Abstract: Fatigue failure of the mechanical parts has always been paid great attention to in mechanical engineering. In recent years the study on the self-healing composite materials with microcapsules provides a new way to solve it. In this paper, the fracture mechanics analysis on the self-healing composite material with microcapsules used for gear is carried out to determine whether it can achieve the self-healing. The results show that, only when the fracture toughness of the capsule shell and that of matrices matches in some way, can the self-healing be achieved. The composite material made of nylon 6 (PA6) as the matrix material, short E glass fiber as the reinforced material, poly ( urea-form aldehyde) encapsulated dicyclopentadiene (DCPD) as the self-healing microcapsule, is studied in this paper. The results show that this formula is feasible.
Abstract: This study presents the characterization of the nonlinearly viscoelastic behavior of double base propellant (DBP) using Schapery-type constitutive model in the different conditions of temperature, strain level and strain rate. A recursive-iterative numerical algorithm is generated for the Schapery-type nonlinearly viscoelastic constitutive and implemented in a displacement-based ﬁnite element (FE) code for ABAQUS user material subroutines. Then, the model parameters are obtained by analyzing the response of creep-recovery tests and constant rate tensile tests at different temperatures, strain levels and strain rates. And find a linear relationship between temperatures and the effective stresses which determine the limit of linear viscoelactic. The FE model with the calibrated time-dependent and nonlinear material parameters is used to simulate the creep-recovery tests and the constant rate tensile tests, and reasonable predictions are shown.
Abstract: This paper describes an adaptive control method for a magnetic drive actuator that used for the laser cutting to realize high speed and high accuracy machining. Firstly, a zero bias current method and a nonlinear compensator are examined and used for the actuator. Secondly, an adative control method is presented. Finally, the coefficient of the gap-current-force is estimated and the effectiveness of the presented control method is verified by experiments. The experimental results show that the coefficient of the gap-current-force reduces exponentially depending on the increase in the length of the air gap. By using the adaptive control, the peak-to-peak vibration amplitude of the lens holder is reduced from 1.95um to 1.55um.
Abstract: The giant magneto-impedance (GMI) effect of amorphous wire and its affecting factors were analyzed. Magnetic impedance (MI) element was designed with a special structure. So the difficulties of complex negative feedback circuit and winding double circuits on amorphous wire were solved. High frequency current pulse generator, signal preprocessing circuit and digital signal processing module were designed. Thus a low magnetic field detector was realized. The sensor and the detector were tested in laboratory. The experiment results proved that the sensor had good linearity at the magnetic field range from -3 Oe to +3 Oe. The sensitivity reached 65 mv/Oe and the sensor had well temperature stability. The magnetic field resolution can reach 50 μOe and small magnetic target can be detected.
Abstract: In order to research the relationship between coupling distance and transmission efficiency, study on the transmission characteristics of magnetic resonant coupling for wireless power transmission system, simulation model of wireless power transmission system via magnetic resonance coupling were established based on the theory of two ports network analysis method. The frequency expression of maximum efficiency and the resonant frequency splitting phenomenon condition of a contact-less power transmission system were derived. In a weak coupling at resonance, magnetic resonant coupling can transfer energy with high efficiency. The resonant frequency changes from two to one depending on the critical condition. Until a certain distance, maximum efficiencies are not got. The transmission characteristics of this system were researched by simulation software and experiments. The results show that the transmission characteristics are consistent with theoretical analysis and simulation.
Abstract: This paper is dedicated to demonstrate the use of the receiver operating characteristic (ROC) and the area under the ROC curve (AUC) for diagnosing forecast skill. Several local search heuristic algorithms to discover which one performs better for learning a certain Bayesian networks (BN). Five heuristic search algorithms, including K2, Hill Climbing, Repeated Hill Climber, LAGD Hill Climbing, and TAN, were empirically evaluated and compared. This study tests BN models in a real-world case, the Vinho Verde wine taste preferences. An average AUC of 0.746 and 0.727 respectively in red wine and white wine were obtained by TAN algorithm. The results show that the use of TAN can effectively improve the AUC measures for predicting quality grade.
Abstract: In this paper, a design of modularized flexible joint servo controller on-chip for a space manipulator system is presented. First of all, the structure and sensor system of dual-joint is introduced. The structural optimization design of the joint torque sensor is carried out with the help of the ANSYS program for weight minimization. Next, the features of the hardware system for the dual-joint controller are described. All sensor information collection within the joints are obtained with FPGA hardware logic elements using System-on-a-Programmable-Chip technology, and the joint space trajectory planning and position control are realized by Nios II soft-core processor, which is embedded in FPGA. Finally, experimental results demonstrate the effectiveness of the compact joint servo controller for the space manipulator system.
Abstract: Mounting accuracy is of great importance to the performance of the Doppler-based navigation techniques. In this paper, a novel method for alignment calibration of IMU and Doppler sensors is presented. The presented scheme is based on the information from INS/GPS integration and Doppler. Different from previously reported techniques, not only the misalignments but also the scale factor error is considered in this study. By using a Kalman filter, the alignment matrix which is consisted of a misalignment matrix multiplying with a scale factor is estimated. The performance of the alignment estimates is evaluated with field experimental data over Yangzi River. Experimental results shown the estimates obtained by the proposed method perform much better than the existing solution. By using the proposed method, the accuracies of the transformed velocity and positioning are both increased.
Abstract: Underwater environment is highly dynamic,presenting significant disturbances to the vehicle in the form of underwater currents.Additionally,the main difficulties associated with underwater control are the parametric uncertainties. The model-based controller need precise hydrodynamic coeffcients or the model of ROV,but in practice it is very hard or impossible.In order to avoid this problem,a model-free high order sliding mode controller is proposed,and design a reasonable transient process which make the controller have a good performance for any initial error condition.Performance of the proposed controller is verified using numerical simulations,implemented in a four freedom nonlinear underwater vehicle model. Simulation results show that exponential fast convergence of position and attitude,overshooting is very small,for any initial condition.And the controller is proposed needs few parameters to adjust. Algorithm is very easy to complie,could meet the engineering needs.
Abstract: For the reusable launch vehicle(RLV), in the cruise stage without power and the initial load phase, due to the aerodynamic pressure is small, and the aerodynamic surface control efficiency is relatively low, it can not achieve the attitude adjustment of the RLV. This design is based on the continuous system, and applies to the model reference adaptive control law algorithms, to achieve the design of the reaction control system(RCS). According to the control torque which is required by the RLV attitude adjustment, the RCS distribution method of mixed-integer programming is used, and the control parameters of the reaction control system is adjusted in real time,thus to achieve the adjustment of the RLV's attitude. Through the software-digital simulation analysis, this method has a good controllability and robustness.At the same time, the stability of the model reference adaptive RCS is analyzed theoretically, and getting a certain amount of stability region.