Quantized predefined-time control for heavy-lift launch vehicles under actuator faults and rate gyro malfunctions.

The quantized control problem for a heavy-lift launch vehicle (HLV) under actuator faults and rate gyro malfunctions is addressed in this paper. A predefined-time observer (PTO) is designed to reconstruct the immeasurable time derivative of attitude tracking errors with the settling time precisely predefined by one design parameter. Thus, parameter tuning for temporal demands is more straightforward and less conservative for the PTO than for fixed-time observers. Using the reconstructed state, a quantized controller is developed to render attitude tracking errors to a small neighborhood of the origin within a predefined time interval (physically realizable) under actuator faults. The controller has three characteristics (1) An unswitched singularity-avoidance layer is derived to ensure the boundedness of control signals. (2) A hysteresis quantizer is used to discretize control signals for applications on the digital onboard platform and reduce communication burden. (3) The settling time of attitude tracking errors is predefined by two design parameters under discretized control signals without using performance functions, avoiding the risks of violating performance functions and sudden controller collapse suffered by the existing quantized predefined-time controllers. Furthermore, stability analysis is impelled using a nonsmooth analysis method and a Lyapunov method. Finally, numerical simulations on an HLV demonstrate the efficiency of the proposed control system.