Haptic Virtual Fixtures for Telemanipulation Using Control Barrier Functions

Teleoperating mobile manipulators can be cognitively demanding due to a lack of depth perception and situational awareness. While virtual fixture constraints can be used to improve teleoperation performance, it is critical to ensure safety of these fixtures in order to enable their use in physical human-robot-interaction (pHRI) tasks. In this work, we propose to use control barrier functions (CBF) to design a virtual fixture architecture that allows us to tune the tradeoff between performance and safety. We design the architecture to ensure tracking performance between the user and robot is maintained outside of virtual fixture violations, and to simultaneously ensure that the robot cannot overshoot into a constraint. We conducted a theoretical and experimental analysis to investigate the relationship between tracking and safety, and present results which indicate that the ratio between the control gain used for tracking and the safety decay rate determine when the CBF filter and CBF-based force feedback become active. Finally, we implemented our proposed virtual fixture architecture on a mobile manipulator platform to investigate its effects on user's performance as they performed a simulated temperature scanning task. Overall, this work highlights the potential benefits of using CBF-based haptic virtual fixtures for conducting pHRI tasks.