Development of a haptic feedback subsystem

This paper describes the components and highlights some specifications of a device that allows several combinations of immersed or desktop vision feedback devices to be integrated with a three degree-of-freedom force-feedback device previously known as the `Reactabot™' and currently known as the `Visitact'. The Visitact is a haptic display robot that provides and receives kinaesthetic information from the user, who can touch and manipulate a surrogate object, and feel external forces exerted upon it by obstructions, within a virtual environment. In essence, the Visitact allows a combination of various immersed or desktop visual solutions to be integrated with a three degree-of-freedom force-feedback device. The mechanical interface senses the forces applied by the user and the haptic control system generates a reaction force that moves the surrogate object in the direction of the applied force. The surrogate object can be accelerated up to ±2g (approximately 20m/s2) sustain forces up to 20N, with a virtual mass in the range 0.7- 4 kg. The device provides force feedback over a large proportion of the user's workspace and enables virtual objects to take on user-specified physical properties such as mass, gravity, weight and drag, and was implemented with force/velocity control to allow the robot to interact with an operator, and to share the same working volume. Two techniques are used during a Visitact session. The user, who is normally sitting, holds the surrogate object and either sees a virtual or augmented representation of it on a computer screen, or through a head mounted display. Currently the Visitact is upgraded to work as a six degree of freedom force feedback device. An attempt to extend the device to serve 6- degree of freedom is briefly described.