Paper Info
Title
Rhythmic Tasks: A New Task Model with Continually Varying Periods for Cyber-Physical Systems
Abstract
Traditional mechanical subsystems in automobiles are being replaced by electronically controlled systems, often with no mechanical backup. This trend towards \"drive-by-wire\" systems is becoming increasingly popular. In these cyber-physical systems, a critical task not meeting its timing deadline can lead to a safety violation and damage to life and/or property. Classical real-time scheduling techniques such as RMS and EDF can be used to guarantee the schedulability of periodic tasks. However, certain critical tasks like the engine control task are activated by engine events such as pulses generated by sensors at the engine crankshaft. The periods of these engine tasks vary continually and even dramatically depending on the engine speed. The conventional periodic task model is inadequate for handling such tasks in cyber-physical systems due to its pessimism when combined with common schedulability analyses. In this paper, we define a new task model called Rhythmic Tasks for tasks having periods that vary due to external physical events. To the best of our knowledge, this is the first model that considers continually varying periods for fixed-priority scheduling in dynamic operating environments. We formally define the rhythmic task model and study its scheduling properties. In the context of rhythmic engine control tasks, we offer schedulability tests for determining the maximum possible utilization under the steady state, which is related to the physical engine speed. We also investigate the range of possible engine acceleration and deceleration rates. We show that excessive acceleration and deceleration can make the system unschedulable. We provide algorithms to find the appropriate ranges for acceleration and deceleration rates. We use a specific case study of engine control to illustrate our analysis.
Year
DOI
Venue
2012
10.1109/ICCPS.2012.14
ICCPS
Keywords
Field
DocType
continually varying periods,cyber-physical system,cyber-physical systems,physical engine speed,engine control,rhythmic tasks,engine crankshaft,engine event,engine control task,new task model,engine task,deceleration rate,possible engine acceleration,engine speed,real time systems,steady state,embedded system,sensors,embedded systems,scheduling,cyber physical systems,engines,engine,real time,rms,acceleration,cyber physical
Crankshaft,Computer science,Scheduling (computing),Real-time computing,Cyber-physical system,Acceleration,Rhythm,Backup
Conference
ISSN
Citations 
PageRank 
2375-8317
36
1.31
References 
Authors
15
3
Name
Order
Citations
PageRank
Junsung Kim124316.69
Karthik Lakshmanan273231.22
Ragunathan (Raj) Rajkumar32868183.27