车辆液压操纵系统动态过程的测试与仿真

建立了某车辆液压系统压力控制阀动力学模型并进行仿真,通过实验验证了所建数学模型和仿 真计算方法的正确性与有效性,研究结果可以为车辆液压系统的设计、改进及预测提供理论依据。

试论钻探机械离合器操纵系的安全性

钻探机械常用的摩擦离合器器离合和操纵系两大机械部分组成,后者用手动机械操纵前者。它们虽有不少优点,但仍有六处安全缺陷:1.无明确的离、合状态显示。2.状态易于失控。3.状态常自行变换。4.操纵系与人体特点失配。5.操纵系统—性差。6.操纵系过分散。当然,缺陷的原因很多,不同型离合器的表现也各异。作者从人——机系统工程角度,讨论了提高钻探机械离合器操纵系本质安全度和工效的途径。

On-Board Data Acquisition System for Automatic Shift System of Vehicle

Data acquisition, analysis and calibrating system affiliated with the vehicle is developed for the research on the automatic shift system (ASS). Considering the vehicle’s hard environment such as vibration, high and low temperature, electromagnetic disturbance and so on, the most suitable project is selected. PC104 transfers data with ECU by serial communication and a solid state disk is used as a FLASH ROM. Some techniques including frequency division of data is adopted in the software design in order to ensure the sampling frequency. The analysis and debug software is also contrived according to the characteristic of the ASS. The system plays an important role in the development of the ASS because of the good reliability and practicability in the application.

Permission and role automatic assigning of user in role-based access control

Role mining and setup affect the usage of role-based access control(RBAC).Traditionally,user's role and permission assigning are manipulated by security administrator of system.However,the cost is expensive and the operating process is complex.A new role analyzing method was proposed by generating mappings and using them to provide recommendation for systems.The relation among sets of permissions,roles and users was explored by generating mappings,and the relation between sets of users and attributes was analyzed by means of the concept lattice model,generating a critical mapping between the attribute and permission sets,and making the meaning of the role natural and operational.Thus,a role is determined by permission set and user's attributes.The generated mappings were used to automatically assign permissions and roles to new users.Experimental results show that the proposed algorithm is effective and efficient.

Disturbance Observer Based Control for Four Wheel Steering Vehicles With Model Reference

This paper presents a disturbance observer based control strategy for four wheel steering systems in order to improve vehicle handling stability. By combination of feedforward control and feedback control, the front and rear wheel steering angles are controlled simultaneously to follow both the desired sideslip angle and the yaw rate of the reference vehicle model.A nonlinear three degree-of-freedom four wheel steering vehicle model containing lateral, yaw and roll motions is built up, which also takes the dynamic effects of crosswind into consideration.The disturbance observer based control method is provided to cope with ignored nonlinear dynamics and to handle exogenous disturbances. Finally, a simulation experiment is carried out,which shows that the proposed four wheel steering vehicle can guarantee handling stability and present strong robustness against external disturbances.

Study on Characteristic of Electric Power Assist Steering System

A pinion-type electric power steering (EPS) equipped on a sedan is reached in this paper. A three-freedom dynamic model of this system is created. The variables affecting assist character is analyzed. The formulas of simpled steering resistance force and the relationship between assist gain and vehicle speed are presented for the first time. Assist character is found based on the parameters of a sedan at last. This assist character is fit for the control rule of the EPS system through analyzing this character. The assist character figure offers reference for system design and control. Furthermore, this research method has generality for assist character of different kinds of vehicles.

Parallel Processing Based on Ship Maneuvering in Identification of Interaction Force Coefficients

The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation genetic algorithm （MPGA） based on real coding that can contemporarily process the data of free running model and simulation of ship maneuvering was applied to solve the problem. Accordingly the optimal individual was obtained using the method of genetic algorithm. The parallel processing of multiopulation solved the prematurity in the identification for single population, meanwhile, the parallel processing of the data of ship maneuvering （turning motion and zigzag motion） is an attempt to solve the coefficient drift problem. In order to validate the method, the interaction force coefficients were verified by the procedure and these coefficients measured were compared with those ones identified. The maximum error is less than 5%, and the identification is an effective method.

Multi-objective optimization of active steering system with force and displacement coupled control

A novel active steering system with force and displacement coupled control(the novel AFS system) was introduced,which has functions of both the active steering and electric power steering.Based on the model of the novel AFS system and the vehicle three-degree of freedom system,the concept and quantitative formulas of the novel AFS system steering performance were proposed.The steering road feel and steering portability were set as the optimizing targets with the steering stability and steering portability as the constraint conditions.According to the features of constrained optimization of multi-variable function,a multi-variable genetic algorithm for the system parameter optimization was designed.The simulation results show that based on parametric optimization of the multi-objective genetic algorithm,the novel AFS system can improve the steering road feel,steering portability and steering stability,thus the optimization method can provide a theoretical basis for the design and optimization of the novel AFS system.

Does investor protection affect the choice of earnings management methods through real activity manipulation and accrual manipulation？ Asian comparison

This paper examines systematic differences in earnings management through real activity manipulation and accrual manipulation across 7 Asia countries. The study proposes arguments that in economies with high investor protection, managers prefer to manage earnings through real activity manipulation rather than through accrual manipulation because accrual manipulation is more likely to draw auditors or regulators scrutiny than real decisions about pricing and production. The study findings are consistent with prediction. Despite being in economies with high investor protection, managers still have bigger discretion in managing earnings through real activities rather than accrual manipulation.

Biosecurity Threats about the Combination of Aerobiology, Morphology and Genetic Manipulation of Fungal Spores

The passive flight of large numbers of mitospores ensures propagation and survival of many fungal species. Moreover, many fungi have a surplus DNA context which allows for easier manipulation and tampering, especially when inserting eukaryotic genes and translation systems. These facts taken together suggest a high prominence of the sporogonic airborne fungi in biosecurity/biodefence priority lists, but due to the low virulence and mortality of the fungal pathogens, they do not figure high, or, sometimes, not at all. The disruptive effect of biosecurity fungal threats is important per se and genetic manipulations are to further it. Novel, long range and high-persistence sampling methods, using robotics and unmanned systems already fielded in other applications may extend surveillance and responsive sampling. Effects-based, proteomic approaches may provide a solution for deliberate incidents, while polyphasic taxonomy may resolve spontaneous incidents and assist medical diagnosis, but in the biosecurity context, where mass collection and processing of samples and speed in producing robust results are vital, complex approaches might be proved more of a hindrance than an asset.

Coordinate control of initiative mating device for autonomous underwater vehicle based on TDES

A novel initiative mating device, which has four 2-degree manipulators around the mating skirt, is proposed to mate between a skirt of AUV （autonomons underwater vehicle） and a disabled submarine. The primary function of the device is to keep exact mating between skirt and disabled submarine in a badly sub sea environment. According to the characteristic of rescue, an automaton model is brought forward to describe the mating proceed between AUV and manipulators. The coordinated control is implemented by the TDES （time discrete event system）. After taking into account the time problem, it is a useful method to control mating by sinmlation testing. The result shows that it reduces about 70 seconds after using intelligent co-ordinate control based on TDES through the whole mating procedure.

Control strategy of a novel electric power steering system integrated with active front steering function

A novel electric power steering system(EPS) integrated with active front steering(AFS) is developed.It has functions of both AFS system and EPS system with two actuator units:the AFS actuator unit and the EPS actuator unit.The AFS actuator unit controls the displacement transfer behavior of the steering system,and improves the handling stability under adverse road conditions by varying the steering ratio directly related to the speed and road conditions.The EPS actuator unit controls the force transfer behavior of the steering system,and improves the steering portability and road feel of the vehicle.Based on a dynamic model,the mixed H2/H∞ control strategy of the EPS actuator and the active steering intervention control strategy of the AFS actuator are designed.The simulation indicates that the novel EPS system with the designed control strategies has obvious advantages in vehicle handling stability and the driver's road feel over the traditional EPS system,and extends the vehicle's steering performance.

Primary studies on integration optimization of differential steering of electric vehicle with motorized wheels based on quality engineering

The model of the differential steering system(DSS) of electric vehicle with motorized wheels and the three-degree-of-freedom dynamic model of vehicle are built.Based on these models,the concepts and quantitative expressions of steering road feel,steering portability and steering stability are proposed.Through integrating the Monte Carlo descriptive sampling,elitist non-dominated sorting genetic algorithm(NSGA-II) and Taguchi robust design method,the system parameters are optimized with steering road feel and steering portability as optimization targets,and steering stability and steering portability as constraints.The simulation results show that the system optimized based on quality engineering can improve the steering road feel,guarantee steering stability and steering portability and thus provide a theoretical basis for the design and optimization of the electric vehicle with motorized wheels system.

Stability control strategy of steer-by-wire system based on LQG/LTR

A control strategy based on LQG/LTR theory for steer-by-wire (SBW) system is proposed in this paper. Firstly, the models of the SBW system and the whole vehicle are constructed. econdly, the control strategy of LQG for SBW system is proposed, in which the LTR is utilized to eliminate the effect from the Kalman filter. Thirdly, simulations based on the co- simulation platform of MATLAB/Simulink and Carsim are performed with the proposed control strategy to identify its performance. At last, field experiments are conducted to further verify the feasibility of the proposed control strategy in real application. The simulation and experiment results indicate that the proposed control strategy has good stability, robustness and feasibility in real application, and is more effective in practical application of SBW system.

Coupling Distant Spins of Surface-State Electrons by Manipulating Their Collective Vibrations

The system of electrons on liquid helium is an interesting candidate to implement quantum computation, due to the long coherence times of the qubits encoded by the electronic spins. In order to implement the quantum logic operations between the spins, we propose here a configuration, similarly to the cooled ions in a trap, to couple the distant electrons via manipulating their center of mass （CM） vibrations. First, we show that the electrons could be confined in a common harmonic oscillator potential by using an electrostatic field. Then, with a single current pulse （applied on the micro-electrode below the liquid helium） the distant electronic spins can be coupled simultaneously to the CM mode. Finally, by adiabatically eliminating the CM mode, effective interaction between the distant spins is induced for implementing the desired quantum computing.

Manipulation of Spontaneous Emission via Quantum Interference in an Elliptically Polarized Laser Field

Manipulation of spontaneous emission from an atom confined in three kinds of modified reservoirs has been investigated by means of an elliptically polarized laser field. Some interesting phenomena such as the multi-peak structure, extreme spectral narrowing, and cancellation of spontaneous emission can be observed by adjusting controllable system parameters. Moreover, these phenomena depend on the constructive or destructive quantum interference between multiple decay channels and which can be changed appreciably by varying the phase difference between the two circularly polarized components of the probe field. These results demonstrate the importance of an elliptially polarized laser field in controlling the spontaneous emission and its potential applications in high-precision spectroscopy.