摘要：For comprehensive characteristics of flow in a gas bearing,lattice Boltzmann method(LBM)is applied for study of the two-dimensional flow between two eccentric cylinders with the inner one rotating at a high *** flow pattern and circumferential pressure distribution are discussed based on critical issues such as eccentricity ranging from 0.2 to 0.9,clearance ratio varying from 0.005 to 0.01 and rotating speed in the range of 3×104—1.8×105 r/*** analysis and discussion on the circumferential pressure distribution affirmed the quasilinear relation between the extremum pressure and rotating ***,a high eccentricity and small clearance ratio contributes most to the fluctuation of the circumferential pressure *** flow pattern inside the channel exhibits separation vortex under a large *** conclusions drawn in this work give rise to prediction of the flow pattern in the gas bearing which is beneficial for evaluating the performance of as well as instructing the design and development.

摘要：A robust anti-swing control method based on the error transformation function is proposed,and the problem is handled for the unmanned helicopter slung-load system(HSLS)deviating from the equilibrium state due to the disturbances in the lifting ***,the nonlinear model of unmanned HSLS is ***,the errors of swing angles are constructed by using the two ideal swing angle values and the actual swing angle values for the unmanned HSLS under flat flight,and the error transformation functions are investigated to guarantee that the errors of swing angles satisfy the prescribed ***,the nonlinear disturbance observers are introduced to estimate the bounded disturbances,and the robust controllers of the unmanned HSLS,the velocity and the attitude subsystems are designed based on the prescribed performance method,the output of disturbance observer and the sliding mode backstepping strategy,***,the Lyapunov function is developed to prove the stability of the closed-loop ***,the simulation studies are shown to demonstrate the effectiveness of the control strategy.

摘要：Because of their volume and power limitation, it is difficult for CubeSats to configure a traditional propulsion system. Atmospheric drag is one of the space environmental forces that low-orbit satellites can use to realize orbit adjustment. This paper presents an integrated control strategy to achieve the desired in-track formation through the atmospheric drag difference, which will be used on ZJUCubeSat, the next pico-satellite of Zhejiang University and one of the participants of the international QB50 project. The primary mission of the QB50 project is to explore the near-Earth thermosphere and ionosphere at the orbital height of 90-300 km. Atmospheric drag cannot be ignored and has a major impact on both attitude and orbit of the satellite at this low orbital height. We conduct aerodynamics analysis and design a multidimensional nonlinear constraint programming （MNLP） strategy to calculate different desired area-mass ratios and corresponding hold times for orbit adjustment, taking both the semimajor axis and eccentricity into account. In addition, area-mass ratio adjustment is achieved by pitch attitude maneuver without any deployable mechanism or corresponding control. Numerical simulation based on ZJUCubeSat verifies the feasibility and advantage of this design.

摘要：A method of enhancing power system stability for a single machine to infinite bus power system is presented. The technique used compromises the effectiveness of Proportional-Integral-Derivative controller （PID）. In order to satisfy the damping characteristics for the proposed power system over a wide range of operating interval, rotational speed, torque angle and terminal voltage signals of the synchronous machine are utilized as control signals of the system. It is well known that these variables have significant effects on damping the generators shaft mechanical oscillations, it＇ll be so easy to validate the most suitable controller as seen from the simulation results.

摘要：Improving structures involves comparing old and new designs on a key *** the percent change in performance is a method to *** paper proposes a cost-effective analogy by generating replicas of additive manufactured aluminum alloy(Al Si10Mg)body-centered cubic lattice(BCC)based turbine blade(T106C)with the same in poly-lactic acid(PLA)material and their comparison in the context of percent change for natural ***,a cavity is created inside the turbine blade(hollow blade).Natural frequencies are obtained experimentally and numerically by incorporating BCC at 50%and 80%of the cavity length into the hollow blade for both *** cost of manufacturing the metal blades is 90%more than that of the PLA *** two material blade designs show a similar percentage variation,as the first-order mode enhancs more than 5%and the second-order mode more than 4%.To observe the behavior in another material,both blades are analyzed numerically with a nickel-based U-500 material,and the same result is achieved,describing that percent change between designs can be verified using the PLA material.

摘要：Due to the good balance between high efficiency and accuracy, meta-model based optimization algorithm is an important global optimization category and has been widely applied. To better solve the highly nonlinear and computation intensive en- gineering optimization problems, an enhanced hybrid and adaptive meta-model based global optimization （E-HAM） is first proposed in this work. Important region update method （IRU） and different sampling size strategies are proposed in the opti- mization method to enhance the performance. By applying self-moving and scaling strategy, the important region will be up- dated adaptively according to the search results to improve the resulting precision and convergence rate. Rough sampling strategy and intensive sampling strategy are applied at different stages of the optimization to improve the search efficiently and avoid results prematurely gathering in a small design space. The effectiveness of the new optimization algorithm is verified by comparing to six optimization methods with different variables bench mark optimization problems. The E-HAM optimization method is then applied to optimize the design parameters of the practical negative Poisson＇s ratio （NPR） crash box in this work. The results indicate that the proposed E-HAM has high accuracy and efficiency in optimizing the computation intensive prob- lems and can be widely used in engineering industry.

摘要：Focusing on controlling the press-assembly quality of high-precision servo mechanism,an intelligent early warning method based on outlier data detection and linear regression is *** regression is used to deal with the relationship between assembly quality and press-assembly process,then the mathematical model of displacement-force in press-assembly process is established and a qualified press-assembly force range is defined for assembly quality *** preprocess the raw dataset of displacement-force in the press-assembly process,an improved local outlier factor based on area density and P weight(LAOPW)is designed to eliminate the outliers which will result in inaccuracy of the mathematical model.A weighted distance based on information entropy is used to measure distance,and the reachable distance is replaced with P *** show that the detection efficiency of the algorithm is improved by 5.6 ms compared with the traditional local outlier factor(LOF)algorithm,and the detection accuracy is improved by about 2%compared with the local outlier factor based on area density(LAOF)*** application of LAOPW algorithm and the linear regression model shows that it can effectively carry out intelligent early warning of press-assembly quality of high precision servo mechanism.

摘要：This paper is focused on control design for high-precision satellite rendezvous systems.A relative motion model of leader-follower satellites described by relative orbit elements(ROE)is adopted,which has clear geometric meaning and high *** improved repetitive control(IRC)scheme is proposed to achieve high-precision position and velocity tracking,which utilizes the advantage of repetitive control to track the signal precisely and conquers the effects of aperiodic disturbances by adding a nonsingular terminal sliding mode(NSTSM)*** addition,the nonlinear state error feedback(NLSEF)is used to improve the dynamic performance of repetitive controller and the radial basis function(RBF)neural networks are employed to approximate the unknown *** rigorous Lyapunov analysis,the stability of the whole closed-loop control system is ***,numerical simulations are carried out to assess the efficiency and demonstrate the advantages of the proposed control scheme.

摘要：One-dimensional ring power system is discredited to a number of nodes each containing a generator with internal reactance and load branch of resistance and reactance with a certain power factor. When a disturbance occurs at any machine in the power system, simulative analysis is performed to verify how the variation of load power factor affecting the behavior of electromechanical wave propagation by using the MATLAB package, from which different situations are presented and discussed. These results show the type of load has no effect on the behavior of electromechanical wave propagation.

摘要：Self-healing metals possess the capability to autonomously repair structural damage during service. While self-healing concepts remain challenging to be realized in metals and metallic systems due to the small atomic volume of the mobile atoms, the slow diffusion unless at high temperatures and the strong isotropic metallic bonds, the scientific interest has increased sharply and promising progress is obtained. This article provides a comprehensive and updated review on the developments and limitations associated with the various modes of potentially healable damage induced in metals and alloys, i.e., stressinduced damage, irradiation-induced damage in bulk materials and contact damage in corrosion protective coatings. The spontaneous intrinsic healing mechanisms not requiring external assistance other than the material operating at the right temperature and an assisted healing mechanism with external intervention are reviewed. Promising strategies to achieve self-healing in metals are identified. Finally, we give some prospects for future research directions in self-healing metals.