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

Introduction
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, real, thresher, and grain discharge mechanism are controlled mechanically or hydraulically, reduce 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 reals, 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. The overall system reliability reached 0.93, exceeding that of typical domestic combine harvesters. 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 results show that integrating electro-pneumatic actuators with PLC-based control effectively addresses key limitations of conventional hydraulic systems in combine harvesters. Faster response times are mainly due to the lower inertia of pneumatic actuators and direct on–off solenoid valve control, which removes delays from fluid compressibility and hydraulic pump circuits. Good agreement between MATLAB/Simulink simulations and field measurements confirms the validity of the dynamic model and the accuracy of the proposed control architecture. Overall energy consumption is reduced by eliminating continuously running hydraulic pumps and leakage losses. The electro-pneumatic system also improves positioning accuracy through closed-loop control with position sensors and reduces vibration by providing smoother motion, lowering impact loads and extending component service life. With a reliability index of 0.93 and successful real-world testing, the system is technically feasible and suitable for industrial use. Overall, it is a promising, cost-effective alternative for modernizing domestic combine harvesters and supports future intelligent, sensor-based control and IoT applications.
Acknowledgement
Thanks to the staff and personnel of New Iran Combine Harvester Company (Sabzabad Hegmataneh).