网络控制系统的带宽管理与优先级调度研究

发布时间：2018-07-27 09:12

【摘要】：网络控制系统是指利用通信网络来交换位于不同地理位置的控制器、传感器和执行器等多个节点之间的数据信息而构成的闭环控制系统,具有智能化、网络化和分布化等特点,可满足大型工业的控制系统结构复杂、规模大和远程控制等需求,因此备受中外学者和工程技术人员的关注。然而由于网络控制系统引入共享网络作为通信介质,必然存在诸如带宽受限、数据包丢失、节点驱动方式和网络诱导时延等问题,相比传统控制系统的设计与分析显得更为复杂,现已成为国内外的研究热点。网络控制系统中多个控制回路共享有限的网络带宽资源,势必产生对有限带宽资源的竞争,当某一控制回路带宽占用率过高,就会影响到其他控制回路以及整个系统的性能。为了保证网络控制系统的控制性能和稳定性,不仅需要优越的控制算法,而且还需要合理调度策略,所以如何动态分配各控制回路的带宽、调整并发优先级是权衡网络带宽资源竞争与控制性能之间的关键。本文从网络带宽受限的角度出发,对网络控制系统中的带宽管理和优先级调度进行研究,分别提出了基于带宽约束的带宽管理策略和基于带宽管理的双参数优先级调度策略,有效地提高了系统的控制性能和带宽资源利用率,主要研究工作内容如下:第一,针对多控制回路的网络控制系统如何将回路的富余带宽逐步及时地回馈以及整体期望带宽超限的优化分配问题,提出了基于带宽约束的带宽管理策略。通过建立全局网络调度器,根据各控制回路的控制性能预估回路控制误差,利用模糊推理方法并按照带宽分配原则(控制性能差的回路逐步获取带宽,提高其控制性能;控制性能良好的回路将多余带宽逐步回馈到网络中,供其他回路使用)周期性地确定各控制回路的期望带宽,分别对期望带宽在带宽约束内和带宽约束外两种情况进行实际带宽分配量的设计。实验分析验证了该调度策略能够有效地提高系统的带宽利用率和控制性能。第二,针对优先级调度的任务重要特性参数单一的稳定性不足以及带宽管理策略与优先级调度策略难以充分结合的问题,提出了基于带宽管理策略的双参数优先级调度策略。在带宽管理策略进行集中带宽调度的基础上,在各传感器节点进行分布式地优先级调度,将带宽管理策略中全局网络调度器输出的采样周期作为网络需求度参数和将任务传输的空闲时间作为网络紧急度参数联合确定优先级参数,其优先级参数调整的原则为:较大负载的控制回路的优先级主要由网络需求度决定,其次取决于网络紧急度;并提出基于CAN扩展帧的标识符分段规划方法,既体现策略的动态特性,又体现其固定唯一性,增大系统的节点容纳量。实验分析验证了该调度策略能够周期性地动态调整各通信节点的优先级并进一步提高了系统的控制性能。
[Abstract]:Network control system is a closed loop control system which uses communication network to exchange data information between controllers, sensors, actuators and other nodes located in different geographical locations. It has the characteristics of intelligence, network and distribution. It can meet the needs of complex structure, large scale and remote control in large industry, so it has attracted the attention of Chinese and foreign scholars and engineers. However, due to the introduction of shared network as communication medium in networked control systems, there are bound to be some problems, such as bandwidth limitation, packet loss, node-driven mode and network-induced delay, etc. Compared with the design and analysis of traditional control system, it has become a research hotspot at home and abroad. Multiple control loops in networked control systems share limited network bandwidth resources, which will inevitably result in competition for limited bandwidth resources. If the bandwidth utilization of one control loop is too high, the performance of other control circuits and the whole system will be affected. In order to ensure the control performance and stability of the networked control system, not only the superior control algorithm is needed, but also the reasonable scheduling strategy is needed, so how to dynamically allocate the bandwidth of each control loop, Adjusting concurrent priority is the key to balance the competition of network bandwidth resources and control performance. In this paper, bandwidth management and priority scheduling in networked control systems are studied from the point of view of bandwidth constraints. Bandwidth management strategies based on bandwidth constraints and two-parameter priority scheduling strategies based on bandwidth management are proposed respectively. The control performance and bandwidth resource utilization of the system are improved effectively. The main contents of the research are as follows: first, A bandwidth management strategy based on bandwidth constraint is proposed to solve the problem of how to feedback the excess bandwidth of the loop step by step and to optimize the allocation of the overall desired bandwidth in the networked control system with multiple control loops. By establishing a global network scheduler, the control error of each control loop is estimated according to the control performance of the control loop, and the control performance is improved by using the fuzzy reasoning method and according to the principle of bandwidth allocation (the loop with poor control performance can obtain the bandwidth step by step; The loop with good control performance returns the excess bandwidth step by step to the network for use by other circuits) and periodically determines the desired bandwidth of each control loop. The actual bandwidth allocation is designed for two cases: the expected bandwidth is within the bandwidth constraint and the other is outside the bandwidth constraint. The experimental results show that the scheduling strategy can effectively improve the bandwidth utilization and control performance of the system. Secondly, a two-parameter priority scheduling strategy based on bandwidth management strategy is proposed to solve the problem of the lack of stability of single important characteristic parameter of priority scheduling and the difficulty of combining bandwidth management strategy with priority scheduling strategy. On the basis of centralized bandwidth scheduling based on bandwidth management strategy, distributed priority scheduling is carried out on each sensor node. The sampling period of the global network scheduler in the bandwidth management strategy is taken as the network requirement parameter and the idle time of the task transmission is taken as the network emergency parameter to determine the priority parameter. The principle of the priority parameter adjustment is: the priority of the control loop with large load is mainly determined by the network requirement degree, the second is the network emergency degree, and the method of segmental planning of the identifier based on the extended frame of CAN is proposed. It not only embodies the dynamic characteristics of the strategy, but also reflects its fixed uniqueness, and increases the node capacity of the system. The experimental results show that the scheduling strategy can dynamically adjust the priority of each communication node periodically and further improve the control performance of the system.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP273

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