When do Indian Rupees get strong compared to US Dollar?

The exchange rate is a relative.

So the Indian Rupee will get stronger (the rate will go lower) when the PERCEPTION of economic fundamentals are positive for India verses the PERCEPTION of fundamentals for the US.

There is another factor which is 'flight to quality'. There is a (false I believe) perception that the US is 'safe' and s, in times of uncertainty, people will gravitate toward the safety of the US Dollar. here is a similar perception held for gold.