He made full preparation for the experiment so that it could be conducted smoothly.1.that引导目的状语从句中常含有情态动词,且与主语相连不用逗号分隔,那么so that引导结果状语从句就与主语相连用逗号隔开?

只要记住一句话
so that
可以翻译为
太~~以至于~~ 就好了

引导结果状语就不是这么用了吧..
是so....that..
比如:
He was so excited that he jumped with joy when he heard the good news.
他太激动了以致于高兴的跳了起来.

so that 不能与语句用逗号隔开,不管做目的还是结果状语,这是对的.但so that 后用不用情态动词,要根据句子实际情况而定,例如：
The term and condition are printed in very small letter so that they are difficult to read.
条款与条件是用很小的字体印刷的,以致难以阅读.
You may flour the pastry board so that the dough doesn't stick to it.
你可以在做糕点的面板上撒些面粉,这样揉好的面粉就不会粘到板上了.

引导结果状语从句是与主语相连，但不必隔开
是这个句型 so...that...
比如，He sang that song so splendid that he win the match.
他唱那首歌唱的很棒，所以他赢了那场比赛