A Survey and Comparison of Petri Net-Based Deadlock Prevention Policies for Flexible Manufacturing Systems

Over the last two decades, a great deal of research has been focused on solving deadlock problems in resource allocation systems such as computer communication systems, workflow systems, and flexible manufacturing systems, resulting in a wide variety of approaches. As a well-defined problem in resource allocation systems, deadlock prevention based on a Petri net formalism has received an enormous amount of attention in the literature. This paper intends to review and compare a variety of Petri net-based deadlock prevention policies reported in the literature. Their comparison is done in terms of structural complexity, behavior permissiveness, and computational complexity. This paper should facilitate engineers in choosing a suited method for their industrial application cases.     

Modular Wireless Real-Time Sensor/Actuator Network for Factory Automation Applications

Modern factory facilities are characterized by highly flexible manufacturing cells and highly dynamic processes, where clusters of fixed or moving sensors and actuators have to be controlled in a limited space under stringent real-time and reliability constraints. In such demanding industrial environments, wireless systems can also be beneficial by improving flexibility, cutting cables, and enabling solutions, which are cumbersome or even not possible to realize with wireline systems, especially in controlling moving or rotating parts. In this paper, we present a conceptual study of a wireless real-time system dedicated for remote sensor/actuator control in production automation. System development is based on user requirements, which were extracted from customer interviews and a market research. Low level measurements of frequency- and space-selective wireless channels in a factory-like environment were carried out. System design aspects, i.e., network topology, multiple access schemes, and radio technologies, will be thoroughly reviewed. The performance of a first prototype implementation will be discussed with emphasis on timing behavior and power consumption, as sensors and actuators of the wireless system are intended to operate without power lines or batteries     

基于参数BP网络的自整定PID控制在柔性结构控制中的应用

针对大射电望远镜(LT)悬索粗调系统为一非线性慢时变大滞后柔性系统的特点,提出用参数BP神经网络自整定PID控制器来实现馈源轨迹跟踪策略.仿真研究表明,该控制算法可以很好地满足馈源系统轨迹跟踪高精度要求.     

A Flexible Hybrid-Firing Controller for Cycloconverter Drives

A firing controller for cycloconverter drives has been developed using a unique combination of digital and analog methods. The cosine wave crossing method of control is used, incorporating digital sinewave generation techniques to produce accurate timing waves that are easily synchronized with a noisy ac line. Conversion to analog signals using multiplying D/A converters provides fast digital control of the output amplitude. Frequency and phase are also precisely controlled with 8-bit digital inputs. A unique circuit detects the conduction state of each SCR and is used to prevent line-to-line shorts, thus simplifying the requirements for an accurate bank selection signal and eliminating the need for large interphase reactors.     

A Digital Controller Assisted Flexible Auto-tuning Method for Continuous-time Filters

A novel auto-tuning method for the integrated continuous-time filter is proposed in this paper. On the one hand, an off-chip digital controller is adopted here to decrease the on-chip hardware as well as to increase the efficiency and the flexibility of the auto-tuning strategy. As a result, both the calibration and the programmability of the cut-off frequency can be realized by software, meanwhile some non-idealities of the circuit can also be compensated by software. On the other hand, the on-chip auto-tuning circuit is designed based on the master-slave architecture, where a novel and simple master circuit is adopted with digital input and output interfaces, thus providing convenient connections for the controller without the ADC or DAC devices. With the PCB technology, a 6th-order active-RC filter with the proposed auto-tuning method is also implemented to verify the validity and the flexibility of this method.     

EVE: A Flexible SIMD Coprocessor for Embedded Vision Applications

In this paper we introduce EVE (embedded vision/vector engine), with a FlexSIMD (flexible SIMD) architecture highly optimized for embedded vision. We show how EVE can be used to meet the growing requirements of embedded vision applications in a power- and area-efficient manner. EVE’s SIMD features allow it to accelerate low-level vision functions (such as image filtering, color-space conversion, pyramids, and gradients). With added flexibility of data accesses, EVE can also be used to accelerate many mid-level vision tasks (such as connected components, integral image, histogram, and Hough transform). Our experiments with a silicon implementation of EVE show that it performs many low- and mid-level vision functions with a 3–12x speed advantage over a C64x+DSP, while consuming less power and area. EVE also achieves code size savings of 4–6x over a C64x+DSP for regular loops. Thanks to its flexibility and programmability, we were able to implement two end-to-end vision applications on EVE and achieve more than a 5× application-level speedup over a C64x+. Having EVE as a coprocessor next to a DSP or a general purpose processor, algorithm developers have an option to accelerate the low- and mid-level vision functions on EVE. This gives them more room to innovate and use the DSP for new, more complex, high-level vision algorithms.     

异构双核系统中多媒体应用的智能任务控制器

针对异构双核的嵌入式系统中MPU和DSP处理器间的频繁通信导致系统性能降低的问题,文中提出了一种适用于多媒体应用的智能任务控制器。该控制器可动态实现任务管理,并有效解决处理器间通信问题。文中采用ESL设计方法,构建双核处理器虚拟器平台,以像素为256×256的JPEG图像编码作为实际应用。结果表明,此智能控制器可减少15%~68%的任务管理时间。     

A Petri Net Control Unit for High-Speed Modular Signal Processors

This paper proposes a hierarchical representation of digital signal processing algorithms suitable for real-time implementations. Petri net models are used to demonstrate every possible operating parallelism in their graphical expression, the marked Petri graph. Moreover, a hierarchical algorithm execution control based on delayed Petri graphs is presented. A strictly modular system architecture suitable for VLSI implementation and data-driven processing is reviewed in its main components. The algorithm representation is then applied to the design of the control part of the system modules. Details at the logic level of the controllers for an array of digital signal processors are presented as an application of the proposed methodology.     

一种着色赋时的面向对象Petri网及在自动制造系统中的应用

着色赋时的面向对象Petri网(Colored Timed Object-Oriented Petri Net,CTOPN)是在面向对象Petri网的基础上,添加了着色令牌和输入输出变迁函数的概念而形成的,是Petri网的扩展形式.给出了CTOPN的基本定义和建立CTOPN模型的方法,给出了CTOPN在自动制造系统(Autommated Manufacturing Systems,AMS)中的应用实例,最后对模型进行了死锁分析.CTOPN可以准确地描述复杂系统的静态结构及动态特性,能够成为面向对象系统的一种形式化的建模工具.     

一种软件自动测试成本的估算控制模型

根据已有的投资回报(ROI)分析模型,结合COCOMO度量结果,在充分考虑回归测试时测试程序维护成本的基础上,提出一种软件自动测试成本估算控制模型.该模型首先提出了平均维护代价因子的概念,并准确地计算出它的阈值,然后通过这个阈值选择合理的测试方式、控制测试成本,从而为整个测试过程提供动态指导和正确的决策方法.     

Communication Systems for Building Automation and Control

Building automation systems (BAS) provide automatic control of the conditions of indoor environments. The historical root and still core domain of BAS is the automation of heating, ventilation and air-conditioning systems in large functional buildings. Their primary goal is to realize significant savings in energy and reduce cost. Yet the reach of BAS has extended to include information from all kinds of building systems, working toward the goal of "intelligent buildings". Since these systems are diverse by tradition, integration issues are of particular importance. When compared with the field of industrial automation, building automation exhibits specific, differing characteristics. The present paper introduces the task of building automation and the systems and communications infrastructure necessary to address it. Basic requirements are covered as well as standard application models and typical services. An overview of relevant standards is given, including BACnet, LonWorks and EIB/KNX as open systems of key significance in the building automation domain.     

A Genetic Fuzzy Controller for Vehicle Automatic Steering Control

This paper presents the design and experimental implementation of a genetic fuzzy controller for automatic steering of a small-scaled vehicle. We first derive a dynamic model of the vehicle via system identification and show that the model exhibits similar characteristics to full-sized vehicles. Subsequently, a stable fuzzy proportional-derivative controller is designed and optimized by genetic algorithms. The control system is transformed into a Lureacute system, and Lyapunov's direct method is used to guarantee the stability of the control system. Experimental studies suggest that the control system is insensitive to parametric uncertainty, load, and disturbances. The performance of the proposed controller is also compared against a conventional proportional derivative (PD) controller. Experimental results confirm that it outperforms the conventional PD controller, particularly in terms of robustness     

A General Harmonic Rule Controller for Run-to-Run Process Control

The existence of initial bias in parameter estimation is an important issue in controlling short-run processes in semiconductor manufacturing. Harmonic rule has been widely used in machine setup adjustment problems. This paper generalizes the harmonic rule to a new controller called general harmonic rule (GHR) controller in run-to-run process control. The stability and optimality of the GHR controller is discussed for a wide range of stochastic disturbances. A numerical study is performed to compare the sensitivity of the GHR controller, the exponentially weighted moving average (EWMA) controller and the variable EWMA controller. It is shown that the GHR controller is more robust than the EWMA controller when the process parameters are estimated with uncertainty.      

柔性结构振动自适应模糊控制与实验研究

针对机敏柔性结构振动主动控制，提出了一种自适应模糊控制方案。在简单模糊控制器基础上引进了自适应环节，并经大量实验研究后总结了量化因子Ke、Kc与比例因子Ku的调整规则。最后对一机敏柔性梁进行了抑振实验，获得了良好的效果。     

Petri网理论及其在自动制造系统中的应用

文中详细综述了Ｐｅｔｒｉ网理论的发展、应用领域、基本定义以及分析方法和建模方法。重点介绍了Ｐｅｔｒｉ网在自动制造系统控制中的应用、发展方向，指出了Ｐｅｔｒｉ网在自动制造系统中的应用前景和作者的看法     

Design and Development of Flexible PDMS Antenna for UWB-WBAN Applications

Wireless Personal Communications - This paper presents the design and development of a flexible Ultra Wide Band (UWB) antenna using polydimethylsiloxane as a substrate. Copper foil having a...     

A Novel Rate Control Method for Low Delay Applications

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Flexible Controller Design and Its Application for Concurrent Execution of Buffer Centric Dataflows

This paper presents a flexible controller structure for concurrent processing of memory centric coarse grain data flows. We propose a design flow based on block level pipelining where concurrency among processing blocks is fully maintained. The controller is dynamically reconfigurable to support dynamic data-flow structure changes by localizing control signals. The proposed control design method isolates controllers and processing logics such that system integration is simplified while controllers are locally configured from orthogonal global information. The controller also supports interfacing with external processors for asynchronous processing. The controller for heterogeneous processing blocks is synthesized and verified using Verilog and SystemC on FPGA. We present an example demonstrating the effectiveness of the controllers where dynamic reconfiguration of the execution is feasible.