共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper, a convex optimization algorithm is proposed to solve the online trajectory optimization problem of boost back of vertical take-off/vertical landing reusable launch vehicles. To achieve high-precision landing of launch vehicles, trajectory optimization of the boost-back flight phase considering the accuracy of entry is carried out, especially in emergencies. The trajectory optimization problem is formulated as an optimal control problem with minimum fuel consumption, and then it is transformed into a series of convex optimization subproblems, which can be solved by primal-dual interior-point method accurately and rapidly. During the transformation, flip-Radau pseudospectral discretization method, lossless convexification and successive convexification technology are applied. To drive the vehicle to predetermined entry points at the expected velocity, terminal constraints are expressed as orbital constraints of the endpoint in the boost-back flight phase. Considering the influence of Earth's rotation, the right ascension of the ascending node of the target orbit is updated according to the time and true anomaly at the end of the boost-back flight phase. Furthermore, the homotopy method is applied to the situation where there is no good initial guess when emergency happens. The algorithm presented in this paper performs well upon the simulation experiments of mission change and thrust decline. With good accuracy, high computational efficiency, and excellent robustness, the convex approach proposed has a great potential for onboard application in reusable launch vehicles and other space vehicles. 相似文献
2.
This paper studies the neural adaptive control design for robotic systems with uncertain dynamics under the existence of velocity constraints and input saturation. The control objective is achieved by choosing a control Lyapunov function using joint error variables that are restricted to linear growth and furthermore by introducing a secant type barrier Lyapunov function for constraining the joint rate variables. The former is exploited to bind the forward propagation of the position errors, and the latter is utilized to impose hard bounds on the velocity. Effective input saturation is expressed, and neural networks are employed to tackle the uncertainty problem in the system dynamics. Feasibility conditions are formulated, and the optimal design parameters are obtained by solving the constrained optimization problem. We prove that under the proposed method, semi-global uniform ultimate boundedness of the closed-loop system can be guaranteed. Tracking errors meanwhile converge to small neighborhoods of the origin, and violations of predefined velocity constraints are avoided. Finally, numerical simulations are performed to verify the effectiveness of the theoretical developments. 相似文献
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Charles Aguiar Daniel Leite Daniel Pereira Goran Andonovski Igor Škrjanc 《Journal of The Franklin Institute》2021,358(2):1376-1402
Overhead cranes are widely used structures for lifting and conveying heavy loads. The development of feedback control systems for such equipment is important due to the large number of potential applications and advantages over manual operation concerning stability and robustness. This paper aims to represent the key nonlinear dynamics of crane systems by means of a state-space fuzzy model with compact rule-base structure. The fuzzy model is useful to assist the design of a fuzzy controller based on the concept of parallel compensation. A well-posed conservative linear-matrix-inequality (LMI) feasibility problem is formulated so that a solution guarantees closed-loop Lyapunov stability, bounded control inputs, quick positioning of the supporting cart, and suppression of load oscillations and collisions. The fuzzy controller is composed by rules with linear control laws derived from local state-space models. The controller warrants asymptotic convergence of the states. Due to the nonlinear nature of the fuzzy model and controller, Jacobian linearization is avoided. The proposed fuzzy control approach for cranes has shown to be more effective and robust than an optimal quadratic controller, and able to move cargo smoothly and safely to a destination. Particularly, constrained and smoother control inputs avoid actuator saturation, and tend to increase its lifetime. Laboratory experiments using the LMI fuzzy controller and actual data validates the approach for cranes in actual scenario. 相似文献
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基于景观连接度的盐城滨海湿地丹顶鹤生境斑块重要性评价 总被引：3，自引：0，他引：3
景观连接度和生境斑块重要性作为测度生境景观生态过程和生态功能的重要指标,已成为评价生境破碎化、识别生境景观中重要生境斑块与垫脚石、辨明恢复生境的关键节点位置的重要方法,对于生境保护、优化与恢复具有重要意义。本文以江苏盐城滨海湿地为研究区域,以人类活动影响较大的丹顶鹤越冬生境为对象,运用景观连接度指标和两种斑块重要性评价方法,考察1992-2012年间越冬丹顶鹤适宜生境时空格局变化特征,并探讨这期间的重要生境斑块与关键节点位置变化。结果发现:1992-2012年间,丹顶鹤生境连接度一直呈下降趋势;巨型斑块和大型斑块对于维持景观生境面积与生境连接度有着极其重要的作用,但处于关键节点位置的小型斑块作为垫脚石和连接要素的作用也不可忽视。从斑块重要性评价方法上来看,dPC指标反映的重要生境斑块更符合实际情况,BC(Betweenness Centrality)指标则可以明确需要恢复的重点生境位置,几种方法各有侧重,在指导区域生态保护与规划等方面各有优势,需综合考虑加以应用。 相似文献
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《Journal of The Franklin Institute》2023,360(4):3047-3076
In this paper, six-rotor UAVs are used in the field of distribution to realize the delivery of materials arriving the demand point by UAVs. Due to the small load capacity of the six-rotor UAV, in response to actual demand, the UAV group will be used to complete the delivery task. Considered to be close to the real requirements, trajectory constraints and dynamic obstacles are established in the trajectory planning based on group perception range. In order to better deal with dynamic obstacles and related constraints, this paper designs a distributed adaptive algorithm based on individual decision-making and group decision-making. Individual decision-making is embodied in the intelligence and adjustment of UAVs, involving actor-critic methods, artificial potential field method ideas and probability finite state machines; group decision-making is embodied in the leadership mechanism and joint decision-making; self-adaptation is embodied in the adaptive adjustment of UAV level in group. In order to avoid collisions between UAV groups, a conflict resolution algorithm is designed. Through simulation analysis, the distributed adaptive algorithm proposed in this paper can not only satisfy all constraints, avoid dynamic obstacles stably, and complete tasks with small fluctuations, but also obtain the most successful decision-making UAV in the group. This article further analyzes and discusses the relevant parameters in the algorithm, and obtains the optimal parameter ranges in individual decision-making and group decision-making. 相似文献
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《Journal of The Franklin Institute》2023,360(13):9579-9601
The current parking trajectory planning algorithms based on geometric connections or formulation of optimization problems in automatic parking systems have strict requirements on the starting position, lower planning efficiency and discontinuous curvature of the reference trajectory. In order to solve these problems, a hierarchical planning algorithm which is combined with nonlinear optimization and the improved RRT* algorithm (Rapidly-exploring Random Tree Star) with Reeds-Shepp curve is proposed in this paper. First, the improved RRT*RS algorithm with the rapid repulsion-straddle experiment is designed for enhancing the efficiency of path planning. Second, because of the shortcomings of the Reeds-Shepp curve that can meet the minimum turning radius but not realize the continuous curvature of the path, a nonlinear optimization problem based on convex-set obstacle constraints is formulated and solved. Finally, simulation results show that the proposed parking trajectory planning algorithm in this paper can plan an effective parking trajectory with continuous curvature in different starting positions and multiple parking scenarios. 相似文献
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为了提高运输规划问题的有效性,降低运输成本,将遗传算法引入到该问题的求解中。运输规划问题的数学模型是带约束的函数优化问题,在该问题模型中引入遗传算法,采用罚函数法处理约束条件,对可行解和不可行解采用不同的适应值函数,结合轮盘赌、竞标赛和精英保存算法作为选择策略,对可行解和不可行解分别采用边界变异和非均匀变异,最终得出最优解。实验结果数值说明该方法的有效性。 相似文献
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现行煤矿采区内风门的打开和闭合基本都靠人工操作,单轨吊机车在行驶过程中撞击风门的事件时有发生。实现风门和阻车器的连锁控制,可以提高采区内的工作效率,进而提高企业的经济效益。设计的采区风门自动化阻车系统具有车辆行驶方向识别,风门的遥控、自动和手动控制,风门和阻车器连锁控制功能。经过运行,整个系统能够正常运行。 相似文献
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《Journal of The Franklin Institute》2022,359(18):10392-10419
This paper proposes a high-precision three-dimensional nonlinear optimal computational guidance law in the terminal phase of an interceptor that ensures near-zero miss-distance as well as the desired impact angle. Additionally, it achieves these ambitious objectives while ensuring that the lead angle and lateral acceleration constraints are not violated throughout its trajectory. This ensures (i) the target does not escape the field of view of its seeker at any point in time (a state constraint) and (ii) it does not demand unreasonable lateral acceleration that cannot be generated (a control constraint). The guidance problem is formulated and solved using newly proposed Path-constrained Model Predictive Static Programming (PC-MPSP) framework. All constraints, both equality and inequality, are equivalently represented as linear constraints in terms of the errors in the control history, thereby reducing the complexity and dimensionality of the problem significantly. Coupled with a quadratic cost function in control, the problem is then reduced to a standard quadratic optimization problem with linear constraints, which is then solved using the computationally efficient interior-point method. Results clearly demonstrate the advantage of the proposed guidance scheme over the conventional Biased PN as well as the recently proposed GENeralized EXplicit (GENEX) guidance techniques. Numerical simulations with variation in initial conditions and Monte–Carlo simulations with parametric uncertainty demonstrate the robustness of the proposed guidance scheme. 相似文献
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土地利用总体规划是一个多目标、多准则问题,应用一种模型或方法难以在多规则约束条件下得到较优的布局方案.在福建省漳州市南部常山华侨经济开发区的土地利用总体规划中,本文借鉴专家解决规划问题的思维方式,将案例推理引入其土地利用总体规划,并以本体作为案例表示方式,结合规则推理实现案例修正,完成土地利用空间布局过程.结果表明:基于本体案例推理与规则推理的土地利用空间布局方法能很好地利用专家的经验知识,在多种规则的约束条件下能得到兼顾经济发展和生态环境保护的较优土地利用空间布局方案.其中,案例修正过程使系统具有自适应、自学习机制,随着系统的应用运行会不断增加新的案例和规则.丰富的案例库和规则库,能更进一步提高土地利用总体规划的效率、科学性和实用性. 相似文献
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A direct approach to path planning of a 2-DOFs (Degrees of Freedom) spherical robot based on Bellman?s dynamic programming (DP) is introduced. The robot moves in an environment with obstacles and employs DP to find optimal trajectory by minimizing energy and preventing obstacle collision. While other path planning schemes rely on pre-planned optimal trajectories and/or feedback control techniques, in this approach there is no need to design a control system because DP yields the optimal control inputs in a closed loop (feedback) form. In other words, after completing the DP table, the optimal control inputs are known for every state in the admissible region and the robot can move toward the final position without colliding with obstacles. This enables the robot to function well in semi- or even non-observable environments. Results from several simulated experiments show that the proposed approach is capable of finding an optimal path from any given position/orientation towards a predefined target in an environment with obstacles within the admissible region. The method is very promising compared to other path planning schemes. 相似文献
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《Journal of The Franklin Institute》2023,360(13):9886-9903
This paper proposes an optimal three-dimensional (3-D) spatial-temporal cooperative guidance (STCG) law for intercepting a maneuvering target with impact angle and time constraints. The guidance problem is studied to achieve spatial cooperation for multi-directional attack in the normal channel and temporal cooperation for simultaneous interception in the tangential channel, respectively. Firstly, the 3-D optimal impact-angle-control guidance (OIACG) is introduced to formulate spatial interception geometry. Based on this law, the relative trajectory length is analytically derived and an accurate time-to-go predictor is formulated against maneuvering targets. In the tangential channel, an optimal temporal cooperative guidance is proposed by leveraging high-dimensional Schwarz inequality method. The proposed algorithm is believed to outperform the existing nonlinear cooperative guidance laws due to its optimality with specific performance index for minimizing the control expenditure. The convergence properties of the proposed STCG law are provided to facilitate its practical implementation. Comparison simulations and application under the realistic pursuer model and target estimation are performed to demonstrate the effectiveness and robustness of the proposed cooperative method. 相似文献
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信产部办公楼场地异常狭小、施工环境差,工期紧、质量目标高．作者在该工程中重点解决钢结构吊装的大型机具,为提高塔吊的效率解决水平运输问题创造场内东西向通道,突破场地瓶颈。 相似文献
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This paper studies adaptive optimization problem of continuous-time multi-agent systems. Multi-agents with second-order dynamics are considered. Each agent is equipped with a time-varying cost function which is known only to an individual agent. The objective is to make multi-agents velocities minimize the sum of local functions by local interaction. First, a distributed adaptive algorithm is presented, in which each agent depends only on its own velocity and neighbors velocities. It is indicated that all agents can track the optimal velocity. Then we apply the distributed adaptive algorithm to flocking of multi-agents. It is proved that all agents can track the optimal trajectory. The agents will maintain connectivity and avoid the inter-agent collision. Finally, two simulations are included to illustrate the results. 相似文献
16.
Abolhassan Razminia Mehdi Asadizadehshiraz Hamid Reza Shaker 《Journal of The Franklin Institute》2019,356(3):1590-1603
In this paper, a generalized trajectory tracking problem for a closed-loop control system is formulated in the optimal control context. A linear time varying plant is considered to track a closed-loop desired trajectory generated by a given mechanism. The theoretical results are obtained based on the Hamilton-Jacobi-Bellman theory in which some generalized semiquadratic value functions are employed as the Lagrangian. In addition, we employ a non-integer order integral of Riemann-Liouville type as the cost functional, so that the trajectory tracking process can be evaluated in an extended optimum manner wherein the fractionality plays the main role. By selecting a suitable fractional order of the integral, a satisfactory optimal control system can be deduced in which least concentration on selecting the weighting matrices is needed. To show the effectiveness of the results, some numerical examples illustrate the potentials. 相似文献
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基于模糊线性规划模型的水-土-作物系统优化配置研究 总被引：1，自引：0，他引：1
为了进一步对陕西省蒲东灌区农业的规划发展,本文将线性规划模型和模糊优化模型应用到灌区土地-水-作物系统的规划和管理之中。该模型用于优化经济效益、作物产量和劳动力的利用,并寻求相关作物种植模式和对土地,水,肥和劳动力利用下农业系统的优化配置。根据研究区域情况,决定采用线性规划模型的三个目标函数输出数据作为模糊规划模型的约束条件,在模糊目标和模糊约束的模糊环境下,取得模糊优化模型的最优解方案。这些非结构化的模型能够很好的将地表水资源和地下水资源有效地联合利用。此外,对灌区农业系统优化配置后的净效益进行了对比评价。结果表明,本文提出的多目标模糊线性规划管理模型应用到农业系统土地-水-作物的优化配置中是可行的,合理地分配土地和水资源,提高了作物产量和净效益。 相似文献
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牵引小车式抓斗卸船机是目前国际国内各港口接卸散货船的重要设备。本文介绍了变频器的工作原理及在桥式抓斗卸船机的应用。抓斗吊车水平纵横两个方向的运动由大、小车完成;垂直运动由起升机负责,它由主卷电机和闭合电机两套独立起升系统组成,并且相互配合,完成抓斗的打开和闭合以及升降运动,从而实现对桥式抓斗卸船机调速和制动控制。 相似文献
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交通运输行业是仅次于电力行业的第二大温室气体排放源，近年来各国对其“低碳化”发展的关注不断提高，运输产业如何承担相应的低碳减排责任，积极变革寻求一种绿色低碳的运输方式成为行业发展的热点问题。低碳多式联运作为一种环境友好型的运输模式，通过综合多种运输方式的技术经济优势可以有效降低运输过程中产生的碳排放量，并逐渐被各大运输公司所关注。本文基于成本和时间双重约束下，将二氧化碳排放量纳入到多式联运研究中，通过碳价函数将二氧化碳的排放量换算为二氧化碳的排放成本，形成考虑整个运输过程的总成本，并在设定时间约束下，建立低碳多式联运优化模型，采用遗传算法求解，得出最佳低碳多式联运组合方式和路线，研究对基于企业层面如何建立多重约束下的低碳联运模式进行探索，并提出了相应的政策建议，研究结论对于促进我国交通运输业供给侧低碳结构性改革具有参考意义。 相似文献
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化肥消费规律及中国化肥矿产需求趋势预测 总被引：6，自引：1，他引：5
磷、硫、钾盐等矿产资源主要用于化肥的生产,是关乎我国农业和国民经济发展的重要物质基础。然而随着我国化肥产量与消费量的逐年增加,磷、硫、钾盐等矿产资源的可持续性以及在化肥施用过程中对环境的负面影响日益受到关注。在此背景之下,本文通过对欧美日韩等发达国家化肥消费历史分析,首次运用单位耕地面积化肥施用量作为研究指标,总结剖析了发达国家化肥消费历史轨迹变化及其动因,揭示了不同情形下,化肥消费规律:即理想状态下,单位耕地面积化肥施用量随着经济的发展呈"S"形规律变化;在化肥施用初期未考虑环境因素的情形下,单位耕地面积化肥施用量随着经济的发展呈倒"U"形规律变化。总结得出北美"理想模式"、西欧模式和日韩模式三种化肥消费变化的模式。以发达国家为借鉴,结合中国资源环境实际情况,预测了我国化肥及磷、硫、钾盐矿产未来需求趋势,结果表明中国磷肥和氮肥消费已到达峰值,未来将缓慢下降,相应的磷、硫资源需求也将到达峰值;钾肥在国际价格没有显著变化的情况下,未来需求将维持目前水平。 相似文献