Abstract:
Grapevine lifting onto trellises has been one of the most important procedures during grape production in the spring. Mechanizing this procedure is crucial to the grape industry in northern China. In this study, a star-wheel finger-chain device was designed for grapevine lifting during mechanized trellising in spring. The device consisted of a star-wheel finger-chain and a crank-rocker mechanism. Among them, the vine picking mechanism was used to lift the grapevines from the ground during operation, and then the star-wheel finger-chain mechanism was used to raise them at the target vine-lifting angle. Theoretical analysis was carried out to determine the structural parameters of the key components, such as the length of the finger, the distance between fingers, and the length of the chain plate. The Multi-Body Dynamics (MBD) was used to simulate the interaction between the device and the grapevines. A simulation model was established in the RecurDyn software. The rotational speed of the crank-rocker, the rotational speed of the sprocket, the spring pre-load, and the chain plate inclination angle were selected as the experimental factors. The average lifting angle and the coefficient of variation of the angle were used as the evaluation indexes. A Box-Behnken (BBD) simulation experiment was conducted to optimize the operating parameters. Finally, the soil bin tests were carried out to verify the performance of the device under the optimal parameters. The structural parameters of the key components were determined after tests. Specifically, the length of the finger was 130 mm, the grabbing gap was 80 mm, the distance between adjacent fingers was 177.8 mm, the chain plate inclination angle was 45°, and the effective conveying length of the finger-chain was 700 mm. Simulation results showed that the influencing factors on the average lifting angle were ranked in descending order: the rotational speed of the sprocket, the rotational speed of the crank-rocker, the spring pre-load, and the chain plate inclination angle. In the coefficient of variation of the angle, the influencing factors were ranked in descending order of the rotational speed of the crank-rocker, the spring pre-load, the rotational speed of the sprocket, and the chain plate inclination angle. The optimal combination of the parameters was obtained: a crank-rocker rotational speed of 51 r/min, a sprocket rotational speed of 66 r/min, a spring pre-load of 27 N, and a chain plate inclination angle of 45°. As such, the average lifting angle in the simulation test was 44.9° with a coefficient of variation of 9.83% under the optimal combination. In the soil bin test, the average lifting angle was 44.7° with a relative error of 0.44%, compared with the simulation. The coefficient of variation was 6.76% with a difference of 3.07% from the simulation. The pole-picking and finger-support device was achieved in the step-by-step lifting of grapevines. The MBD model was established to accurately simulate and optimize the lifting device. The stable lifting angle and excellent uniformity can be expected to fully meet the requirements of grapevine trellising. The finding can also provide a strong reference to an integrated machine for the grapevine lifting and tying in the grape industry.