Santosh -

Some of what you are experiencing can be related to a phenomenom called
"levitation" ... where the interaction of the electric fields from your
drive (and sense) combs causes the combs (and their connecting
structure) which are tied to ground to levitate at a position above
their "rest" position. W. Tang (the father of comb-fingers) covers this
- as well as methods to mitigate this effect - in his doctoral thesis:
"Electrostatic comb drive for resonant sensor and actuator
applications", 1990. He also co-authored a number of papers on
comb-drive levitation. Hope that gets you started.

Stephen Arnold
The George Washington University