Abstract: In this paper,the possible chaotic motion in the self-motion of a planar 3R redundant robot is discussed under the PD controller when the end-effector traces a closed-path repeatedly in the workspace,by the numerical simulation,phase plot and the largest Lyapunov exponent. The numerical results show that the self-motion is chaotic based on the pseudoinverse of the Jacobian method for solving the inverse kinematics of the redundant robot. The delayed feedback control method is used to control the discovered chaotic motion for the first time. It is shown that the chaotic motion can be turned into regular motion with some appropriate parameters.