Analysis and validation of a planar parallel continuum manipulator with variable Cartesian stiffness

Manipulators with variable stiffness provide more flexibility between safety and performance when executing delicate tasks. In this paper, a novel planar parallel continuum manipulator (PPCM) with variable Cartesian stiffness is presented. The proposed manipulator consists of three flexible parallel limbs, with each limb made up with one PR drive and one slender flexible link, while the moving platform connects the links together. Except for the PR drive, there is no other rigid joint in this manipulator. An efficient kinetostatics analysis method is used based on previous research, and the stiffness model is built to compute the Cartesian stiffness. The advantage of the proposed PPCM is its intrinsic stiffness variation capability, which is achieved by the coupled large deflections of the flexible links and redundant actuation. An iterative algorithm is developed to calculate the actuator input under prescribed pose and required stiffness. A prototype of the manipulator is fabricated and its characteristics are validated by experiments. The measured results show that the studied PPCM has high position accuracy and its stiffness can be changed under different postures.