This paper investigates a simplified model for describing the gravitational fields of non-axisymmetric elongated asteroids. The connection between the simplified model and the target asteroid is built by the positions of the equilibrium points. To improve the performance of position matching the equilibrium points of these non-axisymmetric asteroids, a non-axisymmetric triple-particle-linkage model is proposed based on two existing axisymmetric particle-linkage models. The unknown parameters of the simplified model are determined by minimization of the matching error using the nonlinear optimization method. The proposed simplified model is applied for three realistic elongated asteroids 243 Ida, 433Eros and 1996 HW1. The simulation results validate that the current particle-linkage model has better matching accuracy than the two existing particle-linkage model. The comparison between the simplified model and the polyhedral model on the topological cases of the equilibrium points and the distribution of the gravitational potential further validate the rationality and accuracy of the simplified model.

Hydraulic excavator slewing system is an important component of the excavator and its core-component is the rotary motor. When the rotary hydraulic system starts, stops, and reciprocating works, dynamic characteristic of rotary motor anti-reverse valve has a great influence for working condition of the whole system. Through researching working principle of hydraulic system anti-reverse valve, establish dynamic mathematical model of anti-reverse valve, analyze dynamic response of the model, and get the theoretical foundation of the impact of anti-reverse valve middle chamber throttle opening on hydraulic system. According to the actual working condition of the excavator slewing hydraulic system, establish the system AMESim simulation model, take different parameters of the anti-reverse valve throttle opening, conduct simulation and analysis of the anti-reverse valve characteristics, and validate throttle opening has a great influence on dynamic characteristics of the hydraulic system.

The signals of lithium-ion battery degradation are non-stationary and nonlinear. To adaptively extract the health indicator(HI) that can accurately represent the battery degradation characters and improve the prediction precision of battery remaining useful life (RUL), a stacked auto encoder-variational mode decomposition(SAE-VMD) based HI construction framework is proposed. Firstly, the stacked auto encoder(SAE) is used to reduce the noises of battery parameters and lower the data dimensionality and construct a syncretic HI that contains the battery degradation characters. Then the variational mode decomposition(VMD) is employed for effectively separating the syncretic HI into three modalities: the global attenuation, the local regeneration and the noises. The three modalities are selected as HIs to eliminate the HI noises and improve the RUL prediction precision. The RUL prediction results of lithium-ion battery indicate that the HI extracted by using the present method can obtain a better RUL prediction precision and verify the high quality of the extracted HI.

Based on the existing compilation technology of load spectrum, this paper proposed a new method for the compilation of the general standard test load spectrum of aircraft engine. On the premise of meeting operating requirements of the actual condition and the basic life test, it simplifies the test load conditions and overcomes the shortage of the existing technology. According to the actual flight of aircraft engine, the load spectrum of a flight mission profile was divided into three parts: the take-off phase, the middle-flight phase, and the landing phase. The proposed compilation method ensures that the generated load spectrum of the take-off phase and landing phase is consistent with the actual flight, and the load spectrum of the middle-flight phase is programmed according to a certain method so that a simple load cycle sequence can be implemented. On that basis, the load spectrum was analyzed and compiled by subsection. The general standard test load spectrum lays the foundation for carrying out the life test and reduces the error between the test and practical use. Since the parameters of the engine load are standardized in the process of compiling, the method can be widely used in various types of engines.

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