Mechanisms for haptic feedback

This article describes work in progress at the Canadian Space Agency on the design and implementation of haptic devices. Haptic devices are a special class of robotic mechanisms for which structural transparency is a foremost design criterion. Also notable is the fact that often, three or four degrees of freedom, rather than six as in general robotic tasks, are sufficient for many haptic applications. Furthermore, in order to make these devices readily available to many users, it is necessary their kinematic models be sufficiently simple such that they can be controlled by inexpensive means. Various three and four-DOF mechanisms, some of which recently developed by the Canadian Space Agency, are discussed herein in terms of their suitability for haptic applications. For five or six-DOF applications, the concept of the virtual handle is introduced, reducing the problems and complexity usually associated with mechanisms with a high number of degrees of freedom.