| Summary: | In this paper, we propose a novel coordinated control method based on decoupling servo control to design a 4-DOF direct-drive SCARA robot for wafer handling purpose. As the basis of decoupling servo control, the dynamic model of the SCARA robot is obtained with two methods, the Newton-Euler equation, and Lagrangian equation. The validity of this SCARA dynamic equation is confirmed by these two methods. Due to disturbance and model uncertainty, three PD plus robust controllers are individually applied to three axes of the SCARA robot, together with decoupling control on three physically dynamically highly coupled robotic arms. The inverse dynamics of the SCARA robot is analyzed by feedback linearization, and the experimental results show that above PD plus robust controllers and decoupling control reduce the position tracking error effectively. Performance meets with the high speed and high precision requirements in the wafer handling process. The experimental data shows that the decoupling control algorithm makes the SCARA robot performance improved a lot. The position errors during dynamic tracking movement and the static errors are reduced by 4 to 20 times.
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