Development and Implementation of Electro Pneumatic Control Systems for Mechanized Operation of Combine Harvester Functional Units

Grain harvesters, as one of the most complex agricultural machines, have numerous subsystems whose precise control plays a decisive role in reducing harvest losses, increasing crop quality, and improving operator ergonomics. In many conventional combines, parts such as the platform, fork, thresher, and grain discharge pipe are controlled mechanically or hydraulically, which leads to increased wear, high maintenance requirements, and reduced control accuracy. Advances in pneumatic and electrical systems have made it possible to control these parts with higher accuracy, greater safety, and more appropriate automation capabilities. The purpose of this paper is to present a comprehensive structure for the setup and evaluation of a combined electric-pneumatic system in wheat harvesters. In recent years, advanced mechanization in harvesting machines, especially grain combines, has become one of the central issues in increasing productivity and reducing cost per unit area. Currently, many domestic combines use traditional mechanical or hydraulic systems to perform the operations of raising and lowering the harvesting platform, controlling the forks, and discharging straw and wheat, which have limitations such as response delay, oil leakage, high energy consumption, and increased component wear.
Materials and Methods
In this study, a hybrid electric-pneumatic control system was designed, simulated, and implemented for four key parts of the combine harvester: 1- platform raising and lowering, 2- fork control (horizontal and vertical movement), 3- straw control, and 4- wheat discharge through the outlet pipe. In the present design, the electric control circuit is combined with a PLC control unit and pneumatic actuators including solenoid valves and double-way cylinders to achieve accurate and fast control of movements. The system was modeled in MATLAB/Simulink software and tested in a practical environment with position and pressure sensors. This system was designed and manufactured at the Sabzabad Hegmataneh Combine Harvester Factory in Hamadan (New Iran) and field tested in the wheat fields of Shurin village, Hamadan city. The proposed system consists of an electrical control circuit and a pneumatic power circuit. The control circuit consists of an industrial PLC unit, cabin control switches, relays, and a 24V power supply module. The pneumatic circuit consists of an air compressor, a storage tank, a air monitoring unit (FRL), 5/2 solenoid valves, and two-way cylinders.
Results and Discussion
The results of this study demonstrated that the proposed electro-pneumatic control system significantly improved the dynamic and operational performance of the combine harvester. Field experiments showed that the average response time of the controlled mechanisms was reduced to less than 0.8 s, representing a considerable improvement compared to conventional hydraulic systems. MATLAB/Simulink simulations confirmed the faster transient response and higher stability of pneumatic actuators under PLC-based control. Energy consumption measurements indicated a reduction of approximately 23% relative to the hydraulic counterpart. Furthermore, positioning accuracy was enhanced, with a maximum error below 3%. Vibration analysis revealed a reduction of nearly 30%, leading to lower mechanical stress and extended component lifespan. These results confirm the feasibility of electro-pneumatic systems as an effective solution for upgrading conventional harvesting machines and enabling future intelligent control applications.
Conclusion
The obtained results clearly indicate that integrating electro-pneumatic actuators with PLC-based control can effectively overcome several inherent limitations of conventional hydraulic systems used in combine harvesters. The significant reduction in response time observed in all controlled subsystems is mainly attributed to the lower inertia of pneumatic actuators and the direct on–off control of solenoid valves, which eliminates delays associated with fluid compressibility and pump-driven hydraulic circuits. The consistency between MATLAB/Simulink simulations and field measurements confirms the validity of the developed dynamic model and demonstrates that the proposed control architecture is capable of accurately predicting real operational behavior. The reduction in overall energy consumption can be explained by the elimination of continuously operating hydraulic pumps and leakage losses, which are common in traditional systems. Moreover, the improved positioning accuracy observed in the electro-pneumatic system is a direct consequence of closed-loop control using position sensors, allowing precise motion regulation under varying field conditions. The noticeable decrease in vibration levels further highlights the smoother motion profile of pneumatic actuators, which reduces impact loads on mechanical components and contributes to extending service life.The successful design and testing of the system under real harvesting conditions confirm its robustness and adaptability. Overall, the findings suggest that electro-pneumatic control systems represent a promising and cost-effective alternative for modernizing domestic combine harvesters and provide a solid foundation for future integration of intelligent and sensor-based control strategies.This combination not only increased reliability and reduced component wear, but also paved the way for the implementation of intelligent automatic control systems in agricultural machinery. This system, while reducing operator fatigue, also allows for the addition of intelligent sensor-based control and the Internet of Things (IoT). Therefore, the combination of electric and pneumatic control can be recommended as an effective option for the modernization of domestic harvesting systems.