Experimental evaluation of two complementary decentralized event-based control methods

Event-based control aims at reducing the feedback communication effort among the sensors, controllers and actuators in control loops to time instants at which the feedback of information is necessary to meet a desired control performance. This paper presents a new method for the decentralized event-based control of physically interconnected systems and shows its experimental evaluation. The novel method is based on two complementary approaches, called the global and the local approach, which jointly ensure the ultimate boundedness of the closed-loop system. The global approach steers the state of each subsystem into a target region, whereas the local approach keeps the state in this set in spite of exogenous disturbances and the effect of the interconnections to other subsystems. This event-based control method is applied to a continuous flow process to show its practical implementation and to evaluate the analytical results on the basis of experiments.     

A novel approach to periodic event-triggered control: Design and application to the inverted pendulum

In this paper, periodic event-triggered controllers are proposed for the rotary inverted pendulum. The control strategy is divided in two steps: swing-up and stabilization. In both cases, the system is sampled periodically but the control actions are only computed at certain instances of time (based on events), which are a subset of the sampling times. For the stabilization control, the asymptotic stability is guaranteed applying the Lyapunov–Razumikhin theorem for systems with delays. This result is applicable to general linear systems and not only to the inverted pendulum. For the swing-up control, a trigger function is provided from the derivative of the Lyapunov function for the swing-up control law. Experimental results show a significant improvement with respect to periodic control in the number of control actions.     

Design of event-based PI-P controllers using interactive tools

In the field of event-based control, the tuning and synthesis of controllers represent a challenging task where the lack of specific computer-aided design tools makes very difficult the consolidation of emerging approaches. Under this scenario, it recently proposed the PI-P control strategy, a promising alternative which provides the designer with a practical design and an intuitive tuning methodology. This work addresses the design task of PI-P event-based controllers through the use of interactive tools. To this aim, first, a new interactive tool is provided. The tool is the result of implementing the theoretical developments of previous researches with the aim of consolidating the strategy. Second, the tool is used to analyze in detail the design paradigm through their main trade-offs between performance and robustness. The usefulness of analyses developed is experimentally demonstrated through several meaningful designs for typical industrial examples.     

The identification of traffic crash hot zones under the link-attribute and event-based approaches in a network-constrained environment

In the spatial analysis of road traffic crashes, a hot zone methodology explicitly uses the network contiguity of more than one road segment as a criterion in identifying crash clusters. In this paper, 603 simulated patterns of traffic crashes in three simplified hypothetical networks and the empirical crash pattern in Hong Kong from 2008 to 2010 (with a total of 30,490 traffic crashes on 1090 km of roads) are analyzed using the link-attribute approach and the network-constrained event-based approach. Procedures for identifying hot zones using statistical thresholds are developed. This paper represents the first systematic comparison of hot zone results using these two different approaches. The results suggest that the link-attribute approach and network-constrained event-based approach are usually consistent but there are major differences between the two approaches.     

ARCHITECT: A layered framework for classifying technologies of event-based systems

In the past decade, event-based systems (EBS) have received increasing attention from various communities. Central to these systems is the notion of event, which is often generally considered as “a happening of interest”. An EBS encompasses a large range of functionalities on various technological levels (e.g., language, execution, or communication). Existing approaches vary in the scope of implemented functionality and underlying technical concepts. For this reason, comparing EBS solutions is a challenging task. Furthermore, the lack of a unified view on EBS poses challenges to system architects in choosing and combining technologies for building event-based systems.     

Two posture analysis approaches and their application in a modified Rapid Upper Limb Assessment evaluation

This paper presents two posture risk quantification methods: first, an event-based method where the most common and the worst postures are estimated in a task; second, a time-based method where posture distributions are calculated from random samples of observed postures in the task. A ‘click-on-screen’ posture data entry method was developed for the time-based posture analysis method to make the observation process easier and to reduce possible posture categorization bias. Both methods were used to quantify various work posture parameters among a study cohort of 733 subjects from a prospective epidemiological study of upper extremity musculoskeletal disorders. Composite posture indices using a modified Rapid Upper Limb Assessment (RULA) method were also computed using data obtained by the two posture analysis methods. Results showed that both methods were able to distinguish jobs with large differences in certain posture measures. However, they did not produce the same results and could not be used interchangeably. Risk evaluation criteria should be developed, either for specific posture parameters or as a composite index, with a well-defined postural analysis method, so that users can follow exact procedures and obtain comparable results. The event-based method is easy to use and may suit practitioners better, while the time-based method adds more information to the measurement and may suit users who want more detailed information about posture exposure.     

一种基于事件的情境感知框架

为更好地满足用户的个性化需求、支持情境感知服务,提出一种基于事件的情境感知框架。该框架包括传感器层、事件总线和应用服务层,采用事件触发的方式调用应用服务与用户交互,并建立基于规则的事件过滤机制,对无效事件进行屏蔽。应用结果表明,该框架可提高系统的感知性能和重用性。     

A practical tuning methodology for event-based PI control

This paper is focused on the tuning of an event-based PI controller for first-order plus time delay systems (FOPTD). In this work, a novel design and combination of a controller and event generator with an easy-to-use tuning methodology is presented. The event generator combines the Smith predictor structure with the symmetric send-on-delta (SSOD) sampling scheme to compensate the delay and trigger the events. The controller has an adaptive structure with the purpose of improving the set-point tracking and guaranteeing stability under conditions of uncertainty. The approach is focused on FOPTD systems but can be easily extended to higher order systems. Stability and robustness analyses are conducted, and the experimental results verify the effectiveness of the approach.     

一种多门户环境下服务管理框架的设计

多门户环境下门户系统包含门户服务器和多个子门户应用。要维持正常的运行维护,门户系统就需要提供相应的服务。多门户环境下子门户众多,所需的服务数量众多,实现对这些服务的有效管理至关重要。设计了一种多门户环境下基于事件的服务管理框架,引入事件驱动机制,实现了对多门户环境下服务的高效灵活的管理。     

Listener latency profiling: Measuring the perceptible performance of interactive Java applications

When developers need to improve the performance of their applications, they usually use one of the many existing profilers. These profilers generally capture a profile that represents the execution time spent in each method. The developer can thus focus her optimization efforts on the methods that consume the most time. In this paper we argue that this type of profile is insufficient for tuning interactive applications. Interactive applications respond to user events, such as mouse clicks and key presses. The perceived performance of interactive applications is directly related to the response time of the program.In this paper we present listener latency profiling, a profiling approach with two distinctive characteristics. First, we call it latency profiling because it helps developers to find long latency operations. Second, we call it listener profiling because it abstracts away from method-level profiles to compute the latency of the various listeners. This allows a developer to reason about performance with respect to listeners, also called observers, the high level abstraction at the core of any interactive Java application.We present our listener latency profiling approach, describe LiLa, our implementation, validate it on a set of microbenchmarks, and evaluate it on a complex real-world interactive application. We then perform case studies where we use LiLa to tune the perceptible performance of two interactive applications, and we show that LiLa is able to pinpoint performance problems even if their causes are embedded in the largest interactive Java application we are aware of.