Design and experiments of a precision sowing unit with the spoon clip for single peanut seed planting in plot

Seed sowing cannot fully meet the large and different sizes of the peanut plot in recent years. It is a high demand for high adaptability and qualification rate in the precision sowing of a single seed. In this study, a spoon-clip type of precision sowing unit was developed for the single seed in the peanut plot using STM32 single-chip microcomputer control system. A systematic investigation was made on the structures and parameters of key components, such as the ditching, seed metering, and seed distribution, as well as the hardware and software of the precision sowing control system. The main structural parameters and operation mode were then determined in the key components, such as the sowing monomer trenching, seed metering, and seed distribution. The mode of filling seeds was adopted first, and then the dropping seeds were adjusted for the clamping space of the scoop-clamp type seed metering device. The motor drove the seed metering device to feed a single seed into the double-grid seeding assembly. The detection elements (photoelectric sensor, and incremental encoder), and the executive elements (stepping motor) were controlled to realize the orderly filling and seeding in the double-grid seeding assembly. A control system was then designed using STM32 single-chip microcomputer. Furthermore, the system mainboard, power supply, photoelectric sensor, speed sensor, stepping motor, and hardware parts were selected to design the circuit, according to the working mode of the load. The C language was used to realize the detection and execution of the system in the process of uniform seed metering, precise seed distribution, orderly seed sowing, and efficient seed clearing in the single seed sowing unit. The step angle and the driver fraction were set to adjust the number of pulses for the desired angle, according to the pulse regulation mechanism of the stepping motor. The movement track was optimized for the single precision seeding unit in the scoop-clip peanut plot. The influencing parameters were determined as the operating performance of the machine, including the operation speed of the machine and the height of the seed opening from the ground. A single- and double-factor numerical simulation was carried out for the operation parameters of the machines, in order to improve the qualified index of single precision sowing seed spacing for the less missed sowing, replanting, and damage index during sowing. The influencing mechanism of seeding performance was explored to clarify the operation speed in the machines, the height of the seed opening from the ground, and the interaction between them. The test showed that the seeding effect of the machine was the best when the operating speed of the machine was 0.9 m/s, and the height of the seed opening from the ground was 15 cm. Specifically, the qualified rate of the seed spacing was 96.20%, the re-seeding rate was 2.97%, the broken rate was 0.50%, and the miss-seeding rate was 0.33%. The high trafficability and applicability of the whole machine can fully meet the requirements of the plot breeding test. This finding can also provide a strong reference to developing precision seeding technology in peanut plots.