关键词: 平行打纬机构, 弹性连杆, 刚柔耦合模型, 前死心位置, 响应偏差, 比刚度

Abstract: The double-rapier loom is a kind of weaving machine that is mainly used for weaving spacer fabrics. The research on double-layer rapier looms in China started in the middle and late 1980s. The domestic double-rapier looms have been restricted by the limited technical level, the low reliability of the equipment, and the low speed. The general weaving efficiency is only 80-85 weft/min, and the industrial production has not been realized. The relevant foreign products can reach 180 weft/min. Therefore, it is of great significance to study the dynamic characteristics of the beating-up mechanism for speeding up the high-speed process of domestic spacer double-rapier looms.
With the increase of the loom speed, the connecting rod components in the parallel beating-up mechanism with a conjugate cam and four connecting rods will deform more under the action of the inertial load, resulting in deviation between the reed front dead center position and the ideal position, and affecting the beating-up accuracy. To solve this problem, we adopted the method of combining virtual simulation and experiment to study the mechanism. First, we discretized the link components that are regarded as elastomers based on ANSYS software, and jointly used ADAMS software to establish the rigid flexible coupling dynamic model of the parallel beating-up mechanism under the flexible link. The model was simulated every 20 r/min as a data point within the range of 80-300 r/min of the cam speed, modal analysis of the driven link mechanism was carried out, and the influence of different cam speeds on the reed front dead center position was investigated. Then, nodular cast iron, cast aluminum, medium carbon structural steel and alloy structural steel were selected as the connecting rod materials. At the same speed, the mechanism model was simulated to explore the influence of different materials of the elastic connecting rod on the dead center position of reed. At the same time, the experimental platform was built, and the laser displacement sensor was used to measure the deviation between the actual front dead center position and the theoretical position of the reed under different cam speeds, so as to verify the conclusions of the simulation on the impact of the cam speed on the reed front dead center position. The results show that there is overswing phenomenon in the process of the reed beating-up, and the reed dynamic response of the rigid flexible coupling model under the condition of elastic linkage can better reflect the real motion of the beating-up mechanism. The simulation and experimental results show that the overall trend of reed front dead center position deviation is consistent with the change of cam speed. It can be seen that the influence of cam speed on reed front dead center position is nonlinear, and the reed front dead center position is stable and the deviation value is small when the cam speed is within 180 r/min. Based on the simulation analysis, it is concluded that the selection of materials with greater stiffness than elastic connecting rod components is helpful to reduce the reed front dead center position deviation.
The research results have a certain guiding significance for the actual engineering practice, and provide a reference for the design and optimization of high-speed conjugate cams and four-bar parallel beating-up mechanisms.

Key words: parallel beating-up mechanism, elastic linkage, rigid flexible coupling model, front dead center position, response deviation, specific stiffness