A Constant Power Reaching Law for Intelligent Attitude Fault-Tolerant Control of Launch Vehicles

Sliding Mode Control (SMC) is a widely used controlling method in the field of current attitude control of launch vehicles. The effectiveness of reaching the Sliding Surface could influence the effect of the attitude control. Aiming to derive better control quality of attitude angles to launch vehicles by investigating the correlation between rise time, maximum overshoot, settling time, respond speed, and motion smoothness, a novel Comprehensive Evaluation Index Function (CEIF) was designed for balancing response speed and motion smoothness. Further, based on this CEIF, both the control characters influenced by the Constant Reaching Law and those characters influenced by the Power Reaching Law were used to propose the Constant Power Reaching Law (CPRL). Then, a fast terminal sliding mode controller was developed. In the simulation, regardless of when the launch vehicle attitude faults occurred, the CEIF with Monotonic Increase in Each Independent Variable could clearly and accurately represent the control quality of launch vehicle attitude. The fast terminal sliding mode controller (FTSM controller) with CPRL could provide better quality of attitude fault-tolerant control compared with a series of FTSM controllers with different currently established reaching laws.