Robust and Dexterous Dual-arm Tele-Cooperation using Adaptable Impedance Control

TL;DR

This work extends fractal impedance control to robust dual-arm tele-cooperation, enabling stable interaction and seamless switching between teleoperation and manipulation without gain retuning or energy tanks. By leveraging the conservative energy of FIC, independent end-effector controllers can be superimposed to coordinate two arms through synchronous via-points, even under delays and reduced bandwidth. The TeleCoop-FIC framework is demonstrated across haptic and non-haptic modes and a range of tasks, including drilling on diverse materials and human-robot collaboration, showing superior interaction forces, tracking accuracy, and robustness relative to traditional impedance controllers. The approach offers a practical path for dexterous tele-manipulation in challenging environments such as manufacturing and space robotics, with future work aimed at improving precision and generalizing to additional robot platforms.

Abstract

In recent years, the need for robots to transition from isolated industrial tasks to shared environments, including human-robot collaboration and teleoperation, has become increasingly evident. Building on the foundation of Fractal Impedance Control (FIC) introduced in our previous work, this paper presents a novel extension to dual-arm tele-cooperation, leveraging the non-linear stiffness and passivity of FIC to adapt to diverse cooperative scenarios. Unlike traditional impedance controllers, our approach ensures stability without relying on energy tanks, as demonstrated in our prior research. In this paper, we further extend the FIC framework to bimanual operations, allowing for stable and smooth switching between different dynamic tasks without gain tuning. We also introduce a telemanipulation architecture that offers higher transparency and dexterity, addressing the challenges of signal latency and low-bandwidth communication. Through extensive experiments, we validate the robustness of our method and the results confirm the advantages of the FIC approach over traditional impedance controllers, showcasing its potential for applications in planetary exploration and other scenarios requiring dexterous telemanipulation. This paper's contributions include the seamless integration of FIC into multi-arm systems, the ability to perform robust interactions in highly variable environments, and the provision of a comprehensive comparison with competing approaches, thereby significantly enhancing the robustness and adaptability of robotic systems.

Figures (6)

• Figure 1: (a) Haptic: The master moves the replica (Panda, Franka Emika AG) by applying a virtual force ($f_\text{v}$). The interaction force/torque feedback at the end-effector ($F_{\text{FB}}$) is scaled in A$_\text{M}$ to generate the haptic feedback. The operator can also act on the replica end-effector's reference pose ($x_\text{d}$) by activating the master device with its grasp joint or via the GUI. Non-Haptic: The replica is controlled by issuing sequences of $x_\text{d}$ that act as via points for the trajectory of the replica. (b) Dual-arm Tele-cooperation Setup.
• Figure 2: The trajectory and the interaction force for the FIC and IC are compared when drilling a piece of wood.
• Figure 3: Experiment 5.1: Drilling on a curve surface with a constrained angular motion ($\pm 5°$).
• Figure 4: Experiments 2 to 4: Teleoperation drilling of various objects. Experiment 5.1: Human-robot cooperation scenario 1 (Fig. \ref{['fig:dual_arm_curved_drilling']}). Experiment 5.2: Human-robot cooperation scenario 2 (Fig. \ref{['fig:dual_arm_box_in_between_drilling']}).
• Figure 5: Experiment 5.2: The robots start from via point 1 and go back to it. The object is picked up in 3. The drilling occurs in 4 and once the user has finished, the work-piece is removed in 5.