Page 180 - Mechanics of Microelectromechanical Systems
P. 180
3. Microsuspensions 167
where the superscripts 1 and 2 denote the 2-3 and 4-5 members, and the
subscript Fy-uy indicates the direct linear bending stiffness of the compliant
members with respect to their local frames.
Figure 3.37 Half-model of a folded-beam spring
Because one entire folded-beam spring is composed of two identical halves
(as the one sketched in Fig. 3.37) connected in parallel, the total stiffness is:
The stiffness about the y-axis, the other in-plane motion direction, which
is perpendicular to the main (motion) direction, can be found by considering
that a force is applied axially to all four compliant bars. In this situation
the bars will only deform axially, and because they are placed in parallel, the
total stiffness about the y-direction is:
where it has been considered that the two compliant links have constant
cross-sections. When the cross-sections are variable, Eq. (3.110) changes to:
