Evaluation of a Crank-type Walking Cultivator for Upland Farming

Abstract

This research was conducted to evaluate feasibility of a crank-type walking cultivators for weeding in furrowed upland. Methods: A walking cultivator developed by RDA was selected and evaluated with its working speed (S), cultivation depth (CD) and weeding performance (WP). The evaluation was performed in upland field on July and August, 2012. Also kinematic analysis of the machine was performed to draw out design improvements. Results: S in flat, uphill and downhill were about 0.11 m s-1 , 0.11 m s-1 , and 0.13 m s-1 respectively. It was found that S had a low relevance with user conditions. The CD was 35 ~ 40 mm which was satisfied with the RDA guide for weeding machine. A wide variation was observed in values of WP depending on the growth stages of weeds and field conditions. The cultivator showed low performance in eliminating the well-grown weeds. Kinematic simulation revealed that high forward speed caused a high ratio of un-weeded area. Conclusions: The weeding performance of the cultivator was satisfactory for weeds in early growth stage but it showed difficulties in handling on up-slope and in entering up-land. Specifically, the weight of the cultivator was judged as overweight for female workers. The crank-hoe type cultivator was judged as unsuitable for small walking type machine due to weight of the four-bar linkage system. Kinematic analysis revealed that the ratio of crank speed to the ground speed must be 850 rpm s m-1 (255 rpm based on 0.3 m s-1) or greater to avoid uncultivated area. Selection of forward speed is a decisive factor in designing the weeding cultivator.

Multi-Objective Optimal Design and Development of a Four-Bar Mechanism for Weed Control

“…Moreover, four-bar linkage is a well-established mechanism in the path generation of tillage tools under the soil surface [24,[42][43][44][45][46]. Using a four-bar mechanism for weeding could improve some performance indicators of cultivators, such as optimal working depth and soil disturbance [14,25,47]. Nevertheless, there are only a few papers on designing or evaluating four-bar mechanisms for weeding, and there is a lack of studies on this topic [14,25,47]; furthermore, there is no study on the optimal design of mechanical weeders.…”

“…As regards the weeding requirements described in Section 1, the hand motion of farmers during the manual removal of weeds was the source of inspiration for designing and evaluating a cultivator [14,25]. A four-bar mechanism was employed in these studies to imitate this motion.…”

“…It is obvious that this approach exacerbated the above-said error-the mismatch between the desired and generated path. Other researchers [25] employed a four-bar mechanism having been developed by Rural Development Administration of Republic of Korea (RDA). Although there is not enough information about the path generation method of the mechanism, the authors of that paper discussed the drawbacks of the mechanism by means of simulation software.…”

“…Although there is not enough information about the path generation method of the mechanism, the authors of that paper discussed the drawbacks of the mechanism by means of simulation software. The dynamic simulation revealed that the synthesized path of the mechanism was far from the desired one, and such a mismatch is attributable to a wrong design method [25]. Both above-mentioned mechanisms have other serious drawbacks as they were designed without the inclusion of a transmission angle through the design process, which would lead to two different impractical mechanisms.…”

“…Nevertheless, vigorous soil movement would pose problems in narrow rows and bury young crop plants [17]. The weeding depth of cultivators should be over 30 mm and should not exceed 40 mm [19,25]. Accordingly, in order for cultivators to curb their depth of penetration, conditions such as a considerable planting depth and dry surface soil should be available [14].…”