Modified Design of a Precision Planter For a Robotic Assistant Farmer

3-4-Summary 
In this chapter, the design process which leads to the developed planter is discussed. All 
design processes begin with data and information collection. The study of the literature in 
chapter 1, and the data obtained from the experiments in chapter 2 was used for the design 
process. Then the conceptual design was performed with some preliminary calculations on 
different parts that were developed for the planter, such as power transmission for precision seed 
metering system and lifting mechanism. Then static analysis to find the total draft force and total 
vertical force of the developed planter was performed. Optimization analysis was performed to 
minimize the change in the down force of the press wheel, when it moves up and down. 
Minimization in the change of the down force on the press wheel results in steadier down 
pressure on the soil and therefore better emergence results. Also spring design process was done 
to design the springs that provide down force on the gauge wheel and press wheel. Although the 
safety factor that was found for these springs were slightly higher than 1, but a hidden safety 
factor was already included in the calculations. This is due to the fact that the maximum vertical 
displacement that was assumed for the planter is almost twice as its usual value. So another 
safety factor of two was already inside the calculations. 

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Chapter 4- Stress Analysis Using Finite Element Method 
4-1- Introduction 
Finite Element method has been introduced to simplify the problems that involve 
continuity. FEM gives us an approximate answer to real life problems by discretizing them. 
Since the shapes of the parts that are designed for the planter and the loads that are 
applied to them, are not simple and straight forward, so the calculations to find where the 
maximum stress happens and also its magnitude cannot be done by hand. Also complexity of the 
model makes it very difficult to find the interaction between the parts. Thus, to make sure that 
the designed parts have enough strength and do not fail due to high stresses in them, a stress 
analysis needed to be performed. 
Besides that, to validate the FEM results, simple hand 
calculations are done.(Remove)
The process of modeling and performing stress analysis is done using the following steps, 
1) 3D modeling in Solid-Works, 2) Transferring the 3D model to ANSYS, using STEP format, 
3) Geometry adjustments (in case of data loss due to file transfer from Solidworks to ANSYS), 
4)Meshing, 5)Appling loads and boundary condition, 6) Solving the problem, 7) analysis of the 
results 
Since the shape of the parts and boundary conditions are complicated, ANSYS 
Workbench is used instead of ANSYS Classic; because ANSYS WB is more convenient in 
dealing with complex geometries.

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