Safety-Based Dynamic Output Feedback Tracking Control of Time-Varying Input-Output Linearizable Systems With Output Constraints

This study concerns with the tracking control problem for time-varying input–output linearizable systems with output constraints under only measurable output signals. To prevent constraint violation, a high-order control barrier function (HoCBF) is introduced. Furthermore, a continuously differentiable auxiliary reference signal function is constructed to reduce the chattering at the safe boundaries and avoid the constraint violation at the switching time when the constraints become active or inactive. Based on that, blending a time-varying coordinate transformation and the HoCBF conditions, a safety-based dynamic output feedback tracking control method is proposed in an explicit form such that the output is driven to track the reference signal to a small neighborhood and ensured within the constrained region simultaneously. Consequently, it is unnecessary to solve the quadratic program (QP) problem online, which avoids the undesirable infeasibility problem, and facilitates the stability analysis in a closed form by the proposed controller. The effectiveness of the proposed control approach is illustrated by a numerical example.