## 1 Introduction  
Precision sowing techniques have long been a specific requirement for achieving precision seeding [1, 2], and site-specific precision sowing techniques have a key role in promoting maize root development and improving maize yield [3, 4]. The sowing depth consistency, as one of the important indicators of the precision sowing level, is influenced by factors including the surface straw cover density, soil texture changes and topographic changes [5, 6, 7]. Especially since the development of conservation tillage technology, the amount of straw residue cover in the field has increased greatly, resulting in the inability of the seeder to obtain sufficient downforce to ensure a stable groove depth [8, 9]. Downforce is the load applied to the row unit, including the self-weight of the unit and the additional load applied by the profiling mechanism, which is vertically downward and plays a vital role in maintaining a stable and consistent sowing depth [10]. The soil compaction force of the row unit is the remaining load after the downforce systems have applied enough force to engage the disk openers to the target sowing depth and is referred to as the gauge wheel load [11]. However, applying more downward pressure than expected will inevitably result in an overload of the soil compaction force, and it can easily cause excessive compaction of the seed groove. This makes it difficult for the seeds to penetrate the wall for rooting and germination and affects the consistency of corn emergence [12; 13]. In the face of the complex and variable external soil environment, it is necessary to strengthen the research on the control of the row unit downforce. In most areas of the country, mechanical profiling row units are still used, and the downforce of these units is limited by the performance of the springs. The number of springs and the pretightening force need to be adjusted manually according to the actual soil conditions before operation [14]. However, the spring mechanism cannot precisely control the value of the downforce in the face of a complex soil environment, nor can it better suppress the vibration of the machine caused by ground heaving, which is likely to cause problems, such as too shallow seed grooves and regional soil compaction. In order to realize the automatic regulation of the downforce, scholars mostly use hydraulic or pneumatic methods to manage the downforce of seeders [15]. Both hydraulics and pneumatics are the application of fluid power. Hydraulic systems use liquids such as oil to transmit power, whereas pneumatic systems use air to transmit power. A pneumatic system has a cleaner energy source, and its structure is relatively simple. The unlimited supply of air and the ease of compression make pneumatics widely used by agricultural machinery [16; 17]. [PERSON] et al. [18; 19; 20] developed a sowing depth measurement model to adjust the downforce of the row unit by airbag actuation. It is able to maintain a better sowing depth consistency than mechanical downforce regulation. [PERSON] et al. [21] developed the sowing depth quality monitoring and evaluation software based on the pneumatic downforce adjustment device. Tests were conducted at a 6 to 10 km\(\cdot\)h\({}^{-1}\) vehicle speed and the sowing depth data were measured: the mean, pass rate, standard deviation and coefficient of variation were 50.01 mm, 78.9%, 8.95 mm and 17.9%, respectively. Air for pneumatic use is easier to obtain, but on seeders, oil for the hydraulic system can be supplied directly from the tractor system. For hydraulic drives, it is equally convenient and easy. Compared to pneumatics, hydraulics can handle higher loads than pneumatics. Moreover, hydraulics are more accurate and stable than pneumatics in controlling the stroke of the seeder profiling mechanism [22]. Therefore, hydraulically driven profiling devices have been widely studied by scholars [23]. [PERSON] et al.