Robust-Control-Based Design and Comparison of an Adaptive Controller for the VEGA Launcher

Abstract

This article presents the design and evaluation of an adaptive controller for the atmospheric phase VEGA launcher. This design uses an Adaptive Augmenting Control (AAC) architecture to further extend the performance and capabilities of a robust-control structured H∞ controller, which was designed based on the current VEGA control architecture. The main goal of this paper is first, to explore adaptive features for the VEGA control system and second, to evaluate its performance and robustness properties. To that end, the adaptive controller is compared with the structured H∞ baseline controller and a linear parameter varying (LPV) design (both without adaptive augmentation). The three controllers are analysed for several extreme off-nominal condition tests using a high-fidelity, nonlinear simulator of the VEGA launcher. And the main performance indicators for the atmospheric phase are evaluated through a Monte-Carlo campaign. The results show that the adaptive and LPV controllers successfully provide stability under extreme adverse flight conditions over the non-adaptive robust controller. It is also shown that the LPV approach provides a more formal and methodological way to achieve these improvements.

Optimal Tuning of Adaptive Augmenting Controller for Launch Vehicles in Atmospheric Flight

“…The current approach for tuning an The current approach for AAC tuning consists of setting three main elements [2]: 1) upper and lower bounds of the adaptive gain k T equal, respectively, to the low-and high-frequency gain margins (namely, GM aero and GM rigid ) related to the rigid-body dynamics of the nominal system; 2) cutoff frequency of the spectral damper filters, ω HP c and ω LP c ; and 3) gains a AAC , α AAC , and β AAC . The latter two sets of parameters are specified by relying on time-consuming trial-and-error procedures [2,7].…”

“…In Ref. [7], the adaptive augmentation has been applied to a BC for pitch and yaw axes designed using the structured H ∞ control technique. Again, the AAC prevents LOVs and improves BC performance, but the complexity of the adaptive law tuning process in the absence of a specific design methodology and analysis tools is remarked on as a drawback of the approach.…”

“…where K 0.0032, and the other parameters are expressed in terms of the cutoff frequencies ω HP c and ω LP c as[7,8] …”

Genetic Algorithm Based Parameter Tuning for Robust Control of Launch Vehicle in Atmospheric Flight

“…The feasibility of structured H ∞ design methodology for the control of a flexible LV during the ascent phase has been investigated in recent papers [16], [17], which take advantage of the availability of commercial software codes allowing for a streamlined solution of the H ∞ optimization problems in standard form. Nevertheless, in practical scenarios, structured H ∞ control still requires a significant effort and a thoughtful iterative design process, that heavily rely on the designer experience, in order to properly shape the weighting functions so that requirements on stability and robustness performance are met.…”

Improved Adaptive Augmentation Control for a Flexible Launch Vehicle with Elastic Vibration

“…In response to the limitations of the classical approach, in order to increase the robust stability of the launch vehicle attitude-control system, many scholars began to work on advanced control methods, and since 1990, NASA has developed a variety of launch vehicle control techniques in the Advanced Guidance Control program, including trajectory linearization control methods, neural network adaptive control methods, and higher-order sliding-mode control methods; the development of such advanced controls has the potential to improve system performance and increase robustness [8][9][10]. Classical adaptive-control concepts were proposed for attitude-control systems applied to rockets [11][12][13]. However, many adaptive-control concepts are not feasible when applied to high-risk aerospace systems due to the stringent flight environment.…”