Pose Synchronization of Multiple Networked Manipulators Using Nonsingular Terminal Sliding Mode Control

A unified inner‐/outer‐loop distributed design for task‐space robust cooperative tracking of uncertain networked manipulators under directed graphs

“…Differentiating (16) with respect to the time gives rise to the joint-space reference acceleration as…”

“…On the contrary, coordination of robotic end‐effectors is preferable and crucial to accomplishing manipulators' cooperative task, which can enhance the robustness and performance of networked manipulators. The task‐space synchronization problem of multiple manipulators has been studied in References 12‐17. In particular, an input–output passivity framework was proposed in Reference 12 to achieve task‐space cooperative tracking over the balanced and strongly connected digraph.…”

“…In particular, two delay‐dependent and ‐independent schemes were provided in Reference 15 to achieve synchronization of manipulators. The task‐space coordinated tracking of manipulators was obtained in Reference 16 using the nonsingular terminal sliding mode control scheme. The authors in Reference 17 addressed the problem of cooperative transportation of an object via the adaptive control method.…”

“…To the best of our knowledge, there are some issues and design limitations that have not been fully addressed in the existing works 9‐20 . First, the designs in References 9‐20 that require each robot to know the desired task‐space trajectory $$$ {x}_d $$$ in a centralized manner, often lead to less robustness and higher communication cost for real robotic applications. Moreover, the acceleration $$$ {\ddot{x}}_d $$$ is usually unmeasurable in practice.…”

“…Second, all the above‐mentioned results provided algorithms that only ensure convergence in ideal environments (e.g., no uncertainties/frictions and external disturbances), which may not be sufficient for the accomplishment of robust tasks that require high precision and reliable operations. In addition, as compared to works in References 9‐17 that assume the communication graph to be undirected graphs or strongly connected digraphs, which is conservative in reality due to communication constraints, it aims to achieve task‐space coordinated tracking control for networked robotic manipulators over a directed graph with a spanning tree. Third, unlike an open robotic control architecture in References 9‐17, a distributed framework with the unified inner/outer‐loop analysis is desired for task‐space cooperative tracking of networked manipulators, where the design of the outer‐loop controller and the low‐level inner‐loop controller will be unified via a closed robotic control architecture.…”