先拉伞绳法数学模型及拉直力预测

给出了考虑伞绳粘弹性的降落伞先拉伞绳法拉直过程预测方法.建立了拉直过程数学模型的基本方程,理论分析了基本方程中粘性项对张力波在伞绳中传播的作用;弹性张力波不仅使伞衣套一端产生的张力通过伞绳传到前置体一端在时间上滞后一些,而且由于拉直过程中存在着吸收和弥散现象,使两端的张力不能相等.使用该模型计算了伞拉直运动和拉直力,对拉直力动态变化过程进行了分析.计算表明:前置体一端承受的最大拉直力不仅与伞衣底边被拉动瞬间产生的最大张力有关,而且与拉出伞衣底边以后产生的载荷张力有关. 

Mathematical model and snatch force prediction for the lines-first parachute deployment

Prediction method for the lines-first parachute unfurling process was provided, in which the viscoelasticity of suspension lines was taken into consideration.The fundamental equation of the mathematical model of parachute unfurling process was formulated.The effect of viscosity term in fundamental equation on spreading of tensile wave along suspension lines was emphatically analyzed.The viscoelastic tensile wave not only causes delay of tension spreading from the canopy sleeve end to the other end,but also makes the tension at the two ends different due to absorption and dispersion during the parachute unfurling process.The present model was used to calculate unfurling loads and motions of a parachute deployment.The dynamic change of snatch force was analyzed and it shows that the max snatch force borne on the load end is related not only to max tension produced at the moment when the parachute skirt being drawn out,but also to the load tension produced after skirt is drawn out.