Teleoperation of a robotic manipulator in peri-personal space: a virtual wand approach

TL;DR

This work tackles the problem of 6-DoF teleoperation in peri-personal space by introducing a virtual wand mapping that converts rotations into amplified translations via a fixed-length virtual linkage, offering an alternative to direct end-effector control. The authors compare Wand Mapping to a direct mapping on a Kinova GEN3 robot with AR visualization, across 30-target reaching tasks and with/without visualization, using a resolved-rate controller. Results show comparable performance and user perception for both mappings, with the wand approach potentially advantageous for translation-heavy tasks and for body parts with large rotations such as the head or trunk; AR visualization helps mitigate perception delays. The study supports context-dependent mapping choices and points toward hybrid interfaces that combine multiple control modes for disability assistance and near-field teleoperation.

Abstract

The paper deals with the well-known problem of teleoperating a robotic arm along six degrees of freedom. The prevailing and most effective approach to this problem involves a direct position-to-position mapping, imposing robotic end-effector movements that mirrors those of the user. In the particular case where the robot stands near the operator, there are alternatives to this approach. Drawing inspiration from head pointers utilized in the 1980s, originally designed to enable drawing with limited head motions for tetraplegic individuals, we propose a "virtual wand" mapping. It employs a virtual rigid linkage between the hand and the robot's end-effector. With this approach, rotations produce amplified translations through a lever arm, creating a "rotation-to-position" coupling. This approach expands the translation workspace at the expense of a reduced rotation space. We compare the virtual wand approach to the one-to-one position mapping through the realization of 6-DoF reaching tasks. Results indicate that the two different mappings perform comparably well, are equally well-received by users, and exhibit similar motor control behaviors. Nevertheless, the virtual wand mapping is anticipated to outperform in tasks characterized by large translations and minimal effector rotations, whereas direct mapping is expected to demonstrate advantages in large rotations with minimal translations. These results pave the way for new interactions and interfaces, particularly in disability assistance utilizing head movements (instead of hands). Leveraging body parts with substantial rotations could enable the accomplishment of tasks previously deemed infeasible with standard direct coupling interfaces.

Figures (12)

• Figure 1: A comparison of the one-to-one direct mapping mapping (top) and wand (bottom) between a start (lighter) and an end (darker) configuration. In the wand mapping, rotations of the hand produces amplified translations coupled with rotations of the end-effector, while one-to-one direct mapping decouples translations and rotations of the end-effector.
• Figure 2: A representation of the AR visualisation during Wand Mode : the desired end-effector position is shown in blue (and does not appear during the visual perturbation mode), the target is shown in red, and the current robot's end effector is shown in magenta. The robot is servoed to follow the desired configuration (arrow, not shown in the AR headset). A similar representation is show in Direct mapping, without the handle of the hand and solely the desired blue end effector.
• Figure 3: Distribution of the duration per target in s. Green denotes a trial with visualization, and magenta without.
• Figure 4: Distribution of the overshoot of the desired virtual end-effector above the tolerance per target as a percentage, both in translation and in rotation. Green denotes a trial with visualization, and magenta without.
• Figure 5: Normalized Median of the Hand Motion in Translation and Rotation during trials with Visualisation. The lighter area denotes the standard deviation of the curve. The dotted line indicates the separation between the estimated ballistic and adjust phases.