Safe tracking control for free-flying space robots via control barrier functions

Safety is a critical problem for space robots in future complex autonomous On-Orbit Services. In this paper, we propose a real-time and guaranteed method for whole-body safe tracking control of free-flying space robots using High Order Control Barrier Functions (HOCBFs).

We start by utilizing capsule-shaped safety envelopes for an accurate approximation of space robots. This is followed by the development of HOCBF-based safety filters to ensure simultaneous collision avoidance and compliance with specified joint limits. To mitigate feasibility issues, we incorporate the optimal decay method into our safety filter design. Furthermore, we introduce a data-driven re-planning mechanism to avoid local minimums of control barrier functions. Such a mechanism primarily operates through anomaly detection of tracking behavior using One-Class Support Vector Machines.

Numerical experiments demonstrate that our method effectively ensures safety of space robots under complicated circumstances without compromising the system’s ability to achieve its intended goals.