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7/23/2019 EE_exam

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ELECTRIC AND ELECTRONIC SYSTEM IN VEHICLES

- topics -

Crovetti

1. Electric systems in vehicles• The alternator

• Conversion of mechanical power into electrical power

• Practical alternator issues

• Lundell alternator

• Open circuit voltage

• The rectifier

• Diode

• single-phase single-halfwave rectifier

• single-phase two-halfwave rectifier• three-phase single-halfwave rectifier

• three-phase two-halfwave rectifier

• The voltage regulator

• closed-loop alternator performances

• The electrical energy accumulator

• batteries for vehicles

• Starter motor

• operating principle

• dc-motor electromechanical model

• cd-motor mechanical characteristics

• thermal engine cranking• thermal engine starter motor

• electric system requirement at cranking

2. Electric balance in a vehicle• Parking

• Cranking

• Running vehicle

• Battery charge energy balance

• Running vehicle engine balance and alternator

3. Cable• Electrical cable sizing

• breakdown voltage

• maximum operating temperature

• chemical agent resistance

• voltage drop

• power loss

• conductor self-heating

• heat propagation

• cable sizing

• protections

• overcurrent protections

• overvoltage protections• overtemperature protections

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4. Switches• Real switch performances

• Switch types

• mechanical switch

• electromechanical switch

• electronic switch

•mos transistor

• switch configurations

5. Electrical and electronic systems for powertrain• Electric and hybrid powertrain

• electric vehicles

• hybrid vehicles

• series HEV

• parallel HEV

• plugged HEV

• electric energy storage elements

• nominal voltage

• capacity• energy

• maximum power

• power

• maximum recharge time

• cost

• cycle life

• electric machines

• EM vs. ICE

• torque

• minimum RPM

•gearbox

• regeneration

6. Voltage regulators• power efficiency

• output impedance

• RRC

• TDC

• linear voltage regulator circuit

• switching mode voltage regulators

• switching mode power conversion principle

• Buck converter

• CCM operation• DCM operation

• Boost converter

• CCM operation

• DCM operation

• Buck-boost converter

• CCM operation

• DCM operation

• Closed-loop switching mode voltage regulator

7. Actuators and drivers• classification of actuators in vehicles

• linear loads

• non linear loads

• resistive loads

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• inductive loads

• capacitive loads

• resistive load drivers

• PWM driving techniques

• solenoid linear actuators

• operation principle

• driving

• electric motor drivers

• DC motor equivalent circuit

• simple motor driver

• half bridge driver

• full bridge driver

8. ECU design flow• model and model validation

• control algorithm development

• ECU design

• hardware flow

• software flow• ECU test and validation

9. ABS and ESP• Antilock braking system

• braking dynamics

• ABS structure and operation

• Electronic stability program

• ESP control operation

• ESP sensors and actuators

• acceleration sensors

• yaw rate sensor

10. Electromagnetic compatibility• Emissions and susceptibility

• Conducted EMC issues

• EMC oriented design

• current loop decoupling

• decoupling capacitors

• Radiated EMC issues

• EMC oriented design

• shielding

• twisted cables

• EMC issues

11. Gasoline engine control• Gasoline engine control targets

• Operating modes• cranking

• warm up

• open loop A/F control

• closed loop A/F control

• hard acceleration

• deceleration

• idle

• Sensors• EPS and RPM sensors

• optical sensors

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• magnetic reluctance sensors

• hall effect sensors

• magnetoresistive sensors

• Temperature sensors

• resistive temperature sensors

• thermocouples

•semiconductor-based temperature sensors

• Mass air-flow sensors

• Linear angular position sensors

• potentiometric position sensors

• inductive position sensors

• Exhaust oxygen concentration sensor

• Differential pressure sensor

• Gasoline engine control actuators

• fuel injectors

• ignition system

• A/F ratio control

• open loop A/F ratio control

• closed loop A/F ratio control• proportional control

• integral control

• proportional-integral control

Carena• Signal characterisation

• auto correlation

• Fourier transform

• power

• energy

• finite energy of a signal• finite average power

• Random processes

• WSS

• Amplitude modulation

• convolution theorem

• frequency division multiplexing

• Transmission channel

• block scheme

• Loss

• Transfer function

• pulse response

• finite energy signals• finite average power and random signals

• Filtering effect

• Noise

• central limit theorem

• white and gaussian

• baseband

• bandpass

• Sampling

• Nyquist-Shannon sampling theorem

• levels

• quatizing error• Rb

• BSC

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• Digital modulation

Leonardi• Communication networks

• network functions

•transmission, switching, management

• applications

• real time, quasi real time, no real time

• switching

• circuit

• packet

• PDU (PCI+SDU)

• contentions

• QoE, QoS

• layered architecture

• OSI

• Arpa, Internet

• protocols• semantic, sintax, timing

• layering

• SAP

• peer

• virtual circuit

• connection-oriented, datagram

• layers

• physical layer

• data-link layer

• MAC

• error detection and recovery• flow control

• PDU identification

• MAC

• centralized

• distributed

• random

• error correction

• forward

• ARQ

• CRC

• ACK

• timeout interval• buffer

• flow control

• loss less

• on/off

• thresholds in buffers: RTT*rate

• credit

• time to empty buffer > RTT

• time to empty buffer = buffer size / rate

• window protocol

• ACK both for error and flow control

• route W/RTT• network layer

• routing

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• congestion control

• billing

• connection oriented

• datagram

• routing:

• static/dynamic

•IP

• local/global

• hierarchical routing

• intra-AS

• inter-AS

• internet routing

• routing tables

• large, not possible sequential search

• ipv4, ipv6

• most/lin significant bits of IP

• intra-AS

• cost based

• link fail• congestion control (internet TCP)

• proactive

• reactive

• congestion collapse

• transport layer

• error control

• flow control

• sequence control

• TCP

• window protocol

• window size adapted to the rate• packets losses

• congestion info

• exponential increase

• additive increase

• packet lost

• 3 acks for packet loss determination

• different from fixed window protocols

• MAC

• shared medium

• dedicated link

• fixed-assignement circuit switching access schemes

• FDMA, TDMA, CDMA• Packet multiple access

• polling: centralized, bandwidth, delay

• token

• no master

• 1-way protocol propagation delay

• reservation and scheduling

• periods in which slaves can “book”, reserve a slot

• seldom employed in packet switching

• rough synchronisation needed

• random access

• aloha• packets sent without rules

• s-aloha

• station synchronised, the success percentage is doubled

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• CSMA (carrier sense multiple access)

• done on bus

• 1-persistent vs. 0-persistent

• 1 better low traffic

• 0 better high traffic

• propagation delay not null

•CSMA/CD

• more advances

• collision detection

• full duplex line

• arbitrated (CAN)

• conflicts: physiological

• WiFi

• CSMA/CA collision avoidance

• basic access or RTS/CTS

• arbitration

• bit level

• optic vs. copper

• LAN• IEEE 802.x

• .1 internetworking

• .2 logical link

• .3 medium access

• .4 physical

• .11 wifi

• data link layer: logical link + MAC

• MAC addresses

• unique NIC

• 3 most significant bit: manufacturer

• 3 least significant bit: NIC• unicast, multicast, broadcast

• multicast

• solicitation to advertisement

• packet reception

• normal

• CRC fail

• not my MAC address

• promiscuous

• accent all: dangerous

• IEEE 802.3

• 1-persistent: delays low, collisions detected

• frame format• preamble

• SFD

• MAC destination

• MAC source

• length < 1500

• pudding

• frame check

• inter packet gap > 12b

• collision domain

• hub vs. switch

• On vehicle networks• controls of engine: electronics

• real time

• limited length

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• CAN, LIN, Flex-ray, Most

• requirements:

• reliability

• passive elements

• cheap

• versatility

•reliability

• wire failure

• ECU failure

• non-safety applications

• durability

• vehicle life

• hostile environment (military devices)

• general purpose

• real time

• priority-based protocols

• real time protocols

• under utilisation of network

• uC• reduction of devices number

• low power CPU, same architecture

• long-life

• firmware: trade-off between complexity and efficiency

• CAN

• Bosch 1986

• 1 Mb/s

• passive bus

• copper cable

• 3 layers:

• LLC• MAC

• physical

• all elements connected to the same bus

• close network

• functions:

• LLC: acceptance filtering, overload notification, recovery management

• MAC: encapsulation, MAC, ACK

• physical: bit encoding/decoding, bit timing, synchronisation

• encoding: NRZ

• synchro: bit by bit

• timing

• bit period• Pd

• collision management

• arbitration: 0 dominant

• channel sensed at the same time of transmission

• high priority

• data frame structure

• SOF

• 1-dominant bit

• collisions: just if 2 stations start simultaneously

• arbitration

• standard• extended

• alarm to high priority

• RTR, RSR,…: identify the type of frame

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• data field

• samples of a signal

• less overload

• CRC field

• central bit, 15b max

• ACK field

•remote frame

• pull mode

• controller requesting data

• error frame

• 6 dominant bits

• overload frame

• 6 dominant bits

• reserving bus for 1-transmitter

• LIN

• very local

• 20 Kb/s

• low cost

• MAC protocol• master/slave

• master: ECU

• slaves: actuators and sensors

• N collisions

• access time

• Flex Ray

• dual channel bus

• dual channel single star

• rate: 10 Mb/s per channel —> 20 Mb/s

• deterministic protocol —> predictable delay

• faul tolerant• high cost

• MAC layer

• deterministic protocol

• synchronisation network

• equal cycles repeated over time

• static segment

• TDMA access

• at least one slot each station

• null packet if station doesn’t need to transmit

• dynamic segment

• mini-slots

• variable• extra-packets

• arbitration avoids collisions

• ruled by frame ID

• ID lower —> higher priority

• symbol window

• special symbols

• optional

• frame structure

• timing

• synchronisation madatory

• rate high• clock errors

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- exam questions -Crovetti• performance curve of the alternator, alternator/load scheme

• ECU and HIL test

• overvoltages

• fuel control systems in vehicles, how to control injection timing

• alternator voltage regulator

• lundell machine

• overcurrent

• RPM sensors

• buck converter

• sketch an ECU and describe how it works

• pressure sensor

• main advantages and disadvantages of electrical powertrains

• critical parameters for batteries

• boost converter

• linear solenoid actuator driving

• three-phase two-halfwave rectifier• mass flow sensor

• temperature sensors

• main parameters of power cables

• requirements of power electric plant and starter motor in different phases

• ignition for gasoline engines

• types of switches in a vehicle and parameters to classify, high and low side configurations

• hot wire sensor

Carena• autocorrelation

•signal characterisation: properties of signals, bandwidth of transmission through a cable inrelation to the length

• sharing the medium, TDM

• OSI model: physical layer

• how to transfer analog signals

• stochastic process

• ADC process, quantising and SNR

• modulation: formulas and computations of bandwidth requirements

• ADS process and performances

• microphones

• relation between BER and SNR, channel: model and quality

Leonardi• circuit switching vs. packet switching

• layers structure: communication among layers, main features of layers

• automatic request

• MAC: deterministic vs. random access protocols, what is the worst dealing with delays

• CAN: main properties, management of contents, what happens when we loose a content

• LAN routing: how to set the destination of packets

• on board networks: main features, differences with internet

• flow control issues in a network

• CAN vs. flex ray

• CSMA

• forward error correction and automatic request• impact of propagation delay on CSMA

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