现在分词做伴随状语.
附上现在分词和动名词的区别.
动名词类似于名词的性质,可以做主语、宾语或表语,也可以做介词的宾语；比如：Seeing is believing. I like swimming. We look forward to leaving.
现在分词与时态有关,常与be动词连用作为进行时的构成,同时现在分词还可以放在名词之后做后置定语,其实这也是省略了主语和be动词的进行时.比如：I am doing my homework. He was sleeping when I came back. The boy sitting under the tree is my brother.
而同位语的定义是：
一个名词(或其它形式)对另一个名词或代词进行修饰,限定或说明,这个名词（或其它形式）就是同位语.同位语与被它限定的词的格要一致,并常常紧挨在一起.