Cascaded ESO and BLF Based Multi-Task Priority Controller for Redundant Robots with Null Space Compliance

In this study, we address multi-task priority trajectory tracking and null space compliance control for redundant robots, which lack joint velocity and torque sensors, under substantial external disturbances. A cascaded ESO and BLF-based multi-task priority controller is proposed, which can make the robot still keep the position state of each task within the prescribed performance range under the condition of strong external disturbances. First, The cascaded ESO is utilized to estimate joint velocities and compensate for system uncertainties. Then, a trajectory tracking controller for high-priority tasks based on BLF and the null space compliance controller with the lowest priority are designed. Simulation results demonstrate the effectiveness of the proposed method in comparison to alternatives.