# Design and Experimental Study of Potato-Soil Separation Device for Sticky Soils Condition
## 3 Key Component Parameter Design and Analysis
### Parameters of Debris-Cleaning Mechanism and Kinetic Analyses during Cleaning Area  
Winter potatoes in southern China are primarily planted with grass and film mulching [34]. In the mechanical harvesting, other than soil and potatoes, weeds and broken much film were mixed. To clean the flexible haulm and mulch, a debris-cleaning mech  
Figure 5: Analysis of the throwing process of potato-soil mixture. anism was designed. According to Figure 6a, a debris-cleaning mechanism consisted of a rubber roller and smooth roller with relative rotation. Its principal effect was cleaning the inclusion of the flexible haulm and mulch. Moreover, the potato-soil mixture was transported backward. For the debris-cleaning mechanism, the rubber roller and smooth roller were 630 mm in length (\(L_{6}\)), with a gap of 5 mm (\(S_{2}\)), and the smooth roller diameter was 75 mm (\(D_{4}\)), and the rubber roller diameter was 140 mm (\(D_{5}\)). On the rubber roller surface, three prisms aligned in a spiral line were set. The pitch of the helix was equated with the length of the roller (\(L_{6}\)), and the prism height (\(h_{2}\)) was 15 mm. The convex prisms were aligned uniformly and circumferentially with an included angle of 120\({}^{\circ}\) between the adjacent prisms. Furthermore, the cross-section was an isosceles triangle. Under the debris-cleaning mechanism, to ensure an uneventful delivery of the potato-soil mixture, the kinetic analyses of the potato-soil mixture were performed. According to Figure 6b, the potato-soil mixture on the debris-cleaning mechanism was assumed as a sphere with radius \(R_{1}\) and fell between the rubber roller and smooth roller through the first-stage lifting chain throwing. The frictions were expressed as:  
\[\left\{ \begin{array}{l}F_{f4}=F_{4}\mu\\ F_{f5}=F_{5}\mu^{\prime}\end{array} \right. \tag{9}\]  
where \(F_{f4}\) denotes the friction between potato-soil mixture and rubber roller, N; \(F_{f5}\) represents the friction between potato-soil mixture and smooth roller, N; \(F_{4}\) expresses the support force of the rubber roller to the potato-soil mixture, N; \(F_{5}\) denotes the support force of the smooth roller to the potato-soil mixture, N; \(\mu\) represents friction coefficient between potato-soil mixture and rubber roller; \(\mu^{\prime}\) is friction coefficient between potato-soil mixture and smooth roller. The collision force (\(F_{6}\)) applied to the potato-soil mixture was expressed as:  
\[F_{6}=\frac{2M_{2}}{D_{5}}=\frac{2\omega_{2}j_{2}}{D_{5}} \tag{10}\]  
where \(M_{2}\) denotes the moment of momentum when the rubber roller rotates, N\(\cdot\)m; \(D_{5}\) expresses the diameter of rubber roller, m; \(\omega_{2}\) is the angular velocity when the rubber roller rotates, rad\(/\)s; \(j_{2}\) is the moment of inertia of the rubber roller. Figure 6: (**a**) Structural parameters of the debris-cleaning mechanism; (**b**) the kinetic analyses of potato-soil mixture during cleaning area. According to Figure 6b, the potato-soil mixture rotated backwards around position O\({}_{2}\). The rotational centrifugal forces of rubber roller and smooth roller were disregarded, and the moment equation for point O\({}_{2}\) was expressed as:  
\[\Sigma M_{\text{O}_{2}}=F_{4}R_{1}\cos\beta_{2}-R_{1}\Big{(}F_{4}+F_{6}\Big{)}(1 -\sin\beta_{2})-G_{4}R_{1}\cos(\beta_{1}+\beta_{2}) \tag{11}\]  
where \(G_{4}\) denotes the gravity of potato-soil mixture, N; \(R_{1}\) represents the radius of potato-soil mixture, m; \(\beta_{1}\) represents the inclination angle between the gravity (\(G_{4}\)) and the connecting line \(OO_{1}\), \({}^{\circ}\); \(\beta_{2}\) expresses the inclination angle between the supporting force (\(F_{5}\)) and the straight line passing through the point O and perpendicular to the connecting line \(OO_{1}\), \({}^{\circ}\). The necessary conditions for an uneventful delivery of the potato-soil mixture were \(\sum M_{\text{O}_{2}}\geq 0\) and \(\sum F_{OO_{1}}\geq 0\).