Abstract:The corrosion electric field is an obvious physical field feature of vessels due to its special characteristics of low frequency, obvious line spectrum features and cannot be eliminated. There are apparent distribution characteristics corresponding to different coating damage regions of a vessel, which are adequate for determining the possible damaged coating region. Therefore, a novel method combining Refined Composite Hierarchical Fluctuation Revise Dispersion Entropy (RCHFRDE) and improved Harris Hawk Optimization-kernel based extreme learning machine (IHHO-KELM) was proposed. We proposed RCHFRDE to extract the feature of electric field signatures. The feature vectors were input into the IHHO-KELM classifier to detect the damage region. The numerical and physical scale experiments were conducted to validate the feasibility and reliability of the proposed method. This damaged region was efficiently predicted, achieving satisfactory accuracy of 94.67% and 89.00% in numerical and measurement data respectively, which provided a complement for non-contact detection methods, especially with less prior environment information.

Abstract:Aiming at the problem that the traditional subspace-like direction finding algorithm fails in underdetermined scenarios and requires the number of signal sources as a priori information, a GNSS spoofing source direction finding method based on coprime array is proposed to improve the application security of satellite navigation receivers in spoofing environment. Specifically, we first construct the cyclic correlation matrix to reduce the impact of noise on the performance of the coprime array signal processing, and the virtual domain equivalent array signal is obtained by vectoring the cyclic correlation matrix. On this basis, an optimization problem based on sparse signal reconstruction in virtual domain is designed to achieve high-precision, multi-degree of freedom direction finding for sources by minimizing the fitting error. Finally, the simulation results show that compared with traditional subspace algorithm, the proposed algorithm has higher estimation accuracy, and the direction finding results are still reliable under the case of underdetermined.

Abstract:To solve the problem of lack of early reliability evaluation in complex system design process, a model-based system engineering (MBSE) method is proposed to support the design and reliability evaluation of complex systems. With the characteristics of complex system development, a MBSE modeling method based on "Mission, Operation, Function, Logic, Physic and Reliability" (MOFLP-R) was proposed to support design and reliability assessment of complex system. KARMA, a system modeling language based on "Graph, Object, Property, Point, Relationship and Role" (GOPPRR), was used to express the MOFLP-R process. Then, in order to evaluate the reliability of the complex system, the code generation was used to map the diagram to the numerical model. Finally, the method was applied to a hydraulic system case and the results showed that the proposed method is effective for complex system design and evaluation.

Abstract:Particle transport simulation is one of the main applications of high performance computers. But facing to its fast growing compute requirements, the general-purpose microprocessors cannot adapt to the particle transport program features, owing to the complexity architecture of its single core, and then it is difficult to obtain high ratio of performance and power. Therefore, the program features of the particle transport non-deterministic numerical simulation were extracted and analyzed. Based on the characteristics of the algorithm, the architecture of accelerator core was designed, including pipeline structure, branch prediction unit, multi-level Cache hierarchy and main memory design. A specific accelerator architecture was designed in accordance to the particle transport program features. The simulation results of running the particle transport program on the general architecture simulator show that, as compared with ARM Cortex-A15, the proposed specific accelerator can achieve 4.6 times performance improvement under the same power consumption, and 3.2 times under the same area.

Abstract:The boost-glide missile is a kind of precision guided weapons, which flies in complex and changeable flight conditions with high requirements for the guidance law. The flight state variation model of the missile is established, the improved optimal guidance law with the impact angle constraint is derived by the optimal control method, and the longitudinal guidance coefficients and lateral guidance coefficients are introduced into the guidance law. The influence of single guidance coefficient on guidance precision is analyzed and the selection method of guidance coefficients is determined. The influence of fixed impact angle constraint and dynamic impact angle constraint on guidance precision are analyzed according to the requirements of different flight missions. The numerical simulation and the hardware-in-the-loop simulation are finished with a small solid propellant boost-glide test vehicle. The simulated results show that the improved optimal guidance law is reasonable with high guidance precision.

Abstract:Tandem balloon system provides a solution to the problem of long-duration station-keeping of near-space aerostat, and its contained super-pressure balloon needs to be adapted to specific load and boundary conditions. Based on the natural-shape equations, a numerical method of local shape optimization of the two poles of spherical super-pressure balloons is proposed. Through the smooth connection of the numerical solution generatrix segment and the arc generatrix segment, the complete generatrix of super-pressure balloon with a certain angle at two poles is obtained, which is symmetrical up and down. The stress distributions of the super-pressure balloons before and after the local shape optimization are analyzed by the finite element method, and the effectiveness of the local balloon shape optimization method is verified. On this basis, the key factors affecting the effectiveness of local balloon shape optimization are analyzed, including the arc length of the numerical solution generatrix segment, circumferential stress input condition, local shape, and the radius of the arc generatrix segment, providing an important reference for the selection of key parameters in the local shape optimization of spherical super-pressure balloon.

Abstract:Aiming at the problem of fault diagnosis of sensors and actuators of launch vehicles, a multiple model fault detection and isolation algorithm is proposed. The small deviation attitude dynamics model of the launch vehicle is established, and the Kalman filter of the system is designed; Combined with the idea of special observer, multiple Kalman filter banks with different structures are used to generate corresponding residuals, so that a single residual is only sensitive to a fault of the sensor or actuator. The fault isolation strategy is deduced theoretically to achieve the detection and isolation of different fault types of the launch vehicle. Simulation analysis shows that when no fault occurs, the residual results do not exceed the set threshold, and the algorithm does not alarm; When the sensor or actuator fails, the proposed isolation strategy can accurately locate the fault, which verifies the effectiveness of the algorithm.

Abstract:To improve the disassembly efficiency and reduce disassembly energy consumption, the robotic parallel disassembly mode was introduced in the disassembly sequence planning problem, a robotic parallel disassembly sequence planning model was constructed, and a genetic algorithm based on reinforcement learning was designed. To verify the correctness of the model, a mixed integer linear programming model was constructed. In the algorithm, a goal-oriented encoding and decoding strategy was constructed to improve the quality of the initial solution. Q learning was used to select the best crossover and mutation strategies in the iteration process to enhance the algorithm's adaptability. Finally, in an engine disassembly case with 34 tasks, the superiority of the proposed algorithm was verified by comparing with four classic multi-objective algorithms. The analysis of the disassembly schemes shows that the robotic parallel disassembly mode can effectively shorten the completion time and reduce disassembly energy consumption.

Abstract:The proliferation of “low, slow and small” UAVs (unmanned aerial vehicles) poses a serious threat to flight safety in airspace. Accurate analysis of the characteristics of UAV echo signals is of great significance for the detection of non-cooperative UAVs. Based on the time-domain integral echo model of rotor UAV target and the principle of cepstrum algorithm, the frequency-domain expression and cepstrum expression of echo signal were derived, the corresponding relationship between echo signal parameters and frequency-domain and cepstrum characteristics was analyzed, and a parameter estimation method for UAV echo signal was proposed, and the effectiveness of this method was verified by simulation and measured data. The results show that, it can estimate the bandwidth and rotation frequency of UAV echo signal more accurately and provide an important reference for target detection and recognition of UAV.

Abstract:To solve the inter-chiplet deadlock and network connectivity problems caused by link failures in multi-chiplet network, an optimized packet retransmission mechanism for multi-chiplet network was proposed. By using the "message merging" function in the retransmission mechanism, the number of control packets and the network load was reduced; By using the "message forwarding" function and adopting the forwarding to neighbor strategy, the fault-tolerant cost of the inter-chiplet network link failure was reduced. And more balanced load of the intra-chiplet network was realized. The simulation results show that the proposed method can increase the saturation bandwidth by 12.5% - 25% with similar latency compared with the turn restriction strategy. Furthermore, it can increase the saturation bandwidth by up to 50% in case of link failures. "Message merging" can effectively reduce the number of control packets, thus reduce the overall load of the network. "Packet forwarding" has lower fault-tolerance cost and can ach