**3. Results and Discussion**

Based on the results of the experimental data processing, graphs were plotted for the dependence of the completeness of separation of the marketable products of bulbs ν<sup>B</sup> and tubers νT, as well as their damage (Db and Dt), on the mode and technological parameters of the harvesting machine (hL and νP) and the separating rod elevator (vEL) with an adjustable angle canvas tilt. The research results are presented in Figures 5–9.

With a change in the depth of digging onions and potato tubers, there is a variation in the completeness of the separation of and damage to marketable products, which is explained by the presence of an additional soil layer between the roots and the working surface of the bar cloth, with an increase in the depth of the digging while reducing the damage and increasing the completeness of the separation, regardless of the harvested crop (Figure 7A,B)

**Figure 5.** General view of the harvesting machine for root crops and onions, equipped with a separating rod elevator with an adjustable blade inclination angle and a receiving plowshare for digging/picking up root crops and bulbs.

**Figure 6.** General view of the harvesting unit for harvesting root crops and onions, equipped with a separating rod elevator with an adjustable blade inclination angle: 1—MTZ 1221 tractor; and 2—machine for harvesting root crops and onions.

The greatest damage to 1.8% and 1.4% of the commercial products of onions and potatoes, respectively, is observed with a decrease in the depth of digging to 4 cm, which is explained by the difference in their physical and mechanical properties, and the formation of a more stable peel in the potato tubers than a scaly shirt in bulbs.

The difference between the minimum 1.1% and maximum 1.9% damage to the root crops within the identical values of the studied technological parameter is no more than 0.4%, and is expressed by the correlation dependence:

$$\begin{cases} \mathbf{D}\_{\rm B}(\mathbf{h}\_{\rm L}) = 1.88 - 0.47 \cdot \mathbf{h}\_{\rm L} - 0.07 \cdot \mathbf{h}\_{\rm L}^2\\ \mathbf{D}\_{\rm T}(\mathbf{h}\_{\rm L}) = 1.39 - 0.85 \cdot \mathbf{h}\_{\rm L} + 0.53 \cdot \mathbf{h}\_{\rm L}^2 \end{cases} \tag{6}$$

An obvious circumstance is an increase in the completeness of the cleaning of the root crops (Figure 7B), with a decrease in the depth of digging, which is due to a decrease in the supply of soil impurities to the cleaning devices and a simultaneous increase in damage to the marketable products.

The maximum completeness of the cleaning of the bulbs was more than 96%, and is observed at a depth of digging of up to 4 cm, which, when extracting potato tubers from the soil, provides 95.4% of the completeness of the separation.

The minimum value of the completeness of the separation of the root and tuber crops was 91%, and is observed at a depth of 10 cm of digging in the potato tuber nest (which is 91.6% in comparison with the commercial onion products), however, with an increase in the depth of digging to 12 cm, an increase in the completeness of the cleaning is observed by 0.4% and is explained by an increase in the time of the separated mass on the working surface of the rod elevator, in view of increasing its load and reducing the forward speed of its movement. Differences between the completeness of the cleaning of the studied root crops with a change in the depth of digging are observed, on average, up to 0.5%, and are expressed by a correlation dependence:

$$\begin{cases} \mathbf{v\_B(h\_L)} = 98.6 - 2.66 \cdot \mathbf{h\_L} + 0.3 \cdot \mathbf{h\_{L'}}\\ \mathbf{v\_T(h\_L)} = 98.4 - 3.56 \cdot \mathbf{h\_L} + 0.45 \cdot \mathbf{h\_L^2} \end{cases} \tag{7}$$

**Figure 7.** Dependence of: (**A**) damage to bulbs DB and tubers DT %; and (**B**) completeness of separation of onions ν<sup>B</sup> and tubers νT% of the separating rod elevator with an adjustable blade inclination angle from the depth hL of digging share into the soil.

**Figure 8.** Dependence of: (**A**) damage to bulbs DB and tubers DT, %; and (**B**) completeness of separation of onions ν<sup>B</sup> and tubers νT% of the separating rod elevator with an adjustable blade inclination angle from the center distance SL between the shakers.

**Figure 9.** Dependence of: (**A**) damage to bulbs DL and tubers DK%; and (**B**) completeness of separation of onions ν<sup>B</sup> and tubers νT% of the separating rod elevator with an adjustable blade inclination angle from the forward speed vK of the machine.

An increase in the quality of the harvesting of potato and onion tubers using a separating rod elevator with asymmetrically installed shakers is ensured by increasing the time for the discrete comparison of impurities with the slotted openings of the working body, as a result of moving not only along the length, but also the width of the rod elevator. At the same time, the maximum amount of the damage to the bulbs is no more than 1.8% at a constant digging depth of 0.1 cm and a forward speed of the rod elevator vEL and machine vK within 1.0 and 1.2 m/s, respectively. The difference between the maximum and minimum damage to the potato tubers in the studied range of the shaker locations is no more than 0.3%, with a minimum value of 1.52%. In addition, the combination of asymmetrically located shakers on the rod elevator provides a better process of potato tuber separation within 96%, which is 2.3% lower compared to its use in onion harvesting at a technological parameter value of 0.34 cm.

With an increase in the center distance to the maximum allowable value of 0.42 m, a decrease of 91.5% in the completeness of separation is observed in the cleaning of the potato tubers, which is lower than the minimum value of the cleaning of the bulbs by 7%, and is explained by a decrease in the transverse amplitude of the oscillation of the web, due to the connectivity of the potato tubers in the tuber nest of the plant.

The performance indicators are expressed by the correlation dependence:

$$\begin{cases} \mathbf{D}\_{\rm B}(\mathbf{S}\_{\rm L}) = 1.88 - 0.17 \cdot \mathbf{S}\_{\rm L} - 0.02 \cdot \mathbf{S}\_{\rm L}^2 \\ \mathbf{D}\_{\rm T}(\mathbf{S}\_{\rm L}) = 1.54 + 0.03 \cdot \mathbf{S}\_{\rm L} - 0.07 \cdot \mathbf{S}\_{\rm L}^2 \end{cases} \tag{8}$$

$$\begin{cases} \mathbf{v}\_{\text{II}}(\mathbf{S}\_{\text{II}}) = 99.2 - 2.84 \cdot \mathbf{S}\_{\text{L}} + 0.43 \cdot \mathbf{S}\_{\text{L}'}^2\\ \mathbf{v}\_{\text{K}}(\mathbf{S}\_{\text{JI}}) = 98.1 - 3.16 \cdot \mathbf{S}\_{\text{L}} + 0.35 \cdot \mathbf{S}\_{\text{L}}^2 \end{cases} \tag{9}$$

The graphic dependences of the change in the quality indicators of the harvesting of potatoes and onions using a rod elevator with an adjustable blade inclination angle on the forward speed vK of the machine, are shown in Figure 9.

An increase in the studied technological indicator of potato harvesting leads to a decrease in the quality indicators of the minimum values of 1.0% of damage to the tubers, and the 93.8% completeness of separation to the maximum of 1.2% for damage and 97.3% of the completeness of separation.

At the same time, it should be noted that there is a distinctive feature in terms of the damage to onion commercial products, with an increase in the forward speed of the machine from 1.5% to 2.0%, which is explained by an increase in the collisions between the bulbs due to the thickening of their planting, and an increase in the supply of commercial products for separation.

The difference between the minimum values of the damage to bulbs and tubers reaches 1.5% and 1.0%, respectively, with maximum values of 1.2% and 2.0% damage, and is expressed by the equations of parabolic functions:

$$\begin{cases} \mathbf{D}\_{\rm B}(\mathbf{v}\_{\rm K}) = 1.88 - 0.17 \cdot \mathbf{v}\_{\rm K} - 0.02 \cdot \mathbf{v}\_{\rm K'}^2\\ \mathbf{D}\_{\rm T}(\mathbf{v}\_{\rm K}) = 1.54 + 0.03 \cdot \mathbf{v}\_{\rm K} - 0.07 \cdot \mathbf{v}\_{\rm K}^2 \end{cases} \tag{10}$$

The difference between the quality of the cleaning by groups of commercial products is no more than 2%, with an increased completeness of separation of 97.3% for the harvesting of onions and a minimum value for the harvesting of potatoes of 93.8% with a correlation dependence:

$$\begin{cases} \mathbf{v\_{B}(v\_{K})} = 98.7 - 2.56 \cdot \mathbf{v\_{K}} + 0.27 \cdot \mathbf{v\_{K'}^{2}}\\ \mathbf{v\_{T}(v\_{K})} = 98.2 - 1.82 \cdot \mathbf{v\_{K}} + 0.15 \cdot \mathbf{v\_{K}^{2}} \end{cases} \tag{11}$$

Upon analyzing the graphical dependencies (Figure 10), we can say that the maximum damage value is observed for the commercial onion products and is 1.9%, which is 1.7% for potato tubers.

**Figure 10.** Dependence: (**A**) damage to bulbs DB and tubers DT%; and (**B**) completeness of separation of onions ν<sup>B</sup> and tubers νT% of the separating rod elevator with an adjustable blade inclination angle from the translational speed vEL of the rod elevator.

The minimum damage value of 1.2% is for all the groups of the commercial products, and increases with an increase in the forward speed of the rod elevator in the range of 1.0 to 1.8 m/s. The correlation between the damage to the marketable products of potato tubers and onion bulbs is determined by the expression:

$$\mathbf{D}\_{\rm B\prime} \, D\_{\rm T}(\mathbf{v}\_{\rm EL}) = 1.08 - 0.12 \cdot \mathbf{v}\_{\rm EL} + 0.7 \cdot \mathbf{v}\_{\rm EL}^2. \tag{12}$$

The maximum separation completeness of more than 98.8% is observed in onion harvesting, which is higher than the completeness of the potato tubers' cleaning by 1%, at a forward speed of the rod elevator of 1.8 m/s.

At the minimum value of the studied indicator of the harvesting machine, equal to 1 m/s, the completeness of the cleaning has a minimum value for potato tubers of 96%, which is 2% higher than that for onion harvesting.

In addition, the optimal value of the forward speed of the rod elevator, at which the approximation of the cleaning completeness curves is 96.8% at a speed value of 1.3 m/s, is described by the correlation dependence:

$$\begin{cases} \mathbf{v\_{B}(v\_{\rm EL})} = 92.4 - 2.08 \cdot \mathbf{v\_{EL}} - 0.15 \cdot \mathbf{v\_{\frac{2}{\rm EL}}^{2}}\\ \mathbf{v\_{T}(v\_{\rm EL})} = 96.2 + 0.31 \cdot \mathbf{v\_{EL}} + 0.07 \cdot \mathbf{v\_{EL}^{2}}. \end{cases} \tag{13}$$

According to the results of the research, it follows that the optimal ratio of the quality indicators of onion harvesting is ensured when crossing curves approximate the completeness of separation at 95.5% and the damage to the bulbs at 1.2% at a forward speed of 1.38 m/s of the machine for the harvesting of root crops and onions.

The reliability of the conducted studies was assessed by the calculated value of the mathematical expectation М(Х), and the normal law of the distribution of the damage to the commercial products on a bar elevator is:

$$\mathbf{M}(\mathbf{X}) = \mathbf{0}.\mathbf{3}.\tag{14}$$

Student's distribution quantile:

$$\mathbf{T} = \mathbf{q}\mathbf{t} \left(1 - \frac{\alpha}{2}, \boldsymbol{\upsilon}\right) = 2.012. \tag{15}$$

Calculation of statistics criterion and distribution of a random variable over intervals submitted in Table 1.


**Table 1.** Calculation of statistics criterion and distribution of a random variable over intervals.

Graphically, the observed and expected frequencies are determined by constructing scatter plots (Figure 11).

**Figure 11.** Plot of observed values (empirical cumulative distribution) versus expected frequencies (theoretical cumulative distribution).

The mathematical expectation M(X) of the normal distribution law for the separation of the potato tubers and bulbs on the developed cleaning device:

$$\mathbf{M}(\mathbf{X}) = \mathbf{0}.\mathbf{2}.\tag{16}$$

Student's distribution quantile:

$$\mathbf{T} = \mathbf{q}\mathbf{t} \left( 1 - \frac{\alpha}{2}, \boldsymbol{\upsilon} \right) = 2.012. \tag{17}$$

Calculation of statistics criterion and distribution of a random variable over intervals submitted in Table 2.

**Table 2.** Calculation of statistics criterion and distribution of a random variable over intervals.


Graphically, the observed and expected frequencies are presented in the scatter plot (Figure 12).

**Figure 12.** Plot of observed values (empirical cumulative distribution) versus expected frequencies (theoretical cumulative distribution).

The statistical processing of the results of the experimental studies, according to the criteria S2 <sup>y</sup> и S<sup>2</sup> LF, are shown in Figure 13.

**Figure 13.** Statistical characteristics of experience error.

The results of the conducted field studies on a machine for harvesting root crops and onions, equipped with a bar elevator with an adjustable blade inclination angle and an asymmetric arrangement of shakers, showed the high-quality performance of the technological process of separating turnips and potato tubers at the optimal values of the parameters: a completeness of separation of more than 98%, and damage to the products of up to 1.7% at a speed of movement of 1.7 m/s of the separating system; a completeness of separation of more than 98%, and s product damage of up to 1.1% at a speed of up to 1.0 m/s of the harvester, and a separation completeness of more than 98%, and product damage of up to 1.4% at a commercial product extraction depth of 0.02 m.

The results obtained from the studies are consistent with the previously known data on the development and testing of machines in terms of the cleaning of the marketable products of root and tuber crops.

The obtained research results are consistent with the previously known directions for improving the design of harvesters.

Research performed by V.P. Khambalkar and colleagues developed an onion harvester that has been helpful in harvesting the onion bulb effectively. The design of the onion harvester greatly depended on the working width, the depth of the operation, and the conveying capacity. The agro-technical data of the crop has been collected from the university field regarding the depth of the onion bulb, the spacing between the plant and the row-to-row distance, the height of crop, and the polar and equator dimensions of the onion bulb. The overall size of the harvester is 1020 × 600 × 300 mm. The width-to-depth ratio for the optimum operation performance is chosen to be 6:1. The depth of the operation according to the agro-technical requirement comes to be 10 cm. The working width of the machine, with respect to the power availability and the crop sowing characteristics, comes to be 60 cm [18].

#### **4. Conclusions**

For the manufacture and production of the technical means of a potato harvesting machine, it is recommended to choose technological parameters from experimentally confirmed values that ensure the high-quality performance of the harvesting process.

Improving the design and technological schemes of the machines for harvesting potatoes and onions, on the basis of the conducted research, can further be used in the system for monitoring the quality indicators of the machines for the harvesting and postharvest processing of potatoes and other agricultural root crops, which will provide a new level of synthesis of the complex technical systems of agricultural production.

The proposed technological and technical solutions can serve as a basis for expanding the research on and practical implementation of Russia's transition to the sustainable development of vegetable production.

**Author Contributions:** Conceptualization, A.S.; methodology, A.D. and M.G.; software, N.S. and M.G.; validation, A.A.; investigation, A.S.; resources, M.M.; writing—original draft preparation, M.G.; writing—review and editing, A.S.; project administration, A.S.; funding acquisition, N.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was carried out with the financial support of the Russian Science Foundation of the 2022 contest "Conducting research by scientific groups led by young scientists" of the Presidential Program of research projects implemented by leading scientists, including young scientists No. 22-76- 10002.

**Institutional Review Board Statement:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

**Informed Consent Statement:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

#### **References**


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