Virtual Reality (VR) has emerged as a promising solution to address the pressing concern of transferring know-how in the manufacturing industry. Making an immersive training experience often involves designing an instrumented replica of a tool whose use is to be learned through virtual training. The process of making a replica can alter its mass, making it different from that of the original tool. As far as we know, the influence of this difference on learning outcomes has never been evaluated. To investigate this subject, an immersive training experience was designed with pre and post-training phases under real conditions, dedicated to learning the use of a rotary tool. 80 participants took part in this study, split into three groups: a control group performing the virtual training using a replica with the same mass as the original tool ($\mathrm{m}=100\%$), a second group that used a replica with a lighter mass than the original tool ($\mathrm{m}= 50\%$) and a third group using a replica heavier than the original tool ($\mathrm{m}=150\%$). Despite variations in the mass of the replica used for training, this study revealed that the learning outcomes remained comparable across all groups, while also demonstrating significant enhancements in certain performance measures, including task completion time. Overall, these findings provide useful insights regarding the design of tool replicas for immersive training.

This paper describes a new interaction technique called haptic hybrid rotations to overcome the physical angular limitations of force-feedback devices when manipulating virtual objects. This technique is based on a hybrid control of the object manipulated with the device. When approaching the angular mechanical stops of the device, the control mode switches from angular position-control to rate-control. The forcefeedback of the device is used to simulate the use of an elastic device in the rate-control mode. An experiment was carried out to compare this technique with two other common alternatives that are used when manipulating virtual objects with force-feedback devices: rotations scaling, and the clutching technique. Our results showed that haptic hybrid rotations were both the fastest and the most appreciated technique for the proposed experiment.

This paper describes two psychophysical experiments which were conducted to evaluate the influence of the control/display (C/D) ratio on the perception of mass of manipulated objects in virtual environments (VE). In both experiments, a discrimination task was used in which participants were asked to identify the heavier object between two virtual balls. Participants could weigh each ball via a haptic interface and look at its synthetic display on a computer screen. Unknown to the participants, two parameters varied between each trial: the difference of mass between the balls and the C/D ratio used in the visual display when weighing the comparison ball. The data collected demonstrated that the C/D ratio significantly influenced the result of the mass discrimination task and sometimes even reversed it. The absence of gravity force largely increased this effect. These results suggest that if the visual motion of a manipulated virtual object is amplified when compared to the actual motion of the user's hand (i.e. if the C/D ratio used is smaller than 1), the user tends to feel that the mass of the object decreases. Thus, decreasing or amplifying the motions of the user in a VE can strongly modify the perception of haptic properties of objects that he/she manipulates. Designers of virtual environments could use these results for simplification considerations and also to avoid potential perceptual aberrations.