# The Current Development Status of Agricultural Machinery
## 4. Chassis Leveling Systems of Agricultural Machinery
### Mechanisms and Methods for Leveling
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Leveling Mechanism** & **Core Advantages** & **Performance Limitations** & **Performance Indicators** & **Suitable Application Scenarios** \\ \hline Hydraulic Differential Height Type & Excellent contour operation performance; simple particular; good slope adaptability & Poor lateral stability on uphill slopes; ground adhesion loss \(>\) 15\% & Maximum climbing angle: 20–25\({}^{\circ}\); energy consumption per unit mass: 3.2–4.0 kJ/kg\(\cdot\)km; leveling error: \(<\)1.5\({}^{\circ}\); response time: 0.8–1.2 s & Sloping terrain with gentle undulations; contouring on stapping terrain \\ Parallel Four-Bar Linkage Type & Simple structure law failure rate & Limited leveling freedom (single axis); slow dynamic response time: \(>\)2 s; maximum climbing angle: 35–40\({}^{\circ}\); energy consumption per unit mass: 2.5–3.2 kJ/kg\(\cdot\)km; leveling error: \(<\)0.8\({}^{\circ}\); response time: 0.5–0.9 s & Sloping terrain with gentle undulations; contouring on stapping terrain \\ Adjustable Center of Gravity Type & High traction efficiency; good uphill stability; excellent slope adaptability & Complex structure; requires multi-layer chassis & Sleep slope ascent/descent operations; sleep slope \\  & High adaptability to targeted terrain; small turning radius; high flexibility; compact structure & Unsuitable for large-gradient slopes; high cost; complex structure; requires skilled operators & Maximum climbing angle: 25–30\({}^{\circ}\); angle: 25–30\({}^{\circ}\); energy consumption per unit mass: 2.8–3.5 kJ/kg\(\cdot\)km; leveling error: 1.2–2\({}^{\circ}\); response time: 0.4–0.7 s & Rugged slope surfaces; small fragmented plots; gentle slope surface undulations \\ Omnidirectional Leveling Type & High traction efficiency; superior uphill stability; outstanding slope adaptability & High cost; complex maintenance; complex structure; response time: 0.8–2.4 kJ/kg\(\cdot\)km; leveling error: \(<\)0.5\({}^{\circ}\); response time: \(<\)0.3 s & Steep slope ascent/descent operations; steep slope surface undulations \\ \hline \end{tabular}
\end{table} 
Table 3: Comparison of leveling mechanisms in agricultural machinery chassis. et al. [123] introduced a dual cascaded control architecture for combine harvesters based on gray-box modeling. By applying third-order transfer functions to describe the asymmetric dynamics of hydraulic actuators and establishing posture-stroke mapping, they revealed geometric coupling mechanisms between roll angle (dependent on stroke difference) and pitch angle (dependent on stroke sum), enabling coordinated stability control. [PERSON] et al. [124] designed a multi-degree-of-freedom suspension topology system that demonstrates strong terrain adaptability even under imprecise leveling constraints. Domestic research on leveling machinery has made significant progress in structural design and optimization. As illustrated in Figure 12a, the crawler-type leveling tractor developed by Chongqing Xinyuan Agricultural Machinery incorporates a four-point hydraulic leveling mechanism that dynamically balances the vehicle by adjusting the contact area of the tracks in real time. Zoomlion's PL2304 paddy field tractor (Figure 12b) utilizes coordinated servo motor and planetary roller screw actuation, achieving a leveling response time of \(\leq\)0.8 s. This system enables dynamic adjustment of support leg extensions while maintaining a maximum leveling error of \(\leq\)0.8\({}^{\circ}\) during paddy field operations. The DF404-5A orchard management machine developed by Changzhou Dongfeng Agricultural Machinery employs a bionic quadruped hydraulic leveling chassis, which realizes vertical compensation based on pressure sensor data and vehicle mass distribution models. Shandong Wuzheng Group, in collaboration with Shandong Agricultural University, has developed a torsion-frame mountain tractor (Figure 13) that demonstrates enhanced adaptability to sloped terrain through frame torsional articulation [125].