Abstract
Soil compaction is an important procedure of precision seeding operation. In this paper, a precise downforce control system based on fuzzy PID was proposed in order to improve the quality of the soil compaction and the accuracy of setting working parameters. The conventional mechanism of seeders for soil compaction was optimised. The compressing spring of the compaction mechanism was replaced by a linear motor, which is actively controlled to adjust downforce in real time. A force sensor was connected in series with the linear motor to detect the actual downforce from a press wheel acting on soil. The detected downforce was employed as feedback for the fuzzy PID model. A slave real-time control system was constructed by using an STM32 microcontroller. A user interface was designed for the portable master computer system based on the ForLinx embedded platform to facilitate the setting of target downforce and display the actual downforce in real time. Meanwhile, it was able to adjust the system for different operating requirements, such as soil stiffness, moisture, and crop species. Experiments were conducted on a soil bin, and the results indicated that the active control system has better performance than the conventional passive system in downforce control. The downforce was stable with a variance less than 2.6% under different conditions, and it was 8.11% less than the conventional passive system.
Highlights
With the acceleration of agricultural development, researchers had done lots of works on the precise and active seeding [1, 2]
System Structure and Operation Principle. e structure of the system is shown in Figure 1. e system consists of a control system and mechanical structures. e control system includes a master computer system and a slave realtime control system, where the slave real-time control system contains a force sensor, a slave computer controller, a motor driver, a sensor signal amplifier, and a power supply
When the entire system works, the target downforce was set by using a user interface. e slave real-time control system detects loading forces exerted by the linear motor on the compaction mechanism using the force sensor. e slave real-time controller compares the value of the detected downforce with a target value to obtain the difference. en, the slave real-time controller can adjust the loading force on the press wheel by controlling the linear motor to eliminate the difference, so that the closed-loop control of the downforce is achieved. e master computer system was designed to display and store actual downforce values in real time
Summary
With the acceleration of agricultural development, researchers had done lots of works on the precise and active seeding [1, 2]. In order to achieve required soil compaction strength, the spring should be adjusted according to the experience of operators at the beginning of the work. Another novel innovation was used in a seeder whose unique character was to adjust loading forces on compaction mechanism automatically by using a hydraulic system [11]. If the downforce changed because of uneven soil condition, a hydraulic cylinder, part of the hydraulic system, was controlled by operators to ensure a consistent downforce to achieve a uniform SC, yet the results of the SC depended on the experience of operators. A fast, automatic, precise, and self-adjustable control system of the downforce was implemented
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