A Task Space Virtual Fixture Architecture for Teleoperated Surgical System with Slave Joint Limit Constraints

Unintended motion is one of the major causes of intraoperative injuries in teleoperated surgeries. Due to the large workspace discrepancy between master and slave manipulators, the tip of the slave may deviate from the intended master command without prior notice, when the slave is moved beyond its joint limits. Conventional solutions such as the constrained-optimization-based virtual fixture (VF) method suffer from nonintuitive tip motion management and unnatural haptics in high-dimensional systems. To this end, we propose a task space virtual fixture (TSVF) architecture to systematically address those issues by forbidden-region VF design. It decomposes the high-dimensional task space into low-dimensional task subspaces according to its inherent topology. In each subspace, we design a human-centric TSVF geometry and controller to manage the tip behavior by exploiting the nonlinear kinematics mapping. This architecture builds a real-time TSVF system with natural and predictable haptics. To showcase this concept, we design and implement the proposed TSVF system for the state-of-the-art surgical system, da Vinci Research Kit. Simulations, experiments, and human-factor user study verify its effectiveness and intuitiveness. In the user study, our proposed TSVF system demonstrates the most easy-to-understand tip behavior and shows a significant positive effect over haptics likeability.