Stiffness and natural frequency of a 3-DOF parallel manipulator with consideration of additional leg candidates

• Dynamic modeling method for redundant parallel manipulators is given.
• The stiffness and natural frequency are improved by adding one or two additional legs.
• First-order natural frequency cannot be improved much by adding the second additional leg.
• It is better to develop this manipulator by adding only one additional leg B1E1B1E1.

This paper investigates the stiffness and natural frequency of a 3-DOF parallel manipulator with consideration of additional leg candidates. The stiffness model and natural frequency are derived, and then the stiffness and natural frequency of the manipulators are compared. The simulations show that the stiffness and natural frequency of the parallel manipulator with one or two additional legs are higher than those of the manipulator without additional leg. The stiffness performance and natural frequency of the manipulator with one additional leg can only be improved little by adding the second additional leg. It is better to develop this parallel manipulator by adding only one additional leg to construct a symmetrical architecture.