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Distributed Motion Control of Multiple Mobile Manipulators for Reducing Interaction Wrench in Object Manipulation

Wenhang Liu, Meng Ren, Kun Song, Gaoming Chen, Michael Yu Wang, Zhenhua Xiong

TL;DR

The paper addresses the challenge of excessive interaction wrenches during cooperative object manipulation with multiple mobile manipulators by introducing a fully distributed motion-control law that relies only on local force-torque sensing and joint-velocity commands, avoiding dynamic modeling and torque control. It presents a Lyapunov-based stability analysis and demonstrates robustness to communication delays, supported by simulations that explore graph connectivity and delays. The authors validate the approach in physical experiments with two robots manipulating objects of varying stiffness, showing substantial reductions in wrench magnitudes and improved end-effector tracking. The work offers a practical, scalable solution for industrial MMMS where accurate dynamic parameters or external positioning systems are unavailable, enhancing safety and performance in real-world tasks.

Abstract

In real-world cooperative manipulation of objects, multiple mobile manipulator systems may suffer from disturbances and asynchrony, leading to excessive interaction wrenches and potentially causing object damage or emergency stops. Existing methods often rely on torque control and dynamic models, which are uncommon in many industrial robots and settings. Additionally, dynamic models often neglect joint friction forces and are not accurate. These methods are challenging to implement and validate in physical systems. To address the problems, this paper presents a novel distributed motion control approach aimed at reducing these unnecessary interaction wrenches. The control law is only based on local information and joint velocity control to enhance practical applicability. The communication delays within the distributed architecture are considered. The stability of the control law is rigorously proven by the Lyapunov theorem. In the simulations, the effectiveness is shown, and the impact of communication graph connectivity and communication delays has been studied. A comparison with other methods shows the advantages of the proposed control law in terms of convergence speed and robustness. Finally, the control law has been validated in physical experiments. It does not require dynamic modeling or torque control, and thus is more user-friendly for physical robots.

Distributed Motion Control of Multiple Mobile Manipulators for Reducing Interaction Wrench in Object Manipulation

TL;DR

The paper addresses the challenge of excessive interaction wrenches during cooperative object manipulation with multiple mobile manipulators by introducing a fully distributed motion-control law that relies only on local force-torque sensing and joint-velocity commands, avoiding dynamic modeling and torque control. It presents a Lyapunov-based stability analysis and demonstrates robustness to communication delays, supported by simulations that explore graph connectivity and delays. The authors validate the approach in physical experiments with two robots manipulating objects of varying stiffness, showing substantial reductions in wrench magnitudes and improved end-effector tracking. The work offers a practical, scalable solution for industrial MMMS where accurate dynamic parameters or external positioning systems are unavailable, enhancing safety and performance in real-world tasks.

Abstract

In real-world cooperative manipulation of objects, multiple mobile manipulator systems may suffer from disturbances and asynchrony, leading to excessive interaction wrenches and potentially causing object damage or emergency stops. Existing methods often rely on torque control and dynamic models, which are uncommon in many industrial robots and settings. Additionally, dynamic models often neglect joint friction forces and are not accurate. These methods are challenging to implement and validate in physical systems. To address the problems, this paper presents a novel distributed motion control approach aimed at reducing these unnecessary interaction wrenches. The control law is only based on local information and joint velocity control to enhance practical applicability. The communication delays within the distributed architecture are considered. The stability of the control law is rigorously proven by the Lyapunov theorem. In the simulations, the effectiveness is shown, and the impact of communication graph connectivity and communication delays has been studied. A comparison with other methods shows the advantages of the proposed control law in terms of convergence speed and robustness. Finally, the control law has been validated in physical experiments. It does not require dynamic modeling or torque control, and thus is more user-friendly for physical robots.
Paper Structure (14 sections, 28 equations, 14 figures, 2 tables)

This paper contains 14 sections, 28 equations, 14 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Preliminaries
  3. Kinematics of Mobile Manipulator
  4. Force-Torque Sensor
  5. Graph Theory
  6. The Proposed Control Method
  7. Problem Statement and Control Law
  8. Stability Analysis
  9. Simulations
  10. Experiments and Discussions
  11. Experimental Setup
  12. Experimental Results
  13. Discussion and Limitation
  14. Conclusion and Future Work

Figures (14)

  • Figure 1: Three mobile manipulator robots collaboratively manipulate an object. Some basic coordinate frames are labeled.
  • Figure 2: The overall framework. The control process of the $i$-th robot is illustrated.
  • Figure 3: The communication topology for multiple robots. (a) Weakly connected graph. (b) Complete graph.
  • Figure 4: The interaction wrenches between robots and the object. (a) Without the proposed control law. (b)-(d) With the proposed control law.
  • Figure 5: The effect of the delay upper bound on the control law.
  • ...and 9 more figures