Adaptive PI Control Based Stability Margin Configuration of Aircraft Control Systems with Unknown System Parameters and Time Delay

The stability margin is a vital indicator for assessing the safety level of aircraft control systems.It should maintain sufficient stability margin to ensure safety during flight,especially in the process of large maneuver operations.The stability margin is generally quantified by the Bode diagram,which strictly depends on the system parameters and the open-loop transfer function.However,due to the uncertain flight environments,transmission delays of sensors and mode switchings,etc.,there exist large parameter and structure uncertainties in the aircraft control systems,which make it difficult to precisely configure the stability margin to the desired value by the usual control methods.To address this problem,an indirect adaptive control strategy is proposed in this paper,where an adaptive PI control law with the capability of self-configuration of stability margin is developed.The developed control law not only achieves stable time-varying command tracking in the time domain,but also is able to automatically configure the phase margin and gain margin in the frequency domain.Finally,the simulation of the one-degree-of-freedom roll rate control model of the air vehicle verifies the validity of the proposed control method.

Analytical configuration uncertainty propagation of geocentric interferometric detection constellation

Long-term configuration stability is essential for an interferometric detection constellation(IDC),which is closely related to initial uncertainty.Therefore,it is vital to evaluate the uncertainty and characterize the configuration stability.In this study,an analytical method was developed for the configuration uncertainty propagation of a geocentric triangular IDC.The angular momentum and the argument latitude were found to be significantly affected by the initial uncertainty and were selected as the core variables.By averaging the perturbation in one revolution,an analytical solution was proposed for propagating the core orbital elements in one revolution.Subsequently,the analytical solution of the orbit elements during the mission period is obtained by multiplying the solutions in iterative revolutions.The relationship between the selected orbital elements and the configuration stability parameters was established using an analytical solution.The effects of the initial uncertainty in different directions on the configuration and stable domains were studied.Simulations show that the developed method is highly efficient and accurate in predicting the configuration stability.The relative error with respect to the Monte Carlo simulations was less than 3%with a time consumption of 0.1%.The proposed method can potentially be useful for constellation design and stability analysis.