Design of flight control laws for a civil aircraft using mu-synthesis

Flying in formation improves aerodynamic efficiency and, consequently, leads to an energy savings. One strategy for formation control is to follow the preceding vehicle. Many researchers have shown through simulation results and analysis of specific control laws that this strategy leads to amplification of disturbances as they propagate through the formation. This effect is known as string instability. In this paper, we show that string instability is due to a fundamental constraint on coupled feedback loops. The tradeoffs imposed by this constraint imply that predecessor following is an inherently poor strategy for formation flight control. Finally, we present two examples that demonstrate the theoretical results.

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Automatic Flight Control of Unmanned Helicopter Based on Nonlinear Model

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.1492 ◽

2012 ◽

Vol 472-475 ◽

pp. 1492-1499

Author(s):

Run Xia Guo

Keyword(s):

Nonlinear Model ◽

Flight Control ◽

Attitude Control ◽

Lyapunov Stability Theory ◽

Test Results ◽

Unmanned Helicopter ◽

Control Laws ◽

Control Approach ◽

State Dependent ◽

Compensation Technique

The Unmanned helicopter (UMH) movement was divided into two parts, namely, attitude and trajectory motion. And then a two-timescale nonlinear model was established. The paper improved and expanded state dependent riccati equation (SDRE) control approach, deriving analytical conditions for achieving global asymptotic stability with lyapunov stability theory. Proof was given. By combining improved SDRE control with nonlinear feed-forward compensation technique, the full envelop flight attitude control laws could be designed. On the basis of attitude control, trajectory controller was developed. Actual flight tests were carried out. Test results show that the control strategy is highly effective.

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Enhanced Disturbance-Observer-Based Control for a Class of Time-Delay System with Uncertain Sinusoidal Disturbances

Mathematical Problems in Engineering ◽

10.1155/2013/805687 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Xinyu Wen

Keyword(s):

Time Delay ◽

Flight Control ◽

Disturbance Observer ◽

Delay System ◽

Delay Systems ◽

Flight Control System ◽

Control Laws ◽

Nonlinear Disturbance Observer ◽

Dynamic Performances ◽

Uncertain Disturbance

This paper is concerned with disturbance-observer-based control (DOBC) for a class of time-delay systems with uncertain sinusoidal disturbances. The disturbances are decomposed as precise and uncertain parts using nonlinear disturbance observer (DO) after appropriate coordinate transformation. And then the two parts can be compensated by corresponding controller, respectively, such that the classic DOBC method is extended to uncertain disturbance rejection. One novel feature of the proposed method is that even if the precise disturbance parameters are inaccessible, the merits of DOBC can be inherited. By integrating the disturbance observers with feedback control laws with time delay, the disturbances can be rejected and the desired dynamic performances can be guaranteed. Finally, simulations for a flight control system are given to demonstrate the effectiveness of the results.

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