# The Current Development Status of Agricultural Machinery
## 4. Chassis Leveling Systems of Agricultural Machinery
### Mechanisms and Methods for Leveling
Meanwhile, Professor [PERSON]'s research team at Northwest A&F University has developed an  
Figure 11: Foreign slope-adaptive leveling agricultural machinery. (**a**) John Deere 8R-3004 Tractor; (**b**) CR9070 Mountain Tractor; (**c**) Ferrari K10s Mountain Tractor. omnidirectional-leveling unmanned crawler tractor for use in mountainous areas. This system integrates parallel four-bar linkages with dual-frame mechanisms to achieve full-range leveling, significantly improving operational stability and safety on inclined surfaces. The working principle is schematically presented in Figure 14[126]. Figure 12: Domestic leveling agricultural machinery and equipment (China). (**a**) SR1002 (G4) Tracked Tractor; (**b**) Zoomlion PL2304 Paddy Field Tractor. Figure 13: Torsion-articulated mountain tractors. (**a**) Lateral Slope Climbing; (**b**) Longitudinal Slope Climbing; (**c**) Non-Torsion State; (**d**) Torsion-Articulated State. Domestic scholars have made significant advancements in the design of leveling mechanisms. To address issues such as excessive machine tilt, reduced operational quality, and safety hazards during operations in hilly and mountainous terrain, [PERSON] et al. [127] developed an omnidirectional automatic leveling system for tracked machinery based on a three-layer articulated frame structure (Figure 15). This system enables posture adjustment across pitch, roll, and compound inclination conditions. It also incorporates a sliding mode synchronous control method enhanced with disturbance observers to minimize synchronization errors among hydraulic cylinders and improve leveling accuracy. [PERSON] et al. [128] proposed an omnidirectional leveling approach using a four-point adjustable hydraulic chassis for tracked combine harvesters operating in complex environments. Through multi-body dynamics simulations conducted on the ADAMS virtual prototype platform under slope climbing, lateral tilt, and compound posture scenarios, the system demonstrates a notable reduction in rollover risks caused by center-of-gravity (CoG) shifts, achieved through coordinated control strategies involving four hydraulic cylinders. [PERSON] et al. [129] designed a legged-wheel unmanned chassis inspired by locust biomechanics, incorporating pneumatic-hydraulic hybrid actuation. The leveling control system integrates dual-axis (pitch/roll) posture sensing, virtual leg coordination control, and center-of-gravity dynamic compensation algorithms. As a result, the system achieves significantly improved leveling speed and precision, outperforming conventional systems. [PERSON] et al. [130] addressed the  
Figure 14: Omnidirectional leveling principle of mountain tractors. (**a**) Lateral Leveling Schematic Diagram: 1. Slope; 2. Travel System; 3. Master–Slave Linkage Mechanism; 4. Lateral Leveling Hydraulic Cylinder; 5. Lower Chassis. (**b**) Longitudinal Leveling Schematic Diagram: 1. Tractor Body; 2. Upper Chassis; 3. Track Tensioning Wheel; 4. Track; 5. Longitudinal Leveling Hydraulic Cylinder; 6. Fixed Wheel; 7. Track Carrier Wheel; 8. Floating Wheel; 9. Floating Wheel Bracket; 10. Slave Link; 11. Truck Frame; 12. Lower Chassis; 13. Lateral Leveling Hydraulic Cylinder; 14. Master Link; 15. Drive Wheel; 16. Dual-Chassis Mechanism. risk of tipping during slope operations of self-propelled corn harvesters by developing a dynamic balancing control strategy based on a dual-degree-of-freedom (DoF) leveling mechanism. The system integrates lateral (\(-\)10-17\({}^{\circ}\)) and longitudinal (\(\pm\)43.1\({}^{\circ}\)) hydraulic modules into a multi-body structure containing 24 kinematic pairs. A geometric kinematic model was established to correlate cylinder displacement with machine posture, enabling full-range compensation under four-quadrant compound tilt conditions. [PERSON] et al. [131] introduced an active leveling system based on parallel four-bar linkages. Through modeling of tractor lateral slip, they identified imbalanced lateral torque and non-uniform ground pressure distribution as the primary causes of sideslip. [PERSON] et al.