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Component-Based Design of Embedded Control Systems



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Component Based Design of Embedded Control Systems Luca Dealfaro Chamberlain Fong Tom Henzinger Christopher Hylands John Koo Edward A Lee Jie Liu Xiaojun Liu Steve Neuendorffer Sonia Sachs Shankar Sastry Win Williams UC Berkeley Hierarchical Heterogeneous Modeling and Design A model of computation governs the interaction of components at each level of the hierarchy A submodel exposes a domain polymorphic interface that governs the inter domain semantics leader sensors controller bang bang actuators Acc Br Ba follower S PID 1 Ptolemy II Ptolemy II Java based network integrated Many domains implemented Multi domain modeling XML syntax for persistent data Block diagram GUI Extensible type system Code generator on the way http ptolemy eecs berkeley edu Domains Status Domains we understand well Dataflow Process networks CSP Discrete events Continuous time Synchronous reactive Finite state machines Our focus is particularly on how these domains support real time QOS Domains we are working on Publish subscribe Time triggered 2 Concept Demonstration Networked sensors and actuators Multiple networked controllers controllees Hierarchical heterogeneous design Domain polymorphic components Discovery Mutable systems Experimental Setup 1451 2 Ethernet Hub Telemonitor Agilent Tilt sensor NCAP 3 Networked Smart Sensors HTTP queries Ethernet Agilent NCAP HTTP interface 1451 2 Telemonitor Tilt sensor Abstraction of the Sensor as a Software Component Ethernet HTTP queries Agilent NCAP 1451 2 Telemonitor Tilt sensor 4 Smart Sensor Ptolemy II Tilt sensor connected to a plotter Issues Raised Concurrency management with I O Separate thread handles communication Rendezvous with computational thread How to maintain time consistency How to ensure no deadlock 5 Planned Discovery Hub Ethernet Register a Service Agilent JINI NCAP 1451 2 Telemonitor Tilt sensor Planned Discovery Hub Ethernet Agilent Discover a Service JINI NCAP 1451 2 Telemonitor Tilt sensor 6 Planned Discovery Hub Ethernet Download Interface Software Agilent JINI NCAP 1451 2 Telemonitor Tilt sensor Planned Discovery Hub Ethernet Agilent Communicate JINI NCAP 1451 2 Telemonitor Tilt sensor This would provide a vendorneutral software component 7 Actuator Setup Proxy serial port Lego Mindstorm IR tower Linking the Tilt Sensor and Actuators 8 Mutations Dynamic Structural Changes to the Model Thread safe Ptolemy II kernel Domains control when mutations are committed Mutual exclusion protocol in the Workspace object Mutations are queued with the Manager object Manager executes mutations between iterations Meaning of iteration is domain dependent In this example The event thread in the UI queues mutation requests The executing model commits the mutations at safe points Publish and Subscribe Use Jini to discover the publish subscribe fabric Our current realization returns a JavaSpaces interface Future realization will use OCP from Boeing Real time Prioritized delivery handling QOS is not part of JavaSpaces 9 Clock Publisher Subscriber Distributed Lego Controller Tilt sensor data published controller subscribes left 4 xTilt 2 yTilt right 4 xTilt 2 yTilt 10 Other Examples We Have Implemented Other Lego models Hybrid systems Modal controller for navigation Feedback of sensor data Car tracking example Helicopter multi modal controller Pioneer robot control Multi agent coordination Jini discovery of robots Publish and subscribe task distribution Styles of Publish and Subscribe Interactions time stamped events globally time stamped reliable delivery ordered delivery signal coordination synchronous delivery blending of multiple publishers dynamic redirection resourcing persistence history 11 A Key Idea We need a variety of interaction mechanisms In the prototype Jini delivers an interaction mechanism service by delivering code that realizes that interaction mechanism A meta OCP open control platform could similarly deliver any of several interaction mechanisms Example 1 Component says Meta OCP says I need a reliable stream based delivery mechanism to get sampled data from here to there OK here s some code for you and the recipient of your data Delivered code uses TCP IP and sockets bypassing any central infrastructure E g Transporting audio data 12 Example 2 Component says Meta OCP says I need a shared data repository visible to a number of components OK here s some code for you and the recipient of your data Delivered code interacts with a Linda style tuple space E g reading the current temperature from a sensor Example 3 Component says Meta OCP says I need to send time stamped data that must be delivered and dealt with within 3 msec OK here s some code for you and the recipient of your data Delivered code interacts with TAO E g deliver motion control data 13 Next Steps OCP integration Define publish and subscribe semantics Discovery of sensor actuator services Abstraction of sensor actuator services Real time QOS Time driven domain Giotto Multi robot coordination Improved UI particularly to help debugging The Demo Builders Chamberlain Fong Christopher Hylands Jie Liu Xiaojun Liu Steve Neuendorffer Sonia Sachs Win Williams 14


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