*2.3. Test Results of Rhizome Shear Force and Extrusion Force*

It can be seen from Figure 2a,b that the curve of force and displacement in the test data is non-linear. During the shear test, the blade first contacts the outer epidermis of the cabbage rhizome, and the shear force gradually increases. When the blade cuts off the outer epidermis and enters the interior of the rhizome, the shear force will decrease, and the change range is small. When the blade cuts to the lower outer epidermis, the shear force gradually increases until the cabbage rhizome is completely broken. The reason for this is that the material of the outer epidermis of the cabbage is fiber. Compared with the internal matrix, its flexibility is much stronger, so the shear force is at its maximum when it just enters the fiber layer. The maximum compressional force is *F*max = 1198.3 N, and the maximum root cutting force is *F*<sup>C</sup> = 137.138 N. This value can provide the necessary parameter support for the cutting device and the clamping and conveying device of the cabbage harvesting device.

**Figure 2.** Harvest mechanical properties test: (**a**) compressional force–displacement curve. (**b**) Root cutting force–displacement curve.

#### **3. Machine Structure and Working Principles**

#### *3.1. Structure of the Machine*

The low-loss harvesting test platform for cabbage is mainly composed of a cabbage conveying system, cabbage harvesting system, test data acquisition system, and servo motor frequency conversion control box. The conveying system simulates the actual walking state of the cabbage harvesting machine in the field and relies on the cabbage harvesting system to simulate the real harvesting process. The specific structure of the prototype is shown in Figure 3. The conveying system for cabbage mainly consists of a cabbage rootstock clamping cup and conveying chain. The conveying speed (0~0.5 m/s) can be adjusted by the servo motor frequency control box. The cabbage harvesting system is mainly composed of a pulling device, reeling device, flexible clamping conveying device, and double disc cutting device. The speed of the pulling device (0~200 r/min), the speed of the reeling device (0~140 r/min), the speed of the flexible clamping conveyor belt (0~300 r/min), and the speed of the double disc cutting device (0~400 r/min) can also be adjusted by the servo motor frequency control box. Through the torque and pressure sensors installed in the harvesting device, the experimental data acquisition system can collect the motion parameters of the cabbage in the extraction, transportation, cutting, and other links, obtain the motion changes of the cabbage on the test header, find out the damage law, and determine the range of motion combination parameters between different key components. At the same time, the motion trajectory and speed-time curve of a single cabbage plant during transportation are calibrated and tracked. The damage to cabbage after transportation is recorded and saved, and performance indexes such as epidermal damage and cracking are measured.
