Dynamic proxy objects in haptic simulations

Haptic simulations aim to provide users with realistic renditions of increasingly complex virtual environments. These may involve multiple users, multiple hands, and complex virtual tools. For example, in surgical training, simulators must recreate a tool in each hand of the user, interacting with each other as well as with the surrounding tissue. To further such developments, we introduce and demonstrate the concept of dynamic proxy objects. Proxies represent the physical master devices in the virtual world. Associating dynamics with these proxies allows greater control over the proxy motion and behavior, in particular in the context of collisions with fixed objects and between multiple proxies. We utilize first order velocity-based dynamics, so that the proxies remain massless. Geometric constraints are implemented in terms of velocity limits, as are dynamic interactions such as collisions. Complex tools, kinematic relationships, and even closed kinematic chains are incorporated, through Jacobian matrices. This approach is demonstrated in a simple experiment simulating interactions between two straight, slender virtual manipulators on a two-handed haptic console.