Analysis and Design of a Spatial Planetary Noncircular Gear Train for Rice Seedling Transplanting Based on Three Given Positions

Abstract

HighlightsA method for solving a spatial transplanting mechanism with noncircular gears is proposed.A new mechanism for transplanting rice pot seedlings is proposed.A trajectory with a small lateral displacement at the preparation phase is obtained.The working performance is validated by simulations and field tests.Abstract. This study proposes a method of solving the parameters of a spatial planetary gear train with noncircular gears to meet the requirements of wide-narrow row pot seedling transplanting (WPST). First, the planetary gear train was simplified to a spatial open-chain 2R mechanism (planetary carrier). A kinematic model of the 2R mechanism was derived from the three given homogeneous matrices describing the spatial position and attitude information of grasping, extracting, and planting seedlings. Second, the length of each link, attitude of each rotation axis, and relative initial angles were calculated. The model for solving the transmission ratio was deduced. A spatial planetary gear train configuration with a single planet carrier and two-stage driving was derived, in which the middle axis could be determined by combining the selected configuration, represented trajectory, and transmission ratio of each gear pair. Finally, a planetary gear train combining a noncircular gear pair and a helical gear pair was used in the WPST mechanism design. Simulations and tests conducted on a prototype confirmed the correctness of the theoretical model and the practicality of the design. Keywords: Noncircular gear, Planetary gear train, Spatial trajectory, Transmission ratio, Transplanting mechanism.

Design of clamping-pot-type planetary gear train transplanting mechanism for rice wide–narrow-row planting

“…WPST is a planting pattern to plant rice seedlings in wide rows and narrow rows at the same planting density. In China, WPST of rice is mostly planted with a wide-row distance of 400 mm and a narrow-row distance of 200 mm [11,19] . As shown in Figure 1, the distance between adjacent seedling picking positions on the seedling box is 300 mm.…”

“…After the transmission ratio curve of the mechanism is obtained, various PGTMs that can realize spatial trajectory can be acquired by attaching different non-circular gear pairs to reduce the degree of freedom of the 2R mechanism [19] . In this study, the combined transmission of planar non-circular and non-conical gears is adopted.…”

“…In the study, the success rate of seedling picking is 90.15% when the mechanism rotation speed is 90 r/min, which is also higher than that of the previous clamping-pot-type transplanting mechanism [12] . Additionally, compared with the clamping-seedling-type transplanting mechanism of rice WPST in references [11] and [19], the seedlings planted by the clamping-pot-type PGTM for rice WPST has superior uprightness, which reflects the advantages of picking seedlings by clamping soil pots.…”

“…Sun et al [17,18] considered the posture of the transplanting arm when designing the transplanting of rice seedlings in reverse, but the trajectories realized using the mechanism are simple plane trajectories and cannot be used for the spatial trajectories required for WPST. When using the D-H matrix transformation to establish a reverse model of the spatial PGTM, a tedious problem in solving the higher-order polynomial equation occurs [19] .…”

Kinematic synthesis and simulation of a vegetable pot seedling transplanting mechanism with four exact task poses

“…Ge et al [19][20][21] proposed a new algorithm for mechanism synthesis based on kinematic mapping and conducted dimension and type syntheses at the same time, which improved the accuracy of the synthesis of a linkage mechanism. Zhao et al [22] proposed a unified method for accurate and approximate kinematic synthesis of spherical four-bar mechanisms based on motion mapping.…”