H-infinity control for air-breathing hypersonic vehicle based on online simultaneous policy update algorithm

Purpose: The air-breathing hypersonic vehicle (AHV) includes intricate inherent coupling between the propulsion system and the airframe dynamics, which results in an intractable nonlinear system for the controller design. The purpose of this paper is to propose an H∞ control method for AHV based on the online simultaneous policy update algorithm (SPUA). Design/methodology/approach: Initially, the H∞ state feedback control problem of the AHV is converted to the problem of solving the Hamilton-Jacobi-Isaacs (HJI) equation, which is notoriously difficult to solve both numerically and analytically. To overcome this difficulty, the online SPUA is introduced to solve the HJI equation without requiring the accurate knowledge of the internal system dynamics. Subsequently, the online SPUA is implemented on the basis of an actor-critic structure, in which neural network (NN) is employed for approximating the cost function and a least-square method is used to calculate the NN weight parameters. Findings: Simulation study on the AHV demonstrates the effectiveness of the proposed H∞ control method. Originality/value: The paper presents an interesting method for the H∞ state feedback control design problem of the AHV based on online SPUA.