An adaptive tabu search approach for buffer allocation problem in unreliable non-homogenous production lines

The buffer allocation problem, i.e. how much buffer storage to allow and where to place it within the line, is an important research issue in designing production lines. In this study, a novel adaptive tabu search approach is proposed for solving buffer allocation problem in unreliable and non-homogeneous production lines. The objective is to maximize the throughput of the line, which is constrained by the capacity of each buffer space and also the total buffer capacity to allocate to these spaces. Besides proposing a new strategy to tune the parameters of tabu search adaptively during the search, an experimental study is carried out to select an intelligent initial solution scheme among three alternatives so as to decrease the search effort to obtain the best solutions. The performance of the proposed approach is evaluated by computational tests and very promising results are obtained.     

Data-driven dual-rate cascade control and application to pitch angle control of UAV

A data-driven design method for a cascade control system is proposed. The cascade control system consists of inner and outer loops, where the control interval of the outer loop is an integer multiple of the inner loop; hence, the system is a dual-rate system. In the proposed method, controllers in the inner and outer loops are designed based on one-shot data. In such a dual-rate cascade system, since the controllers are designed using different data-rate signals, the lifting technique is applied to align the dual-rate data. To show its effectiveness, the proposed method is compared with a conventional single-rate cascade control method, and numerical simulations and experiments are presented to examine servo and regulation performance.     

Nonlinear robust sliding mode control of a quadrotor unmanned aerial vehicle based on immersion and invariance method

We present an asymptotic tracking controller for an underactuated quadrotor unmanned aerial vehicle using the sliding mode control method and immersion and invariance based adaptive control strategy in this paper. The control system is divided into two loops: the inner‐loop for the attitude control and the outer‐loop for the position. The sliding mode control technology is applied in the inner‐loop to compensate the unmatched nonlinear disturbances, and the immersion and invariance approach is chosen for the outer‐loop to address the parametric uncertainties. The asymptotic tracking of the position and the yaw motion is proven with the Lyapunov based stability analysis and LaSalle's invariance theorem. Real‐time experiment results performed on a hardware‐in‐the‐loop‐simulation testbed are presented to validate the good control performance of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.     

Energy-aware feedback control for a H.264 video decoder

Embedded devices using highly integrated chips must cope with conflicting constraints, while executing computationally demanding applications under limited energy storage. Automatic control and feedback loops appear to be an effective solution to simultaneously accommodate for performance uncertainties due to the tiny scale gates variability, varying and poorly predictable computing demands and limited energy storage constraints. This paper presents the example of an embedded video decoder controlled by several feedback loops to carry out the trade-off between decoding quality and energy consumption, exploiting the frequency and voltage scaling capabilities of the chip. The inner loop controls the dynamic voltage and frequency scaling through a fast predictive control strategy. The outer loop computes the scheduling set-points needed by the inner loop to process frames decoding. The feedback loops have been implemented on a stock PC and experimental results are provided.     

基于平动转动分离的车道线双回路滑模控制研究

针对车辆自主驾驶中的车道线保持问题,基于车辆横向动力学简化线性模型,把车辆运动分为平动与转动,按照平动与转动分离的思想,采用内外回路分层设计的方法,提出了一类以角度稳定为内稳定核心回路,以位置误差跟踪为外回路的双回路控制方案.其内外回路相串联,并由车辆平动位置信息驱动转动角稳定回路,对双回路均采用滑模控制方法.最后,采用详细的仿真分析说明了该设计方法具有明确的物理意义,而且控制律构成不包含系统不确定信息,具有很好的鲁棒性,能够满足工程应用的需要.     

交会对接模拟系统姿态位置耦合有限时间控制

针对航天器交会对接模拟系统的姿态同步和位置跟踪控制问题,在存在外界扰动和系统不确定性的情况下,基于改进的快速非奇异终端滑模面和改进的自适应律,采用双闭环控制结构分别设计内环和外环有限时间姿态位置耦合控制器.所提出的自适应律不仅能有效地抑制扰动和不确定性且能保证控制器是连续的.李雅普诺夫理论推导和仿真结果表明,所提出的控制方法能保证系统内环和外环跟踪误差的有限时间稳定性和准确收敛性.     

Manipulator motion control in operational space using joint velocity inner loops

This paper addresses the operational space motion control—trajectory tracking—of robot manipulators endowed with joint velocity feedback inner loops. A general structure for model-based joint velocity controllers is proposed for the inner loop. The required joint velocity reference is provided by an outer loop inspired from the robot kinematic control approach. It is shown that above two-loops control schemes lead to a nice cascade structure for the corresponding closed-loop systems. A stability result adapted for analysis of this particular kind of systems is developed in the paper; sufficient conditions for global exponential stability of this class of cascade systems are obtained. The effectiveness of the proposed control approach is evaluated on a direct-drive mechanical arm, and compared with a typical control strategy based on inverse kinematics resolution for computation of the desired motion in joint space, and the use of the computed-torque technique. The experimental evidences show better performance of the proposed two-loops controller.     

An optimization approach for coupling problem of berth allocation and quay crane assignment in container terminal

This paper addresses an effective approach to solve the issue of berth allocation and quay crane assignment in a multi-user container terminal. First of all, the studied coupling problem is formulated with the interactions between berth allocation and quay crane assignment considered. Then, an evolutionary algorithm with nested loops was developed to obtain optimal solutions. The algorithm is well structured, where two inner loops are used to solve sub-problems of berth allocation and quay crane assignment respectively; an outer loop is then utilized to find an approximate solution based on the results of the two inner loops. The results of numerical experiments show that the proposed approach can improve the essential operations in container terminals.     

Quadrotor Control Via Robust Generalized Dynamic Inversion and Adaptive Non‐Singular Terminal Sliding Mode

A robust two‐loops structured control system design for quadrotor's position/attitude trajectory tracking is proposed. The aim of the outer loop is to provide the roll/pitch tilting commands to the inner loop, which in turns generates the tilting angles that control the quadrotor's center of gravity in the horizontal plane. The outer loop utilizes Robust Generalized Dynamic Inversion (RGDI) of a prescribed asymptotically stable differential equation in the deviation function of the horizontal position coordinates from their reference trajectories. The inner loop employs an Adaptive Non‐singular Terminal Sliding Mode (ANTSM) to control the tilting angles, in addition to controlling the yaw attitude angle and the vertical position coordinate. The proposed scheme solves the singularity avoidance problems of generalized inversion and terminal sliding mode control. The stability of outer and inner loop is ensured by utilizing positive definite Lyapunov energy function for stable tracking performance against parametric variations and bounded unknown external disturbances. Numerous simulations are conducted on a six Degrees of Freedom (DoF) quadrotor model in the presence of parametric variations, un modeled dynamics, and external disturbances.     

Cascade generalized predictive controller: two in one

The paper presents a cascade generalized predictive controller. The cascade control task is performed by one predictive controller and the cascade feature is incorporated in a special predictor. Simulation results are presented comparing the performances of the proposed control algorithm to traditional cascade loops including two PI or two GPC controllers. The paper investigates the effects of noise filter on the robustness of the control loops in the cascade control structure. It shows, that with the proposed predictor it is possible to adjust independently the robustness of the inner and outer loops, meanwhile in the traditional cascade loop there are cross effects in this sense. Finally a real time application of the proposed algorithm is presented: the cascade GPC was tested in the oxygen control loop of an experimental fluidized bed boiler.     

面向SLP 的多重循环向量化

如今,越来越多的处理器集成了SIMD(single instruction multiple data)扩展,现有的编译器大多也实现了自动向量化的功能,但是一般都只针对最内层循环进行向量化,对于多重循环缺少一种通用、易行的向量化方法.为此,提出了一种面向SLP(superword level parallelism)的多重循环向量化方法,从外至内依次对各个循环层次进行分析,收集各层循环对应的一些影响向量化效果的属性值,主要包括能否对该循环进行直接循环展开和压紧、有多少数组引用相对于该循环索引连续以及该循环所包含的区域等,然后根据这些属性值决定在哪些循环层次进行直接循环展开和压紧,最后通过SLP对循环中的语句进行向量化.实验结果表明,该算法相对于内层循环向量化和简单的外层循环向量化平均加速比提升了2.13和1.41,对于一些常用的核心循环可以得到高达5.3的加速比.     

脉动阵列变换的搜索策略及自动化算法*

对于多重循环中,当内层迭代的上下界为外层迭代的仿射函数时,介绍了搜索脉动变换的一个优化策略和相应的自动化算法.     

Split-path enhanced pipeline scheduling

Software pipelining increases the loop execution throughput by overlapping the execution of successive iterations in a pipelined fashion. For loops with control flows, however, software pipelining is not straightforward because we need to consider the overlap of more than one execution path. Modulo scheduling simply transforms them into straightline loops through if-conversion which, in effect, achieves a fixed, worst-case initiation interval (/spl par/) among all paths. On the other hand, all-path pipelining (APP) and enhanced pipeline scheduling (EPS) can achieve a variable /spl par/ depending on the path that is taken at execution time. Unfortunately, APP concentrates only on the overlap within the same path, entirely losing the overlap between different paths, whereas EPS attempts to overlap all paths together, failing to produce a tight schedule for each individual path, especially when resource constraints are tight. In this paper, we propose a new approach to EPS called split-path EPS (SP-EPS), which first splits each individual path via tail duplication and then performs EPS in a way to guarantee a tight schedule for each path, while producing a competitive cross-path schedule. We also extend SP-EPS to outer loops such that frequent paths that bypass the inner loop are split and then scheduled by SP-EPS. Our experimental results on nontrivial integer benchmarks show that SP-EPS can achieve as much as a geometric mean of 10 percent speedup over EPS when innermost loops are scheduled by SP-EPS, while it can achieve a geometric mean of 11.9 percent speedup when outer loops are also scheduled by SP-EPS.     

基于非线性L1自适应动态逆的飞行器姿态角控制

钊对常规动态逆控制器不能有效抵消系统中的不确定性这一缺点,提出了一种非线性L_1自适应动态逆控制方法.该方法能够克服常规动态逆的不足,在保证系统鲁棒性的前提下,提升飞行器姿态角控制效果.首先,采用时标分离原理,将姿态角控制系统分为内外两个回路:外回路采用常规动态逆控制器,用于姿态角的跟踪控制;内回路采用非线性L_1自适应控制器,用于角速率的控制.其中,L_1自适应控制器由静态反馈控制器和自适应控制器组成:静态反馈控制器通过状态反馈实现,用于保证内回路的稳定和具有期望的闭环特性;自适应控制器由状态观测器、自适应律和控制律组成,用于抵消系统中的不确定性.其次,对所提控制方法的稳定性进行了分析,结果证明了该控制方法能够保证内回路的稳定和外回路的误差有界.最后,在综合考虑多种不确定性的情况下,将本文提出的非线性L_1自适应动态逆控制方法用于某无人飞行器姿态角控制,仿真结果验证了该控制方法的有效性和鲁棒性.     

基于改进降顶算法的非可靠生产线最优缓存分配

缓存分配是生产系统设计中一个重要的优化问题.基于非可靠连续生产线递推分解方法及其统计特性,提出在给定缓冲配制条件下的蒙特卡洛生产线吞吐量仿真估算方法,相比于传统的吞吐量估算模型该方法能更准确地描述各种生产场景.通过构造具有记忆性的禁忌集改进了传统降顶算法,并将其应用于实际缓存最优分配方案搜索中.仿真结果表明,对于各种规模的平衡生产线和非平衡生产线,改进降顶算法都可以快速有效地搜索到最优解.     

Loop coalescing and scheduling for barrier MIMD architectures

Barrier MIMD's are asynchronous multiple instruction stream, multiple data stream architectures capable of parallel execution of variable execution time instructions and arbitrary control flow (e.g., while loops and calls); however, they differ from conventional MIMD's in that the need for run-time synchronization is significantly reduced. The authors consider the problem of scheduling nested loop structures on a barrier MIMD. The basic approach employs loop coalescing, a technique for transforming a multiply-nested loop into a single loop. Loop coalescing is extended to nested triangular loops, in which inner loop bounds are functions of outer loop indices. In addition, a more efficient scheme to generate the original loop indices from the coalesced index is proposed for the case of constant loop bounds. These results are general, and can be applied to extend previous work using loop coalescing techniques. The authors concentrate on using loop coalescing for scheduling barrier MIMDs, and show how previous work in loop transformations and linear scheduling theory can be applied to this problem     

基于准连续高阶滑模的可重复使用运载器再入姿态控制

针对可重复使用运载器再入段的姿态控制问题,提出一种基于准连续高阶滑模的控制方法。将姿态控制系统分为两个回路,分别为角度控制回路与角速度控制回路。角度回路作为外回路产生角速度指令,角速度回路作为内回路跟踪外回路产生的角速度控制指令。为了提高系统的鲁棒性,对两个回路分别设计滑模控制器。外回路中设计基于低通滤波的终端滑模控制方法,以获得平滑的控制量作为角速度指令。内回路设计增加系统相对阶的准连续高阶滑模方法,使控制律中不直接含有符号函数项,保证系统稳定的同时减弱控制器抖振。在具有外界干扰与参数不确定的情况下,使用本文提出的方法进行仿真试验,仿真结果证明了所提出方法的有效性。     

Application of two‐loop robust control to air‐conditioning systems

This paper presents the design and application of a two‐loop robust controller for temperature control in air‐conditioning systems. A Takagi‐Sugeno fuzzy model with uncertain local models is developed to describe the associated nonlinearities and uncertainties in the operation of the air handling units. Parallel distributed compensation is used to design the global control law. The local control law consists of two loops: an inner‐loop integral controller and an outer‐loop min‐max predictive controller with short prediction horizon. A discounting scheme is developed to weight the contribution of the two loops. Experimental results are presented which show that the proposed strategy can achieve acceptable control performance with a minimum of onsite tuning. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于模糊PI混合控制的自主水下航行器推进系统

对转永磁无刷直流电机驱动对转螺旋桨主要应用在自主水下航行器推进系统中,通过调节对转电机转速就可以实现自主水下航行器速度的无级调节.在研究对转永磁无刷直流电机数学模型的基础上,提出一种外环转速环采用模糊PI混合控制,内环电流环采用PI控制的双闭环调速方法.仿真结果表明,与外环、内环均采用PI控制的双闭环调速方法相比,该方...     

选择性循环的并行方法

针对含有大量循环的串行程序存在的问题,提出一种基于线程级前瞻技术的循环选择方案。该方案对循环进行最优选择后建立一个可并行运行的循环集。对于该集合中的循环,选择并行效率高的代码段作并行处理,以加快串行程序运行速度。实验表明,相对于一般的简单内部循环或外部循环并行方法,该方案使9种基准代码的加速比平均上升23.8%,从而提高串行程序并行运行的效率。