# The Current Development Status of Agricultural Machinery
## 2 Power System of Agricultural Machinery Chassis
### Hybrid Power System  
The hybrid power system realizes dynamic coordination between diesel engines and electric motors through an innovative electromechanical coupling architecture. Its core features are manifested in three fundamental aspects: Firstly, a dual-mode power coupling mechanism based on planetary gear sets and intelligent control algorithms enables seamless transition between series and parallel operation modes, ensuring real-time torque compensation across diverse working conditions. Secondly, a multi-dimensional energy management strategy integrates braking energy recovery with power take-off (PTO) shaft reverse-drag power generation. This strategy, combined with state-of-charge (SOC) threshold control protocols, significantly enhances the duration of field operations. Thirdly, an intelligent redundancy design incorporates fault diagnosis systems to guarantee uninterrupted transitions between power sources under varying load demands. By addressing the operational challenges specific to hilly and mountainous terrain, the system effectively overcomes the limited endurance of purely electric agricultural machinery while reducing carbon emissions from conventional diesel-powered equipment. Furthermore, its design aligns with China's strategic development requirements for next-generation agricultural machinery. The operational principle of this oil-electric hybrid system is illustrated in Figure 8.  
Leading domestic and international enterprises have introduced hybrid tractors that achieve energy consumption reductions of 5-10% and carbon emission mitigations of 40-60% while effectively addressing adaptability challenges in hilly terrain. [PERSON] et al. [69; 70; 71] conducted comparative analyses between conventional and hybrid power systems, focusing on the performance characteristics of hybrid tractors equipped with electric continuously variable transmission (e-CVT) functionality. Using simulation techniques, they modeled and evaluated two parallel configurations, two series configurations, and one electro-hydraulic hybrid configuration. The experimental results indicated that the parallel configuration demonstrated superior peak power performance, whereas the series configuration achieved the highest fuel efficiency. The electro-hydraulic configuration was recommended as a viable alternative for engine downsizing. [PERSON] et al. [72] proposed a distributed hybrid electric tractor (DHET) architecture based on an AD-Extenics coupling design methodology. This approach enables intelligent electromechanical integration through powertrain hierarchical decomposition matrices and efficient operating range extension models, thereby establishing a theoretical foundation for future DHET powertrain innovations. [PERSON] et al. [73] developed a novel series-hybrid combine harvester by integrating series hybrid technology with distributed electric drive systems. They constructed mathematical models for key operational components, including chassis propulsion modules, which provide accurate references for selecting electric drive motors and matching hybrid system parameters. This approach simplifies the drivetrain structure while enhancing power transmission efficiency, offering new insights into improving the operational performance of combine harvesters. [PERSON] et al. [74] introduced a novel methodology combining multi-objective particle swarm optimization (MOPSO) and wavelet decomposition algorithms to overcome the limitations of hybrid tractor crash testing. This approach significantly enhances the reconstruction of impact vibration signals, offering substantial value in the design and evaluation of tractor safety performance. [PERSON] et al. [75; 76; 77] developed a hybrid electro-mechano-hydraulic composite powertrain system for tractors to address the challenges of high fuel consumption and poor operational stability under complex and harsh working conditions.