Topology optimization of planar linkage systems involving general joint types

•The topology and dimension of planar linkage mechanisms are simultaneously synthesized.•A new topology optimization method to deal with various joint types is proposed.•The concept of double-springs to connect ground rigid blocks is newly introduced.•Mechanisms with revolute, prismatic and pin-in-slot joints were successfully synthesized.

The simultaneous synthesis of the number and dimension of planar linkage mechanisms has opened a new possibility in mechanism synthesis. Mechanisms with revolute joints were a main concern so far but planar mechanisms with general joints including prismatic joints cannot be synthesized. This study aims to overcome the current difficult by proposing a new synthesis method. The key idea in the proposed approach is to parameterize joint types directly, unlike earlier methods parameterizing ground link skeletons connected by revolute joints. So, we propose a new concept of “double-springs” that can be used to connect a finite number of ground rectangular rigid blocks that discretize a given synthesis domain. Rigid blocks are elaborately connected by two sets of one-dimensional springs, i.e., double-springs and their stiffness values are varied by design variables. The connectivity of the double-springs dictated by the stiffness values determines the synthesized link mechanisms. We explain why it is crucial to use the double-spring concept for the synthesis of general joints such as prismatic joints. Various benchmark problems were considered to demonstrate the validity of the proposed method.