Singularity analysis and nonlinear tracking controller design for a five-bar parallel manipulator

The singularity of a five-bar parallel manipulator is analyzed and a nonlinear tracking controller is designed in this paper. Three types of the singularity are analyzed and the singularity curve equations are formulated by using the Jacobian matrix of the parallel manipulator. The dynamic model is established in the active joint space, and the active joint friction is described with the Coulomb + viscous friction model. Based on the dynamic model, a nonlinear tracking controller eliminating the tracking error with the power function is proposed. The trajectory tracking experiment of an actual five-bar parallel manipulator is carried out. The performances between the proposed controller and the traditional augmented PD (APD) controller are compared.