Development of oblique-planting mechanism for sweet potato seedlings and its electric control system

Naked seedling transplanting is the main way of sweet potato cultivation, and planting operation is the key link of transplanting. Aiming at the problems of poor planting quality and low automation in planting machine of naked sweet potato seedlings in our country, according to the agronomic requirements for planting naked sweet potato seedlings in this study, a kind of oblique planting mechanism of naked sweet potato seedlings and its control system were developed based on the principle of four-link mechanism. The movement trajectory of the planting mechanism was studied by theoretical analysis and simulation, and the key structural parameters of the planting mechanism were determined. An electric control system of planting mechanism was constructed, which consisted of brushless DC motor, rotary encoder and PLC controller. Field experiments showed that when the target plant distance was 20 cm and the operating speed was 0.4-0.6 km/h, the operation quality index of transplanting reached the standard requirements. When the operating speed was 0.4 km/h, the operating performance was better than that of 0.5 km/h and 0.6 km/h. At this speed, the average coefficient of variation of plant distance was 6.71%, and the average passing rate of planting angle and depth were 94.3% and 95.0%, respectively. The comparative test results showed that compared with the traditional mechanical control, the electric drive control at 0.4 km/h, 0.5 km/h and 0.6 km/h speeds reduced the average coefficient of variation of plant distance by 6.25%, 6.37% and 6.19%, respectively, which could effectively solve the influence of the driving instability of the tractor power output shaft on the planting operation trajectory and plant distance.