hu Lian, Luo Xiwen. Cooperative autonomous operation strategy and experiment of the rice harvester together with a rice-transporting vehicle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(15): 1-9. DOI: 10.11975/j.issn.1002-6819.2022.15.001

    Cooperative autonomous operation strategy and experiment of the rice harvester together with a rice-transporting vehicle

    • Many links and complex cooperative operations have posed a great challenge to the autonomous harvesting between rice harvester and transfer vehicle. In this study, a cooperative operation strategy was designed for the autonomous rice harvester and transfer vehicle using Finite State Machine (FSM). The cooperative mode was then divided into four links: independent harvesting, waiting for calls, cooperative truck unloading grain, and transportation. An FSM model was also established to construct the basic components of a collaborative harvesting state machine. After that, the state information matrix was defined to design the specific flow of basic action execution, including the harvester starts harvesting, stops harvesting, starts unloading grain and stops unloading grain. The transfer vehicle was then driven at the waiting point to cooperate with the alignment, then to start or stop grain unloading. As such, the state transition chain of collaborative work was constructed to clarify the transition relationship and trigger conditions between the states in the process of collaboration. The cooperative control logic framework involved the harvester and transfer vehicle, according to the state transition chain architecture. Stateflow tool was selected to simulate and verify the compiled logic framework in the MATLAB platform. The sequential execution was also simplified to introduce the timing and signal transmission delay of internal execution. The simulation results show that the states of the harvester and transfer vehicles were transferred orderly, particularly with the correct conversion of the trigger signal. The test results also show that the control logic strategy performed better for cooperative harvesting. A crawler-type rice collaborative harvesting system was constructed to verify the actual operating performance of the logic strategy, including the crawler rice harvester (Weichai Lovol Heavy Industry RG70V4G-014) and crawler rice transfer vehicle (Weichai Lovol Heavy Industry RG70V4G-015). Among them, the two intelligent agricultural machines adopted the fully electronically controlled chassis with the wire-controlled clutch, header, grain cylinder, and crawler driving system. The dual antenna BDS positioning system (Sina K726) was also equipped, where the data transfer unit (USR-G781) was used in the communication between two computers in the fixed-point cooperative experiment of rice harvesting. The 4/5 G Data Transfer Unit (DTU) with human cloud was adopted at the same time. The autonomous control module was communicated with the control terminal through RS-232. A Self-control terminal (eAgri-800-RS) was installed in the two computers for the harvesting self-control, which communicated with the chassis Electronic Control Unit of the two computers through CAN bus. The software system was developed by Keil uVision 5. The linear path tracking was adopted to follow the model control in the navigation system. The two-computer alignment control was adopted to deal with the position error PID. The collaborative system test was carried out in the Zengcheng Experimental Base of South China Agricultural University. The harvester and transfer vehicle were designed to independently work in the field from the hangar of the base. Specifically, the harvesting speed and width were set at 0.8 m/s, and 1.9 m, respectively. The continuous cooperative working time was not less than 120 min. About 0.7 hm2 of rice were automatically harvested by the ferrule path. Six operations of the automatic cooperative transfer system were carried out to transfer the grain to the truck during this period. The transfer truck waited on the tractor road, and then transferred the harvested grain to the roadside truck, according to the designed fixed-point cooperative operation strategy. The harvester and transfer vehicle returned to the hangar in sequence after harvesting the whole farmland. The harvest and transportation path were also designed in the test plan. Among them, the specific harvesting path was designed to cover the field, where the outer ring was harvested first and then parallel rings, according to the size of the field. The cooperative path was selected on the short-side tractor road. A balance was obtained on the short-side straight-line paths of the harvesting operation. The transfer vehicles only needed to plan a reusable path. The grain alignment transfer work was completed to advance or reverse this path in the whole field. The specific transfer points were calculated from the coordinates issued by the harvester, all of which were located on this path. Consequently, the fixed-point cooperative operation was also realized using the autonomous harvester and the transfer vehicle, according to the predetermined path. The logic signals were successively recorded to normally trigger during network communication under the predetermined logic framework in the test. The whole cooperative process was aligned accurately to successfully complete the fixed-point cooperative harvesting operation and return to the hangar. Therefore, the cooperative operation strategy of double machines for rice harvesting was effective and reliable under the configuration, and the harvesting efficiency was 0.35 hm2/h. The finding can also provide strong support for the cooperative operation of autonomous full coverage harvesting in rectangular rice regions.
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