A two-layered cross coupling control scheme for a three-dimensional motion control system

• The three-dimensional contouring error estimation model is divided into two layers, which presents more flexibility in the control system design.
• A two-layered cross coupling controller (CCC) is proposed, which can design different controllers in different layers.
• Experiments show that the designed two-layered CCC can obtain higher contouring accuracy than traditional CCC both in the bottom layer and the three-dimensional space.

A two-layered modeling and compensation scheme is proposed to reduce the contouring error of a three-dimensional motion control system. In the proposed scheme, the contouring error model of the three-dimensional motion control system is divided into two layers: the top layer and the bottom layer. The proposed multi-layered structure of the contouring error model presents more flexibility in the control system design because the cross coupling controllers in different layers can be designed separately. In this paper, a nonlinear PI controller and a position error compensator are designed in the bottom layer in order to achieve high contouring accuracy in the XY plane, while a unilateral compensator is designed in the top layer to further reduce contouring error in the three dimensional space. Finally, experiments are performed to verify the performance of the proposed two-layered modeling and compensation scheme. Experiment results show that the designed two-layered cross coupling controller can obtain higher contouring accuracy than traditional cross coupling controller both in the XY plane and in the XYZ space.