基于过失速机动动力学的控制方法

为设计过失速大机动飞行控制律 ,按飞行的逆稳态模型考虑非线性因素的影响 ,同时对于陀螺、惯性耦合效应及重力影响进行补偿 ,并直接根据飞行品质要求按隐式模型跟踪法设计反馈控制器。初步设计实例证明 ,这种方法适应于过失速机动动力学特点 ,能够获得发挥飞机操纵潜能、较好地控制飞机实现过失速机动、具有满意飞行品质的控制解 ,并且控制结构易于工程实现。算例还表明 ,即使不加装先进的过失速操纵装置 ,通过对飞行控制律的改进可以进一步发挥飞机本身的气动潜力 。

环境容量与燃油动力机动车数量关系研究

随着城市建设的发展,经济的繁荣,城市燃油动力机动车数量急剧增加,燃油动力机动车尾气的排放量也迅猛增加,使得城市居民的生活环境恶化。对沈阳市在一定环境质量标准下的环境容量进行了计算,并估算出沈阳市可承载的燃油动力机动车数量,为沈阳市控制燃油动力机动车保有量提供一定的依据。通过研究,建立城市发展、交通发展与环境保护的关系,进一步促进城市的可持续发展。

Development and simulation of electric vehicle based on ADVISOR

Based on the electric vehicle simulator ADVISOR（ advanced vehicle simulator）, the electric vehicle which has a wheel driving system was developed and named ELVEC. The ELVEC consists of wheel, axle, body, motor/controller, energy storage, power bus, etc. The acceleration, grading, driving speed and fuel economy of the ELVEC are analyzed. The results show that the ELVEC has good dynamic performance and fuel economy. It is suitable for the driving conditions of the start-accelerate-stop and the low speed driving conditions in urban areas. At the same time, the motor performance, energy storage （batteries） and energy management of the ELVEC are simulated. It is concluded that the efficiencies of the motor, batteries and driveline are high, and the energy management and the fuzzy logic control strategy are efficient.

Kinematics and dynamics analysis of a 3-7R parallel decoupling mechanism

One kind of movable-pair analysis method is adopted to analyze the configuration of a 3-7R （revolute-pair） parallel decoupling mechanism, and the mechanism＇s characteristics are summarized. The mechanism has three orthogonal distributional branch-chains, and all movable pairs are rotational joints. The movable platform of the mechanism has x, y, z translational decoupling directions. Furthermore, in order to verify the mechanism＇s decoupling characteristics, the mechanism＇s kinematics analysis is solved, and the mechanism＇s direct/inverse kinematics model, input/output velocities and accelerations are deduced, which confirm its decoupling movement characteristics. Finally, one kind of mechanism link decomposed-integrated approach is adopted, and the mechanism＇s dynamics model is completed with the Lagrange method, which also proves its decoupling force characteristics. All of these works provide significant theory for the further study of the mechanism＇s control strategy, design, path planning etc.

DYNAMICS ANALYSIS OF 2-DOF SPHERICAL PARALLEL MECHANISM

The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and reciprocal product of the screw, the equation of the motor moment is obtained. Through the transformation of dynamics model, the configuration space method of the dynamics equation and the corresponding coefficients are presented. Finally, the result of an example shows that the inertia moment and the gravity play a more important role than the coriolis and centrifugal moment, and the former is ten times of the latter in the magnitude. So, the latter can be neglected only when the velocity of mechanism is very slow.

ACTUATOR OF LARGE DISPLACEMENT RAINBOW CERAMICS

A new and unique processing method for fabricating stress biased, monolithic ceramic elements for large dis placement actuators is reported. Reduced and internally bised oxide wafer (RAINBOW) ceramics show excellent properties such as high displacement under applied electric field and enhanced load bearing capabilities. The actuating mechanism, structure and properties of the RAINBOW ceramics are reviewed. Finally, the developing direction is also discussed.

VIBRATION CHARACTERISTIC INVESTIGATION OF COUNTER-ROTATING DUAL-ROTOR IN AERO-ENGINE

Two methods for vibration characteristic investigation of the counter-rotating dual-rotors in an aero-en- gine are put forward. The two methods use DAMP tool on the MSC. NASTRAN platform and develope the re- solving sequence. Vibration characteristics of a turbofan engine are analyzed by using the two methods. Com- pared with results calculated using transfer matrix method and test results, the two methods are valuable and have great potential in practical applications for vibration characteristic investigation of aero-engines with high thrust-weight ratio.

Study on Electromagnetic Force and Vibration of Turbogenerator End Windings under Impact Load(Ⅰ): Analysis of Electromagnetic Force of End Windings under Impact Load

In this paper, the boundary value problem (BVP) of 3 D transient eddy current field in the end region in the case that the generator is affected by impact load is specified. Besides, ways to implement discrete methods in both time domain and space domain during the solution of the problem are investigated. The Crank Nicolson scheme is utilized to attain the iterative format of time differential, after taking factors that can ensure both computation precision and stability into consideration. In this paper, the magnetic distribution in the end region of a turbogenerator in the case that the generator is affected by impact load is specified. As a result, it provides foundation for further study of electromagnetic force and electromagnetic vibration in the end region of the turbogenerator.

Study on Electromagnetic Force and Vibration of Turbogenerator End Windings under Impact Load(Ⅱ): Analysis of Vibration of End Windings under Impact Load

On the basis of the study of transient eddy current field in the end region of turbogenerator and electromagnetic force of end region winding, this paper analyzes the electromagnetic vibration of the turbogenerator roundly. A 320 MW turbogenerator is taken as an example to specify the electromagnetic force of end region winding and therefore the vibration in the case that the generator is affected by impact load. Some conclusions are drawn on the basis of the specification. Vibration of windings under imaginary faults is simulated, so that the vibration law of the end winding of turbogenerator can be studied further. On the basis of this, the countermeasure against winding vibration can be advanced.

Study on conveyor non-linear dynamics and its effect on dynamic behavior

A conveyor linear system assumption is based on an approximate description of belt mechanics behavior and constant elastic moduli. It produces analysis errors and improper dynamics simulation in large conveyors. The belt non-linear characteristics based on sag are described and the belt equivalent elastic moduli expression is deduced. The relationship between belt-equivalent elastic module and elastic module is studied, and their ratio varies from 0.1 to 1.0. The non-linear motion equation with a lumped element model is put forward. Its increment equation and numerical solution are built. A dynamics simulation on a conveyor is carried out, mainly to calculate and compare belt speed, acceleration, tension, displacement of gravity take-up and wave period with linear and non-linear models. It shows that the simulation errors between two models vary from 6% to 50%.

MULTI-BODY AEROELASTIC STABILITY ANALYSIS OF TILTROTOR AIRCRAFT IN HELICOPTER MODE

The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.

Simulated and experimental investigation on discontinuous dynamic recrystallization of a near-α TA15 titanium alloy during isothermal hot compression in βsingle-phase field

A cellular automaton（CA） modeling of discontinuous dynamic recrystallization（DDRX） of a near-α Ti-6Al-2Zr-1Mo-1V（TA15） isothermally compressed in the β single phase field was presented.In the CA model,nucleation of the β-DDRX and the growth of recrystallized grains（re-grains） were considered and visibly simulated by the CA model.The driving force of re-grain growth was provided by dislocation density accumulating around the grain boundaries.To verify the CA model,the predicted flow stress by the CA model was compared with the experimental data.The comparison showed that the average relative errors were10.2%,10.1%and 6%,respectively,at 1.0,0.1 and 0.01 s^-1 of 1020 ℃,and were 10.2%,11.35%and 7.5%,respectively,at 1.0,0.1and 0.01 s^-1 of 1050 ℃.The CA model was further applied to predicting the average growth rate,average re-grain size and recrystallization kinetics.The simulated results showed that the average growth rate increases with the increasing strain rate or temperature,while the re-grain size increases with the decreasing strain rate;the volume fraction of recrystallization decreases with the increasing strain rate or decreasing temperature.

IMPROVEMENT OF AERODYNAMIC PERFORMANCE OF SUPERSONIC AIRCRAFT USING CANARD SURFACE WITH TVFC

The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the maximum lift are estimated for the baseline configuration for different Mach numbers and attack angles in subson- ic and supersonic potential flows, using a low-order three-dimensional panel method supported with the semi-empirical formulas of the data compendium （DATCOM）. Total nose-up and nose-down pitching moments about the center of gravity of the complete aircraft in the subsonic region depending on flight conditions and aircraft performance limitations are estimated. A software package is developed to implement the two-dimensional thrust vectoring flight control technique （pitch vectoring up and down） controlled by the advanced aerodynamic and control surface （the foreplane or the canard）. Results show that the canard with the thrust vectoring produces enough nose-down moment and can support the stabilizer at high maneuvers. The suggested surface can increase the aerodynamic efficiency （lift-to-drag ratio） of the baseline configuration by 5%-6% in subsonic and supersonic flight regimes.

On-line real-time path planning of mobile robots in dynamic uncertain environment

A new path planning method for mobile robots in globally unknown environment with moving obstacles is pre- sented. With an autoregressive (AR) model to predict the future positions of moving obstacles, and the predicted position taken as the next position of moving obstacles, a motion path in dynamic uncertain environment is planned by means of an on-line real-time path planning technique based on polar coordinates in which the desirable direction angle is taken into consideration as an optimization index. The effectiveness, feasibility, high stability, perfect performance of obstacle avoidance, real-time and optimization capability are demonstrated by simulation examples.

Dynamic simulation and optimal control strategy for a parallel hybrid hydraulic excavator

The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then the dynamic system model including batteries, motor and engine is built as the simulation environment to obtain control results. A so-called multi-work-point dynamic control strategy, which has both closed-loop speed PI (proportion integral) control and direct torque control, is proposed and studied in the simulation model. Simulation results indicate that the hybrid system with this strategy can meet the power demand and achieve better system stability and higher fuel efficiency.

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modem four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.

Effect of wind fluctuating on self-starting aerodynamics characteristics of VAWT

The present work deals with an investigation of the self-starting aerodynamic characteristics of VAWT under fluctuating wind. In contrast to the previous studies, the rotational speed of the turbine is not fixed, the rotation of the turbine is determined by the dynamic interaction between the fluctuating wind and turbine. A weak coupling method is developed to simulate the dynamic interaction between the fluctuating wind and passive rotation turbine, and the results show that if the fluctuating wind with appropriate fluctuation amplitude and frequency, the self-starting aerodynamic characteristics of VAWT will be enhanced. It is also found that compared with the fluctuation amplitude, the fluctuation frequency of the variation in wind velocity is shown to have a minor effect on the performance of the turbine. The analysis will provide straightforward physical insight into the self-starting aerodynamic characteristics of VAWT under fluctuating wind.

Dynamic modeling and analysis of 3-■RS parallel manipulator with flexible links

The dynamic modeling and solution of the 3-RRS spatial parallel manipulators with flexible links were investigated. Firstly, a new model of spatial flexible beam element was proposed, and the dynamic equations of elements and branches of the parallel manipulator were derived. Secondly, according to the kinematic coupling relationship between the moving platform and flexible links, the kinematic constraints of the flexible parallel manipulator were proposed. Thirdly, using the kinematic constraint equations and dynamic model of the moving platform, the overall system dynamic equations of the parallel manipulator were obtained by assembling the dynamic equations of branches. FtLrthermore, a few commonly used effective solutions of second-order differential equation system with variable coefficients were discussed. Newmark numerical method was used to solve the dynamic equations of the flexible parallel manipulator. Finally, the dynamic responses of the moving platform and driving torques of the 3-RRS parallel mechanism with flexible links were analyzed through numerical simulation. The results provide important information for analysis of dynamic performance, dynamics optimization design, dynamic simulation and control of the 3-RRS flexible parallel manipulator.

Nonlinear multi body dynamic modeling and vibration analysis of a double drum coal shearer

The double drum coal shearer is widely applied for the underground coal exploration in the mining industry.The vibration and noise control are significant factors for the stability design of the double drum coal shearer.In this paper,the vibration properties of a double drum coal shearer are firstly investigated.The horizontal,transverse and torsional vibrations of the motor body and the angle displacements of the rockers are taken into account.The walking units and the hydraulic units are modeled by the stiffness-damping systems.The nonlinear equation of motion of the double drum coal shearer is established by applying the Lagrange’s equation.The nonlinear vibration response of the system is calculated by using the Runge Kutta numerical method.The effects of the shearing loads,the equivalent damping and stiffness of the walking units,the inclination angels of the rockers and the equivalent damping and stiffness of the hydraulic units on the vibration properties of the system are discussed.

Kinematics and dynamics analysis of a three-degree-of-freedom parallel manipulator

Kinematics and dynamics analyses were performed for a spatial 3-revolute joint-revolute joint-clylindric pair(3-RRC) parallel manipulator.This 3-RRC parallel manipulator is composed of a moving platform,a base platform,and three revolute joint-revolute joint-column pair chains which connect the moving platform and the base platform.Firstly,kinematics analysis for 3-RRC parallel manipulator was conducted.Next,on the basis of Lagrange formula,a simply-structured dynamic model of 3-RRC parallel manipulator was derived.Finally,through a calculation example,the variation of motorial parameters of this 3-RRC parallel manipulator,equivalent moment of inertia,driving force/torque and energy consumption was discussed.The research findings have important significance for research and engineering projects such as analyzing dynamic features,mechanism optimization design and control of 3-RRC parallel manipulator.