Biomimetic Research for Folding and Deploying Manners of Monopetalous Flower like Morning Glory

本研究通过花蕾展开方式的观察、花朵展开的图像分析、花瓣和花瓣棱的拉伸试验、花朵的数值模型和纸面模型的建立以及利用模型对花朵展开的模拟，对牵牛花和矮牵牛花展开方式进行了研究。得到的主要结果如下：1。牵牛花和矮牵牛花具有花瓣和花瓣棱复合结构，即花瓣棱支撑着薄花瓣。从拉伸试验中发现，花瓣筋的刚度是花瓣筋的3倍左右。通过展开模拟发现，随着花瓣棱数的增加，全部花瓣释放时的牵牛花半径和牵牛花展开所需的能量都在减小。然而，当牵牛花的花瓣肋数增加时，重叠的花瓣厚度急剧增加，因此很难将卷曲的花瓣放在一个小花蕾中。牵牛花的展开半径遵循logistic曲线，即前期缓慢展开，中期高速展开，后期再缓慢展开，这是一条基本的生长曲线。牵牛花前1619小时发育缓慢，可达15%，后3 ~ 4小时发育迅速，可达40%。停滞12 ~ 14小时后，以较高的速度展开。

In this research, the unfolding manner of morning glory and petunia flowers were studied by means of the observation of unfolding manner in buds, the picture analysis of unfolding of flower, tensile tests for petals and petal ribs, construction of the numerical and paper models of flowers and the simulation of unfolding of flower using the models. The principal results obtained are as follows :1. Morning glory and petunia flowers have compounded structure with petal and petal ribs, i.e. petal ribs support the thin petals. From tensile tests, it was found that the rigidity of petal ribs are about three times greater than that of petals.2. It was found from simulation of unfolding that the radius of morning glory flower when all petals are released and the energy required for the deployment of a morning glory flower decreases with the increase of the number of petal ribs. However, when the number of petal ribs in a morning glory flower increases, the overlapped petal thickness increases dramatically and consequently it becomes difficult to put the rolled petals in a small bud.3. The deploying radius of morning glory flower follows the logistic curve which is a basic growth curve, i.e. the slow deploying speed in the early stage, high speed in the middle and again slow in the last.4. Petunia flower deploys slowly for the first 1619 hours up to 15 % deployment and quickly for the second 3〜4 hours up to 40 % deployment. And then, it deploys with relatively high speed after the stagnation of 12〜14 hours.