Control Enhanced and Parameterized Load Relief technology for a Launch Vehicle

Abstract

The major disturbance to the launch vehicle during the high dynamic pressure period is inflight winds, and it causes extra aerodynamic load and significant magnitude of bending moment. Load relief system is used to decrease the aerodynamic load by reducing the angle of attack to increase the launching capability. This paper focuses on the load control technology when the launch vehicle passes through the strong wind area. Firstly, by analyzing and simulating the load relief system of the traditional launch vehicles including long march 3A, atlas/centaur, Saturn V, titan III and Ariane 5, this paper points out the advantages and disadvantages of classical passive trajectory correction method and four active load control methods. Besides, the control enhanced and parameterized technology (CEPT) is putted forward from the active disturbance rejection control (ADRC) and load relief cell. On the one hand, the error signal observed by the modified state observer is introduced to compensate the uncertain error signal observed by extended state observer in the ADRC loop; on the other hand, the load relief cell is introduced into the initial control system to enhance the load relief capability; at last, the control law of the CEPT controller is parameterized, a method is given to select the gains in the control law, and the load restriction effect under the combination of CEPT and initial controller is shown. Taking a kind of liquid launch vehicle as an example, and considering the inherent elastic vibration and liquid sloshing, this paper compares the load relief effect under different control architectures motioned above. The simulation result indicates that the CEPT controller expands the range of the parameters, enhances the disturbance rejection capacity for the flight control system, and efficiently improves the load control effect.