Modeling of the “Rutgers Master II” Haptic Display

The Rutgers Master II (RM-II) haptic display is a human-machine interface for virtual reality and telerobotics applications. The system reads hand gestures and displays forces to four fingers in real time. Under simple force-control strategies, prototype testing has shown that tuning RM-II for higher output bandwidth (> 15H z) decreases its stability and thus the force display fidelity. The presence of a human in the control loop and the use of pneumatic devices make difficult the selection of system parameters empirically. In order to improve force display fidelity at higher bandwidths it became necessary to model this new device and its interaction with the human hand. This dynamic interactive human-machine model is used to simulate the squeezing of soft and hard virtual springs. The numerical simulation focuses on determining the effect of the display bandwidth Wc and controller lag Td on system stability and fidelity.