Modified Design of a Precision Planter For a Robotic Assistant Farmer

External loads and boundary conditions: The external loads on this part are actually 
the forces that are applied to gauge wheel when interacting with the soil. The forces calculated in 
chapter 3, the vertical and horizontal forces on the gauge wheel are G
y
=1200 N and G
x
=308 N, 
respectively. These forces are in y and x direction of the ground coordinate system. In other 
words, they are horizontal and vertical with respect to the ground. But they will have different 
components with respect to a coordinate system that is parallel to the depth control links faces. 
Their components in the x, y and z direction of this coordinate system can be calculated, using 
the geometry of the assembly, trigonometry functions and the disc and tilt angles of the disc. 
These calculated components can be found in Table 4-1. X, Y and Z components shown in Table 
4-1 are parallel to depth control link’s sides. These external forces are applied on the surface of 
the hole, forces C and D, as shown in Figure 4-3. 
Table 4- 1- Components of external forces in the coordinate system parallel to faces of 
depth control link 
Horizontal 
force 
Vertical 
force 
X component 
276.6 N 
511.1 N 
Y component 
-131.2 N 
1077.8 N 
Z component 
33.5 N 
130.4 N 
Total (N) 
308 N 
1200 N 
At point A, which is the hinge, and point B, which is the pin, cylindrical support is 
defined as boundary condition. Cylindrical support is a type of support that can be used for 

---

80 
cylindrical shape that does not bear tangential load, such as bearings. To model pinned or hinge 
support, radial and axial directions are fixed and tangential DOF is set free to rotate for both 
cylindrical support A and B. 
Remote force can be applied to the part from any point in the space. To define a remote 
force, the location of force, its direction and which part of the body that the force is applied must 
be defined. For depth control link, the remote forces are applied in the center of the hole (see 
Figure 4-3) and to the interior face of the hole. 
Figure 4- 3-Geometry and supports of depth control link 

---

81