Computer-aided Architecture Design and Optimized Implementation of Distributed Automotive EE Systems Ajay Kumar, Antal Rajnak Automotive Programs System Level Engineering Division June 06, 2007 DAC 07, Paper 31.4

Presentation Outline Problem statement Basic AUTOSAR concepts Proposed Tool Flow Experience thus far Suggested improvements / future work Summary

Current Design Environment Manual process with inadequate tool support Insufficient data to support early decision making, leading to early binding and late verification. ECU-focused rather than system-level Validation on physical prototypes Distributed, multi-company, modular supply chain Few if any widely-accepted standards The resulting architectures are seldom optimal in terms of:  Performance  Flexibility / Scalability  Reliability  Life-cycle Cost

Industry trends Increasing use of model-based function development  20-25% of all EE functions covered today Used for: Functional verification Executable specification OEM -> Tier1 Major standardization effort - AUTOSAR  Version 2.1 of specs released – matured  Use gaining momentum in Europe  US and Japan watching closely Step towards development and validation in a virtual environment, using Systems Engineering principles

Basic AUTOSAR concepts AUTomotive Open System ARchitecture Layered software architecture, with clearly defined interfaces Applications implemented as atomic or composed Software Components (SWC) Virtual Function Bus (VFB) – abstraction of all interconnected SWCs, communicating exclusively through ports independent of underlying hardware Run Time Environment (RTE) – implementation of the VFB on a particular ECU Basic Software (BSW) – implementation of the AUTOSAR infrastructure (nearly 40 different modules)

AUTOSAR ECU sw structure source:

Basic AUTOSAR concepts (Cont.) AUTOSAR systems are described by a set of XML based Description Files  Derived from a defined UML metamodel What’s described: ECUs, SWCs, their mapping to ECUs, ECU interconnections etc. What’s missing: Methodology to create these description files

The Implementation Abyss Model based function design – a widely accepted, and used technique AUTOSAR – brings new level of abstraction to function implementers But… The task to translate a model based design into a robust, and efficient system, in a highly distributed environment remains a challenge. How to bridge the implementation abyss?

Proposed SLD methodology Architecture Design  Topology definition  SWC to ECU Vehicle function creation  mapping  VFB-level simulation  Bus scheduling  Initial ECU Scheduling  Metrics generation ECU configuration  Runnables to task mapping  OS task scheduling  Configuration of remaining BSW modules

Proposed System Level Tool Chain Implemented as a set of well connected point-tools. Vehicle System Architect – for the OEMs  Function Editor  Topology Editor  Function Mapper  VFB-level Simulator  Network Cluster Builder  ECU Scheduler  Harness Design Tool (Capital Harness®)  Metrics Generator Vehicle System Builder – for the Tier 1s

Proposed Tool Flow Vehicle Features Vehicle Function Editor Vehicle Topology Editor & Vehicle Function Mapper VFB level simulator Network Cluster Builder & ECU scheduler Wiring Harness Design Tool Metrics Generator Optimized Vehicle Architecture Description

Tool Implementation Challenges Support for concept evaluation for EE-systems in early phases of the design process, when the available level of detail is minimal Connectivity to legacy OEM environments Scalable tool functionality, depending on OEM preferences  Manual / Interactive use mode  Analysis  Synthesis – requirements based design

Vehicle Function Editor Users create atomic or composed SWCs representing vehicle functions Method:  Manual graphical entry  Import from function modeling tools (e.g. Matlab/Simulink) “Envelope” of function is adequate Interface consistency is checked

Vehicle Topology Editor Instantiation of basic elements of the physical architecture (ECU-s, sensors, actuators, buses etc.) Allows creation of “soft” (only partially defined) components in the early phases of design. Import:  Individual components  Pre-existing message matrix  Pre-existing topology Graphically arrange components to form desired physical architecture.

Topology editing & Function mapping Network Generation Topology Import / Creation Functions and SWCs Physical Architecture Extend network Add new ECUs Logical Architecture Connect functions Add new functions Mapped System Architecture Map functions

Vehicle Function Mapper Function: Mapping of vehicle functions to logical ECUs Check of resource demand vs. availability Soft ECUs allocated to real ECUs from library Split of end to end timing requirements btw ECUs and buses Automatic gateway configuration Output: System Configuration Description file ECU extract of SCD Export to Harness design tool

VFB-level Simulation VFB-level view: network of SWCs connected through ports This network can be simulated  Appropriately compiled SWCs with behavior required Verify desired functionality across single, as well as multiple ECUs

Network Scheduling – the Cluster Builder Basic Functionality: Produces schedule tables Creation/modification of frames (PDU-s) and related parameters (ID, period time, x-fer mode etc.) Interactive signal packing and editing of schedule tables Cluster schedulability analysis Expanded functionality: Automatic frame compilers (AFC-s) for CAN/LIN/FlexRay Fully automatic scheduling and frame packing

ECU Scheduler Runnables to tasks mapping Manual configuration and schedulability analysis based on available timing information Configuration of OS and BSW schedulers Tightly coupled to network scheduling.

Unified Timing Model SENSOR SWCBSWBSW BUSBUS BSW GATEWAY BUSBUS BSWBSW APPLICATION SWC BSWBSW BUSBUS BSWBSW ACTUATOR SWC ACTU- ATOR SEN- SOR BSWBSW BSWBSW PUBLISHER LATENCY SUBSCRIBER LATENCY SWC PROP. DELAY GW DELAY BUS PROP. DELAY SENSOR SWCAPPLICATION SWC ACTUATOR SWC Termin- ator Termi- nator MAX. AGE LEVEL 1: VEHICLE FUNCTION LEVEL (AUTOSAR VFB VIEW) LEVEL 2: VEHICLE ARCHITECTURE LEVEL

Metrics generation Compares and ranks a set of alternative architectural solutions in relative terms Component cost is only one aspect - scalability, flexibility and extensibility will heavily influence the results. Scenario based sensitivity analysis is essential to identify decision points Simplified analysis running in the background provides ”live” feedback to user

Vehicle System Builder Function: Create/edit all AUTOSAR-related configuration files Intelligently merge partial configuration files from multiple sources Generate a downloadable binary image of the complete software (Apps+BSW+Config) for the selected ECU.

Vehicle System Builder System File Vehicle System Architect ECU Extract of System File SWC Descript. File Partial ECU Config. File Vehicle System Builder Complete ECU Config. File Compiler/ Linker BSW Config. Generator RTE Generator ECU Binary Image RTE Glue Code Application Software BSW Config. Data BSW Library SWC creation Topology definition SWC to ECU mapping Bus scheduling Initial ECU Scheduling Runnables to task mapping OS task scheduling Config of remaining BSW modules

Correctness by Design Vision: Requirements based Systems Engineering Process Holistic, top-down approach, supported by well connected high-level tools. Development and validation in a virtual environment Values:  Reduced cost  Shortened lead-times  Improved Reliability & Quality

Experience thus far Tool-set for requirements based synthesis of complex CAN and LIN networks and gateways successfully deployed and used in production since 1998 (Volcano Network Architect tool). Users are enthusiastic! But... Timing analysis is not widely used in current automotive design flows.

Suggested improvements / future work Enhanced AUTOSAR Timing Model – to cover important concepts, i.e. jitter, phasing, or precedence required to deal with complex systems Coordinated AUTOSAR Metamodel extensions Evaluation metrics refinement  Define objective metrics and evaluation algorithms to judge: Scalability Flexibility

Summary Bridging the implementation abyss between model based function design and creation of efficient AUTOSAR implementations calls for new methods, and advanced tool support. Challenges:  Usability in early project phases, when only limited amount of data is available  Need to support a flexible set of usage models: (interactive, analytic or full synthesis) The required technology is readily available The AUTOSAR Timing model needs major re-work

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