Intelligent plant protection machinery in large fields is an important means to improve pesticide utilization，enhance the quality of agricultural products，and ensure the sustainable development of agriculture. In order to understand the research status of intelligent plant protection technology and clarify the future development direction，this article focused on three main directions of intelligent operation of high-clearance plant protection machinery：prescription application in large-scale farmland，target spraying on a small scale in land parcels，and variable-speed spraying. From the aspects of perception，analysis，decision-making，and control，the article elaborates on the technical principles of prescription map construction，spatial coordinate transformation methods，and prescription recognition that integrate high-precision satellite positioning，the current level of key technologies for target spraying technology routes and weed recognition，and believed that high-precision spraying based on online prescriptions must be the focus of future research. The article carried out a comparative analysis of the advantages and disadvantages of four speed measurement modes for variable-speed spraying and believed that with the widespread application of satellite positioning in agricultural machinery，satellite-based speed measurement will become the main method of high-precision speed measurement due to its greater versatility，convenience，and accuracy. To explore the current development status of variable spraying control，the article summarized two control methods and implementation methods for pressure-controlled variable spraying. From a comprehensive perspective，pipeline cut-off flow control is the main way to achieve variable spraying，and three control algorithms of segmented control，pulse width modulation，and PID control of flow control were analyzed from the perspective of technical principles，implementation processes，and optimized applications. After the discussion，it is believed that PID control based on machine learning will be an important direction to improve traffic control performance. With the continuous development of artificial intelligence technology，plant protection robots that integrate intelligent perception，analysis and decision-making and autonomous operation capabilities will become the mainstream development direction of plant protection machinery in the future.

Agricultural machinery driverless system is the basis for realizing precision agriculture. Research and development of agricultural machinery driverless system is an effective way to alleviate the shortage of labor force and realize precision agriculture. This paper introduces the latest progress in the navigation and positioning technology, navigation path planning technology and automatic steering technology of agricultural machinery in China and abroad. The navigation and positioning technologies of agricultural machinery based on GPS positioning technology, Beidou positioning technology and visual navigation are expounded respectively. The global path planning algorithm based on full coverage path planning and global point-to-point path planning is expounded. Local path planning based on obstacle avoidance and tracking, and automatic steering technology based on motor power and electronic hydraulic control. These technologies have been relatively mature after years of development, and have been widely applied in agricultural production practice. However, there are still many problems, including the positioning technology is vulnerable to environmental interference, the utilization rate of path planning technology data is low and the dependence on environmental information is high, and the automatic steering technology is complex in the modification process, and it is easy to damage and difficult to maintain in harsh field operations. Based on the above, it is proposed that integrated navigation, multi-sensor fusion technology and modular automatic steering device are the future research directions of agricultural machinery unmanned driving system.

Aiming at the lack of on-line monitoring system of rice harvester's crushing rate, impurities rate and loss rate, this paper constructs an on-line monitoring system of rice harvester's operation quality. The GPS module in the system can realize the real-time monitoring of field operation speed and operation position. On-line detection devices are used to monitor the crushing rate, impurities rate and the loss rate during field operations. Each function module realizes data communication with a man-machine interaction system through CAN bus. A field experiment was carried out to verify the accuracy of the system. The results show that the accuracy of the on-line monitoring system for the rice harvester operation quality is 82.76% for crushing rate, 78.69% for impurities rate, and 73.53% for loss rate. In the field test, when the manual test results of operation quality increase, the system test results increase correspondingly, and when the manual test results decrease, the system test results decrease correspondingly. Therefore, the detection results of manual and system on the change trend of operation quality are consistent. Therefore, the on-line monitoring system of operation quality of rice harvester constructed in this paper can realize visual monitoring, give an alarm in time when the working quality of harvester becomes worse and provide powerful technical support for intelligent rice harvester and research on adaptive control strategy.