Robust parametric approach for tracking control of an air-breathing hypersonic cruise vehicle

To realize the stabilization and the tracking of flight control for an air-breathing hypersonic cruise vehicle, the linearization of the longitudinal model under trimmed cruise condition is processed firstly. Furthermore, the flight control problem is formulated as a robust model tracking control problem. And then, based on the robust parametric approach, eigenstructure assignment and reference model tracking theory, a parametric optimization method for robust controller design is presented. The simulation results show the effectiveness of the proposed approach.

A Cascade Approach for Global Trajectory Tracking Control of Underactuated AUVs

A global trajectory tracking controller is presented for underactuated AUVs with only surge force and yaw moment in the horizontal plane. A transformation is introduced to represent the tracking error system into a cascade form. The global and uniform asymptotic stabilization problem of the resulting cascade system is reduced to the stabilization problem of two subsystems by use of the cascade approach. For the stabilization of the subsystem involving the yaw moment, a control law is proposed based on the feedback linearization method. Another subsystem is stabilized by designing a fuzzy sliding mode controller which can offer a systematical means of constructing a set of shrinking-span and dilating-span membership functions. In order to demonstrate the practicability of the proposed controller, control constraints, parameter uncertainties, and external disturbances are considered according to practical situation of AUVs. Simulation results show very good tracking performance and robustness of the proposed control schemes.

A NEW MODELING AND FILTERING APPROACH FOR TRACKING MANEUVERING TARGETS

A new modeling and filtering approach for tracking maneuvering targets is presented in thispaper.The approach,which makes optimal estimate for the model With the random variable possible,depends on random step modeling of target maneuvers.In the new model,the unknown targetacceleration is treated as a random variable and then estimated directly.A detector is designed tofind out the target maneuvers and the estimation algorithm will be restarted when the maneuvers oc-cur.Combination of three-dimention Kalman filter with a detector forms a tracker for maneuveringtargets.The new tracking scheme is easy to implement and its capability is illustrated in two trackingexamples in which the new approach is compared with Mooses’on the performance.

China's Economy Approaching the World Economic Track

The year 1993 was the fifteenth of China’s reform and opening to the outside. Its economy sustained double digit growth for two years running. Last year, domestic GNP was RMB3,138 billion, a 13.4 percent increase compared with the previous year’s 13.2 percent.

AN EFFECTIVE APPROACH TO SHORT-AND MEDIUM-RANGE PREDICTION OF TRACK AND INTENSITY OF TROPICAL CYCLONES

An objective prediction approach to the 6 h- 144 h track and intensity of tropical cyclones over the northwestern Pacific is proposed. On the basis of both analog deviation technique and completed historical sample curve library, the track or intensity prediction for each forecast period are determined respectively through the optimum weighted superposition of displacement or intensity change of the cases, with different number and weighted coefficient corresponding to minimal analog deviation, from different tropical cyclone or different stage of the same cyclone. so that the prediction results for both forecast period and entire process are optimal. The verification suggests that the approach exhibits better forecast performance than other previous forecast methods by having remarkable decreasing forecast errors in short- and medium-range forecast of both track and intensity,and that the approach can also be used to predict effectively the decay process of tropical cyclone and is able to predict anomalous track and tropical depression.

Parametric approach to track following control of FFSM

A robust task space tracking scheme is proposed for the free-flying space manipulator system. The dynamic equations of the system are derived via the law of momentum conservation, and then a linear state space representation is formulated by local linearization. A parametric approach is applied by using the eigenstructure assignment theory and the model reference method. A feedback stabilizing controller and a feedforward compensation controller are built based on the approach. Then an optimization procedure is followed after that to obtain the desired requirement and characteristics. Simulation results are presented to show the effectiveness of the proposed method.

Robust visual tracking algorithm based on Monte Carlo approach with integrated attributes

To improve the reliability and accuracy of visual tracker,a robust visual tracking algorithm based on multi-cues fusion under Bayesian framework is proposed.The weighed color and texture cues of the object are applied to describe the moving object.An adjustable observation model is incorporated into particle filtering,which utilizes the properties of particle filter for coping with non-linear,non-Gaussian assumption and the ability to predict the position of the moving object in a cluttered environment and two complementary attributes are employed to estimate the matching similarity dynamically in term of the likelihood ratio factors;furthermore tunes the weight values according to the confidence map of the color and texture feature on-line adaptively to reconfigure the optimal observation likelihood model,which ensured attaining the maximum likelihood ratio in the tracking scenario even if in the situations where the object is occluded or illumination,pose and scale are time-variant.The experimental result shows that the algorithm can track a moving object accurately while the reliability of tracking in a challenging case is validated in the experimentation.

基于分数阶滑模控制的无人机轨迹跟踪控制器设计

四旋翼无人机在农业、工业和国防等领域广泛应用,但其复杂的系统特性和对扰动的敏感性使得控制变得困难。首先,考虑分数阶方法具有良好的鲁棒性以及调节灵活性的优点,将整数阶积分滑模面和改进的分数阶指数趋近律相结合,设计出了一种新的分数阶积分滑模控制器。然后,将所设计的分数阶积分滑模控制器应用于四旋翼无人机轨迹跟踪控制问题。仿真结果表明,所提控制器作用下的四旋翼无人机进行轨迹跟踪时响应速度快、无超调,且对外界干扰具有较强的鲁棒性。

基于干扰观测器的四旋翼无人机轨迹跟踪控制

针对四旋翼无人机轨迹跟踪控制过程中易受多源外界干扰影响的问题,为了进一步提升其控制精度和抗干扰性能,该文使用了一种基于指数收敛干扰观测器的双幂次趋近率滑模控制策略。首先,基于牛顿-欧拉方法建立了四旋翼无人机数学模型,并将四旋翼无人机控制系统分为外环位置环和内环姿态环的双回路控制结构;其次,分别在位置子系统和姿态子系统采用了滑模控制方案,并重点针对姿态环设计了基于双幂次趋近率的滑模控制器;最后,设计了一种指数收敛干扰观测器,对四旋翼无人机所受多源外界干扰进行实时观测和补偿。与传统内外环控制结构的PD控制方案相比,仿真实验验证了所提控制策略具有更优的动态响应性能和更高的控制精度,且抗干扰能力得到极大增强。

轮式移动机器人沿相同目标轨迹的编队运动控制

为使轮式移动机器人编队能在某些特殊地形中沿着狭长路线顺利地执行任务,需要通过控制实现所有移动机器人沿着相同的路径运动。为了实现这一编队运动控制任务,本研究采用了领航跟随法的控制策略。首先,将目标路径曲线设计成动态跟踪目标的形式,通过动态跟踪目标中的相对曲率实现领航者对目标曲线精确跟踪。然后,找出领航机器人与跟随机器人的相对角度和目标轨迹曲线之间的关系,采用双闭环控制器设计思路实现领航者和跟随者沿相同轨迹运动。在双闭环控制器中,外环采用直接Lyapunov函数方法构造姿态控制器,内环使用时变障碍Lyapunov函数法构造力矩控制器。最后,基于Matlab进行数值仿真,验证所提控制策略的有效性和鲁棒性。

基于船舶操纵仿真试验的弯曲河段复线船闸引航道方案论证和优化

临淮岗复线船闸上游折线形引航道设置警示分隔墩后,下游引航道回流严重、横向流速局部超标。针对安全航行的问题,开展船舶操纵仿真试验。结果表明:上游引航道宽度、转弯半径可满足船舶安全进出闸的需要;曲进直出的折线形引航道布置方案,上行出闸船舶为航行安全的控制工况,在停泊段双排停靠1000吨级船舶时,安全富余较小;两闸之间的警示分隔墩平面布置长度过长对出闸船舶的航行存在不利影响,其纵向布置范围不应与停泊段重叠;下游引航道不超标部分宽度可满足船舶安全航行需要。

Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.

Optimal tracking control for nonlinear large-scale systems with persistent disturbances

This paper studies the optimal control with zero steady-state error problem for nonlinear large-scale systems affected by external persistent disturbances.The nonlinear large-scale system is transformed into N nonlinear subsystems with interconnect terms.Based on the internal model principle,a disturbance compensator is constructed such that the ith subsystem with external persistent disturbances is transformed into an augmented subsystem without disturbances.According to the sensitivity approach,the optimal tracking control law for the ith nonlinear subsystem can be obtained.The optimal tracking control law for the nonlinear large-scale systems can be obtained.A numerical simulation shows that the method is effective.

Optimal tracking control for linear time-delay large-scale systems with persistent disturbances

An optimal tracking control （OTC） problem for linear time-delay large-scale systems affected by external persistent disturbances is investigated. Based on the internal model principle, a disturbance compensator is constructed. The system with persistent disturbances is transformed into an augmented system without persistent disturbances. The original OTC problem of linear time-delay system is transformed into a sequence of linear two- point boundary value （TPBV） problems by introducing a sensitivity parameter and expanding Maclaurin series around it. By solving an OTC law of the augmented system, the OTC law of the original system is obtained. A numerical simulation is provided to illustrate the effectiveness of the proposed method.

Approximate Optimal Tracking Control for Near-Surface AUVs with Wave Disturbances

This paper considers the optimal trajectory tracking control problem for near-surface autonomous underwater vehicles(AUVs) in the presence of wave disturbances. An approximate optimal tracking control(AOTC) approach is proposed. Firstly, a six-degrees-of-freedom(six-DOF) AUV model with its body-fixed coordinate system is decoupled and simplified and then a nonlinear control model of AUVs in the vertical plane is given. Also, an exosystem model of wave disturbances is constructed based on Hirom approximation formula. Secondly, the time-parameterized desired trajectory which is tracked by the AUV's system is represented by the exosystem. Then, the coupled two-point boundary value(TPBV) problem of optimal tracking control for AUVs is derived from the theory of quadratic optimal control. By using a recently developed successive approximation approach to construct sequences, the coupled TPBV problem is transformed into a problem of solving two decoupled linear differential sequences of state vectors and adjoint vectors. By iteratively solving the two equation sequences, the AOTC law is obtained, which consists of a nonlinear optimal feedback item, an expected output tracking item, a feedforward disturbances rejection item, and a nonlinear compensatory term. Furthermore, a wave disturbances observer model is designed in order to solve the physically realizable problem. Simulation is carried out by using the Remote Environmental Unit(REMUS) AUV model to demonstrate the effectiveness of the proposed algorithm.

A new nonlinear output tracking controller via output-feedback

In this paper, the output tracking control is investigated for a class of nonlinear systems when only output is available for feedback. Based on the multivariable analog of circle criterion, an observer is first introduced. Then, the observer-based output tracking controller is constructively designed by using the integral backstepping approach together with completing square. It is shown that, under relatively mild conditions, all the closed-loop signals are uniformly bounded. Meanwhile the system output asymptotically tracks the desired output. A simulation example is given to illustrate the effectiveness of the theoretical results.

Technical Note on a Track-pattern-based Model for Predicting Seasonal Tropical Cyclone Activity over the Western North Pacific

Recently, the National Typhoon Center （NTC） at the Korea Meteorological Administration launched a track-pattern-based model that predicts the horizontal distribution of tropical cyclone （TC） track density from June to October. This model is the first approach to target seasonal TC track clusters covering the entire western North Pacific （WNP） basin, and may represent a milestone for seasonal TC forecasting, using a simple statistical method that can be applied at weather operation centers. In this note, we describe the procedure of the track-pattern-based model with brief technical background to provide practical information on the use and operation of the model. The model comprises three major steps. First, long-term data of WNP TC tracks reveal seven climatological track clusters. Second, the TC counts for each cluster are predicted using a hybrid statistical-dynamical method, using the seasonal prediction of large-scale environments. Third, the final forecast map of track density is constructed by merging the spatial probabilities of the seven clusters and applying necessary bias corrections. Although the model is developed to issue the seasonal forecast in mid-May, it can be applied to alternative dates and target seasons following the procedure described in this note. Work continues on establishing an automatic system for this model at the NTC.

基于AP-DWA优化的无人机动态避障航迹规划

针对传统动态窗口法在无人机航迹规划中存在无人机绕飞障碍物较远,只针对静态障碍物等问题,提出一种结合人工势场的优化动态窗口法。通过对障碍物坐标进行与时间相关的参数化,以实现动态障碍物的构建。根据人工势场法构造环境势场,并以仿真航迹末段势场值替换传统动态窗口法中的障碍物距离评价指标,避免无人机远距离绕飞障碍物。根据障碍物移动速度计算障碍物动能,将障碍物动能转化为障碍物移动方向上斥力势场,避免无人机与动态障碍物冲突。通过不同环境下的航迹规划实验表明,在静态环境下,所提算法缩短了航迹长度,提高了航迹经济性;在动态环境下,方法可以有效进行动态障碍物的避障,航迹可操作性高。

基于快速非奇异终端滑模的隧道工程车辆轨迹跟踪研究

针对工程车辆轨迹跟踪控制方法中存在的跟踪精度低、响应速度慢、易抖动等问题,提出了一种鲁棒的非奇异快速终端滑模控制方法。首先,建立工程车辆的运动学模型和位姿误差模型。考虑到传统终端滑模存在的奇异性问题,设计了积分型非奇异快速终端滑膜控制器,使系统误差在快速收敛的同时抑制了控制器的抖振。其次考虑到传统趋近律趋近速度慢等问题,基于反步法分别设计了线速度和角速度控制律,并选用fal函数和反双曲正弦函数组合来设计趋近律,提高了系统的稳定性和趋近速度并且削弱了滑模控制的抖振。最后在Matlab软件中和传统的非奇异终端滑模控制器控制效果进行对比实验仿真。实验结果表明,与传统的非奇异终端滑模控制器相比,本文提出的非奇异快速终端滑模控制策略在跟踪精度和不同运动的鲁棒性方面具有明显的优势。

基于改进指数幂趋近律的机械臂轨迹跟踪控制

针对机械臂轨迹跟踪系统在指数趋近律控制下产生的响应不迅速以及控制过程中系统抖颤等问题,给出了一个改进指数幂趋近律。首先通过在传统指数趋近律的恒速率项中导入新型分段函数来改善控制系统的响应,接着再在指数项中引入系统状态变量来抑制系统的抖颤现象。为了降低模型偏差和不确定干扰而对机械臂系统的影响,采用趋近律结合机械臂动力学模型的方式设计滑模控制律,并使用模糊算法进行对模型偏差和不确定干扰的自适应预测和在线补偿。最后,根据李雅普诺夫定理,证明了闭环控制过程的可靠性。仿真结果表明:所提供的控制方式不仅完成了对机械臂轨迹的准确追踪控制,同时提高了控制系统的工作速度,并有效控制了抖颤现象。