راه‌اندازی واحدهای درو، کوبنده و تخلیه کمباین برداشت غلات توسط سیستم محرک جک بادی

Introduction
Agricultural mechanization has become a crucial component in addressing the increasing global demand for food production while minimizing production costs and environmental impacts. Among agricultural machinery, combine harvesters play a vital role by integrating multiple harvesting processes such as cutting, threshing, separating, and unloading into a single operation. However, most conventional combine harvesters rely on hydraulic and mechanical actuation systems for controlling their primary functional units, including the header, threshing, and unloading mechanisms. Although these systems are well established, they are often characterized by relatively high energy consumption, complicated maintenance requirements, the risks of hydraulic oil leakage, and performance degradation under prolonged field use.
In recent years, pneumatic actuation systems have gained attention in various agricultural and industrial applications due to their advantages, including simpler design, lower weight, faster response time, no risk of oil leakage, and reduced operational costs. Studies such as those by Johnson (2023) and Gryboś (2024) have reported significant energy-saving potentials for pneumatic systems compared to conventional drives in different industrial settings. However, the use of pneumatic systems in combine harvesters has been limited, and there is a lack of comprehensive research evaluating their performance under real field conditions, particularly regarding durability, energy efficiency, and operational reliability.
This study was conducted to design, develop, and evaluate a pneumatic actuator (air cylinder) system as a substitute for traditional hydraulic and mechanical systems in combine harvesters. The main objectives were:
To reduce energy consumption and operational time during harvesting.
To improve the reliability, uniformity, and responsiveness of the drive system.
To assess the durability and maintenance costs under real working conditions.
To evaluate the economic feasibility of implementing pneumatic actuation in grain harvesters.
 
Materials and Methods
The study was carried out on a New Iran model straw combine harvester manufactured by Sabz Abad Hegmataneh Company in Hamedan Province, Iran. The field experiments were conducted on the Ehsan wheat variety.
The research followed a multi-stage approach comprising conceptual design, 3D modeling, dynamic simulation, prototype development, and field testing. Initially, a complete 3D model of the pneumatic actuation system was developed in SolidWorks 2018. Dynamic simulations, including analyses of displacement, velocity, acceleration, and force analysis under varying loads, were performed using MSC ADAMS. The prototype was then integrated into the combine harvester to replace the conventional hydraulic and mechanical drives of three key units:
The header unit for height adjustment,The threshing unit for concave clearance control,The unloading system for operating the auger pipe and grain discharge.
The experimental design was a randomized complete block design (RCBD) with three replications and three treatments: pneumatic, hydraulic, and mechanical drive systems. Key performance indicators included:
Energy consumption (kWh) measured using flow and pressure sensors,Unloading time (s) recorded using a stopwatch,Threshing efficiency (%) and uniformity of power transmission measured under field conditions,Durability (h) tested under dusty and humid environments,An economic evaluation of initial and annual maintenance costs.
Statistical analyses were performed using IBM SPSS Statistics 26, employing independent t-tests and one-way ANOVA followed by Duncan’s multiple range tests at a 5% significance level.
 
Results and Discussion
The experimental results revealed that the pneumatic system significantly outperformed the conventional hydraulic and mechanical systems across all major performance parameters.

Energy Consumption

The pneumatic system consumed only 12.3 ± 0.8 kWh, representing a 23% reduction compared to the hydraulic (15.9 ± 1.1 kWh) and mechanical systems (16.4 ± 1.1 kWh). Similar energy-saving benefits were reported by Boyko and Weber (2024) in industrial pneumatic drives, indicating that air-actuated systems inherently require less energy due to the absence of continuous fluid pumping losses typical in hydraulic circuits.

Unloading Time

The unloading time of the grain tank decreased significantly from 54.3 ± 2.0 s (hydraulic) and 55.1 ± 2.1 s (mechanical) to 39.2 ± 1.5 s for the pneumatic system—a 28% reduction. Faster unloading allows for reduced combine downtime and improved field capacity, which is crucial for large-scale grain production systems.

Threshing Efficiency and Power Transmission Uniformity

Threshing efficiency reached 91.0 ± 2.2% with the pneumatic system, compared to 84.5 ± 2.5% for the hydraulic and 82.3 ± 0.3% for the mechanical systems. The smoother motion of pneumatic actuators minimized vibrations and shocks, reducing grain breakage and ensuring more uniform power delivery to the threshing drum.

Durability and Reliability

Durability testing under harsh field conditions (dust, moisture, and variable loads) showed that the pneumatic system maintained stable performance for 1200 operational hours, while the hydraulic and mechanical systems deteriorated after 930 h and 850 h, respectively. Reduced wear and the absence of hydraulic oil contamination were key contributing factors to the extended lifespan.

Economic Evaluation

The initial cost of the pneumatic system was 17% lower than that of the hydraulic system, while annual maintenance costs were reduced by 35%. The absence of hydraulic fluids, filters, and frequent servicing requirements resulted in significant long-term cost savings, making the pneumatic system economically attractive for farmers.

Effect of Field Variables

ANOVA results indicated that grain moisture content, threshing drum speed, and combine forward speed significantly influenced grain losses (p < 0.05). However, under optimized operational settings, the pneumatic system consistently exhibited lower grain loss and better performance than conventional systems.

Simulation Insights

Dynamic simulations in ADAMS revealed that pneumatic actuators provided smoother acceleration profiles, reduced peak forces during start-up, and minimized mechanical shocks. These findings align with those of Dettu et al. (2023), who reported similar benefits in precision agricultural machinery using pneumatic controls.
Collectively, these results demonstrate that pneumatic systems not only improve operational efficiency but also enhance machine reliability, reduce environmental risks associated with oil leaks, and support the broader goal of sustainable agricultural mechanization.
 
Conclusion
This research confirms that integrating pneumatic actuators into combine harvesters can significantly enhance energy efficiency, operational speed, durability, and cost-effectiveness compared to conventional hydraulic and mechanical systems. Key findings include:
A 23% reduction in energy consumption,A 28% decrease in unloading time,Improved threshing efficiency (91%) with reduced grain losses,Extended operational life up to 1200 hours,A 17% lower initial cost and a 35% reduced maintenance expenses.
Given these advantages, pneumatic actuation represents a promising alternative for next-generation agricultural machinery aiming for sustainability, cost reduction, and improved productivity. Future studies should explore hybrid pneumatic-hydraulic systems and incorporate advanced control algorithms, such as fuzzy logic and machine learning, to further optimize system performance under diverse field conditions.