俄罗斯经济步出低谷的政策规迹

据俄罗斯国家统计委员会最新公布的数字表明,俄罗斯经济在多年持续下滑以后开始走出低谷。 1997年的前8个月,俄罗斯工业生产增长速度达到1.4％,国内总产值为1688万亿卢布,保持1996年同期的水平。职工平均月薪为88.5万卢布(约合150美元),比1996年同期增长2％,生活在贫困线以下的人数比去年同期减少9％。

反铲液压挖掘机运动学分析及轨迹规划

这城以某型反铲液压挖掘机为研究对象,用螺旋理论对挖掘机进行了自由度分析,对挖掘机进行了参数建模,并基于螺旋理论、微分及对位置方程直接求导的三种方法对挖掘机进行了速度加速度分析,并给出了求解速度加速度的算例,最后求解了挖掘机的工作空间;挖掘机实际工作过程中,由于土壤环境的复杂性,为保证挖掘机平稳连续的工作,在一定运动学约束范围下提出了一种基于粒子群算法的无障碍最优时间轨迹规划;文章进行了挖掘机的Adams仿真实验,对Matlab中进行的数值轨迹规划进行了仿真,结果证明了Matlab中轨迹规划的正确性。文章为反铲液压挖掘机的设计提供了一种参考,提出的无障碍最优时间多项式插值规迹规划在避障的同时节省了工作时间,使挖掘机能更加高效平稳的工作。

凸曲面平头立铣刀刀位轨迹的自动生成

提出了一种用平头立铣刀代替球面刀数控加工凸曲面的刀位轨迹自动生成新方法。利用该方法在计算机上成功地实现了刀位轨迹的自动生成。

下颌骨的应力迹线与骨小梁构筑的关系

根据下頜光弹的等倾线图,描绘出主应力迹线规迹。在下颌侧位X线照片和去除唇侧及颊侧密质骨板的标本上,观察骨密质和松质的配布,以及骨小梁的排列和方向,试行探讨骨小梁方向与主应力迹线的关系。用光弹法求得的主应力迹线有两个系列:S_1系在下颌体近水平方向,在下颌支近垂直方向分布;S_2系力线与S_1系诸力线呈正交。在标本和X线照片上,主应力迹线规迹不同程度地在骨小梁的排列上有所反映。

一种新的最优地形跟随轨迹算法

考虑地形因素和敌方威胁的潜在影响，研究了在安全保障前提下，飞行时间－地形庶蔽程度综合最优的地形跟随飞行轨迹问题， 提出一种新的最优地形跟随飞行轨迹的算法。首先定义了最小危险曲面， 通过坐标变换将飞行器的运动方程变换到该曲面上； 再运用极小值原理， 求出满足飞行时间－地形遮蔽最优的轨迹的微分方程组； 最后用一维搜索算法， 通过寻求微分方程的初值解出了最优轨迹。仿真结果表明该算法所产生的三维轨迹光滑连续， 不仅能紧密跟踪地形， 而且能自动回避威胁和障碍。

THREE-DIMENSIONAL TRAJECTORY OPTIMIZATION WITH DIRECT METHOD

The principle of direct method used in optimal control problem is introduced. Details of applying this method to flight trajectory generation are presented including calculation of velocity and controls histories. And capabilities of flight and propulsion systems are considered also. Combined with digital terrain map technique, the direct method is applied to the three dimensional trajectory optimization for low altitude penetration, and simplex algorithm is used to solve the parameters in optimization. For the small number of parameters, the trajectory can be optimized in real time on board.

遨游市场敢为先

去年,销售总额突破1.16亿大关,实现利润371万元,跻身于全国农机供应市级公司同行业之首。这就是文登市农机股份有限公司,在去年农机市场大滑坡的不利形势下,谱写的辉煌一页。我们透过这家公司的创业规迹,来探讨一下它称雄市场的奥秘。

Path planning for UAVs formation reconfiguration based on Dubins trajectory

Multiple UAVs are usually deployed to provide robustness through redundancy and to accomplish surveillance,search,attack and rescue missions.Formation reconfiguration was inevitable during the flight when the mission was adjusted or the environment varied.Taking the typical formation reconfiguration from a triangular penetrating formation to a circular tracking formation for example,a path planning method based on Dubins trajectory and particle swarm optimization(PSO)algorithm is presented in this paper.The mathematic model of multiple UAVs formation reconfiguration was built firstly.According to the kinematic model of aerial vehicles,a process of dimensionality reduction was carried out to simplify the model based on Dubins trajectory.The PSO algorithm was adopted to resolve the optimization problem of formation reconfiguration path planning.Finally,the simulation and vehicles flight experiment are executed.Results show that the path planning method based on the Dubins trajectory and the PSO algorithm can generate feasible paths for vehicles on time,to guarantee the rapidity and effectiveness of formation reconfigurations.Furthermore,from the simulation results,the method is universal and could be extended easily to the path planning problem for different kinds of formation reconfigurations.

4D ConflictFree Trajectory Planning for Fixed-Wing UAV

Four-dimensional trajectory based operation(4D-TBO)is believed to enhance the planning and execution of efficient flights,reduce potential conflicts and resolve upcoming tremendous flight demand.Most of the 4D trajectory planning related studies have focused on manned aircraft instead of unmanned aerial vehicles(UAVs).This paper focuses on planning conflict-free 4D trajectories for fixed-wing UAVs before the departure or during the flight planning.A 4D trajectory generation technique based on Tau theory is developed,which can incorporate the time constraints over the waypoint sequence in the flight plan.Then the 4D trajectory is optimized by the particle swarm optimization(PSO)algorithm.Further simulations are performed to demonstrate the effectiveness of the proposed method,which would offer a good chance for integrating UAV into civil airspace in the future.

Multi-robot task allocation for exploration

The problem of allocating a number of exploration tasks to a team of mobile robots in dynamic environments was studied. The team mission is to visit several distributed targets. The path cost of target is proportional to the distance that a robot has to move to visit the target. The team objective is to minimize the average path cost of target over all targets. Finding an optimal allocation is strongly NP-hard. The proposed algorithm can produce a near-optimal solution to it. The allocation can be cast in terms of a multi-round single-item auction by which robots bid on targets. In each auction round, one target is assigned to a robot that produces the lowest path cost of the target. The allocated targets form a forest where each tree corresponds a robot’s exploring targets set. Each robot constructs an exploring path through depth-first search in its target tree. The time complexity of the proposed algorithm is polynomial. Simulation experiments show that the allocating method is valid.

Trajectory planning and tracking control for underactuated unmanned surface vessels

The trajectory planning and tracking control for an underactuated unmanned surface vessel(USV) were addressed.The reference trajectory was generated by a virtual USV,and the error equation of trajectory tracking for underactuated USV was obtained,which transformed the tracking and stabilization problem of underactuated USV into the stabilization problem of the trajectory tracking error equation.A nonlinear state feedback controller was proposed based on backstepping technique and Lyapunov's direct method.By means of Lyapunov analysis,it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property.Numerical simulation results are presented to validate the effectiveness and robustness of the proposed controller.

Cooperative merging control strategy of connected and automated vehicles on highways

To improve traffic performance when on-ramp vehicles merge into the mainstream,a collaborative merging control strategy is proposed to determine the merging sequence and trajectory control of vehicles.Merging trajectory planning takes the minimization of vehicle acceleration as the optimization objective.Either the variational method or the quadratic programming method is utilized to determine arrival time,optimal time and control variables for each vehicle.As a supplement,the adaptive cruise control(ACC)model is used to calculate each control variable in each time interval on special occasions.Simulation results show that the cooperative merging control strategy outperforms the optimal control strategy.The root mean square(RMS)of acceleration and the root mean square error(RMSE)of time headway are significantly decreased,with the reductions up to 90.1%and 25.2%,respectively.Under the cooperative control strategy,the difference between the average speed and desired speed consistently approaches zero.In addition,few or no collisions occur.To conclude,the proposed strategy favours the improvements in passenger comfort,traffic efficiency,traffic stability and safety around highway on-ramps.

Dynamic collision avoidance for cooperative fixed-wing UAV swarm based on normalized artificial potential field optimization

Cooperative path planning is an important area in fixed-wing UAV swarm.However,avoiding multiple timevarying obstacles and avoiding local optimum are two challenges for existing approaches in a dynamic environment.Firstly,a normalized artificial potential field optimization is proposed by reconstructing a novel function with anisotropy in each dimension,which can make the flight speed of a fixed UAV swarm independent of the repulsive/attractive gain coefficient and avoid trapping into local optimization and local oscillation.Then,taking into account minimum velocity and turning angular velocity of fixed-wing UAV swarm,a strategy of decomposing target vector to avoid moving obstacles and pop-up threats is proposed.Finally,several simulations are carried out to illustrate superiority and effectiveness.

4-D Trajectory Prediction and Dynamic Planning of Aircraft Taxiing Considering Time and Fuel

Most of the traditional taxi path planning studies assume that the aircraft is in uniform speed,and the optimization goal is the shortest taxi time.Although it is easy to solve,it does not consider the changes in the speed profile of the aircraft when turning,and the shortest taxi time does not necessarily bring the best taxi fuel consumption.In this paper,the number of turns is considered,and the improved A*algorithm is used to obtain the P static paths with the shortest sum of the straight-line distance and the turning distance of the aircraft as the feasible taxi paths.By balancing taxi time and fuel consumption,a set of Pareto optimal speed profiles are generated for each preselected path to predict the 4-D trajectory of the aircraft.Based on the 4-D trajectory prediction results,the conflict by the occupied time window in the taxiing area is detected.For the conflict aircraft,based on the priority comparison,the waiting or changing path is selected to solve the taxiing conflict.Finally,the conflict free aircraft taxiing path is generated and the area occupation time window on the path is updated.The experimental results show that the total taxi distance and turn time of the aircraft are reduced,and the fuel consumption is reduced.The proposed method has high practical application value and is expected to be applied in real-time air traffic control decision-making in the future.

UAV trajectory planning algorithmfor data collection in wireless sensor networks

In order to maximize the value of information(VoI)of collected data in unmanned aerial vehicle(UAV)-aided wireless sensor networks(WSNs),a UAV trajectory planning algorithm named maximum VoI first and successive convex approximation(MVF-SCA)is proposed.First,the Rician channel model is adopted in the system and sensor nodes(SNs)are divided into key nodes and common nodes.Secondly,the data collection problem is formulated as a mixed integer non-linear program(MINLP)problem.The problem is divided into two sub-problems according to the different types of SNs to seek a sub-optimal solution with a low complexity.Finally,the MVF-SCA algorithm for UAV trajectory planning is proposed,which can not only be used for daily data collection in the target area,but also collect time-sensitive abnormal data in time when the exception occurs.Simulation results show that,compared with the existing classic traveling salesman problem(TSP)algorithm and greedy path planning algorithm,the VoI collected by the proposed algorithm can be improved by about 15%to 30%.

Kinematic Analysis and Trajectory Planning of J-Groove Welding Robot

This paper introduces the complexity and particularity of tube-sphere intersection weld(J-groove weld) and establishes the mathematical model of tube-sphere intersection trajectory.Based on the characteristics of J-groove welds,the computational process of welding gun orientation is first simplified.Then the kinematic algorithm of a welding robot is obtained according to screw theory and exponential product formula.Finally,Solidworks and SimMechanics are employed to simulate the kinematics of the welding robot,which proves the feasibility of the kinematic algorithm.

NSGA Ⅱ based multi-objective homing trajectory planning of parafoil system

Homing trajectory planning is a core task of autonomous homing of parafoil system.This work analyzes and establishes a simplified kinematic mathematical model,and regards the homing trajectory planning problem as a kind of multi-objective optimization problem.Being different from traditional ways of transforming the multi-objective optimization into a single objective optimization by weighting factors,this work applies an improved non-dominated sorting genetic algorithm Ⅱ(NSGA Ⅱ) to solve it directly by means of optimizing multi-objective functions simultaneously.In the improved NSGA Ⅱ,the chaos initialization and a crowding distance based population trimming method were introduced to overcome the prematurity of population,the penalty function was used in handling constraints,and the optimal solution was selected according to the method of fuzzy set theory.Simulation results of three different schemes designed according to various practical engineering requirements show that the improved NSGA Ⅱ can effectively obtain the Pareto optimal solution set under different weighting with outstanding convergence and stability,and provide a new train of thoughts to design homing trajectory of parafoil system.

Optimal Trajectory Planning of the Dual Arm Manipulator Using DAMM

This paper presents an optimal trajectory planning method of the dual arm manipulator using Dual Arm Manipulability Measure （DAMM）. When the manipulator carries an object from a certain position to the destination, various trajectory candidates could be conskied. TO select the optimal trajectacy from the several candidates, energy, time, and the length of the tmjecttay could be utilized. In order to quantify the carrying effidency of dual-arms, DAMM has been defined and applied for the decision of the optimal path. DAMM is defined as the interaction of the manipulability ellipsoids of the dualarras, while the manipulability measure irdicates the relationship between the joint velocity and the Cartesian velocity for each ann. The cast function for achieving the optimal path is defined as the Summation of the distance to the goal and inverse of this DAMM, which aims to generate the efficient motion to the goal. It is confirmed that the optimal path planning keeps higher manipulability through the short distance path by using computer simulation. To show the effectiveness of this cooperative control algorithm experimentally, a 5-DOF dual-ann robot with distributed controllers for synchronization control has been developed and used for the experiments.

High-quality trajectory planning for heterogeneous individuals

Based on trajectory planning with maximum velocity and acceleration constraints, a novel high-quality trajectory planning method was proposed for heterogeneous individuals in crowd simulation. The proposed method ensured that the individual’s path was smooth and its velocity was continuous. Based on the physiological constraints of humans with maximum velocity and acceleration, time-optimal trajectory and feasible region were derived by solving kinodynamic planning problem. Subsequently, a high-quality trajectory planning algorithm was designed to compute the trajectory with appropriate variation of velocity. The simulation results demonstrate that the proposed trajectory planning method has more authenticities and can generate high-quality trajectories for virtual humans in crowd simulation.

Special Wide Area Path Planning Method of an Autonomous Mobile Robot Using GPS

Using sensor and GPS to make a trajectory planning for the stationary obstacle, autonommus mobile robot can asstmae that it is placed at the center of the map, and from the distance information between autonomous mobile robot and obstacles. But in case of active moving obstacle, many components and information need to process since their moving trace should be considered in real time. This paper mobile robot＇s driving algorithm of unknown dynamic envirormaent in order to drive intelligently to destination using ultrasonic and Global Positional Systern （GPS）. Sensors adjusted the placement dependment on driving of robot, and the robot plans the evasion method according to obstacle which are detected by sensors. The robot saves GPS coordinate of complex obstacle. If there are many repeated driving, robot creates new obstacles to the hr, ation by itself. And then it drives to the destination resolving a large range of local minirmnn point If it needs an intelligent circtmtantial decision, a proposed algorithm is suited for effective obstacle avoidance and arrival at the destination by performing simulations.