Rather than Robert drive in his present state, I'd prefer to drive him home myself.

=I'd prefer to drive him home myself rather than Robert drive in his present state. (rather than =instead of )

请问专家老师，划线部分是什么句法成分？

句子结构为：主语(a)+prefer to do sth rather than sb(b) do sth

主语A宁愿做某事，也不要B做某事（表示一种选择）

  I prefer to watch TV rather than go out.
 =Rather than go out, I prefer to watch TV.
 我宁愿呆在家里也不出去。 

rather than 是介词还是连词，后面引导的是句子还是短语？谢谢老师的解答。

解答如下

以上为连词用法,用来连接句子，或者并列成分，后面可接短语。

rather than 要…而不…，与其…倒不如

We'll have the meeting in the classroom rather than in the auditorium. 

我们与其在礼堂里开会, 不如在教室开会。 

They thus increased their annual grain production rather than diminished it. 

他们这样增加了而不是减少了粮食年产量。 

rather than 用法归纳如下

rather than 是一个并列连词，用法比较复杂，现归纳如下：

【一】rather than 与would 连用时，构成“would rather...than...”句式，意思是“宁愿……而不愿……”，表示主观愿望，即在两者之中选择其一。

She'd rather die than lose the children. 

她宁愿死也不愿失去孩子们。

【二】 rather than 不与would连用时，表示客观事实，意为“是……而不是……；与其……不如……”。它连接的并列成分可以是名词、代词、形容词、介词(短语)、动名词、分句、不定式、动词等。现分述如下：

【1】连接两个名词或代词

He is an explorer rather than a sailor. 

与其说他是一个海员，不如说他是一个探险者。

You rather than I are going to go camping. 

是你而不是我要去要野营。

注意：rather than 连接两个名词或代词作主语时，谓语动词应与rather than 前面的名词或代词在人称和数上保持一致。

【2】连接两个形容词

The sweater she bought was beautiful rather than cheap. 与其说她买的这件羊毛衫便宜不如说它漂亮。

【3】连接两个介词(短语)或动名词

We will have the meeting in the classroom rather than in the great hall. 我们是在教室里开会，不是在大厅里。

She enjoys singing rather than dancing. 

她喜欢唱歌，而不喜欢跳舞。

【4】连接两个分句

We should help him rather than he should help us. 

是我们应该帮助他而不是他应该帮助我们。

【5】连接两个不定式

I decided to write rather than (to) telephone. 

我决定写信而不打电话。

注意：rather than 后接不定式时，不定式可以带to，也可以不带to, 如上句。但rather than位于句首时，则只能接不带to 的不定式。如：Rather than allow the vegetables to go bad, he sold them at half price. 他唯恐蔬菜烂掉，把它们以半价卖掉了。

 【6】连接两个动词

He ran rather than walked. 

他是跑来的，而不是走来的。

注意：这里rather than 后用了walked，而没有用walk，表示客观事实，而不是主观愿望。如果换成walk，则作“宁愿……而不愿 ……”解。