Design of a whole row pneumatic seedling pick-up device for fully-automatic field transplanters with reciprocating movement and intelligent control system

摘要

The pick-up device is the key to realize automatic transplanting, thus a whole row pneumatic seedling pick-up device for fully-automatic field transplanters were developed with reciprocating movement in the predetermined trajectory of picking end-effector and its intelligent control system. The pick-up device which consists of six or eight picking end-effectors, one tracing chute and frame were designed specifically. After designing the structural parameters of the mechanism to establish a closed-loop vector equation of the rod-group, we planned the required picking-trajectory by polynomial fitting. To verify the consistency of the simulated trajectory and theoretical trajectory, MATLAB combined with the envelope method was used to fit the shape ofthe track chute, then a 3D model of picking device was set up by SOLIDWORKS and a kinematics simulation based on ADAMS. The air cylinder and photoelectric sensor were used to control the reciprocating motion of the end-effector, which can move slowly toextract seedlings from the plug tray and return quickly to drop seedlings at designated locations in the predetermined trajectory. The coordinated control scheme of seedling transmission, picking and dropping was designed in detail, then a control program was compiled, which included seedling transmission accurately, seedling picking in vertical direction, and returning to fixed position rapidly for seedling dropping. After correcting the seedling dropping time of the cylinder, the results showed that when the cylinder thrust was 40 mm and the seedling pushing speed was 0.54 m/s, the optimal seedling pushing time should be 0.074s. The seedling dropping accuracy tests of the cylinder indicated that the average maximum deviation of seedling dropping position (AS) was 1.97 mm, when the frequency of seedling picking was 18 plants/claw/min, the minimum value of AS was 0.25 mm. To ensure the work efficiency while ensuring the picking quality, the working parameters were selected as frequency of seedling picking was 18 plants/claw/min, moisture content was 60%, depth of seedling picking was 40 mm and clamp angle was 10", the finally picking quality was 97.73%. This indicated that the designed pick-up device could meet the requirements of seedling picking and dropping reciprocating movement under the operation of the optimized control system.