  As the performance of autonomous systems increases, safety concerns arise,
especially when operating in non-structured environments. To deal with these
concerns, this work presents a safety layer for mechanical systems that detects
and responds to unstable dynamics caused by external disturbances. The safety
layer is implemented independently and on top of already present nominal
controllers, like pose or wrench tracking, and limits power flow when the
system's response would lead to instability. This approach is based on the
computation of the Largest Lyapunov Exponent (LLE) of the system's error
dynamics, which represent a measure of the dynamics' divergence or convergence
rate. By actively computing this metric, divergent and possibly dangerous
system behaviors can be promptly detected. The LLE is then used in combination
with Control Barrier Functions (CBFs) to impose power limit constraints on a
jerk controlled system. The proposed architecture is experimentally validated
on an Omnidirectional Micro Aerial Vehicle (OMAV) both in free flight and
interaction tasks.
