Search Results (5)

The precision of simulation plays a pivotal role in determining the design parameters of the pressure pipe and distributor in a pneumatic centralized seeding system. This study adopted the discrete element method (DEM) to investigate wheat seed models and their motion characteristics within a pneumatic precision seed-metering device. Using Xinchun No. 6 wheat as the experimental subject, multi-sphere combination models (5, 7, 9, and 11 balls) were employed to describe the seed particle morphology. Moreover, by utilizing the coupling method of the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD), along with bench tests, the air suspension velocity of seeds and the motion characteristics of the seed-supplying device were analyzed under different particle models. The physical properties of the wheat seeds were measured during the experiments. The simulation results indicated that, as the seed supply rate increased, the airflow velocity distribution within the model became more uniform, enhancing the stability of the suspension velocity. Comparisons between experiments and simulations validated the reliability of the particle models, with the minimum relative error in the suspension velocity determined as 0.21% for the 9-balls model. In addition, compared to the other models, the 9- and 5-balls models more accurately simulated the dynamic behavior of seeds within the seed-supplying device. For the 9-balls model, the relative error of particle velocity in the seed-supplying device is 1.39%, and, in the simulation of displacements in the X and Y directions of the seed-supplying device, the average error is 9.51%. The effectiveness of the multi-sphere combination models was verified, indicating their ability to accurately reflect the dynamic behavior of wheat seeds and improve the design and optimization efficiency of pneumatic precision seed-metering devices. Full article

Nowadays, we can find many studies about evaporative cooling pads, but a uniform methodology does not exist for experimental tests, and many factors are less studied. Our goal is to design and build a versatile experimental facility that enables the characterization of these pads under different operating conditions: airflow (velocity), relative humidity, temperature, pad thickness, pad material and water distribution system. The test bench will permit the use of different water distributors and any type of pad material with three different thickness. Full article

The distribution of airflow field in the pneumatic centralized cylinder metering device cavity, airstream distributor and different angle seed feeding tubes was investigated based on the pneumatic centralized cylinder direct-seeding metering device to study the effect on the movement law of rice seed. In total, three suction hole sizes (1.5 mm, 2 mm and 2.0 mm 45° wedge) were used for CFD simulation. The results showed that under the same inlet vacuum, the pressure at the 1.5 mm hole is higher than the other two types of holes, and the five measurement points of the 2 mm hole are more stable than the other two types of holes. At the positive pressure seed feeding area, the inlet pressure was set as 1.5 kPa, and the outlet pressure was set as 0 Pa. The pressure distribution at different measuring points showed that the 2 mm 45° wedge had the most uneven positive pressure distribution, and the 1.5 mm hole had higher positive pressure distribution than the 2 mm hole in general. Three different structured airflow distributors were designed. CFD simulation experiments showed that the arc transition type presented better uniformity than the other two types. The uniformity experiments at the ends of the seed-feeding tubes indicated that the airflow velocity had the trend of large in the middle and small at two sides. Finally, the movement law of the rice seeds in seed feeding tubes at different angles was obtained by using high-speed photography. The results showed that the rice seeds in tube C (maximum angle) presented a movement posture of falling sector a and kept falling after colliding in sector b; the rice seeds in tube B (the second angle) presented a movement posture of falling in sector a and kept falling after colliding in sector b. The above research provides a reference for the optimal design of a pneumatic centralized cylinder metering device. Full article

Currently, a significant trend in control in robotic systems is developing and improving linear and nonlinear control algorithms to improve the overall quality of production with high accuracy and adaptability. The present study considers a synergistic synthesis of throttle control of a pneumatic distributor valve and backpressure control for piston rod positioning. The article presents the synthesis of control laws for the position of a pneumatic cylinder piston using the method of analytical design of aggregated regulators (ADAR) of synergetic control theory (STC), which allows operation with nonlinear mathematical models, eliminating the loss of information about the object during linearization. A comparative calculation of the energy efficiency of backpressure control and throttle control methods was carried out, while the numerical value of the total airflow with throttle control is 0.0569 m³⁄s and, with backpressure control, it is 0.0337 m³⁄s. Using a P controller in a linear model gives a transient oscillatory process damped in 2–2.5 s. When using a PID controller, the process has an overshoot equal to 11.5%, while the synergistic controller allows you to smoothly move the drive stem to a given position without overshoot. The parametric uncertainty analysis of the considered mathematical model is carried out. The model’s main parameters are identified, which change the actual functioning of the system under study. The inconsistency of applying classical control laws based on typical controllers to parametrically indeterminate mathematical models is shown. Full article

This study concerned the quality of mini-tablets’ coating uniformity obtained by either the bottom spray chamber with a classical Wurster distributor (CW) or a swirl distributor (SW). Mini-tablets with a diameter of 2.0, 2.5, and 3.0 mm were coated with hypromellose using two different inlet air distributors as well as inlet airflow rates (130 and 156 m³/h). Tartrazine was used as a colorant in the coating layer and the coating uniformity was assessed by spectrophotometric analysis of solutions obtained after disintegration of the mini-tablets (n = 100). Higher uniformity of coating material distribution among the mini-tablets was observed in the case of SW distributor, even for the biggest mini-tablets (d = 3.0 mm), with an RSD no larger than 5.0%. Additionally, coating thickness was evaluated by colorimetric analysis (n = 1000), using a scanner method, and expressed as a hue value. A high correlation (R = 0.993) between inter-tablet variability of hue and UV-Vis results was obtained. Mini-tablets were successfully coated in a fluid bed system using both a classical Wurster distributor as well as a swirl generator. However, regardless of the mini-tablets’ diameter, better film uniformity was achieved in the case of a distributor with a swirl generator. Full article