Grounding mobile force feedback in the real world

We describe a prototype mobile force-only feedback system called 'Limbot' constructed by placing a six degree-of-freedom force feedback system onto a two degree-of-freedom motorised platform. Existing mobile force-feedback platforms are typically designed to expand the virtual haptic workspace and support exploration of large haptic objects in the style of traditional Virtual Reality (VR) interfaces. Systems which focus on the VR paradigm typically preclude navigation of real environments because attention is primarily directed at the graphical display. In contrast, our device is unconstrained and designed for force-only explorations of real wide-area environments, for example as part of a location-based pervasive game. In order to achieve such wide-area exploration and navigation, our platform allows the user to couple and decouple the force feedback encoders to control the platform's wheels. The device's encoders switch between 'traditional' virtual exploration of a haptic object and as a real navigation controller for the base platform motors. Initial testing of our prototype highlights (i) that our positioning and mobility approaches require that we consider haptic perspective more closely; (ii) that the necessary speed and control of repositioning requires easily backdrivable base motors; and (iii) that our mobile force feedback experience is an unavoidably social experience in the real world, inspiring quick movements between haptic and robotic modes of operation.