In order to solve the problem of the threshing performance of a large combine harvester being reduced due to the non-adjustable diameter of the threshing drum, a variable-diameter threshing drum with movable radial plates based on the principle of concentric regulation was studied. It was mainly composed of a mechanism for adjusting the diameter by moving the radial plates, six fixed threshing tooth rods, six retractable threshing tooth rods and the single piston rod hollow hydraulic cylinder. The threshing gap can be adjusted by a stepless change of the drum diameter. By using RecurDyn simulation and field performance tests, the adjustable ranges of diameter and gap of the movable variable-diameter threshing drum were 670~710 mm and 10~30 mm. Based on the feed amount of the combine, the rotation speed of the threshing drum and the threshing gap (the diameter of the drum) as the influencing parameters, and the grain entrainment loss rate, grain un-threshed rate and grain breakage rate as the evaluation indexes, the three-factor and three-level response surface tests were carried out, and the result data were analyzed using Design-Expert 13.0. The optimal threshing gap and rotation speed of the threshing drum were determined under different feeding quantities. A comparative test was carried out to adjust and fix the threshing gap and rotation speed of the threshing drum in real time according to the change in feeding amount. The results showed that when the working parameter combination under different feeding amounts was adjusted in real time, the entrainment loss rate was 0.65%, the un-threshed rate was 0.063% and the breakage rate was 0.47%. Compared with the threshing gap and the rotation speed of the threshing drum being fixed, the entrainment loss rate, the un-threshed rate and the breakage rate were reduced by 44.9%, 27.6% and 34.1%, respectively. A threshing drum with variable diameter was provided for a large multi-crop harvesting combine to realize the concentric stepless adjustment of the threshing gap.

The objective is to address the issue of excessive vibration in the cab of the combine harvester. This study addresses excessive cab vibration in the Linhai 4LZ-7.0 combine harvester by analyzing vibration signals under two working conditions using the Short-Time Fourier Transform. The results identified the vibrating screen and grass crusher as primary resonance sources, with maximum vibration along the X-axis. Simulation revealed that their first-order modal frequencies coincided with external excitation frequencies, causing resonance transmission to the cab. To resolve this, the driving pulleys of both components were redesigned and replaced. Post-modification testing showed a 90% reduction in the cab vibration level index from 1215 to 112, a 26% decrease in root mean square values, and the elimination of resonance peaks in frequency spectra. By modifying excitation frequencies to avoid structural resonance, cab vibration was effectively mitigated, significantly improving operational comfort. This paper is the first to pinpoint the primary resonance source and avert harvester resonance by altering its external excitation, delivering an effective, low-cost engineering fix for agricultural-machinery manufacturers; the abstract has been updated accordingly.

Agricultural machinery operates under complex field conditions involving uneven terrain, crop flow impacts, variable speed and load, dust, moisture, and multi-source structural excitation. These factors make vibration-based fault diagnosis more challenging than that of conventional rotating machinery because weak fault features are often masked by non-stationary background vibration and operating condition disturbances. This review provides a structured synthesis of vibration-based fault diagnosis for agricultural machinery, focusing on tractors, combine harvesters, harvesting machinery, and key components such as bearings, gearboxes, transmission systems, headers, threshing drums, cleaning sieves, vibrating screens, chassis, frames, and cab systems. The review first analyzes vibration sources, fault mechanisms, and signal degradation under field conditions. It then summarizes vibration sensors, data acquisition, preprocessing, time–frequency analysis, feature representation, machine learning, deep learning, transfer learning, and multi-source information fusion. Applications are reviewed from component-level diagnosis to whole-machine monitoring. Key challenges include field data scarcity, variable conditions, sensor reliability, data leakage, model generalization, edge deployment, standardization, and long-term validation. Future research should emphasise high-quality field datasets, physics-informed and explainable models, robust cross-condition diagnosis, multimodal sensing, edge intelligence, digital twins, and predictive maintenance. This review highlights the need to connect vibration mechanisms, diagnostic models, and engineering deployment requirements for reliable agricultural machinery health monitoring. Rather than treating sensors, components, algorithms, and deployment issues as separate topics, this review organizes the literature around field-specific vibration disturbances, validation evidence, deployable diagnostic requirements, and future implementation priorities.

To address the pronounced issue of noise and vibration within the combine harvester cab, this study proposes a hybrid simulation and experimental validation approach that integrates the pivot noise transfer function (NTF) with a finite element method (FEM)-based vibroacoustic coupling analysis. A coupled finite element model combining the cab structure and its internal acoustic cavity was developed, with the excitation path characteristics explicitly defined. The coupled interaction between structural and acoustic modes, along with its influence on noise transmission, was systematically examined. The analysis revealed a significant transmission peak near 18 Hz at critical pivot Point D under specific excitation directions, indicating strong directional sensitivity in the excitation–response relationship. Experimental validation showed that the discrepancy between simulated and measured responses, including the NTFs, remained within 15%, confirming the accuracy and applicability of the proposed method. This research offers a reliable analytical framework and practical reference for noise and vibration reduction in agricultural machinery cab design.

The whole-stalk harvesting and baling of reeds (Phragmites australis (Cav.) Trin. ex Steud) require a header with high efficiency and low loss rate. Based on an analysis of reed characteristic parameters, this paper proposes a T-shaped layout header design for whole-stalk reed harvesting. The design employs bilateral transverse conveying chains and a longitudinal clamping conveying chain, coordinated with a baler at its end, to achieve integrated harvesting and baling of whole reed stalks, thereby improving efficiency. By analyzing the relationship between key header parameters, such as the height of the lifting lugs on the transverse conveying device, the speeds of the transverse and longitudinal conveying chains, and the forward speed of the header, and the posture of the reeds, the causes of header loss during reed harvesting with the T-shaped header are identified. On this basis, a set of design criteria for the key parameters of the T-shaped whole-stalk reed header is established. A T-shaped reed whole-stalk harvesting header was designed according to these criteria and tested in harvesting experiments with varying preset values for forward speed and lower transverse conveying chain speed. Experimental data show that under optimally matched parameters, the header achieves a low average loss rate (L_h ≤ 2.0%) and a high average harvesting efficiency at the rated forward speed (up to 1.0 hm²/h, including baling), verifying the correctness of the theoretical analysis and the design criteria. The research results provide theoretical and experimental support for the design of conveying systems in headers for tall-stalk crops such as reeds.

The absence of discrete element contact parameters for suitable harvest rapeseed pods hinders accurate DEM simulations. This study presents the first systematic calibration of discrete element contact parameters for “Ningza 158” rapeseed pods using physical and simulation experiments. Experimentally determined properties included external dimensions, density, pod–steel coefficients (restitution, static friction, rolling friction), and pod–pod restitution. Using the measured angle of repose as the objective, significant parameters were screened, optimized, and modeled via Plackett–Burman, steepest climbing, and central composite response surface tests. The optimal parameter combination was then validated against the angle of repose, completing the calibration. The results showed that the density, Poisson’s ratio, and shear modulus of rapeseed pods at the suitable harvest period were 346.63 kg·m⁻³, 0.35, and 10.5 MPa, respectively. The coefficients of restitution, static friction, and rolling friction for pod–steel and pod–pod were 0.2994, 0.4206, 0.0435, 0.1024, 0.3110, and 0.0380, respectively. Under this simulation parameter combination, the angle of repose obtained from the simulation was 71.23°, yielding a relative error of 2.12% compared with the actual value of 69.75°. Note that this validation is limited to static accumulation behavior. The calibrated parameters can be a basis for future dynamic validation studies on harvest loss mechanisms, provided additional dynamic validation is performed.