Steer-by-Wire over real-time Ethernet: A TTEthernet based...
Transcript of Steer-by-Wire over real-time Ethernet: A TTEthernet based...
Steer-by-Wire over real-time Ethernet:A TTEthernet based safety-critical Application
CoRE Working Group
Department Informatik, Hamburg University of Applied Sciences
AbstractReal-time (RT) Ethernet is a new, scalable approachto reduce the complexity of in-vehicle networkssignificantly and therefore is a viable candidate forfuture automotive communication. To prove thecapabilities of such a network a real-time Ether-net prototype platform was built, to achieve timingand bandwidth characteristics of typical automo-tive applications. The use-case shows a steer-by-wire application which fulfils the challenging real-time demands of control processes.
Motivation•Using typical hardware for automotive domains
•Achieving timing requirements of in-car com-munication
•Fulfilling demands of real-time capable controlprocesses
ArchitectureSynchronization
•Sub-modules for reception and transmission ofsynchronization frames respectively are provided
•Client functionality provided by receive-moduleonly, whereas masters activate transmission too
•Fault tolerance capable through dynamic down-and upgrading
Scheduler
•Handling time-triggered events, as well as exter-nal events, demands a hybrid design
•Advanced interrupt driven approach through hi-erarchical order of possible tasks
•Preemptive scheduling supports immediate exe-cution of crucial events
Buffer
•Support for multiple buffer types to fulfil differ-ent demands
•Mapping to RT Ethernet buffer structure preventsexpensive memory operations
•Dedicated buffer reduces complexity of algorithmin runtime toO(1)
Fig. 1: Architecture of a TTEthernet platform
Bridge•Tunneling of CAN messages over TT Ethernet
•Connect CAN busses over common network
•Offers VirtualCAN interface for applications
Platform•Based on high integrated system-on-chip
•ARM 9 clocked with 200 MHz
•Four configurable communication channels
•Supports various communication technologies
•Data switching architecture replaces AMBA
•Time base with adjustable resolution of2−28 ns
Network Topology
Steer
CAN-Bus
Bridge
Controller
RT EthernetSwitch 1
CANopen-Bus
Wheel Force sensor
Bridge
RT EthernetSwitch 2
Fig. 2: Network topology of demonstrator
Scheduling
Motor
Force sensor
Bridge Wheel
Zeit µs
100 200 800700300 600500400 900 1000
Real-time Ethernet SYNC Phase
1100 1200 1300 1400 1500
0x252
1600
Controller
Steer
Switch 1
Bridge Steer0x200
0x2100x201
0x211
0x20A
0x21A
1700 1800 1900 2000
Switch 2
0x80 0x1820x183
Fig. 3: Scheduling of time-triggered communication
Controller•Generates CAN messages for communication with
sensors and actors
•Realizes force feedback for driving response
•Sport and cruise mode by demand
• Interface for custom adjustment of parameters
Results• Jitter of schedules<300 ns
•Oscillation behaviour at start-up
•Oscillation ends after runtime<2 s
•Controller delay time 930µs
Fig. 4: Measurement results of jitter and oscilla-tion behaviour at start-up
References[1] K. Muller, T. Steinbach, F. Korf, and T. C. Schmidt, “A Real-time
Ethernet Prototype Platform for Automotive Applications,” in Pro-ceedings of the 1st IEEE International Conference on ConsumerElectronics - Berlin (ICCE-Berlin), 2011, to appear.
[2] J. Kamieth, “Entwurf einer Mikrocontroller basierten Bridge zurKopplung von CAN Bussen ber Time-Triggered Realtime Ethernet,”Aug. 2011, Bachelorthesis.
[3] K. Muller, “Time-Triggered Ethernet fur eingebettete Systeme:Design, Umsetzung und Validierung einer echtzeitfahigenNetzwerkstack-Architektur,” Aug. 2011, Bachelorthesis.
[4] V. Stepanov, “Mikrocontroller und CAN-basierte verteilteRegelungeiner Steer-by-Wire Lenkung mit harten Echtzeitanforderungen,”Aug. 2011, Bachelorthesis.
Contact information: Franz Korf, Thomas C. Schmidt, Till Steinbach, Florian Bartols, Kai Muller, Vitalij Stepanov, Friedrich Groß: HAW Hamburg, Dept. Informatik, Berliner Tor 7, D-20099 Hamburg
Email: {korf, schmidt,till.steinbach, florian.bartols, kai.mueller, vitalij.stepanov, friedrich.gross}@informatik.haw-hamburg.de