Improved LQG Method for Active Gust Load Alleviation

Against a background of various techniques for gust load alleviation (GLA), this paper aims at proposing an improved linear quadratic Gaussian (LQG) method, which is robust to variations of flight parameters, structural parameters, and modeling errors and suitable for application in structure/control design optimization. This new technique differs from the traditional LQG methodology by the introduction of properly constructed fictitious high-frequency noise. Furthermore, to accurately measure the stability margins of the multi-input multi-output (MIMO) controllers, a variable-structure μ analysis method is proposed. The parameters of the Dryden continuous gust model are adjusted according to the structural natural frequencies to meet the design requirements, and model reduction combined with input signal scaling is applied to reduce the controller order. Using a general transport aircraft (GTA) model, the robust performance and robust stability of the improved LQG method are compared with those of modern robust controllers, including the H∞ controller and the μ-synthesis controller. The numerical results demonstrate the successful application of this new technique.