Control barrier function based visual servoing for Mobile Manipulator Systems under functional limitations

This paper proposes a new control strategy for Mobile Manipulator Systems (MMSs) that integrates image- based visual servoing (IBVS) to address operational limitations and safety constraints. The proposed approach based on the concept of control barrier functions (CBFs), provides a solution to address various operational challenges including visibility constraints, manipulator joint limits, predefined system velocity bounds, and system dynamic uncertainties. The proposed control strategy is a two-tiered structure, wherein the first level, a CBF-IBVS controller calculates control commands, taking into account the Field of View (FoV) constraints. By leveraging null space techniques, these commands are transposed to the joint-level configuration of the MMS, while considering system operational limits. Subsequently, in the second level, a CBF velocity controller employed for the entire MMS undertakes the tracking of the commands at the joint level, ensuring compliance with the predefined system's velocity limitations as well as the safety of the whole combined system dynamics. The proposed control strategy offers superior transient and steady-state responses and heightened resilience to disturbances and modeling uncertainties. Furthermore, due to its low computational complexity, it can be easily implemented on an onboard computing system, facilitating real-time operation. The proposed strategy's effectiveness is illustrated via simulation outcomes, which reveal enhanced performance and system safety compared to conventional IBVS methods. The results indicate that the proposed approach is effective in addressing the challenging operational limitations and safety constraints of mobile manipulator systems, making it suitable for practical applications.