MobiDock: Design and Control of A Modular Self Reconfigurable Bimanual Mobile Manipulator via Robotic Docking

TL;DR

The paper addresses the challenge of coordinating multiple mobile manipulators by introducing MobiDock, a modular reconfigurable system in which two independent robots dock to form a single, unified bimanual platform. It combines a vision-based docking procedure using AprilTag markers with a threaded screw-lock mechanism, enabling autonomous reconfiguration and a unified post-docking control law. Experimental results show that the docked configuration achieves superior dynamic stability (lower RMSA and Jerk) and higher angular precision, while maintaining trajectory tracking comparable to a single module and completing tasks more quickly than two independent robots. The work demonstrates that hardware-level reconfiguration can reduce software coordination complexity and improve performance in cooperative manipulation tasks in real-world environments.

Abstract

Multi-robot systems, particularly mobile manipulators, face challenges in control coordination and dynamic stability when working together. To address this issue, this study proposes MobiDock, a modular self-reconfigurable mobile manipulator system that allows two independent robots to physically connect and form a unified mobile bimanual platform. This process helps transform a complex multi-robot control problem into the management of a simpler, single system. The system utilizes an autonomous docking strategy based on computer vision with AprilTag markers and a new threaded screw-lock mechanism. Experimental results show that the docked configuration demonstrates better performance in dynamic stability and operational efficiency compared to two independently cooperating robots. Specifically, the unified system has lower Root Mean Square (RMS) Acceleration and Jerk values, higher angular precision, and completes tasks significantly faster. These findings confirm that physical reconfiguration is a powerful design principle that simplifies cooperative control, improving stability and performance for complex tasks in real-world environments.

Figures (14)

• Figure 1: Key components of the proposed MobiDock system and its experimental applications: (a) the post-reconfigured bimanual robot system, (b-c) the independent mobile manipulator modules before docking, (d) the mechanical docking mechanism, (e) the system undergoes a stability test while lifting a box, (f) a cooperative manipulation experiment demonstrates the system's performance by picking up trash and putting it in a bin.
• Figure 2: A 3-wheeled omnidirectional robot model.
• Figure 3: The key components and a final configuration of the docking mechanism: (a) exploded view of the proposed screw-based docking mechanical design. The docking hubs are attached to one of the wheels of the two robots. During the docking process, the female hub remains stationary while the male hub rotates to fasten the docking. (b) Overview of the two modules fully docked, forming a single, rigid reconfigured system.
• Figure 4: The initial operational phase of a MobiDock module, (a) the robot rotates to find the target tag, with its manipulator parallel to the docking mechanism, (b) the camera is then rotated downward to precisely detect and localize the tag.
• Figure 5: Illustrations of AprilTag and camera axes. Lateral $X_\text{offset}$ and depth $Z_\text{offset}$ offsets guide the robot to center the camera on the tag, ensuring precise alignment during approach.