Haptic Displays

Haptic (force) feedback provides a dramatic increase in the realism and performance of many distributed systems, including teleoperated master/slave robot systems and haptic displays for immersive simulation (i.e., virtual reality). High-fidelity haptic displays require high update rates (1 kHz), but the limited bandwidth and transmission delays that characterize network-based simulations tend to destabilize haptic displays and greatly diminish realism. To enable high-fidelity haptic displays to be used effectively in network simulations, Creare has developed the following two control algorithms:

• Passive Transmission Line Model (PTLM) is an information encoding scheme that passivates time delays by modeling the equivalent of forward and backward traveling waves, mimicking the stability found in many “natural” systems.
• Haptic Dead Reckoning (HDR) employs a simplified local dynamics model and force feedback loop to provide high local update rates while a physics-based environment model updates the parameters of the local HDR model at slower (network-compatible) rates.

Under funding from the U.S. Army Simulation, Training, and Instrumentation Command (STRICOM), Creare has utilized these techniques to build a pair of networked Humvee (HMMWV) simulators (in partnership with Reality by Design) and a network-based vehicle driving simulator. The Humvee simulators delivered to STRICOM utilize High Level Architecture (HLA) for network communication, Creare’s PTLM software, and include 3-D video and steering wheel torque output.

Creare’s tabletop networked driving simulator applies PTLM and HDR and includes a proprietary vehicle dynamics model. It also provides 3-D video and steering wheel torque output. This tabletop driving simulator is now being employed to test the feasibility of a Virtual Reality-Enhanced Physical Therapy System for the National Institutes of Health.