Robust Dynamic Control With Null-Space Compliance Using a Disturbance Observer for Surgical Robot

In robotic surgery, secure and precise operation in collaborative human-robot tasks is critical, underscoring the need for robust dynamic control strategies tailored to such scenarios. To address the challenge of precise control under uncertain external disturbances, we propose a method utilizing null space control of a redundant robotic manipulator integrated with a nonlinear disturbance observer (DO). This approach extends the classical DO by decoupling the compensation of disturbances in the task space and the null space, ensuring task-space precision while preserving null-space compliance. Experimental comparisons with existing methods demonstrate superior tracking accuracy and disturbance rejection under unknown external interactions. Finally, to simulate human-robot collaboration (HRC) in robot-assisted minimally invasive surgery scenarios, remote center of motion (RCM) constraint trajectory tracking experiments under external disturbances show that this method effectively balances motion constraint precision and system resilience against disturbances.