**1. Introduction**

Cabbage is one of the staple vegetables in China. It is planted in four seasons in the north and south of China [1]. It reaches 900,000 hm2, and the total yield accounts for about 50% of the total yield of cabbage in the world [2]. At present, cabbage is still mainly harvested manually, and problems such as increased labor, increased labor intensity, and increased production costs have become increasingly prominent [3].

The soft and easily damaged characteristics of cabbage make their mechanized harvesting quality fluctuate during actual production work. The conveying mechanism structure of cabbage is mostly chain clamping [4], screw conveying [5], and clamping conveying [6]. The CKM-1 [7] and NKH-1 [8] single-row cabbage harvesters developed by the USSR adopt chain clamping and conveying, which have low harvesting efficiency and great damage. Hansen [9] from the United States applied for a patent for a cabbage harvester using a reverse rotation of the double helix conveyor and then transported it to the rear for cutting and packing; Bleinroth [10], Baker [11], and Mori G et al. [12] developed a cabbage harvester using a similar double helix conveying method. Cheng Zhou [13] and Dongdong Du [14] of

**Citation:** Tong, W.; Zhang, J.; Cao, G.; Song, Z.; Ning, X. Design and Experiment of a Low-Loss Harvesting Test Platform for Cabbage. *Agriculture* **2023**, *13*, 1204. https://doi.org/10.3390/ agriculture13061204

Academic Editor: Jin Yuan

Received: 22 May 2023 Revised: 31 May 2023 Accepted: 5 June 2023 Published: 7 June 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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China improved and optimized the double helix conveying mechanism and increased the chain clamp mechanism to clamp the root of cabbage and cooperate with the double helix conveying to transport backward synchronously, but the test effect was still not satisfactory and the conveying damage was too large. In order to reduce the damage to cabbage during the conveying process, the conveyor belt conveying structure was invented and applied to the cabbage harvester [15]. Compared with screw conveying, clamping conveying can improve conveying stability and reduce cabbage damage by changing the clamping belt material and tensioning mechanism [16]. Lenker et al. [17] and Wadsworth et al. [18] used rubber as a conveyor belt to complete the transportation of cabbage. Bleinroth et al. [19] designed a pressure-top conveying structure based on the conveyor belt. When the conveying speed of the pressure-top conveyor belt is consistent with the pulling-out speed, the cabbage can be kept upright and pressed during the conveying process, which is conducive to the formation of lotus-type cabbage cutting and improves the accuracy of root cutting. In summary, the current research in the field of low-loss cabbage harvesting technology is relatively weak. The existing cabbage harvesting equipment is not suitable for China's planting agronomy, and there is still a problem of large harvesting damage. Integrating flexible clamping and conveying technology into the design of cabbage harvesting and conveying structures may be a breakthrough to solve the high damage rate in the cabbage harvesting process [20,21].

Therefore, this paper aims to improve the operational performance of the cabbage harvester and reduce harvesting damage. Cabbage was selected as the research object, and on the basis of clarifying the mechanical and physical parameters of cabbage, a low-loss harvesting test platform for cabbage was designed. By obtaining the critical conditions for the damage of cabbage in the harvesting process, the attitude migration law of cabbage in the harvesting mechanism was clarified, which provided a reference for the development and structural improvement of low-loss harvesting equipment for cabbage.

### **2. Analysis of Mechanical Harvesting Characteristics of Cabbage**

The cross-section of the rhizome cutting of cabbage during the harvest period is composed of the central pith, xylem, and phloem fiber layers from inside to outside. The matrix leaves are thicker, the moisture content of the long-term exposed external leaves is lower than that of the internal leaves, and the toughness is stronger. The internal leaves have a high moisture content and are brittle. The basic physical properties and harvesting mechanical properties of cabbage were determined: the rhizome length, diameter, and pulling force were measured for cabbage. The universal testing machine was used to test the crushing, rhizome cutting force, water content, and cutting force of a single plant. The mechanical parameters such as root shear characteristics and ball crushing force under different water content conditions were tested, respectively, which provided a theoretical basis and data support for the study of cabbage harvesting equipment. See Figure 1.

**Figure 1.** Determination of basic physical parameters and harvesting mechanical properties test of cabbage: (**a**) Physical characteristics acquisition: 1: *Wd*: Expansion degree 2: *Hd*: transverse diameter 3: *Gd*: vertical diameter (**b**) Physical characteristics acquisition process. (**c**) Determination of pull-out force. (**d**) Compression test. (**e**) Root cutting force test.
