  The barrier function method for safety control typically assumes the
availability of full state information. Unfortunately, in many scenarios
involving uncertain dynamical systems, full state information is often
unavailable. In this paper, we aim to solve the safety control problem for an
uncertain single-input single-output system with partial state information.
First, we develop a synthesis method that simultaneously creates a barrier
function and a dynamic output feedback safety controller. This safety
controller guarantees that the unit sub-level set of the barrier function is an
invariant set under the uncertain dynamics and disturbances of the system.
Then, we build an identifier-based estimator that provides a state estimate
affine to the uncertain model parameters of the system. To detect the potential
risks of the system, a fault detector uses the state estimate to find an upper
bound for the barrier function. The fault detector triggers the safety
controller when the system's original action leads to a potential safety issue
and resumes the original action when the potential safety issue is resolved by
the safety controller.
