Kinematics simulation and parameter optimization experiment for transplanting synchronous puncher

Plant fiber film can solve the weeding problem of organic rice cultivation, as opaque film disrupts the weed's photosynthesis; and it also can be completely degraded before the harvest. Nevertheless, rice seedlings are transplanted directly through the seedling-separating needles, which causes that the roots of seedlings are seriously damaged. In order to solve this problem, a transplanting synchronous puncher was designed based on general rotary transplanting mechanism, which mainly consisted of 4 parts, including seedling-separating needle, longitudinal puncher, transverse puncher and seedling-pushing device. With the motion of seedling-separating needle, the longitudinal puncher punched 2 longitudinal holes at first, and then the transverse puncher fastened to seedling-pushing rod cut the joint of the longitudinal holes. The structure parameter of transverse puncher could be chosen on the basis of seedling-separating needle and seedling-pushing rod. The width of transverse puncher was 15 mm, and the length of transverse puncher was 40 mm. So the longitudinal puncher was the key component, which decided the punching effect of the film hole. According to the equations of puncher and seedling-tip's motion and the constraint condition of operation process, the structure parameter of longitudinal puncher was calculated in theory, which was that the length of longitudinal puncher was from 50 to 70 mm, and the angle between puncher and needle was from -10° to 10°. The three-dimensional (3D) model of transplanting synchronous puncher was built by the Solidworks, and the virtual prototype was simulated by the automatic dynamic analysis of mechanical systems (ADAMS) to analyze the key points' motion trails of longitudinal puncher. A virtual orthogonal test of 3 factors with 3 levels was performed with the simulation model. The rotational speed selected was 225, 250 and 300 r/min. The length of longitudinal puncher was selected to 50, 65 and 80 mm. The angle between puncher and needle included -20, 0 and 20°. The length of film hole and the deviation between film hole and needle were selected as the response function. Experimental results indicated that the rotational speed had the most significant effect on the length of film hole, followed by the length of longitudinal puncher, and the angle between puncher and needle was the least. Since the longitudinal puncher was mounted on the needle, the length of film hole changed with seedling distance. Seedling distance was codetermined by rotational speed and forward speed, and forward speed maintained constant during the process. For the deviation between film hole and needle, the contribution rate from high to low was as follows: the angle of puncher and needle, the rotational speed and the length of longitudinal puncher. Meanwhile the optimization result of structure parameter should meet the agronomic requirements. Under the condition of the 3 seedling distances 120, 140 and 160 mm, the length of longitudinal puncher was 65 mm and the angle between puncher and needle was 0°, the length of film hole was in the range of 31.8-42 mm, and the deviation between film hole and needle was in the range of 0.21-0.78 mm. To verify the optimization results, a transplanting synchronous puncher testbed was fabricated according to the parameter design and simulation result. The experiment was conducted on August 30, 2015 at the laboratory of Northeast Agricultural University. Based on the testbed, the optimization results were obtained. According to the actual situation that the deviation between film hole and needle couldn't be measured, the percent of pass of film hole was selected as the evaluation index. The verification results were as follows: the length of film hole was in the range of 23.8-43.14 mm, and the percent of pass of film hole was over 92%. It shows the transplanting synchronous puncher not only meets the requires of film hole, but also has a high efficiency. The study provides useful insights for the related design and has an important significance.