Modified Design of a Precision Planter For a Robotic Assistant Farmer

Solution and results discussion: Figure 4-21(a) and 4-21(b) shows the equivalent (Von 
mises) stress for vertical pull bar in pulling condition and lifting condition, respectively. The 
method to find the correct value for maximum stress is the same as what discussed before for 
other parts. The maximum stress in pulling condition is found to be 19 MPa, and in lifting 
condition 28 MPa. These values result in a safety factor of 13.2 and 8.9, respectively. 
(a) 
(b) 
Figure 4- 21- Equivalent (Von mises) stress for vertical pull bar, in (a) pulling condition 
and (b) lifting condition 
4-2-7- Horizontal pull bar 
This part is also analyzed the same as vertical pull bar in two different configurations, 
pulling and lifting. From the analysis of the vertical pull bar, the reaction forces at supports can 
be found. These forces are used in analysis of horizontal pull bar. 

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Meshing: Meshing for this part is shown in figure 4-22 and is used for both 
configurations. Finer mesh and smaller element sizes are used for regions with stress 
concentration. 
External loads and supports: The first 80 mm of the horizontal pull bar goes inside the 
hitch that is available at the back of the mobile robot to pull the implement. A pin is used to keep 
the bar inside the hitch. Reaction forces found from the analysis of vertical pull bar are the 
external loads on this part. 
In pulling condition, external loads are reaction force and moment at points A and E and 
reaction force at point B in Figure 4-20(a). 
Figure 4- 22- Meshing for horizontal pull bar 
In lifting condition, external loads are the reaction force at pin, point B in Figure 4-20(b) 
and the cable tension. The cable tension is transferred to the horizontal pull bar via the winch and 

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the bolts. Figure 4-23(a) and 4-23(b) shows the external forces and supports for horizontal pull 
bar in pulling and lifting conditions, respectively. 
(a) 
(b) 
Figure 4- 23- Geometry, external loads and supports for horizontal pull bar, in (a) pulling 
condition, and (b) lifting condition 

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