# The Current Development Status of Agricultural Machinery
## 3. Chassis Travel Mechanism System of Agricultural Machinery
### Tracked Classis Systems
[106] developed a standardized driver posture model to evaluate the structural integrity and load-bearing capacity of tracked harvesters. The experimental results indicated stable operation under 3.5-ton loads across speed ranges of 1 m/s, 1.5 m/s, and 2 m/s. [PERSON] et al. [107] proposed a vertical stress distribution model at the interface between rubber tracks and soil, which improved predictions of soil stress and compaction risks for tracked agricultural vehicles. [PERSON] et al. [108] conducted field measurements and simulation analyses of the MHT 8002 HV tracked harvester, identifying that average ground pressure remained \(\leq\)70 kPa. Dynamic load, effective contact length, and track tension were identified as key influencing factors, offering insights for balancing chassis stability with soil protection. [PERSON] et al. [109] explored both straight-line and in situ steering principles of conventional single-side braking gearboxes to reduce soil compaction and residue accumulation. Based on this analysis, they designed and manufactured a bidirectional steering gearbox prototype, which demonstrated smooth steering performance without soil buildup. [PERSON] et al. [110] analyzed the mechanisms and influencing factors of soil compaction caused by tracked combine harvesters operating in waterlogged paddy fields. Their findings indicated that increasing travel speed effectively reduces compaction risks in rice stubble soils. [PERSON] et al. [111] conducted multi-speed compaction tests and revealed that self-excited vibrations from tracked harvesters induce soil \"bouncing phenomena,\" leading to increased structural damage in subsurface soil layers. [PERSON] et al. [112] proposed a novel integrated driveline-steering chassis design for tracked harvesters to overcome the limitations of conventional hydrostatic transmission systems, such as low transmission efficiency and large turning radii. They established a track-ground slippage dynamics model (\(\sigma_{1}=\frac{S_{S}-S}{S_{S}},\sigma_{2}=\frac{S-S_{S}}{S},\sigma_{1}, \sigma_{2}\) denote the slip ratios of the low-speed side and high-speed side tracks, respectively. \(S_{S}\) represents the actual travel distance (m) of the tracks, while \(S\) indicates the theoretical travel distance (m) of the tracks) combined with an empirical steering parameter correction model. By quantifying actual displacement deviations between the inner and outer tracks, their study revealed the direct influence of soil shear deformation on steering accuracy. [PERSON] et al. [113] developed a self-propelled tracked broccoli harvester that exhibits strong terrain adaptability and superior obstacle-crossing performance during field operations. In addition to conventional full-track chassis, the wheel-track hybrid chassis has emerged as a distinctive locomotion system that integrates the advantages of both tracked and wheeled configurations, playing an increasingly important role in modern agricultural production. This hybrid design typically incorporates traditional wheels on the front axle and track assemblies on the rear axle. Such a configuration enables agricultural machinery to maintain sufficient mobility for traversing soft, muddy, and uneven terrains while preserving the steering agility and operational convenience characteristic of wheeled systems. [PERSON] et al. [114] evaluated the seeding performance of conventional dual-wheel tractors compared with semi-track configurations. Field experiments demonstrated that the rear semi-track system (front wheels + rear tracks) offered significant improvements over the traditional dual-wheel setup (tires on both axles) during soybean planting operations. [PERSON] et al. [115] proposed a multi-body dynamics modeling approach to analyze the interaction between flexible tracks and soft soil.