Search

The characteristics and shortcomings of the current multi-port direct current (DC) to DC (DC/DC) energy router were analyzed.A multi-port DC/DC energy router for the energy Internet was optimized and designed.Through the analysis of the operating voltage requirements under different working conditions,the full-bridge proportional design of the sub-module was proposed.On this basis,an alternating current (AC) to DC (AC/DC) decoupling control strategy to realize riding through the DC fault without de-blocking any devices was proposed.The multi-port DC/DC energy router was used to realize the interconnection of multiple DC power grids with different voltage levels.It not only retained the advantages of low cost and low loss of the traditional DC autotransformer,but also effectively improved the shortcomings that the DC autotransformer cannot ride through the DC fault.Finally,the simulation test was carried out in the MATLAB/Simulink environment to verify the stability of the technology in the normal operation,the feasibility of suppressing the DC fault and the effectiveness of the control strategy.

To meet the requirements of deployable structures in aerospace engineering with light weight and high stiffness, this paper proposes the triangular space membrane deployable mechanism based on deployable booms, then conducts dynamic analysis and multiobjective optimization. The configuration design and mass calculation for the membrane mechanism are carried out, including its unfolding support mechanism and tensioned membrane scheme. With a view to performing the dynamic characteristics analysis and parametric studies, the finite element simulation model of the membrane mechanism, including boom, cable and membrane, is built and validated against test results obtained by Polytec. On the basis of the simulation results, a surrogate model of fundamental frequency is established by adopting the response surface method and applied to multiobjective optimization combined with the mass formula. Then, the optimal dynamic and lightweight design parameters are solved via the genetic algorithm. The results provide an indication to aid with the design and analysis of space membrane deployable mechanisms according to the required properties and space mission requirements.

In this paper, we propose an effective human and nonhuman pyroelectric infrared (PIR) signal recognition method to reduce PIR detector false alarms. First, using the mathematical model of the PIR detector, we analyze the physical characteristics of the human and nonhuman PIR signals; second, based on the analysis results, we propose an empirical mode decomposition (EMD)-based symbolic dynamic analysis method for the recognition of human and nonhuman PIR signals. In the proposed method, first, we extract the detailed features of a PIR signal into five symbol sequences using an EMD-based symbolization method, then, we generate five feature descriptors for each PIR signal through constructing five probabilistic finite state automata with the symbol sequences. Finally, we use a weighted voting classification strategy to classify the PIR signals with their feature descriptors. Comparative experiments show that the proposed method can effectively classify the human and nonhuman PIR signals and reduce PIR detector’s false alarms.