Abstract:Aiming to solve the problem of poor adaptability in the process of mechanized banana crown-cutting, an adaptable banana crown-cutting device by stalk-surrounding and insert-cutting was designed, which was based on constant-force mechanism, and the radial adaptability and rotational adaptability of banana crown-cutting device were analyzed. A constant-force mechanism was introduced in the device, including two oblique compression springs provided negative stiffness and one horizontal compression spring provided positive stiffness, which enhanced the radial adaptability of the device. The force-displacement characteristic curves and stiffness-displacement characteristic curves of the constant-force mechanism were analyzed and the key parameters were also optimized. The stiffness coefficient of oblique spring in the constant-force mechanism was 12N/mm and the stiffness coefficient of horizontal spring was 3N/mm. In the initial state, the inclination angle of the oblique spring was 36.87°. The diameter of the enveloping circle was 80~100mm when the device was in constant force state, meanwhile, the constant force was 180N. Based on the Hooke hinge, reversible cutting platforms that can release two free rotational degrees were designed. The cutting platforms’ rotational angle was set as ±10°, according to the curvature of banana stalks. According to the geometric parameters of the established 3D model, the working space at the end of the cutter was a spherical surface with a radius of 300mm. The flexibility matrix of the cutter-end was analyzed. The result showed that when the rotational angle of the cutting platform was 0°, the flexibility of the cutter-end was the largest and the maximum value was 0.8182mm/N,and when the rotational angle of the cutting platform was 10°, the flexibility of the cutter-end was the smallest and the minimum value was 0.77mm/N. The results showed that the flexibility of the cutter-end was decreased gradually when the cutting platforms’ reversal angle became bigger. The tests showed that 81.25% of samples fulfilled requirements, the quality of the incisions were good. The machine, which was reasonably designed, fulfilled the requirements of banana crown-cutting.
