Abstract: Dynamic modeling of single link robot arm with consideration of clearance in planetary gear reducer is discussed, and the influence of the clearance on dynamic response of the mechanism is analyzed. The contact state of gear pair is described with two-state model and the dynamic model of planetary gear reducer with consideration of clearance and time-varying meshing stiffness is built by adopting lumped mass method. Based on assumption of Euler-Bernoulli beam and the assumed mode method, the elastic deformation of the flexible robot arm is presented. Therefore, equations of motion (EOM) of the system are obtained based on Lagrange equation and the solution is carried out by using Adams variable step-size multistep integral method. The results indicate that the responses of the robot system change obviously when clearance in gear reducer is considered and the clearance become the dominant factor to influence the positioning precision of the robot arm with the increment of clearance. The results provide theoretical basis of improving the positioning precision of the robot arm.

Key words: Clearance, Flexible robot arm, Nonlinear dynamics, Planetary gear