The current automatic scallion-transplanting machine is a complicated mechanism composed of two linkage mechanisms and two band carriers. It delivers seedlings inefficiently because of the movement ...limitations of the linkage mechanism. This paper proposes a new high-order non-circular gear train for an automatic scallion-seedling feeding mechanism. The proposed gear train has an asymmetrical transmission ratio; i.e., its transmission ratio varies. This allows the mechanism’s execution component to move in a long displacement and rotate in a large rotation angle. The long displacement enables the execution component to reach the designed working position, and the large rotation angle allows it to feed a scallion in the required pose. A mathematical model for calculating the asymmetrical transmission ratio was established according to the closure requirements and the full-cycle motion of the driven gear pitch curve. Then, the parameter-design model of the new seedling-feeding mechanism was established, based on precise pose points and trajectory-shape control points. Moreover, an aided-design program was developed to obtain the parameter-solution domain of the scallion-seedling feeding mechanism. The mechanism parameters, which met the seedling-feeding function, were optimized to determine the transmission ratio, using a program and a kinematic simulation. Finally, a prototype of the mechanism was produced, and a seedling-feeding experiment was carried out. One-thousand seedlings were tested at a rate of 100 seedlings per minute, and the statistical success rate was 93.4%. Thus, the automatic scallion-seedling feeding mechanism significantly improves the efficiency of automatically transplanting scallions.
The start-up process is important for ensuring the end quality of slot coating products. This study uses ANSYS Fluent to explore the start-up process of slot coating with Carreau-type non-Newtonian ...fluid. The relationship between the pressure change in the coating bead at the slot outlet and the stabilization process of the coating bead is analyzed, and the effects of the downstream die lip angle and downstream die lip length on the size of the coating bead are discussed. The simulation results show that the pressure at the slot outlet directly affects the stabilization of the coating bead, and accelerating the coating bead stabilization pressure can accelerate the start-up process. When other parameters remain unchanged, reducing the downstream die lip angle or length can reduce the size of the coating bead, thereby accelerating the start-up process.
The noncircular synchronous belt drive mechanism has demonstrated certain achievements and has been used in special fields. Research regarding noncircular synchronous belt drive mechanisms has ...focused on optimization design and kinematic analysis in China, whereas two pulley noncircular synchronous belt transmissions have been developed overseas. However, owing to the noncircular characteristics of the belt pulley, the real-time variation in the belt length slack during the transmission of the noncircular synchronous belt is significant, resulting in high probabilities of skipping and vibration. In this study, a noncircular tensioning pulley is added to create a stable three-pulley noncircular synchronous belt driving mechanism and a good synchronous belt tensioning, with no skipping; hence, the non-uniform output characteristic of the driven pulley is consistent with the theoretical value. In the circular noncircular noncircular three-pulley noncircular synchronous belt mechanism, the pitch curve of the driving synchronous belt pulley is circular, whereas those of the driven synchronous belt and tensioning pulleys are noncircular. To minimize the slack of the belt length of the synchronous belt and the constraint of the concavity and circumference of the tensioning pulley, an automatic optimization model of the tensioning pulley pitch curve is established. The motion simulation, analysis, and optimization code for a three-belt-pulley noncircular synchronous belt drive mechanism is written, and the variation in belt length slack under different speed ratios is analyzed based on several examples. The testbed for a circular–noncircular–noncircular three-pulley noncircular synchronous belt transmission mechanism is developed. The test shows that the three-pulley noncircular synchronous belt drives well. This study proposes an automatic optimization algorithm for the tensioning pulley pitch curve of a noncircular synchronous belt transmission mechanism; it yields a stable transmission of the noncircular synchronous belt transmission mechanism as well as non-uniform output characteristics.
Four-bar linkage has been used in motion generation synthesis for a long time, but there are inevitably some shortcomings such as order defects and poor design flexibility. In this work, a planetary ...gear train with noncircular gears is proposed to realize planar motion generation synthesis. Compared with the four-bar linkage, it has the advantages of a compact structure, full rotatability, and flexible design. The planetary gear train with noncircular gears is composed of two interrelated parts: a two-stage noncircular gear pair and the
RR
dyad. The synthesis method is divided mainly into three steps: First, the constraint equation of
RR
dyad for planar motion generation is established, and a solution region of the double revolute joint (
RR
) dyads is calculated by kinematic mapping theory. Second, after the full rotatability identification of
RR
dyads and the determination of each transmission ratio, the centrodes of two-stage noncircular gear pairs, which correspond to the specific
RR
dyad, are obtained. Finally, the planetary gear train with noncir-cular gears is established to pass the given poses. This method has a universal significance and can be applied to many practical cases.
Among all kinds of transplanting mechanisms which are the important parts of transplanters, the planetary gear train transplanting mechanism is widely used for its excellent transmission performance, ...but it is difficult to design the gear pitch curves and structural parameters according to the trajectory and pose requirements of transplanting. The current design method of the non-circular planetary gear train transplanting mechanism cannot ensure the precise position and posture in the crucial points of transplanting trajectory, nor take both the anticipated trajectory and the smoothness of the gear pitch curves into account, it will only get one solution which is available for mechanism design. In order to solve those problems, the non-circular planetary gear train transplanting mechanism is analyzed as a combination of the bar-group and gear train system. According to the transplanting requirements, three points with precise position and posture which called pose points in the trajectory are given to obtain the solution domain of the parameters of bar-group, and then trajectory shape control points are inlet to design the desired shape of the transplanting trajectory and obtain the transmission ratio curve which can be used to get the gear pitch curve. The most suitable parameters of bar-group in solution domain are selected based on the smoothness of the gear pitch curves. This article establishes three-dimensional model of the mechanism and utilizes the ADAMS to carry out a motion simulation; all simulation results are consistent with theoretical design results, which confirm that the design method based on prescribed pose points and trajectory control points is adequate for the transplanting mechanism. With the proposed method, the selectivity of the mechanism’s parameters solution is increased, and transmission performance benefits from the integrated design of trajectory control and the smoothness of the pitch curves.
At present, the research objects of rigid-body guidance synthesis are mostly limited to pure linkages, and there is little research on the combined mechanisms of gears or cams and linkages. In order ...to expand the research objects of rigid-body guidance and improve the kinematic mapping theory, this paper proposes a rigid-body guidance method of noncircular gear-five-bar combined mechanisms. A noncircular gear-five-bar mechanism can be regarded as a combination of a 2R (two revolute joints) open chain, a 3R (three revolute joints) open chain and a pair of noncircular gears. Firstly, the circle point curves and circle center point curves of the 2R and 3R open chains are obtained by using kinematic mapping, and they are formed into a double crank five-bar linkage. Secondly, the B-spline curve is used to fit the rotation angle relationship of the gear pair to obtain the pitch curves of noncircular gears. Finally, aiming at correcting patients’ abnormal gait, a noncircular gear-five-bar exoskeleton knee joint rehabilitation device is designed based on four task poses. The prototype is developed and the wear test is carried out. The test results verify the correctness of the rigid-body guidance synthesis method and the effectiveness of rehabilitation training.
In this study, the motion characteristics of manual stirring were analyzed to achieve the goal of realizing a highquality mechanized imitation of manual stirring for oolong tea. A test bench for ...collecting the motion characteristics of manual stirring was designed, and the standard manual stirring motion characteristic curve was obtained. According to the requirements of the stirring motion characteristics, a variable-speed and variable-amplitude stirring mechanism was proposed, the kinematics model and reverse design model of the stirring mechanism were established, auxiliary analysis and design software were written, and the non-circular gear pitch curve and cam profile curve were obtained. A three-dimensional model of the stirring machine was established, a virtual prototype of the stirring machine was built, and the simulation experiment was completed by using the ADAMS software. A prototype of the stirring machine was developed, and the stirring experiment was conducted on the prototype. The maximum deviation of the pitch angle is 2.8772°, and the maximum deviation of the roll angle is 1.5948° according to the analysis and comparison of the actual curve data and the theoretical data curve. The experimental results showed that the simulation angle curve and the actual angle curve were consistent with the theoretical standard manual stirring motion characteristic curve, which verified the correctness of the design and modeling of the stirring mechanism. The tea was mechanically stirred by the stirring mechanism to achieve the desired stirring effect, which verified the feasibility of the stirring machine.
Aiming at the problem that the existing garlic-root-cutting equipment requires the orientation and orderly conveying of garlic, a garlic orientation and orderly conveying method based on machine ...vision and mechanical orientation mechanisms was proposed and a garlic orientation and orderly conveying device was designed. To realize garlic posture recognition, garlic and garlic roots were used as detection objects, the YOLOv5s objection detection model was used to establish a garlic feature detection model, and the model was trained. The garlic orientation and orderly conveying device was developed and a garlic posture recognition test and garlic orientation and orderly conveying test were completed. The test results show that the success rate of posture recognition is 98.67% and the average accuracy rate of the garlic deviation angle is 99.11%. When the conveying speed is 95 mm⋅s−1 and the rotating speed is 55 rpm, the orientation success rate is 95.6% and the conveying efficiency reaches 75 garlic per minute, which meets the design requirements. The accuracy of the garlic posture recognition method and the rationality of the garlic orientation and orderly conveying device design are verified, and the automatic orientation and orderly conveying of garlic is realized.
To solve the problem of large-sized blocks in single-process broccoli cutting, this paper proposes the design of broccoli secondary cutting equipment, in which the screening device with differential ...round belts, spiral attitude-adjusting mechanism, double-baffle conveyor belt, block-centering chute and disc-type cutter are analyzed and designed. According to the simulation of the motion of the blocks on the differential belts, the speeds of the two belts were 300 mm/s and 600 mm/s, respectively. The kinematic analysis of the spiral attitude-adjusting mechanism was performed, and the speed of the spiral rod was calculated to be greater than 64.5 rpm. The speed of the double-baffle conveyor belt was greater than 10.61 rpm to not obstruct the blocks and achieve diversion. A force analysis of the inclined centering chute was performed to reduce the damage during block conveying, and the inclination angle of the inclined centering chute was calculated to be greater than 27.02°. The parameters of the blade and its driving motor were calculated. Effective secondary cutting equipment for broccoli was thus developed. After secondary cutting, the size difference of two small florets obtained was between 0–8 mm, the success rate of cutting was 94.8%, and the efficiency was 47 pieces/min, which verified the reasonableness and feasibility of the second cutting equipment scheme.
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