Manu S Ravindra, Colorado State University

AN AUTOMOTIVE SURVEY

AUTOMOTIVE ELECTRONICS• What is it ?

Kommandogerat – BMW 801 Radial engine series Radial engine

CONTEMPORARY ECU TRENDS• Around 80 to 100 in a an automobile

ENGINE CONTROL UNIT• A typical modern example

STEER-BY-WIRE (SBW) SYSTEMS – AN EXAMPLE• Power steering

COMMUNICATION BETWEEN ECU’S• Standard communication protocols are used.

CAN (Controller Area Network)

LIN (Local Interconnect Network)

MOST (Media Oriented Systems Transport) are a few examples.

FLEXRAY – THE FUTURE• A hybrid protocol

Time Triggered (TT) messages and Event Triggered (ET) messages

• Consists of two segments – Static segment (ST) and Dynamic segment (DYN)

• Uses TDMA for communication (Time Division Multiple Access)

SYSTEM MODEL• N1, N2 and N3 are nodes.

• Controller Host Interface (CHI)

• CPU

SYSTEM ARCHITECTURE• Implemented by two schedulers.

• Static Cyclic Scheduler

--- non-preempt tasks.

--- start time is decided at the design time or “off-line”.

• Fixed Priority Scheduler

--- preempt tasks.

--- scheduled based priorities.

A SCHEDULING EXAMPLE• Τ1 and T6 are SCS scheduled tasks.

• The rest of the tasks are FPS tasks.

A TYPICAL FLEX-FRAME

THE PROTOCOL• Communication occurs in periodic cycles

• Each cycle consists of two intervals – ST and DYN intervals

• ST and DYN segment lengths can be different but are fixed over the cycles.

• Symbol Window and a network idle timer.

• Frame Identifier

PAYLOAD SEGMENT• Slot counters – Static and Dynamic

• Dynamic mini-slot counters

• Node with frame identifier equal to the current slot counter is allowed to communicate.

CLOCK SYNCHRONIZATION• Backbone of FlexRay operation.

• Clock system in a distributed system would be subject to “clock-drift”.

• Clock drift is an inevitable inherent delay in the arrival of clock from one point to another.

• But a global clock reference is needed to keep track of time.

• FlexRay uses ‘micro-ticks” and “macro-ticks”.

• “Cluster time” is used as a reference of global clock.

NODE CLOCK CORRECTION• Measure clock delay.

• Determine clock correction term.

• Apply clock correction term (clock rate correction/clock state correction/both).

AN OVERVIEW OF THE EVOLUTION

WHY FLEXRAY ? FAULT TOLERANCE• Topological Flexibility.

• Synchronous Clock.

• Conceptual separation.

MODERN ELECTRONIC CONTROL UNITS• Energy was considered to be “freely available” until now.

• Energy consumption is directly related to CO2 emmission of the vehicle.

E/E Architecture

- Partial networking.

- AUTOSAR.

AUTOSAR (AUTOMOTIVE OPEN SYSTEM ARCHITECTURE)• An awesome group of companies working towards delivering the best on production lines

to the world!

• Similar to the SAE (Society of Automotive Engineers) – Another awesome group. The biggest!

POWER AND ENERGY EFFICIENCY Optimize energy consumption of electronic components.

Use of networking policies to save power and energy policies. (Communication Energy)

COMMUNICATION ENERGY• Sub-networking.

• A “sleep” and “wake-up” object.

CAN – CONTROLLER AREA NETWORK• CSMA – Carrier Sense Multiple Access

• Speeds up to 1 Mbps are achievable.

• Bus topology.

• Nothing specific in the protocol to put a node to sleep / turn-off.

• A “sleeping” node “wakes up” if there is any activity on the bus.

• CAN sleep object is a random sleep object.

FLEXRAY • TDMA – Time Division Multiple Access.

• Speeds up to 10 Mbps are achievable.

• Sleep object same as CAN.

• Wake up is performed by sending out a specific symbol.

LIN – LOCAL INTERCONNECT NETWORK• Connects sensors and actuators.

• One wire communication protocol.

• Speeds up to 20kbps.

• Master slave network is employed. One way communication. One master controls one or more slaves. Therefore there is no need for conflict avoidance / collision.

MULTI-CORE MCU’S• Homogeneous and Heterogeneous multi-core MCU’s.

• Multicore benefits.

- Code segregation

- Redundancy

- Monitoring

- Dedicated use of cores

• Non-volatile Memory

THANK YOU