Abstract: An approach for the inverse displacement analysis of a plane symmetric 3-SPR parallel mechanism is presented. Influences of the structural angle of the R joint on the complicity of inverse displacement equations and the singularity are investigated, leading to an analytical solution and a singularity free design as long as the angle is set to be 90º. On the basis of monotonic analysis, a set of homogeneous dimensionless parameters can be achieved by minimizing two global performance indices represented by the mean value and standard deviation of the condition number of the velocity Jacobian.

Key words: Dimensional synthesis, Parallel mechanism, Singularity analysis