Optimal design of compliant mechanism with planar 3-RRR structure

Stiffness is one of the most important mechanical characteristics, which can be defined as the capacity of a mechanical system to sustain loads without excessivechanges of its geometry. The stiffness of a mechanism depends on several factors, such as actuators, material and of the links and mechanical transmission mechanisms. Nowadays, many mechanisms especially parallel ones are designed to gain some of their mobility from the deflectionsof flexible members rather than from movable joints only. This group is widely known as compliant mechanisms in which compliancy in the joints and the links, affects thestiffness of the mechanism. In the present study, using Castigliano's theorem the stiffness matrix of a 3- RRR planarparallel mechanism with flexible links is derived. Then, using PSO method the mechanism is optimized based on a mixed performance that is a weighted sum of global stiffness index and its workspace.

Keywords:

Compliant parallel mechanism , Stiffness , Castigliano , Optimization