Modified Design of a Precision Planter For a Robotic Assistant Farmer

5-2-2- Indoor tests 
Indoor tests were designed to study the draft force required to pull the implement by the 
robot. But at the same time the accuracy of seeding has also been studied. 
This test was performed in the soil bin, college of Engineering, University of 
Saskatchewan. All the settings has been prepared to simulate the conditions of a farm land.
Test setup: The planter was attached to the mobile robot and it was pulled while disc was 
inside the soil. Soil has been prepared, with medium packing (See to chapter 2) and with about 
13% soil moisture. The working length of the soil bin for this test was around 5 m. A vacuum 

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was used to provide the negative pressure needed for seed singulator suction. To measure the 
draft force, two load cells were used. One end of each load cell was attached to the mobile robot 
and the other end was attached to the planter while pin of the hitch which connects the planter set 
to the robot was removed (See Figure 5-7). 
Figure 5- 7- Load cells attached between the mobile robot and planter, 1) Grizzly mobile 
robot, 2) Hitch (pin removed), 3) Load cell, 4) Planters set, 5) Hand winch 
Each of these load cells can carry up to 5000 lb force. To make sure that the load cells are 
carrying all the load of the pulling force, the connecting pin of the hitch of the robot has been 
removed and the connection inside the hitch was lubricated to reduce the friction inside the hitch 
as much as possible. The connection must remain inside the hitch to keep the planter in up-right 
position and pushed down the disc into the soil. Although the friction inside the hitch will carry 
some of the pulling force, but it can be calculated and be added to the value that is read by the 
load cells.

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The signal from the load cells are sent to amplifiers and from the amplifiers to the data 
acquisition and then to a laptop computer to be recorded. The data acquisition software records 
10 values per second for each load cell. The power for the vacuum, amplifiers and laptop was 
provided by a 12V DC battery. The voltage was inverted to 110 V AC, using a 1500 W power 
invertor so it can provide enough current for all the equipment. The equipment were mounted on 
top of the mobile robot which pulls the planter set in the soil bin (See Figure 5-8). 
Figure 5- 8- Mobile robot pulling the planters set inside the soil bin 
Calibration: Load cells were calibrated before attaching to the robot and the planter set. 
Specific weights were loaded on the load cell and the output voltages were recorded. The gain of 
the amplifiers were set to have maximum output of 10V for 200Kg mass. Figure 5-9 shows the 
calibration setup and figure 5-10 shows the data obtained from calibration. 

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Figure 5- 9- calibration setup 
Figure 5- 10- Calibration graph for Load cell, V = 0.0505m - 0.0004 
Calibration graph shows that the output of the load cell is completely linear with almost 
zero intercept. 
Procedure: The male and female parts of the hitch were lubricated and the planter set 
was attached to the mobile robot. Load cells were attached to mobile robot and planter using 
chains. The depth of cut was set and the planters were lowered down and discs were pushed into 
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