Page 349 - Mechanics of Microelectromechanical Systems

336 Chapter 5
monitored by means of longitudinal electrostatic sensing in a controlled
feedback loop. Dimension the electrostatic actuator area A for an initial gap
such that minimum displacement increments can be
produced by minimum voltage increments The spiral spring is
defined by and E = 160 GPa. The
electrical permittivity is Also determine the pull-in voltage.

Figure 5.66 One-spring and electrostatic actuation

Answer:

Problem 5.2
A microaccelerometer, as the one of Fig. 5.4 (a), uses a constant
rectangular cross-section flexure hinge with cross-section
defined by and and E = 150 GPa. The tip mass has a
length and its mass is The electrical permittivity is
and the initial gap is The sensor has to be able to
detect accelerations as small as Determine the voltage that is
generated under these circumstances.

Answer:
U=10.11 V

Problem 5.3
The rotary electrostatic transducer of Fig. 5.6 (a) is used instead of the
one studied in Example 5.3. Determine the number of beam suspensions
having the cross-section defined by that will make this
microsystem perform identically to the one of Example 5.3 under identical
actuation and geometrical/material conditions.

Answer:
n = 3