Integrated guidance and control for reusable launch vehicles with actuator failures

Onboard trajectory reshaping, integrated guidance & control play essential roles for next generation reusable launch vehicles (RLVs), especially in an anomalous event such as actuators failure. This paper proposed a three-block feedback architecture for vehicle of high lift-to-drag ratio. The inner (control) loop employs an adaptive PID method with inverse dynamic approach for control allocation. The adaptive PID module generates gains automatically and calculates pitch, yaw and roll axis bandwidth, which is used by outer (guide) loop for adapting the control actuator failures. An linear quadratic regular (LQR) tracking law is utilized in the outer loop, studies indicates that the gains are insensitive to changes in the reference trajectory, thus the gains pre-computed off line still can give a satisfactory tracking performance while trajectory is changed. When one or more actuators can not work normally, control reconfiguration and guidance adaptation together may fails to recover the flight mission. In these cases, the on line trajectory reshaping moves in. A method which is based on Newton iterative can replan a trajectory in 5 seconds and ensures that the vehicle has sufficient robustness for perturbations and actuator failures. The results indicate that trajectory reshaping in company with control reconfiguration and guidance adaptation can recover most of the missions when severe actuator failure occurs.