During the operation of the rice combine harvester， the fuselage tilts due to the tilt and unevenness of the ground affect its maneuverability and operational reliability. Aiming at the problem of leveling due to the tilt of the field surface， this research developed an innovative dual-parallelogram chassis lifting mechanism for rice harvesters designed a hydraulic system to adjust the chassis height by extending the cylinder. Using Adams simulation software， a detailed model of the lifting chassis was constructed to analyze its performance， revealing a direct correlation between the hydraulic cylinder extension and chassis elevation. Notably， the mechanism could achieve leveling on slopes with inclination angles of up to 7.5°. Comprehensive evaluations of the liftable chassis system were conducted under both static and dynamic conditions. In the static tests， the system exhibited the capacity for comprehensive or unilateral auto-leveling contingent upon the tilt， with leveling times and angular variations confined to 3.6 s and ±0.4°， respectively. In dynamic tests conducted on sloped fields and paddy soils， the system reduced post-leveling mean tilt angles and standard deviations remained below 1.2° and 0.6°， respectively. These results demonstrated a substantial improvement in the stability and reliability of the chassis during operations. This research provides valuable insights into the design and optimization of automatic leveling mechanisms and structural innovations for harvester chassis.

In order to address the issues of large inclination angles and poor pass ability encountered by small-scale combine harvesters operating in hilly regions，a design and experimental study were conducted on an automatic lifting hydraulic system for the combine's chassis. This research developed the overall structure of the automatic lifting hydraulic system for the chassis，designed and selected key components such as hydraulic cylinders with built-in displacement sensors and directional proportional valves，and proposed methods for leveling and lifting the chassis by extending or retracting the hydraulic cylinders based on the transverse inclination angle. The study employed two leveling modes：automatic and manual，to level the chassis. The hydraulic system was simulated using AMEsim software，revealing stable pressure and flow within the hydraulic cylinders during direction reversing，along with smooth displacement velocity. A leveling control strategy centered on a PLC controller and PID control method was designed，which adjusted the length of the hydraulic cylinders to regulate the chassis's attitude and to conduct a static leveling experiment. Results indicated the proportional directional valve，when adjusted to a position between 20% and 45%，it can effectively regulate the velocity of both the extension and retraction movements of the hydraulic cylinders. The adjustment time increased with larger inclination angles，but the overall adjustment error remained below 0.5° within an inclination range of 7.7°，which can meet the requirements for transverse leveling of the combine harvester's chassis. This research introduced a hydraulic system and control method to realize leveling based on the transverse angle，providing a reference for the design of the chassis leveling hydraulic system for small-scale combine harvesters.