Many embedded systems operate in multiple modes, where mode switches can be both time- as well as event-triggered. While timing and schedulability analysis of the system when it is operating in a single mode has been ...
详细信息
Many embedded systems operate in multiple modes, where mode switches can be both time- as well as event-triggered. While timing and schedulability analysis of the system when it is operating in a single mode has been well studied, it is always difficult to piece together the results from different modes in order to deduce the timing properties of a multi-mode system. As a result, often certain restrictive assumptions are made, e.g., restricting the time instants at which mode changes might occur. The problem becomes more complex when both time- and event-triggered mode changes are allowed. Further, for complex systems that cannot be described by traditional periodic/sporadic event models (i.e., where event streams are more complex/bursty) modeling multiple modes is largely an open problem. In this paper we propose a model and associated analysis techniques to describe embedded systems that process multiple bursty/complex event/data streams and in which mode changes are both time- and event-triggered. Compared to previous studies, our model is very general and can capture a wide variety of real-life systems. Our analysis techniques can be used to determine different performance metrics, such as the maximum fill-levels of different buffers and the delays suffered by the streams being processed by the system. The main novelty in our analysis lies in how we piece together results from the different modes in order to obtain performance metrics for the full system. Towards this, we propose both - exact, but computationally expensive, as well as safe approximation techniques. The utility of our model and analysis has been illustrated using a detailed smart-phone case study.
Making good operation decisions during abnormal power plant conditions represents in many cases the possibility to avoid a unit trip or having economical losses. This paper introduces AsistO, an intelligent assistant ...
详细信息
Many embedded platforms consist of a heterogeneous collection of processing elements, memory modules, and communication subsystems. These components often implement different scheduling/arbitration policies, have diff...
详细信息
Many embedded platforms consist of a heterogeneous collection of processing elements, memory modules, and communication subsystems. These components often implement different scheduling/arbitration policies, have different interfaces, and are supplied by different vendors. Hence, compositional techniques for modeling and analyzing such platforms are of interest. In prior work, the real-time calculus framework has proven to be very effective in this regard. However, real-time calculus has heretofore been limited to systems with uniprocessor processing elements, which is a serious impediment given the advent of multicore technologies. In this paper, a two-step approach is proposed that allows the power of real-time calculus to be applied in globally-scheduled multiprocessor systems: first, assuming that job response-time bounds are given, determine whether these bounds are met; second, using these bounds, determine the resulting residual processor supply and streams of job completion events using formalisms from real-time calculus. For this methodology to be applied in settings where response-time bounds are not specified, such bounds must be determined. Though this is an issue that warrants further investigation, a method is discussed for calculating such bounds that is applicable to a large family of fixed job-priority schedulers. The utility of the proposed analysis framework is demonstrated using a case study.
Over the last few years, real-time Calculus has been used extensively to model and analyze embedded systems processing continuous data/event streams. Towards this, bounds on the arrival process of streams and bounds o...
详细信息
Over the last few years, real-time Calculus has been used extensively to model and analyze embedded systems processing continuous data/event streams. Towards this, bounds on the arrival process of streams and bounds on the processing capacity of resources serve as inputs to the model, which are used to calculate end-to-end delays suffered by streams, maximum backlog, utilization of resources, etc. This "functional'' model, although amenable to computationally inexpensive analysis methods, has limited modeling capability. In particular, "state-based'' processing, e.g. blocking write - where the processing depends on the "state'' or fill-level of the buffer - cannot be modeled in a straightforward manner. This has led to a number of recent proposals on using automata-theoretic models for stream processing systems (e.g. Event Count Automata [RTSS 2005]). Although such models offer better modeling flexibility, they suffer from the usual state-space explosion problem. In this paper we show that a number of complex state-dependencies can be modeled in a lightweight manner, using a feedback control technique. This avoids explicit state modeling, and hence the state-space explosion problem. Our proposed modeling and analysis therefore extend the original real-time Calculus-based functional modeling in a very useful way, and cover much larger problem domain compared to what was previously possible without explicit state-modeling. We illustrate its utility through two case studies and also compare our analysis results with those obtained from detailed system simulations (which are significantly more time consuming).
It is now widely believed that FlexRay will emerge as predominant protocol for in-vehicle automotive communication systems. As a result, there has been a lot of recent interest in timing and predictability analysis te...
详细信息
It is now widely believed that FlexRay will emerge as predominant protocol for in-vehicle automotive communication systems. As a result, there has been a lot of recent interest in timing and predictability analysis techniques that are specifically targeted towards FlexRay based electronic control units (ECU) networks. In this work, the DECOMSYS tool is used for mapping the tasks on different ECUs, configuring the scheduling policy used at each ECU, and specifying the FlexRay parameters (e.g. slot sizes and message priorities). The overall system requirements are simulated by flashing such FlexRay based ECU network specifications into the DECOMSYS node. The design tools such as DECOMSYS mostly rely on simulations. As a result, they are time-consuming to use and unable to provide formal performance guarantees, which are important in the automotive domain. In our previous works, we have proposed a real-time Calculus (RTC) based compositional performance analysis framework for an ECU network that communicates via FlexRay bus. The RTC based framework allows computation of performance analysis parameters such as the maximum end-to-end delay experienced by any message, the amount of buffer required at each communication controller and the utilization of the different ECUs and the bus. In this paper, we have plugged in the RTC based framework into the DECOMSYS tool. The combined setup consisting of DECMSYS and RTC based framework can be utilized to obtain hard performance guarantees, which can then be cross-validated using simulation.
This paper examines the capturability of a guidance law that provides a desired angular acceleration of the heading angle to a pursuer. The guidance law has originally been proposed by Fajen and Warren[13], in order t...
详细信息
This paper reports on AnnieWAY, an autonomous vehicle that is capable of driving through urban scenarios and that has successfully entered the finals of the 2007 DARPA Urban Challenge competition. After describing the...
详细信息
Web portals are currently an important means to access Internet information. The use of Web portals permits a vast amount of data to be obtained rapidly. However, the quality of the data recovered by the user is funda...
详细信息
Web portals are currently an important means to access Internet information. The use of Web portals permits a vast amount of data to be obtained rapidly. However, the quality of the data recovered by the user is fundamental. We therefore propose a thesis in which a model, denominated as SPDQM (SQuaRE Portal Data Quality Model) will be defined. The proposed model will be based on a previous model, PDQM (Portal Data Quality Model) and the SQuaRE (Software product Quality Requirements and Evaluation) standard. Finally, upon the model's completion, an automatic tool with which to asses the data quality (DQ) in Web portals will be developed.
This paper addresses the problem of steering a quadrotor vehicle along a predefined *** problem is formulated so as to dynamically prescribe an adequate time evolution along the path and simultaneously bound the effec...
详细信息
This paper addresses the problem of steering a quadrotor vehicle along a predefined *** problem is formulated so as to dynamically prescribe an adequate time evolution along the path and simultaneously bound the effect of position errors on the *** proposed solution consists of a nonlinear state feedback controller for thrust and torque actuations combined with a path following timing law that i)guarantees global asymptotic convergence of the path following error to zero,for a large class of three-dimensional paths,ii) ensures that the actuation does not grow unbounded as function of the position errors,and iii) allows for zero thrust actuation to be applied when the vehicle is converging to the *** results are presented to assess the performance of the proposed controller.
Nowadays, Web portals serve as an important means to access information. It is common for users to use information obtained from the web to carry out their daily tasks. These users need to ensure that this information...
详细信息
ISBN:
(纸本)9789896740092
Nowadays, Web portals serve as an important means to access information. It is common for users to use information obtained from the web to carry out their daily tasks. These users need to ensure that this information suits their needs. PDQM (Portal Data Quality Model) is a model that assesses the quality of portal data. PDQM has been defined in such a way that every time that one wishes to evaluate a different portal context, a specific configuration of the model must be used. In an attempt to go beyond this limitation and with the idea of making PDQM a more generic model, we have adjusted it to be applied to vortals, the largest category of portals. This article describes the first phase of adapting PDQM.
暂无评论