Modeling and Optimal Control for 2-DOF Differential Robot Joint Based on Cascade Extended State Observer

This paper presents a novel 2-degree-of-freedom (2-DOF) differential robot joint (DRJ), actuated by two permanent magnet synchronous motors (PMSMs), to enhance the load capacity and flexibility of robot joint. The dynamic model of the DRJ has been developed, explaining the coupling principles of the DRJ and the sources of system disturbances for the first time. A novel control system based on CESO and LQR was designed to address the challenges of observing high-order non-integral chain systems and the lack of robustness in traditional resonance suppression methods. Additionally, the main advantages of this innovative scheme include utilizing only motor-based sensors, exhibiting good load adaptability, and demonstrating an effective dynamic response. Simulation demonstrate that the proposed control strategy significantly improves the torque and velocity performance of the 2-DOF DRJ compared to traditional approaches.