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In order to absorb the vibration from the flywheel, a nonlinear energy sink ( NES) is presented in this paper. The NES is composed of a linear spring and the parallel Euler buckled beams. A discrete multi-degree-of-freedom dynamic model, including the flywheel, the NES and the supporting structure is built. The systematic dynamic equations under the transient and steady loadings, respectively, are solved by fourth-order Runge-Kutta method. Based on these calculating results, it is shown that the NES exhibits the efficiency of energy transfer from the linear system, which includes the supporting structure and the flywheel, to the NES. Meanwhile, the targeted energy transfer has been excited. Then, a detailed computational research of the different types of nonlinear energy transitions that occur under the three-level inputting energy is provided. As a result of these studies, the medium-level exciting energy leads to the effective targeted energy transfer from the linear system to the NES. Under this condition, it exhibits that apparent responses of the NES in a wider frequency range. According to the calculating results under the experimental data from the flywheel, it can be concluded that the NES has suppressed the influences from the disturbance of the flywheel effectively. [ABSTRACT FROM AUTHOR]

In order to meet the requirement of inertial navigation system (INS) for low cost and high performance and solve problems of high cost and large volume of the traditional single master INS, low cost MEMS inertial sensors are installed in skew redundant configuration. Based on the Kalman filter, a new optimal data fusion approach based on virtual sensors is proposed, thus the dynamic model of measurement system is simplified, the computational effort is reduced, and the measurement accuracy is improved. The distributed navigation system based on skew redundant sensors is designed by installing multiple skew redundant inertial measurement unit (SRIMU) nodes in different parts of the carrier. With analysis on the sensor network architecture, the measurement fusion of the distribution navigation system is designed by using the equivalent model based on virtual sensors. The simulation results verify that the optimal data fusion based on virtual sensors improves the measurement accuracy and that the distributed navigation system provides the high accuracy navigation information and suppresses the impact of carrier's local stochastic perturbation on navigation performance. [ABSTRACT FROM AUTHOR]

Rocket nozzle is a key structural part of high-thrust liquid rocket engine. There are a hundreds of cooling channels around the nozzle, to ensure the reliable cooling and preheat the fuel. However, it is very difficult to machine the cooling channel due to large size, complex profile, low rigidity, etc. In this article, an integrated digital method for cooling channel machining composed of profile measuring, data processing and channel milling is proposed. Because of large difference between the actual contour and the design model, the channel bottom should be redesigned by using the measured geometric information. Therefore, the varying-thickness and varying-depth cooling channel of nozzle with high order contour or parametric shapes can be machined. Further, a special digital machining system is developed based on an open numerical control platform for the dual-channel vertical milling machine. Finally, an experiment utilizing a typical rocket nozzle is implemented to verify the feasibility of the system. It has been proved that the digital machining system can meet the machining requirements for liquid rocket engine nozzle. [ABSTRACT FROM AUTHOR]

A novel subspace tracking algorithm based on subspace distance is proposed in this paper. The proposed algorithm provides robust orthonormal vector estimation adapting to signal subspace and noise subspace. Simulation results demonstrate that the proposed algorithm is numerically stable, because it does not accumulate roundoff errors. Moreover, the proposed method performs well in subspace tracking and it has a low complexity of 3NL + O(N). [ABSTRACT FROM AUTHOR]