Event-Triggered Adaptive Fixed-Time Tracking Control of Strict-Feedback Systems With Flexible Performance Guarantees

Abstract

This paper is concerned with the fixed-time tracking control problem for strict-feedback systems with unknown nonlinearities, suddenly strong disturbances, and event-triggered input. A novel prescribed performance fixed-time control methodology is proposed to handle this problem. In the control design, a new finite-time performance function is combined with a fixed-time tracking performance function, which not only constrains the operation range of the tracking error but also relaxes the initial condition. Then, the linkage between the prescribed performance function (PPF) and the tracking error is established, thus making the proposed novel scheme better cope with suddenly strong disturbances in order to reduce the risk of the singularity problem of the conventional PPF. In addition, the designed scheme does not require complex error transformations and does not have any requirements for the initial system values, which simplifies the overall design of the scheme. Moreover, owing to the introduction of the event-triggered method, the scheme is more cost-effective in terms of control cost. Finally, the above theoretic findings are illustrated by simulation studies. Note to Practitioners—This paper investigates a flexible fixed-time control scheme with prescribed performance that allows for transient design. The motivation stems from the fact that the vast majority of existing prescribed performance approaches confine the system states or tracking errors within a predefined bound. However, in practical applications such as network transmission congestion control and automotive braking control, the transient behavior of the system often requires further design. Achieving such performance typically requires redesigning the performance function, which is often challenging. Furthermore, in practical applications, sudden external disturbances that inevitably disrupt system operation cannot always be promptly counteracted by actuators due to their delayed response, which may exacerbate singularity issues in prescribed performance schemes. To address these prevalent practical challenges, the proposed scheme in this paper develops a novel flexible fixed-time prescribed performance control strategy. This approach eliminates the need for repeated performance function redesign while effectively accommodating large-magnitude sudden disturbances. Consequently, it achieves comprehensive transient and steady-state performance design, significantly enhancing the method’s adaptability and robustness.