Operating Speed Analysis of a 1.54 kW Walking-Type One-Row Cam-Follower-Type Cabbage Transplanter for Biodegradable Seedling Pots

Abstract

Improving the operational speed of cabbage transplanters is essential for precision seed-ling placement and labor efficiency. In South Korea, manual cabbage transplanting can demand up to 184 person-hours per hectare, often leading to delays during peak periods due to labor shortages. Moreover, the environmental urgency to reduce plastic waste has accelerated the adoption of biodegradable pots in mechanized systems, supporting global sustainable development goals. This study aimed to determine optimal working conditions for a 1.54 kW semi-automatic single-row cabbage transplanter designed for biodegradable pots. The cam-follower-based planting mechanism was analyzed to identify ideal forward and rotational speeds, while evaluating power consumption and seedling placement quality. The mechanism includes a crank-driven four-bar linkage, with an added restoring spring for enhanced motion stability. A total of nine simulation trials were conducted across forward speeds of 250, 300, and 350 mm/s and planting unit speeds of 40, 50, and 60 rpm. Simulation and experimental results confirmed that a forward velocity of 300 mm/s and crank speed of 60 rpm produced optimal outcomes, achieving a vertical hopper displacement of 280 mm, minimal soil disturbance (2186.95 ± 2.27 mm²), upright seedling alignment, and the lowest power usage (17.42 ± 1.21 W). Comparative analysis showed that under the optimal condition, the characteristic coefficient λ = 1 minimized misalignment and power loss. These results support scalable and energy-efficient transplanting systems suitable for smallholder and mid-sized farms, offering an environmentally sustainable solution.

1. Introduction

Cabbage (Brassica rapa subsp. pekinensis) serves as a vital raw material in the preparation of kimchi, a staple in Korean cuisine [1]. The cultivated area of autumn cabbage declined by 1.2%, decreasing from 13,152 ha in 2023 to 12,998 ha in 2024 [2]. In South Korea, the annual per capita intake of kimchi has been reported as 36.6 kg [3]. This reflects the prominent dietary role of cabbage in the country. To accommodate the consistently high demand for kimchi, cabbage cultivation now takes place throughout the entire year, rather than being restricted to autumn planting periods [4].

Vegetable cultivation primarily uses two distinct methods: direct seeding, where seeds are sown directly into the field (e.g., beans and okra), and transplanting, involving the initial raising of seedlings in nursery beds before transferring them into the field (e.g., cabbage and peppers) [5]. Manual transplanting is laborious and time-consuming, comprising around 40% of overall operational time and necessitating an estimated 184 person-hours per hectare [6,7]. This presents a significant difficulty during peak harvest seasons, which frequently encounter manpower shortages. To reduce dependence on manual labor and satisfy the growing need for vegetable production, the mechanization of agricultural operations, beginning with the labor-intensive transplanting phase, is essential [8].

Two primary approaches for seedling production in mechanized transplanting are the growing in plug trays [9] and the usage of biodegradable paper pots [10]. Transplanting from conventional plastic trays frequently results in root damage, but biodegradable trays facilitate undamaged transplantation, maintaining root integrity and promoting enhanced plant growth [11]. Plastic waste threatens agricultural sustainability by modifying soil physicochemical qualities, including bulk density, water retention capacity, and structure, while also enabling the infiltration of microplastics into groundwater aquifers [12]. In contrast, biodegradable seedling pots present a sustainable alternative, decomposing naturally in the soil after use and thereby reducing environmental pollution [13]. Biodegradable plug trays facilitate uniform seedling development and are well-suited for mechanical transplanting; however, their structural stability may be compromised during the trans-plantation process [14]. In line with the continuing shift toward agricultural mechanization, about 63.3% of upland farmland in Korea was cultivated using machinery by 2022 [15].

Transplanters incorporate multiple processes, including seedling selection, movement, metering, and planting, all crucial for optimal design [16,17]. The planting mechanism is essential, as the main objective of a vegetable transplanter is to precisely embed seedlings into the soil without inflicting damage [18]. The planter motion affects critical factors such seedling spacing, depth, alignment, planting rate, mis-planting rate, and overall operational efficiency [19]. During the transplanting procedure, the planter hopper must keep to an optimal trajectory that allows it to penetrate the soil with least exertion, place the seedling at the correct depth and orientation, and extract from the soil without disturbing the planted seedling [20].

To achieve this optimal trajectory and validate design parameters, kinematic and operating speed analysis is essential to guarantee the mechanism functions correctly [21,22]. Prior research has established transplanting systems through kinematic analysis. A clamping-stem mechanism using a double-crank linkage was modeled and optimized in MATLAB [23], and kinematic simulations were conducted to derive displacement trajectories of the seedling needles and motion characteristic curves [24]. Jiaodi et al. [25] developed the planetary five-bar transplanting mechanism, developed its kinematic model, and identified optimal parameters to satisfy motion trajectory specifications. Genetic algorithms were applied to optimize the link length of semi-automated transplanters, de-creasing weight while preserving trajectory precision [26]. A high-speed transplanter for processing biodegradable pot trays in diverse row and column configurations was introduced, employing circular blades with lateral movement for separating trays into individual cells at a pace of 60–90 plants per minute [5]. Recent developments in planting technologies have introduced precision-controlled metering systems specifically designed for vegetable transplanters. These systems often feature a 3-DOF articulated robotic arm integrated with automated seedling conveyors [27], optimized for handling tomato seedlings in eco-friendly degradable pots. Iqbal et al. [18] analyzed how different working speeds affect the functional efficiency and energy use of dibbling-type planters, aiming to pinpoint the optimal rate for operating a gear-assisted dibbling unit in pepper transplanting machinery. Reza et al. [28] improved planting efficiency by increasing the working speed of a rotary-driven planting setup in a self-propelled onion transplanter. Their objective was to determine the best movement speed for accurate seedling placement. Through a series of simulated scenarios, they assessed performance under variable conditions to identify ideal speed configurations for a newly designed linkage system. Furthermore, Paudel et al. [29] studied a hopper-based planting module in slow-moving, semi-automated vegetable transplanters, considering the integration of feeding systems compatible with biodegradable plug-tray seedlings.

Recent field and design studies highlight the impact of forward speed on planting precision and system synchronization. An integrated automatic transplanting system achieved ideal plant spacing and transplanting rates at a speed of 2.0 km/h with appropriate tray-feed timing [30], whereas a precise variable-rate potato electronic metering mechanism exhibited efficient mis-planting detection and replanting functionalities under controlled assessment [31]. A different study indicated that transplanting efficiency reached its peak (91.7% TE, 96.7% OE) at a velocity of 1.2 km/h, utilizing a metering system specifically designed for that speed range [32]. Investigations into cup-hanging planters at medium-to-high velocities demonstrated notable alterations in planter–soil interaction, potentially influencing insertion quality [33]. Finally, research on an onion transplanter revealed the necessity of aligning the rotation of the planting mechanism with the forward speed (1:1 ratio) to guarantee vertical planting and minimize errors [28].

The transplanter systems, including seedling selection, movement, and metering, must be synchronized with the forward speed of the planter unit to guarantee accurate seedling delivery [6]. Effective synchronization is essential for attaining uniform planting intervals, accurate planting depth, and comprehensive operating efficiency [34,35]. Higher speeds elevate the probability of inflicting mechanical harm to seedlings, disrupting plastic mulching film, and misaligning seedlings, thereby negatively impacting plant growth and overall production [36]. The planter unit speed must be thoroughly evaluated and calibrated to ensure optimal performance prior to finalization for transplanter operation. This study was a part of an overall study to develop a cam-follower-type semi-automatic cabbage transplanter for biodegradable pot seedlings. In this system, seedlings are manually fed into the transplanter, where a conveying hopper transfers them to the planter unit for transplantation. The objective of the paper was to investigate the influence of transplanter speed on transplanting performance, determining optimal working speeds for the double-parallel cam-follower-type planter unit to enhance efficiency, reduce potential damage to plants, and improve operator comfort.

2. Materials and Methods

2.1. Operational Principle of the Transplanting System

Cabbage seedlings are commonly positioned along elevated beds, typically arranged in either paired or single planting lines. A standard configuration involves spacing rows approximately 600 mm apart on the same ridge, with an intra-row distance of about 400 mm [37]. Prior to transplanting, these seedlings are nurtured in either plug trays or biodegradable paper containers, often placed within plastic holding trays. According to Seo et al. [38], cylindrical paper containers with dimensions of 40 mm in both diameter and height have shown to outperform plug trays by promoting stronger seedling development and enhancing transplant success. After roughly a month of cultivation, the young plants reach a suitable stage for field transplantation. Following around 30 days of growth, the seedlings attain the optimal stage for mechanical transplantation. At this juncture, they ought to be planted at a depth commensurate with the height of the seedling pot to guarantee good establishment and sustained growth [39].

Figure 1 presents the conceptual design of a semi-automatic, single-row walking-type cabbage transplanter currently under development. The machine is composed of three integrated subsystems that collectively accomplish the transplanting operation: a seedling feeding and extraction unit, a transport mechanism, and a precision soil-insertion system. The process begins with manual feeding, wherein seedlings grown in biodegradable pots are placed into the conveying device by the operator. Subsequently, the transport system (a) delivers the seedlings from the feeding tray to the planting section in a synchronized manner, ensuring minimal disturbance to the root plug. Finally, the insertion system (b) positions the seedlings into the soil at the desired depth and orientation, providing firm anchorage for subsequent growth [21]. For seedling insertion into the soil, the mechanism incorporates a crank-driven four-bar linkage coupled with a restoring spring to enhance motion stability (Figure 1b). The four-bar linkage governs the kinematic path of the planting element, enabling a controlled trajectory that reduces shock during soil penetration and ensures consistent planting depth. The crank input provides continuous motion, while the restoring spring mitigates vibrations and dynamic oscillations, thereby improving repeatability of the planting action. This configuration offers several technical advantages: (i) smoother motion transfer compared to cam-driven alternatives; (ii) reduced inertial loading on the linkage arms, which minimizes wear and extends service life; and (iii) improved synchronization between seedling release timing and soil penetration. Moreover, the adoption of a compliant spring element provides passive damping, allowing the system to absorb minor variations in soil resistance without compromising insertion accuracy. Collectively, these features contribute to enhanced stability, precision, and durability of the transplanting process under varying field conditions.

Unlike conventional semi-automatic transplanters, which often rely on rigid cup-type conveyors or complex mechanical arms, this design emphasizes modularity and simplified kinematics to achieve accurate placement while reducing mechanical complexity and operator fatigue. The coordinated functioning of these subsystems is expected to improve transplanting precision, enhance operational efficiency, and provide adaptability for biodegradable pot handling, thereby addressing key limitations of existing mechanized transplanting systems.

Seedlings are individually retrieved from the tray and subsequently delivered to the seedling conveyor through a transport mechanism. At the bottom of each row, two compaction wheels are affixed to compress the soil, thus preserving the integrity of the mulch film and ensuring the seedlings remain upright post-transplantation. The planting unit integrates several fundamental mechanical components, namely, the driving, connecting, driven, and supporting links, as well as a planting hopper. The driving mechanism functions according to a crank-rocker principle, while the supporting link anchors the driven element to the base structure. A lengthened lever serves to connect downstream linkages with the hopper and simultaneously accommodates a cam–follower mechanism that orchestrates the cyclical opening and closing of the hopper jaws during the seedling handling and deposition process. As the vertical and horizontal rotary motions generate an elliptical planting trajectory, the hopper collects cabbage seedlings at its uppermost rotational point after receiving them from the conveyor. At this stage, the cam nose remains disengaged from the follower, ensuring the hopper jaws remain shut. As the hopper descends toward the lowest point of its path, the cam nose re-engages the follower, prompting the opening of the hopper jaws and releasing the seedlings into the soil. This cycle is repeated with each planting instance. Figure 2 shows the procedure in which seedlings are retrieved from the conveyor and subsequently replanted into the soil. The rotational motion of the planting apparatus, coupled with the linear travel speed of the transplanter, jointly determines the ideal operational conditions required for consistent and effective seedling transplantation.

The key variables and parameters used in the trajectory modeling and simulation are listed in

Table 1. Notations, definitions, and units of variables.

Notation	Definition and Unit
${\mathrm{v}}_{\mathrm{t}}$	Linear velocity of the transplanter, ms−1
$\mathsf{\omega }$	Angular speed of the planting mechanism, rad−1
$\mathsf{\theta }$	Angle of the planting hopper relative to the vertical axis, $\mathrm{r}\mathrm{a}\mathrm{d}$
${\mathrm{R}}_{\mathrm{t}}$	Radius of rotation, $\mathrm{m}$
${\mathrm{R}}_{\mathrm{s}\mathrm{t}}$	Necessary rate of seedling feed, seedling min−1
${\mathrm{P}}_{\mathrm{i}}$	Target spacing between seedlings, $\mathrm{m}$
${\mathrm{N}}_{\mathrm{t}}$	Number of simultaneous planting rows, integer
n	Rotational velocity of the planting unit, rpm
${\mathrm{C}}_{\mathrm{d}}$	Aerodynamic drag coefficient of the seedling, numeral
A	Projected frontal area of the seedling, m2
S	Mean mass of the seedling, g
g	Acceleration due to gravity, ms−2
$\mathsf{\rho }$	Air density at 27 °C, gm−3
${\mathrm{F}}_{\mathrm{t}}$	Time duration of seedling free fall, s
${\mathrm{V}}_{\mathrm{S}}$	Seedling velocity during free fall, ms−1
$\mathsf{\alpha }$	Constant, numeral
h	Vertical drop height of the seedling, m
$\mathsf{\lambda }$	Characteristic coefficient, numeral

, which provides the notations, definitions, and units for each variable discussed in this study.

2.2. Theoretical Evaluation

2.2.1. Optimization of Rotational Speed for Transplanting Mechanism

Accurate determination of both rotational and translational speeds is fundamental to the effective design of transplanting systems. Prior investigations concerning walking-type transplanters have reported that suitable forward travel speeds typically range between 150 and 390 mm/s [5,40]. A Korean-developed model designed specifically for Chinese cabbage transplantation was optimized to operate at a forward velocity of 300 mm/s [8]. In this study, the working forward speed was selected within the range of 250 to 350 mm/s, with further trials conducted to identify the optimal rotational velocity. The angular velocity of the planting unit is determined in accordance with both the designated spacing between seedlings and the ground speed of the equipment. The rotating speed is determined by the range of forward velocities and the specified planting pattern, as outlined in Equation (1) [6,28].

$$n={\displaystyle \frac{{30v}_t}{P_i}}$$

(1)

The rate at which plants are supplied to the system can be calculated based on Equation (2), as outlined by Srivastava et al. [41].

$$R_{st}={\displaystyle \frac{60v_t{n}_t}{P_i}}$$

(2)

An essential element of the transplanting procedure is guaranteeing that seedlings are oriented vertically and aligned within the hopper. The effective insertion of seedlings into the hopper is determined by various aspects, such as the necessary seedling supply rate, the period of free fall, and the vertical distance the seedlings must travel. These elements must be meticulously synchronized with the hopper rotational speed to ensure seamless seedling distribution throughout operation. Seedlings must be placed onto the hopper when it attains its maximum vertical position. The time required for seedling descent must align with the lateral motion of the dibbling unit. Furthermore, this decent interval must be harmonized with the rotational dynamics of the transplanting system, as well as the seedling delivery frequency and method employed. The descent time for the seedlings can be computed through Equation (3), given that the delivery characteristics of the seedling feed system affect the angular velocity (n) of the planting unit.

$$F_t={\displaystyle \frac{60}{8n}}$$

(3)

The descent speed of a cabbage seedling in free fall is influenced by aerodynamic resistance and is further governed by its inherent physical characteristics. This relationship is quantitatively described by Equations (4) and (5) [6].

$$v_s=({\displaystyle \frac{\sqrt{g}}{\alpha }})\tanh (F_t\alpha \sqrt{g})$$

(4)

where α is a constant that can be determined as specified in Equation (5)

$$\alpha ={\displaystyle \frac{A\rho g{C}_d}{2S}}$$

(5)

According to Kim et al. [35] and Dihingia et al. [42], 30-day-old cabbage seedlings are considered ideal for mechanical transplanting procedures.

2.2.2. Consistent Horizontal Velocity of Seedling Placement

At the lowest point of the hopper operational path where cabbage seedlings are placed into the soil, it is essential to maintain a constant horizontal velocity. The method referred to as “zero-speed delivery” is realized when the lateral velocity of the dibbling hopper aligns with the forward velocity of the transplanter. This alignment ensures that seedlings are positioned accurately at the required depth in the soil, which is critical for effective transplantation [6]. At that specific point in the hopper trajectory, acceleration is absent, enabling smooth release of seedlings during withdrawal from the ground. To ensure precise deposition, the horizontal velocity during seedling placement must fully offset the forward velocity of the transplanter. The mathematical relationship between the forward velocity of the transplanter (${\mathrm{v}}_{\mathrm{x}}$) and the horizontal velocity of the hopper (${\mathrm{v}}_{\mathrm{t}}$) is expressed in Equation (6).

$$\dot{X_A}-L_5\dot{{\theta }_4}sin{\theta }_4=-v_x=-v_t$$

(6)

To evaluate the effectiveness of zero-speed seedling delivery during the transplanting process, it is essential to examine the operational trajectory of the mechanism. A mathematical representation of the dibbling path, illustrated in Figure 3, was developed based on a Cartesian coordinate framework. In this model, the forward movement of the transplanter is assigned to the negative direction along the x-axis, while the upward motion toward the soil surface is considered the positive direction along the y-axis. The coordinate origin is positioned at the lowest point of the dibbling path, which is used as the reference location for the hopper mechanism. The motion behavior of this system can be mathematically defined by Equations (7) and (8).

$$x=v_t-R_{t}sin\omega t$$

(7)

$$y=R_t-R_{t}scos\omega t$$

(8)

The rotational radius ${\mathrm{R}}_{\mathrm{t}}$ corresponding to the trajectory of the dibbling hopper can be calculated based on Equation (9).

$$R_t=\dot{X_A}+L_{5}cos4\left(\pi -\theta \right)+L_7\sin (\pi -\theta )$$

(9)

To mitigate the adverse effect of the mulching film on the surface of the planting bed, a characteristic coefficient factor (λ) was incorporated into the analysis. This coefficient is formulated as the ratio between the circumferential velocity of the planting unit and the linear velocity of the transplanter [36] and is mathematically described by Equation (10).

$$\lambda ={\displaystyle \frac{R_t\omega }{v_t}}$$

(10)

To ensure precise and synchronized seed placement, the kinematic behavior of the planting mechanism must be thoroughly characterized. The design incorporates a multi-bar linkage system, which governs the motion of the planting hopper. By analyzing the dynamic response of this system, one can predict the velocity and trajectory of the seed-delivery unit as it traverses the soil surface. This analysis is essential not only for maintaining uniform planting intervals but also for minimizing impact forces that may compromise seed viability. The following Figure 3 illustrates the configuration and motion trajectory of the planting mechanism, highlighting the spatial path governed by the linkage assembly and the influence of operational parameters such as angular velocity and translational speed.

2.3. Procedures for Simulation and Validation

2.3.1. Simulation of Motion and Operational Speed

A motion and kinematic design analysis was conducted using commercial mechanical design and simulation software (SOLIDWORKS 2018, Dassault Systèmes, SolidWorks Corp., Waltham, MA, USA) to determine the optimal operational speed of the transplanting unit. A 3D model of the transplanter was developed and underwent simulation experiments at varying forward velocities, aligned with the typical range of human walking speed [18]. The simulation process comprised three primary steps: establishing geometric and kinematic constraints of the transplanting mechanism within the 3D model; conducting motion analysis to determine angular velocity profiles, seedling drop trajectories, and soil penetration paths; and extracting quantitative performance metrics, including displacement curves and estimates of power requirements.

Various trajectory scenarios were produced by adjusting the forward velocity from 250 to 350 mm/s and the rotational velocity of the dibbling mechanism from 40 to 80 rpm, based on seedling spacing and drop height specifications. The simulation results were analyzed across different situations to determine the configuration that reduced soil disturbance while ensuring uniform planting depth and trajectory stability. The simulation findings were subsequently tested against field test data, confirming that the chosen operational settings ensured stable and efficient planting.

2.3.2. Testing and Validation of the Prototype

To validate the findings from the simulation analysis, an experimental prototype of the dibbling unit was fabricated and evaluated using a purpose-built test platform constructed from 80 × 40 mm aluminum profile frames. This test structure incorporated four U-grooved wheels (bore diameter: 30 mm; outer diameter: 38 mm) to ensure stable and uniform horizontal translation. A 1200 W three-phase induction motor (model: EON10248, Xinming Electronics Co., Ltd., Yantai, China) powered the system, which was linked to a chain and sprocket transmission. This setup enabled the motion of the test platform at controlled speeds in both forward and reverse directions along a set of parallel aluminum tracks, as illustrated in Figure 4. An additional pair of aluminum profiles, each with a diameter of 30 mm, was used to support the rails, with a spacing of 900 mm between them. The vertical position of the rails could be adjusted, and they were configured at a height of 600 mm above the ground to ensure the intended planting depth was reached. Motor speed was regulated within the frequency range of 0 to 60 Hz through the application of a frequency inverter (model SV-iG5A, LS Industrial Systems Co., Anyang, Republic of Korea), which enabled fine-tuned control over the transplanter’s operating parameters. To monitor power consumption during the dibbling process, a torque measurement device (model DYN-200, Shanghai Qiyi Co., Ltd., Shanghai, China) was integrated into the power transmission system connecting the electric motor and the dibbling unit. This sensor delivered a measurement precision of 99.8%. A custom-developed software tool (Python 3.10; Python Software Foundation, Wilmington, DE, USA) was utilized for acquiring and processing torque data. The output data were then refined using a 20-point symmetric moving average algorithm, as described by Rohrer et al. [43].

Soil disturbance and misplacement rates associated with the dibbling unit were assessed by transplanting cabbage seedlings at linear velocities of 250, 300, and 350 mm/s, while keeping the rotational velocity of the dibbling assembly constant at 60 rpm. Cabbage seedlings aged 30 days were manually placed into the hopper from a fixed elevation, and the rate of seedling placement inside the dibbling unit was monitored. Transplantation procedures were conducted five times across three raised beds (6000 × 350 × 200 mm). The experiment evaluated several performance parameters, including the extent of soil disruption, seedling placement accuracy, planting depth consistency, and planting spacing uniformity. Measurements related to soil disruption and uniformity in planting depth were taken with Vernier calipers, with each parameter measured five times to ensure repeatability.

The experiment was carried out inside a plastic-covered greenhouse at the agricultural test field at Chungnam National University, Daejeon, Republic of Korea. The soil at the experimental location was sandy loam, comprising 75.6% sand, 18% silt, and 6.4% clay. Additional soil characteristics were quantified, including Cone Index values (up to a depth of 150 mm) using a portable cone penetrometer (Rika Kogyo Co., Ltd., Saitama, Japan). Measurements of soil moisture, temperature, volumetric water content, and electrical conductivity (EC) were conducted using a multi-parameter soil sensor (model: WT1000B, Mirae Sensor, Seoul, Republic of Korea). The sensor showed a measurement error of less than 1%. The associated measurement uncertainties were ±1% for soil water content, ±0.1 dSm/s for EC, and ±0.5 °C for soil temperature. A detailed summary of the soil characteristics is presented in

Table 2. Major soil characteristics of the experimental field.

Parameter		Value
Soil moisture content (%)		22.15 ± 1.26
Soil temperature (°C)		33.4 ± 0.4
Soil EC (dSm/s)		1.38 ± 0.13
Bulk density (gcm/s)		1.35 ± 0.04
CI (MPa)		0.62 ± 0.08
Soil texture (Sandy loam)	Sand (%)	75.6
	Silt (%)	18
	Clay (%)	6.4

.

2.4. Biodegradable Pot Seedlings Selection and Properties

The experiment employed cylindrical biodegradable containers composed of paper, each having a diameter of 25 mm, a height of 40 mm, and an approximate volume of 20,000 mm³, as depicted in Figure 5. These containers were fabricated using recycled paper and were packed with a mixture consisting of commercially available growth substrate, peat moss, and perlite. The mixture was specifically formulated to offer a suitable cultivation environment for cabbage seedling development. Each pot contained a single cabbage seed and was maintained for 30 days under controlled environmental conditions, with consistent irrigation to promote uniform seedling development.

During the transplanting evaluation, the combined mass of the biodegradable paper containers and the potting substrate under different moisture conditions were recorded. Moisture levels were regulated to 6 ± 2%, 9 ± 2%, and 12 ± 2% on a dry basis, which corresponded to mean masses of 20.0 ± 2.0 g, 21.0 ± 2.0 g, and 22.0 ± 2.0 g, respectively. These settings ensured that the seedlings were appropriately conditioned for performance analysis during the transplanting process. The morphological features of the selected potted seedlings are detailed in

Table 3. Morphological characteristics of the chosen potted seedlings.

Parameter	Numerical Value
Seedling height (mm)	85
Width of seedling leaves (mm)	32
Weight of seedling (g)	20
Age of seedling (days)	30
Leaf count	4–5

.

3. Results

3.1. Optimal Rotating Motion of the Planting Device

The angular velocity of the planting unit in the cabbage transplanter is governed by both the forward motion of the machine and the spacing requirement between individual seedlings. In the current study, under operational velocities ranging from 250 to 350 mm/s and a target spacing of 400 mm, the estimated rotational speed of the planting unit was found to be within the range of 40 to 70 rpm, as depicted in Figure 6a. The drop height of seedlings was identified as a significant factor in achieving accurate placement, since greater fall distances can intensify the influence of aerodynamic drag, thereby increasing the risk of misplacement. In addition, the vertical distance between the release point and the trajectory of the hopper must be considered. Based on these considerations, a free-fall height of 80 mm was selected. The hopper speed corresponding to this condition was computed as 60 rpm, as shown in Figure 6b.

Validation experiments conducted under this configuration achieved a seedling placement success rate of 96.87%. Results further demonstrated that seedlings possessing a straighter stem form and fewer leaves were placed with higher accuracy. Vibrational forces acting on the transplanter during operation also significantly contributed to displacement of seedlings during the fall phase. These findings offer valuable guidance for adjusting the rotational velocity of the planting unit, enhancing the accuracy of seedling placement and minimizing errors in the cabbage transplanting process.

3.2. Seedling Placement of the Planting Device by Forward Velocity

Figure 7 presents the modeled movement paths of the planting unit at travel speeds of 250, 300, and 350 mm/s, under a constant rotational velocity of 60 rpm for the planting component. Simulation findings indicated that optimal seedling placement marked by consistency and precision was achieved at a forward velocity of 300 mm/s. This condition yielded the most effective deposition results.

Three planting cases were analyzed, differentiated by the characteristic coefficient λ, with values defined as λ > 1, λ = 1, and 0 < λ < 1. These corresponded to forward travel speeds of 250, 300, and 350 mm/s, respectively. The respective kinematic profiles for each condition are shown in Figure 7a–c.

In the case of 250 mm/s, the λ value exceeded 1. Under this condition, the trajectory of the planting mechanism showed disruption, causing irregular seedling release. A curvature transition point was identified at the lowest location on the cycloidal path, situated beneath the soil surface. While the horizontal motion of the cycloid aligned with the transplanter speed across most of the path, it diverged at the curvature transition. Despite the match in average horizontal velocity, the mismatch at the turning point caused seedlings to be forced forward due to timing misalignment. This transition point occurred at the base of the movement arc. After seedling release, the cycloidal path progressed forward, while the seedlings, due to their physical dimensions, remained in partial contact with the mechanism, increasing the risk of mechanical damage during continued movement.

The planting unit produced an insertion path in the soil for seedling placement by penetrating the surface at one point and exiting at another, occasionally causing damage to the mulch covering. As depicted in Figure 7a, the case of λ > 1 was found to be less effective for cabbage transplantation. When λ equaled 1 and the transplanter moved forward at 300 mm/s, the trajectory of the hopper tip beneath the soil followed a linear path. This indicated that the hopper entered and exited the soil at the same point relative to the released seedling. This occurred because the horizontal velocity of the hopper tip at the release position matched in magnitude but was opposite in direction to the forward velocity of the machine. Consequently, the seedlings were placed with consistent horizontal speed, as shown in Figure 7b, which helped maintain their upright orientation during embedding. The matched entry and exit positions minimized disturbance to the mulch layer. Achieving a coefficient value of λ = 1 proved optimal for machine operation, particularly at 300 mm/s, which was targeted as the recommended operating speed.

Seedling motion during release is illustrated via the tangent angle of the path. When the coefficient λ was between 0 and 1, corresponding to a transplanter velocity of 350 mm/s, the trajectory beneath the soil surface formed a shallow cycloidal curve, as seen in Figure 7c. The horizontal velocity at each cycloidal point aligned with the machine’s travel speed. This outcome emphasized the importance of synchronizing horizontal velocity and release timing due to the limited window for proper seedling placement and soil engagement. Under these conditions, maintaining consistent release velocity became challenging, leading to irregular contact zones and increased potential for mechanical damage to seedlings and surface materials.

To further validate the simulation model,

Table 4. Comparison between simulated trajectory and experimental results at different forward speeds and λ conditions.

Speed (mm/s)	λ	Planting Distance (mm) (Simulated)	Planting Distance (mm) (Experimental)	Experimental Mis-Planting Rate (%)
250	>1 (1.2)	410	408	12.54
300	=1 (1.0)	450	448	9.12
350	<1 (0.85)	490	492	15.84

presents a comparison between the predicted trajectory-based outcomes (simulated) and actual field observations (experimental), including mis-planting rate and planting distance. As shown, at λ = 1 (300 mm/s), the simulation and experiment closely align, both yielding ideal seedling positioning and minimal mis-planting. This quantitative match strongly confirms the theoretical design principle that a 1:1 speed ratio (λ = 1) ensures optimal deposition performance.

3.3. Seedling Spacing Based on Forward Speed

The distance between transplanted cabbage seedlings is primarily influenced by the rotational velocity (rpm) of the rotary delivery system and the linear travel speed of the transplanter.

Table 5. Simulated planting intervals (mm) as a function of transplanter travel speed and rotational speed of the seedling delivery system.

Forward Speed (mm/s)	Operating Speed of the Planting Hopper (rpm)
	40	50	60	70	80
250	500	460	400	390	370
300	540	500	400	420	400
350	600	570	500	490	460

presents the predicted plant-to-plant spacing under various combinations of these two variables, providing a numerical basis for evaluating planting accuracy and system efficiency.

As shown in Figure 8, the planting intervals achieved during field experiments are visually documented to reflect actual transplanting performance. Specifically, Figure 8a shows the appearance of the transplanted seedlings in the field, while Figure 8b displays a representative measurement of the plant-to-plant distance, highlighting the precision achieved under optimal conditions. The recommended distance for cabbage transplantation typically varies from 350 to 450 mm to facilitate optimal growth. The combination of a rotating rate of 60 rpm and a forward velocity of 300 mm/s produced a planting interval of roughly 400 mm, which is within the ideal range. This design yields a transplanting frequency of 60 plants per minute, facilitating both efficiency and agronomic standards.

3.4. Power Requirements of the Planting Device

The performance of the transplanter was analyzed at three distinct travel speeds, 250, 300, and 350 mm/s, while recording the corresponding input power for each case. As illustrated in Figure 9, the planting system demonstrated a stable oscillatory trend in power consumption throughout the transplanting cycle. The measured power usages for the dibbling mechanism at forward speeds of 250, 300, and 350 mm/s were 26.19 ± 1.52 W, 17.42 ± 1.21 W, and 28.27 ± 1.92 W, respectively. Among these, the lowest energy requirement occurred at 300 mm/s.

At this optimal speed, the horizontal velocity of the seedling delivery mechanism was properly synchronized with the dibbling point, effectively neutralizing external reactive forces during seedling placement. In contrast, when operating at 250 mm/s and 350 mm/s, the planting hopper encountered unbalanced forces that alternated in direction pulling it rearward and forward which negatively influenced the uniformity of seedling positioning. During seedling deposition, the hopper made contact with the soil, and the tension on it varied based on the forward speed. At 250 mm/s, the hopper followed a cycloidal path, digging a larger hole in the soil, leading to increased power consumption. Conversely, at 350 mm/s, although a similar hole was created, the forward pull of the hopper reduced the power requirement. This explains why power consumption at 350 mm/s was slightly lower compared to 250 mm/s.

The planting system completed one full operational cycle in under one second. As shown in Figure 9, the lowest and highest power demands were recorded at the seedling pick-up and soil-insertion stages, respectively. During the pick-up phase, the mechanism remained elevated, resulting in reduced energy consumption. In contrast, maximum power usage occurred during soil contact, where the hopper encountered increased resistance due to ground impact.

Field evaluation results were found for transplanter forward speeds of 250, 300, and 350 mm/s while maintaining a crank rotation speed of 60 rpm. Each treatment was carried out thrice under uniform conditions, and the data is presented as mean ± standard deviation (n = 3). A one-way ANOVA was performed, accompanied by Tukey’s HSD post hoc test to ascertain the statistical significance of differences in speeds.

Table 6. Summary of field test results under different transplanter travel speeds during seedling placement.

Forward Speed (mm/s)	Mis-Planting Rate (%)	Soil Disturbance (mm2)	Power Requirement (W) (max.)
250	12.54 ± 0.12 a	3296.32 ± 2.05 a	26.19 ± 1.52 a
300	9.12 ± 0.04 b	2186.95 ± 2.27 b	17.42 ± 1.21 b
350	15.84 ± 0.13 c	3482.37 ± 2.67 c	28.27 ± 1.92 c

Data are expressed as mean ± standard deviation (n = 3). Superscript letters within columns indicate statistically significant differences (p < 0.05), based on Tukey’s HSD post hoc comparison following one-way ANOVA.

illustrates that forward speed significantly influenced the mis-planting rate, soil disturbance, and peak power consumption (p < 0.05). Superscript letters (a, b, c) denote statistically distinct groups within each column. A forward speed of 300 mm/s produced the most advantageous results, featuring the lowest mis-planting rate (9.12 ± 0.04%), minimal soil disturbance (2186.95 ± 2.27 mm²), and decreased power consumption (17.42 ± 1.21 W). Conversely, speeds of 250 and 350 mm/s resulted in markedly elevated mis-planting rates and power usage. These findings highlight the essential importance of forward speed in the quality and efficiency of transplantation.

The accuracy of the simulation model was evaluated using two statistical metrics: root mean square error (RMSE) and the coefficient of determination (R²). The RMSE for planting distance was 1.24 mm, and the R² value was 0.992, indicating high predictive accuracy. Likewise, for power consumption, the RMSE was 0.73 W with an R² of 0.984. These results indicate that the simulated outputs closely matched the experimental data, validating the effectiveness of the simulation model in representing real-world performance.

4. Discussion

This investigation evaluated a transplanting system developed for a biodegradable pot cabbage transplanter, concentrating on improving operational and rotational speeds to improve transplanting success and uprightness percentages. The improved mechanism was built and evaluated using a test bench structure, and the results demonstrated a high correlation between predictions from theory and results from experiments, confirming the design accuracy. A comparative review of theoretical and practical data revealed that a forward velocity of 300 mm/s produced the most advantageous performance. The success percentage for seedling placement at this velocity was 92.34%. Comparable research on a modified linkage cum hopper-type transplanter featuring a recyclable plug-tray feeding mechanism has indicated that at a working velocity of 300 mm/s and a crank rotation of 60 rpm, the smallest figures for soil intrusion area, intrusion perimeter, and horizontal hopper displacements were recorded [29]. Our findings validate previous research indicating that best transplanting efficiency occurs at speeds between 1.2 and 2.0 km/h, with Magar et al. [32] reporting a transplanting efficiency (TE) of around 91.7% and an operational efficiency (OE) of about 96.7% at 1.2 km/h, while Khadatkar et al. [30] noted excellent spacing and rates at 2.0 km/h. As anticipated, it was also noted that velocities exceeding this range correlated with increased mis-planting, aligning with reports of increased missing counts at greater speeds. Evidence indicates that accurate synchronization, exemplified by the alignment of planting mechanism time, leads to seedlings being oriented upright and enhances accuracy [28].

Earlier studies employing various transplanter configurations have utilized travel speeds ranging from 250 to 450 mm/s for five-bar duckbill-type systems [20], 250 to 350 mm/s for gear-driven dibbling types [6], and 100 to 200 mm/s for gear-driven rotary types [28], reporting seedling success rates between 90% and 94%. In the current study, a seedling drop height of 80 mm was determined to be optimal for ensuring accurate placement. According to previous investigations [42,44], an effective range of free-fall height for transplanting lies between 60 and 90 mm. Despite differences in machine speed and the characteristics of the seedlings, the observed transplanting success rates in this experiment aligned well with those reported in prior research. Additionally, regarding power consumption, previous studies by Iqbal et al. [6] and Reza et al. [28] reported values of 28.96 W and 36.53 W, respectively. These findings are generally comparable to the results of this study, which recorded a lower power consumption of 17.47 W. A summary of the comparative performance metrics including forward speed, success rate, free-fall height, and power consumption across these different transplanter designs is provided in

Table 7. Comparative performance of transplanter designs.

Study	Mechanism	Speed (mm/s)	Success Rate (%)	Power (W)	Key Feature
[29]	Linkage + plug tray	200–300	N/A	N/A	Low intrusion and displacement
[28]	Rotary gear-driven	100–200	94	36.53	Compact rotary system
[6]	Gear-driven dibbler	250–350	92	28.96	Walking-speed transplanter
[20]	Five-bar duckbill	250–450	90–94	N/A	Speed-adjusted hopper
This study	Cam-follower, biodegradable pot	250–350	92.34	17.47	λ = 1 optimization, uprightness

.

The experimental results further revealed that the planting mechanism operated with optimal efficiency, demonstrated by minimal power usage, when the characteristic coefficient (λ) was set to 1.

The forward-speed range of 250–350 mm/s is suitable for greenhouse operations; however, shifting to open-field applications presents considerable challenges. Irregular terrain causes vibrations in row units and chassis, which has been demonstrated to diminish planting accuracy and elevate spacing variability [45]. Biodegradable pots, susceptible to moisture and mechanical disruption, may encounter instability and displacement under such conditions. Subsequent efforts include field testing across diverse soil roughness, incorporating damping mechanisms, adaptive feeding/placement synchronization, and assessment of seedling resilience under vibratory stress. When compared to widely recognized operational guidelines for tray-type transplanters (about 0.3–0.6 m/s), the experimental speeds of 0.30–0.35 m/s align with usual practice, while 0.25 m/s indicates a cautious sub-nominal condition. The observed performance trends specifically steady seedling placement at 0.30–0.35 m/s and heightened susceptibility to spacing fluctuation beyond this range align with anticipated outcomes for speed-mechanism synchronization in tray-fed systems. The transplanter utilized in this research was the semi-automatic riding transplanter, currently under development. While manufacturer-specific recommendations are currently unavailable, the existing findings closely correspond with the commonly accepted commercial operating range of 1–2 km/h, hence reinforcing the practical significance of the given results. The controlled environment allowed for the isolation and detailed observation of kinematic and mechanical performance, which would be difficult to achieve in highly variable outdoor conditions.

While this study demonstrates promising results for cabbage seedling transplantation using a cam-follower-based transplanting mechanism, several aspects remain unaddressed that could influence field-level performance. The preliminary studies were performed in a controlled-environment greenhouse, which reduced environmental variability like uneven surfaces, soil moisture discrepancies, wind, and precipitation. This approach allowed for the examination of forward speed impact on transplanting performance without confounding variables, although it fails to account for potential field-level impacts. Soil compaction, terrain irregularity, and environmental disturbances (e.g., temperature, humidity, wind speed) influence speed matching, seedling stability, and mulch-film integrity, and they should be assessed in future field studies to corroborate and expand upon the current finding.

This study was conducted under a specific soil condition (Table 2) and utilized cabbage seedlings raised in biodegradable paper cups to evaluate the effects of forward speed under controlled settings. As soil penetration resistance and surface friction vary considerably across sandy, clayey, and mixed soils, the optimal travel speed and seedling stability identified here may not be directly transferable to other soil textures. Likewise, the geometry and structural properties of biodegradable cups influence pickup stability and placement dynamics, suggesting that container design remains a critical factor in transplanting performance. Future research will therefore encompass multi-location field trials across diverse soil types and container designs to establish broader operational guidelines. Although this study employed a single type of biodegradable paper cup, several transferable design parameters can guide adaptation to other crops and seedling systems. These include cup diameter (typically 30–50 mm) [46], stem stiffness (requiring clamp forces below the rupture threshold of the stem), friction coefficient between the clamp and cup wall (ideally <0.4 for reliable release) [47], and release height (≤100 mm to minimize tilt and mechanical shock) [48]. Nevertheless, cup-specific properties such as wall stiffness, thickness, and weight have been shown to significantly affect handling stability, release uniformity, and planting accuracy [49,50]. As such, the present findings cannot be fully generalized to other pot materials or morphologies. Future work will expand the scope of evaluation to include compressed peat pellets, alternative biodegradable containers, and conventional plastic plug trays. Comparative trials with other crops, including tomato and pepper, will be conducted to validate the design rules and refine crop-specific calibration strategies, ensuring broader applicability of the semi-automatic transplanting system.

All experiments were conducted in triplicate, and statistical significance was determined using one-way ANOVA with Tukey’s HSD post hoc analysis. While the replication level was sufficient to detect significant differences in forward speed, the limited sample size (n = 3) constrains the statistical robustness and generalizability of the findings. Future studies will expand replication across multiple sites and cropping seasons to improve statistical reliability and ensure broader applicability. Another limitation of this study is the exclusion of biological performance indicators such as seedling damage, root anchorage quality, and post-transplant survival. The present work focused primarily on mechanical performance parameters, such as mis-planting, soil disturbance, and power consumption, under controlled conditions. However, successful establishment and survival remain critical measures of transplanting efficacy. Subsequent investigations will therefore include systematic assessments of seedling integrity and post-transplant establishment across diverse soil textures and container types. Furthermore, the kinematic simulations conducted in commercial software were based on idealized mechanical assumptions, excluding potential real-world effects such as slippage, linkage deformation, vibration, and mechanical wear. Incorporating these factors in future modeling and validation will improve predictive accuracy, enhance system durability assessments, and provide more comprehensive performance benchmarks for practical deployment.

5. Conclusions

This study investigated a rotary delivery mechanism integrated into a semi-automatic, self-propelled cabbage transplanter. Several key insights were derived, including the identification of optimal operating conditions, specifically a 60 rpm rotational speed and a planting frequency of 60 seedlings per minute. A seedling drop height of 80 mm was found to be essential for accurate placement. Kinematic analysis of the mechanism movement confirmed its ability to deliver seedlings in a vertical and stable orientation while minimizing soil disruption, particularly at a forward velocity of 300 mm/s.

Experimental field validation using a prototype machine confirmed consistency between simulation outputs, theoretical predictions, and real-world performance. The research highlighted the effectiveness of the cam-follower-based dual-rotary planting mechanism for cabbage transplantation and emphasized the importance of maintaining a 1:1 ratio between the planting unit rotational speed and the transplanter travel velocity. These outcomes provide valuable advancements toward the automation of seedling transplanting operations, supporting future innovations in agricultural engineering.

Future research will focus on advancing the current semi-automatic system into a fully automatic walking-type transplanter equipped with a clamp-based seedling picking mechanism, thereby reducing dependence on manual feeding. In addition to the biodegradable paper cups employed in this study, compressed peat pellets and other biodegradable containers will be evaluated to expand system applicability across diverse seedling types. The development of a walking-type, clamp-assisted pickup unit is expected to provide the foundation for more efficient and sustainable transplanting by ensuring consistent handling and placement accuracy. These improvements are anticipated to enhance operational efficiency, increase crop adaptability, and accelerate the mechanization and digital integration of transplanting practices, contributing to the broader adoption of intelligent and ecologically sustainable agricultural technologies.