## 3 Precision Sowing Conditions of consistent Sowing-Depth Regulation
### Consistent Sowing-Depth Regulation Technology--Soil Compacting
At present, the soil-compacting device in the traditional viscosity-reduction and resistance-reduction technology is mainly seen in the soil-compacting roller research, based on the existing device to optimize the design [62], while the bionic-viscosity reduction and resistance-reduction technology is designing a new device with the principle of the structure and function of living organisms [63]. In terms of soil-compacting pressure regulation, the real-time regulation of the soil-compacting pressure of the soil-compacting roller is in the initial stage, and most soil-compacting devices do not have the real-time adjustment function. A few realize the real-time adjustment function, but the accuracy needs further improvement. [PERSON] et al. proposed a real-time measurement method based on soil firmness for the problem of the complex and inaccurate measurement of the compacting pressure of the soil-compacting device in the seeding operation. The model can achieve accurate real-time measurement of the soil-compacting pressure, which provides a technical basis for the subsequent research on real-time regulation of the soil-compacting pressure. The detection method did not achieve the regulation of the soil-compacting pressure of the ballast roller, and only reached the real-time extraction of the soil-compacting pressure [64]. [PERSON] conducted a study on the soil-covering and compacting device of a corn seeder to achieve indirect control of the sowing depth during operation by real-time adjustment of the hydraulic pressure on the profiling mechanism and real-time regulation of the soil-compacting pressure by adjusting the spring elongation of the device's soil-compacting mechanism to ensure the requirement of soil compactness during operation [65]. Compared to the earlier domestic research, foreign precision-seeding monomer development, especially the soil-compacting device, can achieve a soil compacting operation in high-speed operating conditions. The research is becoming more and more mature. The existing research on soil-compacting wheels in China is based on the low- and medium-speed operating environment; promising research results have been achieved in recent years. However, in the high-speed operating environment, the research on domestic soi- compacting devices has a large gap in comparison to foreign countries. The John Deere Company designed a rapid adjustment device that can change the relative angle of the soil-compacting wheel and the soil-compacting pressure [66]. RFM AG developed a spring-coil soil-compacting device that can automatically de-soil and perform soil sealing during operation [67]. [PERSON] designed a claw-type soil-compacting device that does not adhere to excessive soil, and can be used for various large seeding units. The operation can be achieved by compacting the seed and soil in the center so that they are in close contact. Moreover, the side column can break the soil surface and avoid surface over-compaction [68]. In summary, the research on soil compacting devices at home and abroad can be divided into three areas. The first one is the design of the soil-compacting wheel to reduce viscosity and resistance. The overall innovative research is carried out by bionics, using insects and animals as reference prototypes to design the soil-compacting wheel with reduced resistance, to avoid slippage [69]. The second is the soil-compacting pressure regulation, the design of the device to effectively realize the sowing operation process of real-time control of the sowing depth and compaction, but only if the device has both soil covering and compaction functions and there is room for wireless transmission upgrades in the system control. The third type is soil compacting under high-speed operating conditions; the research is mainly carried out in foreign countries first; the soil-compacting device can realize the soil-compacting operation under high-speed operating conditions, and the investigation is becoming more and more stable.