## 3 Control System for Work Vehicle
### Working Width Adjustment Control System  
In the structural design, the upper fertilization monomer is attached to the rear wheel frame. By adjusting the spacing between the rear wheels, the monomer can achieve horizontal movement. This adjustment primarily relies on two fixed electric cylinders located at the top. Each pushrod is operated through two controls: one on the control panel  
Figure 16: Servo system wiring diagram.  
Figure 15: Voltage grouping wiring diagram.  
and another via a stroke switch mounted on the fertilization monomer, as illustrated in Figure 17.  
During the actual field operation, the working width adjustment mechanism can flexibly adjust the position of the fertilizer application monomer according to the row spacing of corn. Before the operation, the user sets the working width through the button on the control panel. In the process of working, if the vehicle trajectory deviates or the row spacing of the plants changes, resulting in the monomer being too close to the plants, the limit switch on the monomer will be triggered. This sends a signal to the control system, activates the relay, and makes the electric cylinder move the monomer away from the plants until the switch is not in contact, achieving the optimal width. The two electric cylinders at the top work together to ensure stable and accurate horizontal movement, adapt to the field conditions, and improve the fertilization accuracy. This study selected a reset type limit switch with an operating force of 150 g and a travel of 25 mm. After continuous field operation tests, the triggering accuracy of the limit switch system remained above 95% in harsh environments such as high temperature, high humidity, and sand and dust. To ensure long-term reliability, the surface of the limit switch needs to be cleaned of dust and debris after each use of the vehicle, and the wear of the metal contacts should be checked every 50 h of cumulative work, and severely worn parts should be replaced in a timely manner.  
The wiring diagram for the regulating system is presented in Figure 18. In this diagram, SB 11 and SB 21 represent the button switches, while components SQ 11 and SQ 21 denote the limit switches. The electromagnetic relays are identified as KA 1 and KA 2, rated for a DC voltage of 24 V and a maximum current of 5 A.  
The system operates through these relays, where the normally open contacts are 5 to 9 and 8 to 12. When the relay KA1 is activated, the open contacts 5 and 9, 8 and 12 inside KA1 close, forming a circuit with the electric cylinder motor, and the electric cylinder rotates forward at this time. When the relay KA2 is activated, the open contacts inside KA2 close, and the power supply polarity connection is opposite to that of forward rotation,  
Figure 17: Installation diagram of the limit switch.  
Figure 18: Vehicle width adjustment circuit diagram.  
and the push rod rotates in reverse at this time. This configuration ensures that the electric cylinder can work in both forward and reverse directions according to the polarity of the power supply.  
Importantly, if both probes are triggered simultaneously, the electric cylinder motor will not operate due to a short circuit, thereby implementing a safety interlock mechanism.