Objective  There is a low degree of mechanization in China, especially the lack of machinery for hilly orchards. At present, the flower thinning, fruit-separated, bagging, picking and other heavy works of orchards mainly rely on artificial ladders. In order to improve the harvest efficiency, safety and stability of orchard harvesting machinery, we designed an automatic-leveling high-position platform suitable for apple orchards in hilly areas.

  Method  Based on the characteristics of orchard terrain and the height of fruit trees, the design requirements and leveling methods of the platform, the size of different parts of pitch and roll, the thrust required by the hydraulic cylinder, the relationship between platform angle and the displacement of hydraulic cylinder were determined. A mathematical model of the platform control system was established. Then, we used an incremental PID controller to simulate the control leveling performance in Simulink with different interference signals. An extreme inclination slope experiment in Adams was designed, where the platform was simulated to verify the safety under different postures, different lifting heights and varied loads.

  Result  The mathematical relationship of each part was established, and the basic dimensions of each part were determined so as to establish the three-dimensional model of the platform. In the control system simulation, the pitch and roll control systems can quickly return the platform to the horizontal position under the step interference signal. The leveling time was 1.6 and 2.1 s, respectively, and the overshoot was 0. Under the sinusoidal interference signal, the pitch and roll control system can keep the platform near 0°, and the fluctuation range was between 0.15° and 0.19°. The limit tilting slope simulation experiment of the platform revealed that the platform’s tilting stability decreased with the increase of lifting height and load. Compared with the case without leveling, the minimum limit tilt angle with leveling increased by 24.77%, so the safety of platform significantly improved.

  Conclusion  The designed automatic leveling high-position platform in orchards can always maintain level under different interferences, with good anti-tilting ability, safety and reliability, and can meet the needs of hilly orchards.