现在分词作伴随状语时,动作的对象必须是句子的主语吗?

不对,伴随状语的动作发出者（也叫逻辑主语.注意：不是动作对象）应该是句子的主语,而it 不能做conduct research的主语.
应该是：
It will help me to achieve my career goal:to be a scientist who conducts research in a national lab.（注：冒号也可改为破折号）
或者：It will help me to achieve my career goal:to be a scientist conducting research in a national lab.
或者：It will help me to achieve my career goal of becoming a scientist who conducts research in a national lab.
另外,非限定动词（不定式、分词等）都存在逻辑主语的问题.it will serve to achieve中to achieve的逻辑主语从结构上看应该是前面的代词it,但实际上应该是“我”,所以改为：It will help me to achieve