Bionic Design and Parameter Optimization of Rotating and Fixed Stem- and Leaf-Cutting Devices for Carrot Combine Harvesters

To solve the problems of the high rhizome damage and low net cutting during carrot combine harvesting, the following research was performed. The designed carrot stem- and leaf-cutting device was taken as the research object, and a bionic design idea was adopted. MATLAB software was used to extract and optimize the tibial curve of the mantis forelimb, and its shape was applied to the cutting edges of a single-disc rotating cutter and a straight fixed cutter, whose key structural parameters were determined. The kinematic and dynamic models of the cutter, stems, and leaves were established to explore the critical conditions of smooth cutting. A single-factor experiment was performed. The results show that the rhizome damage and the stems and leaf net cutting increased when the rotation speed of the clamping conveyor pulley increased. The flatness of the cutting surface first increased and subsequently decreased. At a speed of 102 r/min, the rhizome damage was 2.86%, the net cutting of stems and leaves was 92.82%, and the flatness of the cutting surface was 85.39%. The net cutting of stems and leaves and the flatness of the cutting surface increased as the disc cutter speed increased, while the rhizome damage decreased. When the rotation speed reached 165 r/min, the rhizome damage, the net cutting of stems and leaves, and the flatness of the cutting surface were 1.97%, 89.59%, and 91.48%, respectively. The bench test and field experiment results showed that the cutting performance of the optimized bionic cutter group is significantly better than that of the conventional knife group. The rhizome damage, net cutting of stems and leaves, and flatness of the cutting surface were 4.01%, 92.05%, and 84.05%, respectively, which meet the agronomic requirements for carrot harvesting.