For haptic displays to provide convincing tactile feedback, the simulation of the dynamic response of the modeled object must be accurate and efficient enough to run in real time. However, for situations such as the simulation of topical searches for hypodermic tumors, the need for real-time solution and accuracy are incompatible with existing technologies. Under NASA sponsorship, Creare is bridging the gap between the need for real-time touch perception for convincing immersive environments and bandwidth limitations in performing real-time updates of complex virtual reality (VR) models of dynamic systems.

Creare is developing and testing an impedance-based haptic display control system for use in haptically rendering grid-based immersive environments. Creare is demonstrating its haptic display control technology on a biomedical application which involves:

• Finite element modeling,
• Hardware design and fabrication, and
• Psychophysical testing.

The focus of the technology demonstration is the detection of hypodermic inclusions and tumors within a VR environment that has been constructed from medical data, such as MR, CT, or X-ray images. As an example, we are demonstrating the ability to tactically sense bones within the forearm from an X-ray image (see figure at right). Creare's haptic display control technology will lead to practical applications of virtual reality for simulated surgery and for training technicians, clinicians, and submarine and aircraft pilots. The real-time haptic rendering software is portable between hardware platforms and includes the low-level responsibilities of communicating with the haptic display and for providing impedance control commands to the haptic display in response to the user's inputs.

Forearm X-ray image used in technology demonstration