Walking Sensation in Low and High-Viscosity Fluids Using a Lower-Limb Force-Feedback Exoskeleton with MR Fluid Brake �The Effect of Changes in Visual on Users' Subjective Evaluation�

In recent years, various haptic devices have been used to reproduce the senses of touch and force when interacting with virtual fluids. This study focuses on reproducing the resistance force experienced during underwater walking movements in a virtual reality (VR) space using a lower-limb force-feedback exoskeleton. To realize disaster simulations with a greater sense of fear and realism for the user, we focused on the necessity of parameter design based on human subjective evaluation when constructing a force-feedback model for the sensation of underwater motion. This study aims to clarify the influence of visual viscosity information on the user's subjective evaluation. Based on the drag model and the added mass force model proposed in previous research, we constructed a composite model in which the contribution ratio of both can be varied. It is conducted an evaluation experiment by combining two types of fluid visuals with different viscosities and four force- feedback conditions. The analysis revealed that visual viscosity information affects the criteria for judging the sensation of viscosity and the way force feedback is perceived. Furthermore, it became clear that as the viscosity changes, the correlation structure among the subjective evaluation items also changes.