Hilly and mountainous areas are characterized by complex, rugged terrain, steep slopes, narrow and winding operation spaces, and scattered natural or man-made obstacles such as field ridges and stone steps. These geographical features have posed substantial challenges to maneuverability, slope stability, and obstacle passing of conventional agricultural power chassis. It is an urgent demand for adaptable and efficient powered platforms in such regions. In this study, a micro articulated power chassis was specially designed to clarify the structural configuration and mechanism. The compact dimensions of 1650 mm × 1000 mm × 1100 mm were specifically improved for sufficient load bearing on narrow mountain roads, dense crop rows, and narrow field ridges. Mechanical articulated steering was adopted for the flexible folding and relative rotation between the front and rear frames. Turning radius was significantly reduced to fully meet the requirements of hilly areas, in terms of maneuverability, stability, and terrain trafficability. A multi-objective optimization model was constructed with three critical indicators as objective functions: the minimum turning radius (to enhance maneuverability in confined spaces), the maximum uphill stability angle (to prevent forward tilting during ascending), and the maximum downhill stability angle (to avoid backward tilting when traveling down slopes). These variables included the hinge position of the articulated structure and wheelbase parameters. Non-dominated sorting genetic algorithm (NSGA-II) was applied to optimize the Pareto best solution set. A wide range of schemes were used to balance these mutually conflicting goals. Systematic theoretical calculations and dynamic simulations were conducted on power transmission paths, articulated steering kinematics, and load distribution on sloped terrain. Three performance indicators were evaluated, including steering performance (evaluated by minimum turning radius and steering angle range), slope stability (quantified by longitudinal and lateral stability angles), and obstacle crossing (assessed by chassis posture during obstacle crossing). The simulation results demonstrate that the chassis was achieved the maximum articulation angle of 30.19°, indicating excellent maneuverability in narrow spaces; The maximum longitudinal and lateral stability angles reached 33.8° and 30.8°, respectively, indicating strong resistance to tilting on sloped terrain; when crossing obstacles with an average height of 165 mm, the chassis maintained continuous wheel grounding without any posture deviation, indicating excellent terrain adaptability. Field tests were conducted in a typically hilly agricultural area. The test data verified the reliability of the simulation. Once the rear frame was in an unconstrained state (consistent with actual operational conditions), both frames generated slight deflection due to uneven terrain loads and steering forces, directly leading to an increase in actual turning radius, compared with theoretical calculations. Geometric correction of the minimum turning radius was performed using measured frame deflection angles, where the average minimum turning radius was corrected to 2 145.55 mm. Additionally, the average articulation angle was 29.95° after measurement in field tests. It was highly consistent with the simulation (30.19°), thus verifying the accuracy of the first design. The chassis exhibited no overturning or sideslip under both unloaded and loaded conditions when traveling up and down a 24° slope or moving on a 15° lateral slope. Obstacle-crossing tests showed that the chassis successfully passed over 210 mm high field ridges and 150 mm high stone steps. Finally, a comparison was conducted on existing similar agricultural power chassis, in terms of maneuverability (minimum turning radius), slope stability (longitudinal and lateral stability angles), and terrain trafficability (maximum obstacle-crossing height). The micro articulated power chassis performed best to verify the practicability of the scheme, fully meeting the large-scale requirements in hilly and mountainous areas.

Deep-pine operation is often required for the high-power tractor for traction at present, leading to low operating efficiency. More importantly, the total power consumption of vibratory deep-pine operation is ever-increasing with the increase of vibration frequency. Therefore, there is an urgent need to carry out research on the high-efficiency vibratory deep-pine machine for high operational efficiency and low energy loss. In this study, a deep loosening machine was designed to cooperate with the cutting and local vibration. The loosening mode was adopted for the cutting first and vibration second, i.e. the front deep loosening shovel was fixed to break the soil. The angle of entry was always in the position of the lowest soil resistance. The rear shovel was vibrated around the shaft to loosen the soil. The soil resistance was reduced to increase the range of loosening for less crushing of soil, in order to effectively reduce the consumption of vibration energy. The discrete element method (DEM) was used to analyze the effect of cut-and-vibrate deep loosening on soil disturbance. Hertz Mindlin with Bonding model in EDEM was used to establish the contact model among soil particles. The cut-and-vibrate and traditional deep loosening were simulated to compare at the same time. The experimental model of the deep-pine shovel was established using SolidWorks2022 software and then saved in a format suitable for EDEM. The model was also imported into EDEM for constraining, driving, and simulation. The motion state of the simulation model was divided into two strokes of breaking and vibratory deep loosening, according to the actual vibratory during deep loosening. The cut-and-vibrate co-operative mode effectively reduced the tillage resistance of the deep-pine machine; The one-factor test showed that the optimal intervals operating speed and vibration frequency were 0.9-1.1 m/s, and 9-15 Hz, respectively; The orthogonal test demonstrated that the optimal parameters were obtained for the deep-pine operation: operating speed 0.96 m/s, tillage depth 300.24 mm, and vibration frequency 11.43 Hz. The actual performance of drag reduction was tested on the cut-and-vibrate deep-threader. The simulation was also combined with the best operating parameters of deep-threading. The field tests were conducted, where the forward speed of the tractor was set at 1.0 m/s, the operating depth was 300 mm, and the vibration frequency was set at 9, 12, and 15 Hz. The field test showed that the cut-and-vibrate deep pine machine shared the outstanding drag reduction under the same speed and plowing depth, compared with the non-vibrating deep pine machine. The plowing resistance was reduced by 15.43%-37.56%; The power consumption was reduced by 8.87%-32.32%. The drag reduction was the most significant when the vibration frequency was 12 Hz. The plowing resistance was reduced by 37.56%, the power consumption was reduced by 32.32%, the solidity of the soil was reduced by 74.11%, and the soil disturbance coefficient was 56.32%, and the deep pine depth of 309 mm, deep pine was reduced by 15 Hz. The stability coefficient for the deep pine depth of 30.9 cm was 98.16%. The deep pine depth and its stability were in line with the industry standard. The cutting and vibration co-production deep pine machine shared outstanding performance to reduce the resistance and consumption. The finding can provide a new reference to optimize the vibration deep pine machine.