Path-Following Based on Nonlinear Model Predictive Control with Adaptive Path Preview

This paper presents a Nonlinear Model Predictive Controller(NMPC)for the path following of autonomous vehicles and an algorithm to adaptively adjust the preview distance.The prediction model includes vehicle dynamics,path following dynamics,and system input dynamics.The single-track vehicle model considers the vehicle’s coupled lateral and longitudinal dynamics,as well as nonlinear tire forces.The tracking error dynamics are derived based on the curvilinear coordinates.The cost function is designed to minimize path tracking errors and control effort while considering constraints such as actuator bounds and tire grip limits.An algorithm that utilizes the optimal preview distance vector to query the corresponding reference curvature and reference speed.The length of the preview path is adaptively adjusted based on the vehicle speed,heading error,and path curvature.We validate the controller performance in a simulation environment with the autonomous racing scenario.The simulation results show that the vehicle accurately follows the highly dynamic path with small tracking errors.The maximum preview distance can be prior estimated and guidance the selection of the prediction horizon for NMPC.

Study on robust terrain following control

Based on classical terrain following (TF) algorithm (adaptive angle method), a new method for TF controller is proposed by using angle of attack. A method of obtaining terrain outline data from Digital Elevation Map (DEM) for TF control is discussed in order to save store space. The block control model, which is suitable for backstepping design, is given for nonlinear model of aircraft. Making full use of the characteristics of the system and combining block control principle, backstepping technique, a robust controller design method is proposed. Uncertainties in every sub-block are allowed, and can be canceled by using the idea of nonlinear damping. It is proved that the state tracking errors converge to the neighborhood of the origin exponentially. Finally, nonlinear six-degree-of-freedom simulation results for the aircraft model are presented to demonstrate the effectiveness of the proposed control law.

Rapid Optimal Generation Algorithm for Terrain Following Trajectory Based on Optimal Control

Based on the optimal control theory, a 3-dimensionnal direct generation algorithm is proposed for anti-ground low altitude penetration tasks under complex terrain. By optimizing the terrain following(TF) objective function,terrain coordinate system, missile dynamic model and control vector, the TF issue is turning into the improved optimal control problem whose mathmatical model is simple and need not solve the second order terrain derivative. Simulation results prove that this method is reasonable and feasible. The TF precision is in the scope from 0.3 m to 3.0 m,and the planning time is less than 30 min. This method have the strongpionts such as rapidness, precision and has great application value.

Virtual Simulation System with Path-following Control for Lunar Rovers Moving on Rough Terrain

Virtual simulation technology is of great importance for the teleoperation of lunar rovers during the exploration phase, as well as the design of locomotion systems, performance evaluation, and control strategy verification during the R&D phase. The currently used simulation methods for lunar rovers have several disadvantages such as poor fidelity for wheel-soil interaction mechanics, difficulty in simulating rough terrains, and high complexity making it difficult to realize mobility control in simulation systems. This paper presents an approach for the construction of a virtual simulation system that integrates the features of 3D modeling, wheel-soil interaction mechanics, dynamics analysis, mobility control, and visualization for lunar rovers. Wheel-soil interaction experiments are carried out to test the forces and moments acted on a lunar rover’s wheel by the soil with a vertical load of 80 N and slip ratios of 0, 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.6. The experimental results are referenced in order to set the parameters’ values for the PAC2002 tire model of the ADAMS/Tire module. In addition, the rough lunar terrain is simulated with 3DS Max software after analyzing its characteristics, and a data-transfer program is developed with Matlab to simulate the 3D reappearance of a lunar environment in ADAMS. The 3D model of a lunar rover is developed by using Pro/E software and is then imported into ADAMS. Finally, a virtual simulation system for lunar rovers is developed. A path-following control strategy based on slip compensation for a six-wheeled lunar rover prototype is researched. The controller is implemented by using Matlab/Simulink to carry out joint simulations with ADAMS. The designed virtual lunar rover could follow the planned path on a rough terrain. This paper can also provide a reference scheme for virtual simulation and performance analysis of rovers moving on rough lunar terrains.

PREDICTIVE CONTROL FOR OPTIMAL PATH TERRAIN FOLLOWING SYSTEM

In this paper output predictive algorithm is applied to the design of predictive controller for an optimal path terrain following system. In this way, the error of path tracking is decreased to a minimum degree simply and efficiently and the computation time for the optimal path is shortened greatly. Therefore, the real-time processing of the optimal path terrain following system is made to be very helpful.

NONLINEAR PREDICTIVE CONTROL FOR TERRAIN FOLLOWING

ＮＯＮＬＩＮＥＡＲＰＲＥＤＩＣＴＩＶＥＣＯＮＴＲＯＬＦＯＲＴＥＲＲＡＩＮＦＯＬＬＯＷＩＮＧＣｕｉＨｕｔａｏ（崔祜涛），ＧｅｎｇＹｕｎｈａｉ（耿云海），ＹａｎｇＤｉ（杨涤）（ＨａｒｂｉｎＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇｙ，Ｐ．Ｏ．Ｂｏｘ１３７，...

Design of Wiener-Hopf optimal controller and its application in terrain following system

state space algorithms are proposed for the three degree of freedom (3DOF) optimal Wiener Hopf controller for a class of systems with time delay feedback sensors and employed in the design of a terrain following control system, with the influence caused by the delay of baric altimeter successfully eliminated.

An Application of Optimal Preview Control in Terrain Following System

An optimal preview method is applied to the design of terrain following controller for cruise missile. In this method, tracking errors and control increments are both considered in the quadratic cost function. Integrating the general optimal servo system with a preview feedforward compensation that feeds forward future command and future disturbance produces an optimal preview servo system. In the terrain following system, the flight altitude of the cruise missile is a command signal, and its future information can be known apriori. Hence, we have designed a terrain following controller with a basic state feedback and a feedforward compensation for future altitude information. Simulation results show that the performance of the terrain following system with such an optimal preview controller has been improved dramatically.

Coordinates over Complex Terrain in Atmospheric Model

In the terrain following coordinate,Gal-Chen and Somerville[1]and other proposed a vertical coordinate z∝(z−z_(bottom))/(ztop−z_(bottom))and constant spatial intervals ofδx andδy along the other directions.Because the variation ofδx andδy was ignored,their coordinate does not really follow the terrain.It fails to reproduce the divergence and curl over a complex terrain.Aligning the coordinate with real terrain,the divergence and curl we obtained from the curvilinear coordinate are consistent with the Cartesian coordinate.With a modification,the simulated total mass,energy,and momentum from the Navier-Stokes equations are conserved and in agreement with those calculated from Cartesian coordinate.

Coordination of Multi-leaders and Multi-followers in Supply Chain of Value-Added Telecom Services

In order to study supply chain of the telecom value-added service,a multi-leaders and multi-followers Stackelberg game model with multiple telecom operators and multiple service providers whose income is composed of information fee division and advertisement was constructed.Then a demonstration was simulated,and the results were compared with the situation of service providers' income only from information fee division.The simulated and compared results indicate that,the enterprises in the supply chain have the nature of pursuing the maximum profits in capital markets;meanwhile,first-mover advantages and some enterprise can get more profits with the information asymmetry.

Trade credit financing for supply chain coordination under financial challenges:a multi‑leader–follower game approach

This study is designed to solve supply chain inefficiencies caused by some members’financial problems,such as capital shortages and financing restrictions in a stochastic environment.To this end,we have established a supply chain finance framework by designing two novel coordinating contracts based on trade credit financing for different problem settings.These contracts are modeled in the form of multi-leader Stackelberg games that address horizontal and vertical competition in a supply chain consisting of multiple suppliers and a financially constrained manufacturer.However,previous studies in the trade credit literature have addressed only simple vertical competition,that is,seller-buyer competition.To solve the proposed models,two algorithms were developed by combining population-based metaheuristics,the Nash-domination concept,and the Nikaido-Isoda function.The results demonstrate that the proposed supply chain finance framework can eliminate supply chain inefficiencies and make a large profit for suppliers,as well as the financially constrained manufacturer.Furthermore,the results of the contracts’analysis showed that if the manufacturer is required to settle its payments to suppliers before the end of the period,the trade credit contract cannot coordinate the supply chain because of a lack of incentive for suppliers.However,if the manufacturer is allowed to extend its payments to the end of the period,the proposed trade credit financing contract can coordinate the supply chain.Finally,the sensitivity analysis results indicate that the worse the financial status of the manufacturer,the more bargaining power suppliers have in determining the contract parameters for more profit.

基于GIM技术的输变电工程三维基础设计场景构建

为提升输变电工程三维基础设计场景构建效率,提出基于GIM技术的输变电工程三维基础设计场景构建。通过无人机扫描目标区域的环境信息,运用Grid建模方法生成三维地形图。以电网信息模型技术为核心,设计三维参数化建模方法,通过调整参数值,快速编辑输变电工程本体结构。经过坐标系转换,将输变电本体结构放置于三维地形场景内,合成输变电工程三维基础设计场景。再通过LOD细节模型,实现可视化三维场景的高效渲染。实验结果显示:应用所提方法构建三维场景模型耗费时间为21.5 min,较其他方法构建耗时最高降低了70.22%,效率得到了很大程度的提高,具有较为优越的应用性能。

Effects of Terrain-Following Vertical Coordinates on High-Resolution NWP Simulations

With increasing resolution in numerical weather prediction （NWP） models, the model topography can be described with finer resolution and includes steeper slopes. Consequently, negative effects of the traditional terrain-following vertical coordinate on high-resolution numerical simulations become more distinct due to larger errors in the pressure gradient force （PGF） calculation and associated distortions of the gravity wave along the coordinate surface. A series of numerical experiments have been conducted in this study, including idealized test cases of gravity wave simulation over a complex mountain, error analysis of the PGF estimation over a real topography, and a suite of real-data test cases. The GRAPES-Meso model is utilized with four different coordinates, i.e., the traditional terrain-following vertical coordinate proposed by Gal-Chen and Somerville （hereinafter referred to as the Gal.C.S coordinate）, the one-scale smoothed level （SLEVE1）, the two-scale smoothed level （SLEVE2）, and the COSINE （COS） coordinates. The results of the gravity wave simulation indicate that the GRAPES-Meso model generally can reproduce the mountain-induced gravity waves, which are consistent with the analytic solution. However, the shapes, vertical structures, and intensities Of the waves are better simulated with the SLEVE2 coordinate than with the other three coordinates. The model with the COS coordinate also performs well, except at lower levels where it is not as effective as the SLEVE2 coordinate in suppressing the PGF errors. In contrast, the gravity waves simulated in both the Gal.C.S and SLEVE1 coordinates are relatively distorted. The estimated PGF errors in a rest atmosphere over the real complex topography are much smaller （even disappear at the middle and upper levels） in the GRAPES-Meso model using the SLEVE2 and COS coordinates than those using the Gal.C.S and SLEVE1 coordinates. The results of the real-data test cases conducted over a one-month period suggest that the three modified vertical coordinates （SLEVE1, SLEVE2, and COS coordinates） give better results than the traditional Gal.C.S coordinate in terms of forecasting bias and root mean square error, and forecasting anomaly correlation coefficients. In conclusion, the SLEVE2 coordinate is proved to be the best option for the GRAPES-Meso model.

含跟网/构网型混联多馈入系统协调优化配置方法

随着传统同步机组被电力电子设备逐步取代,电力系统由原来的“物理同步”逐渐转变为“控制同步”。因此,由变流器控制环节引发的稳定问题受到广泛关注。已有研究表明,含跟网/构网型设备的混联多馈入系统中构网型设备能够抑制弱电网下由跟网型设备并网引起的次同步振荡,然而其在强电网下容易导致系统出现低频振荡现象。而目前电力系统仍处于向“双高”系统转变的过渡阶段,关于不同电网强度下混联多馈入系统中跟网/构网型变流器对电网电压支撑能力的量化评估及其在多频段下的协调优化配置方法仍不清晰。为此,该文首先对单馈入跟网/构网型变流器并网系统进行模态分析,探究不同电网强度下跟网/构网型变流器对应的主导振荡模态在多频段下的分布特性,并形成混联多馈入系统的协调优化配置原则。其次,基于模态解耦的思想对混联多馈入系统的稳定性进行等效近似,揭示多频段下系统主导振荡模态阻尼比与跟网/构网型支撑能力量化指标之间的关系。由此,提出一种面向系统小干扰稳定性提升的跟网/构网型协调优化配置方法。最后,通过仿真算例验证所提混联多馈入系统等效近似方法的正确性和协调优化配置方法的有效性。

基于Leader-Follower策略的双联AGV协同运载控制方法

针对面向大部件协同运载的双联AGV系统,融合单台全向移动AGV的路径跟踪运动学模型与Leader-Follower策略下的队形保持方法建立了一种双联AGV的协同偏差模型。基于该模型,采用Lyapunov反演法,提出一种双联AGV协同运载的运动学控制模型。最后通过软件仿真和系统实验验证了该控制模型的运行稳定性、精确性和协调性。

Optimized Vertical Layers for the Hybrid Terrain-Following Coordinate Minimizing Numerical Errors in a 2D Rising Bubble Experiment near Steep Terrain

The basic terrain-following(BTF)coordinate simplifies the lower boundary conditions of a numerical model but leads to numerical error and instability on steep terrain.Hybrid terrain-following(HTF)coordinates with smooth slopes of vertical layers(slopeVL)generally overcome this difficulty.Therefore,the HTF coordinate becomes very desirable for atmospheric and oceanic numerical models.However,improper vertical layering in HTF coordinates may also increase the incidence of error.Except for the slopeVL of an HTF coordinate,this study further optimizes the HTF coordinate focusing on the thickness of vertical layers(thickVL).Four HTF coordinates(HTF1–HTF4)with similar slopeVL but different vertical transition methods of thickVL are designed,and the relationship between thickVL and numerical errors in each coordinate is compared in the classic idealized thermal convection[two-dimensional(2D)rising bubble]experiment over steep terrain.The errors of potential temperatureθand vertical velocity w are reduced most,by approximately 70%and 40%,respectively,in the HTF1 coordinate,with a monotonic increase in thickVL according to the increasing height;however,the errors ofθincreased in all the other HTF coordinates,with nonmonotonic thickVLs.Furthermore,analyses of the errors of vertical pressure gradient force(VPGF)show that due to the interpolation errors of thickVL,the inflection points in the vertical transition of thickVL induce the initial VPGF errors;therefore,the HTF1 coordinate with a monotonic increase in thickVL has the smallest errors among all the coordinates.More importantly,the temporal evolution of VPGF errors manifests top-type VPGF errors that propagate upward gradually during the time integration.Only the HTF1 and HTF4 coordinates with a monotonic increase in thickVL near the top of the terrain can suppress this propagation.This optimized HTF coordinate(i.e.,HTF1)can be a reference for designing a vertical thickVL in a numerical model.

地形跟随飞行能量协调在线轨迹规划与跟踪

针对定速地形跟随飞行全局离线规划方案数据存储量大、机动飞行油耗大等问题,提出基于级联模型预测控制(cascaded model predictive control,CMPC)的能量协调在线轨迹规划与跟踪方案。首先,利用飞行器纵向质点运动学模型设计模型预测控制(model predictive control,MPC)在线轨迹规划器。从能量分配原理出发确定速度变化规律,对于飞行时总能量不变而导致能量分配不合理的情况,引入虚拟控制量实现总能量动态调节,完成能量协调策略设计。其次,引入地形粗糙度概念描述地形起伏程度,基于此提出规划器自适应时域方案,对于不同地形实现预测时域动态调节。结合MPC轨迹跟踪控制器,并利用真实地形数据进行仿真实验。实验结果表明,所提方案可在与全局离线规划方案航迹差异不大的前提下,实现在线轨迹规划,显著降低油耗,提高航程极限,完成复杂地形的机动飞行任务。

数值预报模式垂直坐标发展与改进综述

大气具有斜压性质和层结特性,对于大气三维运动及静止大气热力状态的刻画离不开垂直坐标的选择。垂直坐标更是构建数值预报模式的基础,经常根据不同的垂直坐标形式来区分不同类型的大气动力框架,如几何高度框架、等压面框架和等熵面框架等。伴随垂直坐标的发展,模式预报性能在不断提升,模式版本也在不断演进。本文简要回顾了垂直坐标的发展历史,重点介绍了目前国内外主要非静力业务模式垂直混合坐标的处理思路与方法,同时指出模式垂直分辨率及预报变量垂直分布形式的选择考量。最后对数值预报模式垂直坐标设计与应用进行总结,并给出未来发展展望。

改进蚁群算法在地形跟随航线规划问题中的应用

针对飞机地形跟随航线规划需要,提出了一种基于改进蚁群算法的通用解决方案。该方法通过空间等分的思想将三维地图重构为解空间,并通过一系列改进措施提升蚁群算法效率,包括围绕加强蚁群中最优蚂蚁的正增益、减弱最劣蚂蚁的负增益,设计信息素更新策略;综合考虑可行航路点距离、高度、转弯角度的影响,设计节点移动策略;采用粒子群算法,智能优化求解蚁群算法的核心参数等,实现地形跟随航线的快速生成。通过具体算例验证了该方法的先进性和可行性。

Adaptive control for attitude coordination of leader-following rigid spacecraft systems with inertia parameter uncertainties

This paper studies the leader-following attitude coordination problems of multiple spacecraft in the presence of inertia parameter uncertainties. To achieve attitude coordination in the situation that even the leader's attitude is only applicable to a part of the following spacecraft, a nonlinear attitude observer is proposed to obtain an accurate estimation of the leader's attitude and angular velocity for all the followers. In addition, a distributed control scheme based on noncertainty equivalence principle is presented for multiple spacecraft' attitude synchronization. With a dynamic scaling, attitude consensus can be achieved asymptotically without any information of the bounds of the uncertain inertia parameters. Furthermore, once the estimations of inertia parameters reach their ideal values, the estimation process will stop and the ideal value of inertia parameter will be held. This is a special advantage of parameter estimation method based on non-certainty equivalence. Numerical simulations are presented to demonstrate that the proposed non-certainty equivalence-based method requires smaller control toque and converges faster compared with the certainty equivalence-based method.