MR-UBi: Mixed Reality-Based Underwater Robot Arm Teleoperation System with Reaction Torque Indicator via Bilateral Control

We present a mixed reality-based underwater robot arm teleoperation system with a reaction torque indicator via bilateral control (MR-UBi). The reaction torque indicator (RTI) overlays a color and length-coded torque bar in the MR-HMD, enabling seamless integration of visual and haptic feedback during underwater robot arm teleoperation. User studies with sixteen participants compared MR-UBi against a bilateral-control baseline. MR-UBi significantly improved grasping-torque control accuracy, increasing the time within the optimal torque range and reducing both low and high grasping torque range during lift and pick-and-place tasks with objects of different stiffness. Subjective evaluations further showed higher usability (SUS) and lower workload (NASA--TLX). Overall, the results confirm that \textit{MR-UBi} enables more stable, accurate, and user-friendly underwater robot-arm teleoperation through the integration of visual and haptic feedback. For additional material, please check: https://mertcookimg.github.io/mr-ubi