Dynamic Physical Constraints: Emulating Hard Surfaces with High Realism

In this paper, we present a novel haptic technique for emulating hard surfaces with high realism; such a technique has significant potential utility in certain orthopedic surgery applications such as joint replacement surgery where the goal is to prevent incursions beyond a virtual surface during bone cutting operations. The Dynamic Physical Constraint (DPC) concept uses a unidirectional physical constraint that is actively positioned to limit movement between two manipulator links; the concept is applicable to providing virtual constraints in both 2D and 3D workspaces. Simulation results demonstrate the potential feasibility of the concept, and a prototype device was built for testing. The DPC device provides a convincing sensation of a real, hard virtual surface which can be smoothly tracked when the end effector is in contact with the surface. Incursion across the surface with the prototype was well submillimetric and within the accuracy constraints required for joint replacement applications.