Abstract:

Objective Electronic weft insertion mechanisms can significantly enhance both stability and flexibility in the weft insertion process. However, current electronic weft insertion systems maintain a constant input motion, which fails to meet the requirements for regulating variable-stroke weft insertion motion characteristics. Therefore, this study proposes a variable-speed motion model based on an asymmetric modified cycloid function for optimizing the weft insertion process. This model is expected to enable precise control of weft insertion motion characteristics while improving insertion efficiency, thereby providing critical technical support for the development of high-speed weaving equipment.

Method This study adopts an integrated approach combining theoretical modeling, numerical simulation, and experimental validation to systematically investigate weft insertion motion in narrow channels. First, an asymmetric modified cycloid function model with dual control variables (κ and k) is established based on variable-stroke weft insertion requirements. Subsequently, MatLab simulations verify the model capability to maintain consistent dwell time across different channel lengths. To validate practical application, an electronic weft insertion platform is developed using electronic cam technology for motion control, demonstrating superior performance in both motion smoothness and speed enhancement compared to conventional pulse control. Furthermore, comparative analysis between encoder-collected trajectory data and simulation results further confirms the model's accuracy and engineering feasibility.

Results Comparative experimental results based on the electromechanical system platform demonstrate that the proposed variable-speed motion exhibits significant performance advantages over traditional pulse control in actual weft insertion operations. During the first phase of experiments, the optimal operating parameters for constant-speed motion were determined. When the rapier head travel distance reached 30 mm, measurements within the 50-90 mm/s speed range revealed that the displacement fluctuation in the thickness direction increased with speed. In the 70-80 mm/s range, the fluctuation stabilized near the critical value of 0.25 mm, which ultimately confirmed 75 mm/s as the optimal constant-speed for weft insertion. In the second phase, by applying electronic cam technology to increase the cam spindle angular velocity from 5 rad/s to 9 rad/s, experimental data showed that a dwell time of 0.47 s could be achieved at ω = 7 rad/s, corresponding to an average speed increase to 87 mm/s. Theoretical calculations demonstrated that the variable-speed motion could increase the average weft insertion speed by 16% across all weft insertion channels while reducing weft insertion time by 13.8%. For experimental validation, high-precision servo motor encoders were used to collect real-time motion trajectory data. Under the extreme channel condition (i = 54), the maximum measured end displacement error was 2.32 mm, with a relative error of 0.53%.

Conclusion The variable-speed motion model developed in this study dynamically regulates motion characteristics during variable-stroke weft insertion by adjusting the speed ratio coefficient (κ) and the asymmetry coefficient (k). Numerical simulations and experimental results was used to validate the model's accuracy and feasibility. Specifically, for shorter channels, the rapier head enters with higher velocity and acceleration, while these parameters are proportionally reduced for longer channels. Compared to traditional constant-speed pulse motion, this model significantly increases weft insertion speed, reduces insertion time, and improves preform forming efficiency. Moreover, this technology is not limited to blended soft-hard preforms but can also be extended to other 3-D fabric forming processes involving rapier weft insertion.

Key words: soft-hard blended preform, electronic weft insertion, variable-stroke, variable-speed law, motion characteristic control