# The Current Development Status of Agricultural Machinery
## 2 Power System of Agricultural Machinery Chassis
### Hydraulic Power System  
The hydraulic power system of the chassis operates based on fluid dynamics and hydrostatic transmission principles, transmitting power through pressurized fluid to achieve energy conversion and precise control. As depicted in Figure 5, this system provides superior compliance, high torque output, and enhanced adaptability to complex operational conditions compared to traditional mechanical power systems. These advantages have facilitated its extensive adoption in agricultural machinery, including high-clearance crop protection equipment, harvesters, and specialized tractors. Western countries initiated the application of hydraulic drive systems in agricultural machinery as early as the 1970s, establishing substantial technological leadership compared to China. As shown in Figure 6, representative high-clearance self-propelled crop protection machinery from international manufacturers utilizes fully hydraulic-driven chassis to achieve high operational efficiency, providing superior maneuverability and stability. However, their large-scale chassis designs and high costs limit their suitability for China's hilly and mountainous terrains. Figure 5: Hydraulic powertrain architecture. In recent years, domestic researchers have made substantial advancements in the development of hydraulic-driven chassis systems. These efforts have significantly narrowed the technological gap between China and Western countries in agricultural machinery design and implementation. [PERSON] et al. [38] designed a specialized hydraulic-driven chassis tailored for paddy field machinery to address challenges related to operational stability and insufficient power output. Their research focused on the hydraulic behavior of critical components during system operation. The experimental results demonstrated that the chassis exhibits low deviation characteristics and enhanced anti-slip performance under sloped or rugged paddy field conditions. [PERSON] et al. [39] proposed an optimized design method for hydro-pneumatic suspension systems in high-clearance self-propelled sprayers based on an improved multi-objective particle swarm optimization (MOPSO) algorithm. This approach significantly enhanced vibration damping performance, demonstrating superior overall characteristics compared to conventional suspension systems. [PERSON] et al. [40] developed a hydrostatic chassis drive system for large-scale plant protection machinery. The system integrates a single-pump four-motor closed-circuit configuration with a flow divider valve to achieve anti-slip functionality, thereby improving operational stability. [PERSON] et al. [41] designed a novel hydraulic chassis for rice transplanters using a single-pump four-motor drive architecture. An anti-slip valve block was incorporated to effectively prevent slippage in the distributed hydraulic motors during operation. [PERSON] et al. [42] introduced a slip control strategy for hydrostatic drive systems in high-clearance  
Figure 6: Large foreign plant protection machinery. (**a**) John Deere R4030 Self-propelled Sprayer; (**b**) MAZZOTTI MAF Series Sprayer; (**c**) Dammann DT2400H Series Sprayer; (**d**) HAGLE STS Series Sprayer. sprayers. By establishing a bilinear relationship between slip rate and adhesion coefficient, this method effectively mitigates the negative effects of uneven terrain on driving stability. [PERSON] et al. [43] presented a hydrostatic drive system for high-clearance corn detasseling machines, incorporating a four-wheel independent suspension structure. Simulation and experimental studies confirmed that the suspension system can effectively reduce ground impact forces and improve the performance of the drive system. [PERSON] et al. [44] developed a fully hydraulic remote-controlled power chassis. Field tests demonstrated stable performance during uphill/downhill movement, ridge crossing, and ditch traversal, meeting the mobility requirements for hilly and mountainous terrains. [PERSON] et al.