Human body schema exploration: Analyzing design requirements of Robotic Hand and Leg Illusions

Abstract

Understanding the integration of user-proximal robots in the body schema of their human users has a distinct potential to improve human-robot interaction. Robotic devices can help to investigate the psychological fundamentals of body schema integration. While the Rubber Hand Illusion experiment indicates how artifacts can be perceived as a part of the own body, it relies on a passive limb that does not perform motions during the examinations. Novel setups aim at Robotic Hand/Leg Illusions induced by robotic devices which imitate human motions. Although such devices distinctly extend experimental possibilities, their design is rather proprietary and unstructured up to now. This paper analyzes the requirements of robotic hand and leg illusion setups based on systematic discussion of a multidisciplinary team of researchers from engineering and psychology. In a comparative study, requirements are collected and structured, their similarities and differences are determined, and the most important ones are extracted yielding design implications. The requirements with the highest priority are setup characteristics that concern the occurrence and quality of the illusion, i.e., hiding the real limb, anatomical plausibility, visual appearance, temporal delay, and softwarecontrolled experimental conditions. Based on the results, the design of future robotic devices for the exploration of human body schema integration might be guided and supported.

Can Wearable Haptic Devices Foster the Embodiment of Virtual Limbs?

“…The use of a tele-operated robotic hand as the rubber hand has been shown to elicit a much stronger RHI when compared with the classical rubber hand paradigm, probably since participants experience themselves as agents of the rubber hand movement [21]. Beckerle et al analyzed technical design requirements that concern the occurrence and quality of the illusion [28] to induce a substantial robotic hand illusion. They characterized hiding the real limb, anatomical plausibility, visual appearance, temporal delay, and software controlled experimental conditions as most important.…”

Mechatronic designs for a robotic hand to explore human body experience and sensory-motor skills: a Delphi study

“…The questionnaires ask for practical experience of the experts. After surveying the experts' professional backgrounds and email contacts, the following text was presented to give them an introduction to the topic and the corresponding design requirements based on [10]:…”

“…According to previous hardware requirement analyses (Beckerle et al, 2016), the occurrence and quality of integration relies on hiding the real limb, anatomical plausibility (i.e., robotic hand motion/position/orientation), similar visual appearance of robotic and human hand, and technically-caused delays. Target applications are usually putting rather low mechanical load on the hand, e.g., grasping balls or handling empty bottles.…”

“…Fundamental psychological studies explored factors that influence the integration effect, e.g., form [6] and skin tone [7]. The introduction of robotic hands extended the capabilities of such paradigms for psychological research, especially regarding the manipulation of multisensory stimulation [8][9][10]. Beyond this, it opened up applications forin the design of robotic devices that interact tightly with their human users, e.g., assistive and rehabilitation robotics [1,11].…”

“…An analysis of the requirements of human-in-the-loop experiments targeting embodiment showed that most robotic devices used in such experiments exhibit proprietary designs and controls [10]. The technical solutions applied in psychology-related literature are less sophisticated or do not represent the full capabilities of the human hand [25][26][27].…”