Strict Zeroing Control Barrier Function for Continuous Safety Assist Control

Control barrier functions (CBFs) have been yielding successful implementations in various control strategies. In this letter, we propose a human assist controller using a zeroing CBF (ZCBF). To ensure the forward-completeness of every solution to a nonautonomous system, we provide the “strict” definition of a ZCBF. Then, we obtain a global condition for a ZCBF from the strict conditions. We simultaneously prove that the proposed controller ensures the forward-completeness and the safety of a nonautonomous system. The effectiveness of the proposed controller using a strict ZCBF is confirmed by a mathematical example.