Blended control allocation and lateral-directional stability of the reusable launch vehicles

This paper addresses the blended control allocation of the reusable launch vehicles (RLV) during reentry. The continuous aerodynamic control surfaces and the reaction control jets are the two kinds of actuators that provide attitude control moments cooperatively. The blending strategy of the two kinds of actuators is determined using the mixed-integer linear programming method. Due to the strong couplings between roll and yaw, the lateral-directional motion is a two-input quantized system, and its stability in the presence of allocation errors is analyzed based on the quantized control theory. It turns out that couplings among axes are not always bad. By taking advantages of the input couplings, less reaction control jets are required as compared to the case with a single input. Simulations are provided to verify the blended control strategy.