Open Access

Although extensive safety measures and safe working procedures have been applied to improve and secure metal working machines, they still put their operators at risk. These risks might often result from manipulation errors, in particular if safety measures are ignored. In this contribution, a safety evaluation strategy has been developed that applies VR and mixed reality technologies to investigate the usability of working machines. An automatically controlled machine tool was simulated and connected to a real input panel, usually employed in industrial settings. However, Human-Machine Interfaces are sometimes built in a way that does not prevent the operator from cognitive misinterpretations which in turn might result in mistakes. To take that into account, a control program for a lathe was altered by hiding a typical programming mistake in the lines of code. Subjects were given the task to evaluate the program in single step mode and to report abnormalities while running the simulated lathe, comparable to new control program checks at real machines. An evaluation of the study demonstrated that even experienced metal workers accepted the simulation and reacted as if the given task was real. Behavioural data of considered subjects showed comparable profiles and most subjects rated the VR- based approach as a reasonable means for investigating work safety problems.

When illusory self-motion is induced in a stationary observer by optic flow, the perceived distance traveled is generally overestimated relative to the distance of a remembered target (Redlick, Harris, & Jenkin, 2001): subjects feel they have gone further than the simulated distance and indicate that they have arrived at a target's previously seen location too early. In this article we assess how the radial and laminar components of translational optic flow contribute to the perceived distance traveled. Subjects monocularly viewed a target presented in a virtual hallway wallpapered with stripes that periodically changed color to prevent tracking. The target was then extinguished and the visible area of the hallway shrunk to an oval region 40° (h) × 24° (v). Subjects either continued to look centrally or shifted their gaze eccentrically, thus varying the relative amounts of radial and laminar flow visible. They were then presented with visual motion compatible with moving down the hallway toward the target and pressed a button when they perceived that they had reached the target's remembered position. Data were modeled by the output of a leaky spatial integrator (Lappe, Jenkin, & Harris, 2007). The sensory gain varied systematically with viewing eccentricity while the leak constant was independent of viewing eccentricity. Results were modeled as the linear sum of separate mechanisms sensitive to radial and laminar optic flow. Results are compatible with independent channels for processing the radial and laminar flow components of optic flow that add linearly to produce large but predictable errors in perceived distance traveled.