| 1. |
- Andersson, Martin, et al.
(författare)
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Co-simulation of Mobile Wireless Networked Embedded Systems in Physical Environments
- 2005
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Ingår i: RTiS 2005 – Proceedings of Real Time in Sweden 2005, the 8th Biennial SNART Conference on Real-Time Systems (Skövde University Studies in Informatics). - 1653-2325. - 9163173492 ; 2005:1
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Konferensbidrag (refereegranskat)abstract
- Embedded systems are becoming increasingly networked and aredeployed in application areas that require close interaction withtheir physical environment. Examples include distributed mobileagents and wireless sensor/actuator networks. The complexity ofthese applications make co-simulation a necessary tool during systemdevelopment. This paper presents a simulation environment thatfacilitates simulation of computer nodes and communication networksinteracting with the continuous-time dynamics of the real world.Features of the simulator include interrupthandling, task scheduling, wired and wireless communication, localclocks, dynamic voltage scaling, and battery-driven operation.Two simulation case studies are presented: a simple communicationscenario and a mobile robot soccer game.
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| 2. |
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| 3. |
- Andersson, Martin, et al.
(författare)
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Simulation of Wireless Networked Control Systems
- 2005
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Ingår i: Proceedings of the 44th IEEE Conference on Decision and Control and the 2005 European Control Conference. - 0780395689 ; , s. 476-481
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Konferensbidrag (refereegranskat)abstract
- Embedded systems are becoming increasingly networked and are deployed in application areas that require close interaction with their physical environment. Examples include distributed mobile agents and wireless sensor/actuator networks. The complexity of these applications make co-simulation a necessary tool during system development. This paper presents a simulation environment that facilitates simulation of computer nodes and communication networks interacting with the continuous-time dynamics of the real world. Features of the simulator include interrupt handling, task scheduling, wired and wireless communication, local clocks, dynamic voltage scaling, and battery-driven operation. Two simulation case studies are presented: a simple communication scenario and a mobile robot soccer game.
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| 4. |
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| 5. |
- Bini, Enrico, et al.
(författare)
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Delay-Aware Period Assignment in Control Systems
- 2008
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of optimal static period assignment for multiple independent control tasks executing on the same CPU. Previous works have assumed that the control performance can be expressed as a function of the sampling rate only. Arguing that the control delay has a large impact on the control performance, in this work we include the control delay in the cost function. The delay is estimated using an approximate response-time analysis. Assuming linear cost functions for the controllers then allows us to solve the optimal period assignment problem analytically. The performance improvements over previous methods are verified in evaluations on synthetic task sets as well as detailed co-simulations of the controllers, the plants, and the scheduler.
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| 6. |
- Buttazzo, Giorgio, et al.
(författare)
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Comparative Assessment and Evaluation of Jitter Control Methods
- 2007
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Konferensbidrag (refereegranskat)abstract
- Most control systems involve the execution of periodic activities, which are automatically activated by the operating system at the specified rates. When the application consists of many concurrent tasks, each control activity may experience delay and jitter, which depend on several factors, including the scheduling algorithm running in the kernel, the overall workload, the task parameters, and the task interactions. If not properly taken into account, delays and jitter may degrade the performance of the system and even jeopardize its stability. In this paper, we evaluate three methodologies for reducing the jitter in control tasks: the first one consists of forcing the execution of inputs and outputs at the period boundaries, so trading jitter with delay; the second method reduces jitter and delay by assigning tasks shorter deadlines; whereas, the third method relies on non preemptive execution. We compare these techniques by illustrating examples, pointing out advantages and disadvantages, and evaluating their effects in control applications by simulation. It is found that the deadline advancement method gives the better control performance for most configurations.
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| 7. |
- Castañé, Rosa, et al.
(författare)
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Resource Management for Control Tasks Based on the Transient Dynamics of Closed-Loop Systems
- 2006
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Konferensbidrag (refereegranskat)abstract
- This paper presents a resource management strategy for control tasks that maximizes control performance within the available resources by readjusting the task periods at run-time. A feedback scheduler is used to determine on-line the optimal task periods considering the response over a finite time horizon of the plants controlled by arbitrary linear control laws. We show how this problem can be expressed as an optimization problem, where the objective function relates the sampling periods to the transient responses of the controlled plants, and where restrictions are based on EDF schedulability constraints. For the general case, the solution of the optimization problem is computationally expensive, and thus, an approximate procedure to be executed on-line has been developed. We present simulation results that validate the presented approach.
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| 8. |
- Cervin, Anton, et al.
(författare)
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Analysis of Overrun Strategies in Periodic Control Tasks
- 2005
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Ingår i: Proceedings of the 16th IFAC World Congress. - 008045108X
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Konferensbidrag (refereegranskat)abstract
- The paper considers period overruns in control tasks with variationsin execution time (or response time). A simple model is used, wherethe input and output operations are assumed to be time-triggered,and the execution-time distribution of the task is assumed to beknown. Three overrun strategies, called Abort, Skip, andQueue, are modeled as discrete-time jump linear systems and areanalyzed with regard to control performance. The analysis isexemplified on an integrator process. It is argued that the Skipstrategy has good performance, is easy to analyze, and is simple toimplement in real-time operating systems. Some extensions to moredynamic models are also given.
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| 9. |
- Cervin, Anton, et al.
(författare)
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Control loop timing analysis using TrueTime and Jitterbug
- 2006
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Ingår i: 2006 IEEE Conference on Computer Aided Control System Design, 2006 IEEE International Conference on Control Applications, 2006 IEEE International Symposium on Intelligent Control. - 0780397975 ; , s. 290-295
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Konferensbidrag (refereegranskat)abstract
- A modern control system is typically implemented as a multitasking software application executing in a real-time operating system. If the computer load is high, the controller will experience delays and jitter, which in turn degrade the control performance. Arguing for an integrated design approach, the paper describes two computer tools for implementation-aware control analysis: TrueTime and Jitterbug. An example is given where the tools are used together to evaluate the performance of various control task implementations
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| 10. |
- Cervin, Anton, et al.
(författare)
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Control-Scheduling Codesign of Real-Time Systems: The Control Server Approach
- 2005
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Ingår i: Journal of Embedded Computing. - 1740-4460. ; 1:2, s. 209-224
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the control server, a real-time schedulingmechanism tailored to control and signal processing applications. Acontrol server creates the abstraction of a control task with aspecified period and a fixed input-output latency shorter than theperiod. Individual tasks can be combined into more complexcomponents without loss of their individual guaranteed fixed-latencyproperties. I/O occurs at fixed predefined points in time, at whichinputs are read or controller outputs become visible. The controlserver model is especially suited for codesign of real-time controlsystems. The single parameter linking the scheduling design and thecontroller design is the task utilization factor. The proposedserver is an extension of the constant bandwidth server, which isbased on the earliest-deadline-first scheduling algorithm. Theserver has been implemented in a real-time kernel and has also beenvalidated in control experiments on a ball and beam process.
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