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2 2015

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Simultaneous state and parameter estimation based actuator fault detection and diagnosis for an unmanned helicopter

Wu C., Qi J., Song D., Qi X., Han J.

International Journal of Applied Mathematics and Computer Science

2015

Vol. 25, no. 1

175--187

Simultaneous state and parameter estimation based actuator fault detection and diagnosis (FDD) for single-rotor unmanned helicopters (UHs) is investigated in this paper. A literature review of actuator FDD for UHs is given firstly. Based on actuator healthy coefficients (AHCs), which are introduced to represent actuator faults, a combined dynamic model is established with the augmented state containing both the flight state and AHCs. Then the actuator fault detection and diagnosis problem is transformed into a general nonlinear estimation one: given control inputs and the measured flight state contaminated by measurement noises, estimate both the flight state and AHCs recursively in each time-step, which is also known as the simultaneous state and parameter estimation problem. The estimated AHCs can further be used for fault tolerant control (FTC). Based on the existing widely used nonlinear estimation methods such as the unscented Kalman filter (UKF) and the extended set-membership filter (ESMF), three kinds of adaptive schemes (KF-UKF, MIT-UKF and MIT-ESMF) are proposed by our team to improve the actuator FDD performance. A comprehensive comparative study on these different estimation methods is given in detail to illustrate their advantages and disadvantages when applied to unmanned helicopter actuator FDD.

Foci for Determining the Insensitivity Features of Nanometer RDX: Nanoscale Particle Size and Moderate Thermal Reactivity

Wang Y., Song X., Song D., Zhang J., Song K.

Central European Journal of Energetic Materials

2015

Vol. 12, no. 4

799--815

In this paper, the reasons why nanometer RDX showed lower sensitivity than micro RDX is discussed. Herein we supposed two factors affect the sensitivity of nanometer RDX. Firstly, according detonation physics models, a nanometer particle size results in small hot spots and a high critical temperature. These features suggested high safety for nanometer RDX based on the hot spot theory. A further factor is the thermal reactivity of nanometer RDX, which considerably affects the safety of nanometer energetic materials. Employing the Kinetic Compensation Effect, we calculated the kinetic parameters of micro and nanometer RDX. The results indicated that there was no obvious distinction between the activation energies of micro and nanometer RDX, which implies almost the same reactivity of micro and nanometer RDX. Incorporating the results of small hot spots, high critical temperature, and the unchanged reactivity of micro and nanometer RDX, we concluded that nanometer RDX should exhibit low sensitivity as an intrinsic feature.