Analysis On The Dynamic Behavior Of Back Rest System And The Control Of Warp Tension For An Air-jet Loom

For the developing of textile industry, new weaving machine is increasingly used. In high speed, the instance that vibration becomes more serious and work environment of warp ends gets worse are favorable to end breakage and it drops the productive efficiency. The dynamic characteristic of back rest which is the detecting and regulating element of warp tension is very important to the fluctuation of warp tension. Taking type WG—2000 air-jet loom for subject researched and weaving process of certain tabby for instance, the mathematical model of back rest system of the loom is built in order to research its dynamic behavior and control the warp tension. So, the scheme for reducing vibration and making ends'working environment better can be found.Firstly, the operating principle of main mechanisms of type WG—2000 loom and their effects on warp are analyzed systematically and conclusions have been made that shedding motion, beating-up motion, warp loosing motion and back rest oscillating motion are major factors resulting in the change of warp tensile deformation. Then, according to the condition that the resultant moment of spring force and warp tension about the same axis is zero, the static model of back rest has been built. Furthermore, the static characteristic has been analyzed and the parameters used in dynamic analysis have been obtained.On the basis of static analysis and considering the damping moment and inertial moment, the simple single-degree-of-freedom dynamic model of back rest system is built according to the equilibrium principle. By fourth-order Runge-Kutta algorithm, the oscillation of back rest is numerically obtained and the warp tension is also calculated. The result shows that the oscillating of back rest and the changing of warp tension drive to be more complicated and their rangeability and mean value will diminish, but the natural frequency and the damp coefficient which can keep the warp tension optimum will increase, as the beam diameter becoming smaller and smaller. After that, the more accurate two-degree-of-freedom model is built. The further research on which the effect of beam diameter and system damp on natural frequency, back rest oscillation and warp tension comes to a conclusion which is consistent with single-degree-of-freedom model analysis and the motion of the left and right side of back rest is almost in synchronism. So, the simple single-degree-of-freedom model can meet the required precision in dynamic analysis of the system.In order to verify the reliability of mathematical model of back rest system, an experiment on testing warp tension is performed in weaving field. The comparison and analysis on theoretical and tested data show that the model built is correct.According to the characteristic of type WG—2000 air-jet loom and the dynamic analysis on back rest system and borrowing ideas from research production of magnetorheological technology, a type of magnetorheological damper used on back rest system of the loom is designed and its dynamic model is further deduced. Then,by replacing viscous damp of former dynamic model with magnetorheological damp and setting relevant parameters of the magnetorheological damper according to the optimal damp coefficients in different beam diameters, dynamic model of back rest system based on magnetorheology is built. Solve by numerical method and the oscillation of back rest and warp tension can be got. The results indicate that magnetorheological damper can theoretically satisfy the requirement of reducing back rest vibration and controlling warp tension in whole weaving stage.The theorically modeling, comprehensive analysis, conclusions obtained, experimental data, and so on, which are performed in the the paper and aim at type WG—2000 air-jet loom back rest system can be benefit for the designing of the loom and improving of weaving process.