Barrier Function-Based Command Filtering in the Presence of Input Saturation: A Composite Auxiliary Signal Approach

This paper presents an adaptive command filtered control scheme using composite auxiliary signals for a class of uncertain strict-feedback nonlinear systems subject to input saturation. To explicitly constrain the filtered errors, barrier functions are incorporated into the command filtering loop, effectively mitigating their adverse impact on system stability and alleviating the “explosion of complexity" phenomenon inherent in backstepping designs. Furthermore, by constructing a composite auxiliary system, the proposed method achieves a unified compensation mechanism for both bounded filtered errors and input saturation effects. Compared with existing approaches, the proposed strategy simultaneously addresses filtered error and input saturation issues without relying on smooth saturation approximations, thereby avoiding approximation-induced errors and enhancing overall control performance. The effectiveness and practical applicability of the method are validated through numerical simulations and real-time experiments conducted on a Franka Emika Panda robotic arm.