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

Unintended motion has been one of the major causes of intra-operative injuries in tele-operated 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 like the constrained optimization based Virtual Fixture (VF) method suffered from non-intuitive 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 sub-spaces according to its inherent topology. In each sub-space, 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 designed and implemented the proposed TSVF system for the state-of-the-art surgical system, da Vinci Research Kit (dVRK). Simulations, experiments, and human-factor user study verified its effectiveness and intuitiveness. In the user study, our proposed TSVF system demonstrated the most easy-to-understand tip behavior and showed a significant positive effect over haptics likeability.