Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing) Why do we use multiplexing on cars?

Transcription

1 Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing) Why do we use multiplexing on cars?

2 EVOLUTION DU CABLAGE METRES (longueur de cablage) NOMBRE D INTERCONNEXIONS LA DIMINUTION DU VOLUME DU CABLAGE : ENJEU MAJEUR MCN001 After 1995, the target for car builders was to reduce the size of harness.

3 Définition : One way of communication ( the bus) is shared between several users ( the stations). In concrete terms : More simple harness. - réduce the cost, - réduce the volume of the harness, - réduce the number of connectors. Possibility to exchange data between all the ECU in the car. - increase driving pleasure, - reduce the number of sensors.

4 What is MULTIPLEXING? Station A Station C Station B The data exchange between all the stations in the car are sent on the bus in «numeric form».

5 THE BINARY NOTATION Data gives information coded in binary system, that means with 0 or 1. 0 or 1 is called «a bit». A group of 8 bits is called «a BYTE». It is possible to translate decimal numbers in binary code. example : 8 =>

6 THE BINARY NOTATION For example : O or 1 are corresponding to a certain level of voltage on a wire. « » : 8 Bits = 1 BYTE 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit «0» «1» «0» «1» «0» «1» «1» «0» «0» «1»

7 THE BINARY NOTATION DATA are converted in a series of BITS called «A FRAME» on the BUS.

8 On cars, the FRAME is transmitted in SERIAL MODE on the BUS. The serial transmission Station A BYTE to transmit: FRAME Station B

9 - THE BUS Station A Station B Station C Station D Station E The BUS The role of the bus is to allow the exchange of data between all the stations ( ECU in the car) Like that, the bus links all the ECU together.

10 - The wired bus. The bus is composed of 2 isolated copper wires ( small section ( 0,6mm²). For safety, the frame is driven by one wire and the opposite of the frame is driven by the other wire. The 2 wires of the bus are twisted ( to avoid electromagnetic problems)

11 For some applications, the bus is composed of : One wire only ( economic solution). Optical fiber ( high speed of transfer). Radio signal ( easy to fit)

12 - The multiplexing interface in each ECU connected to the bus : Inputs ECU Multiplexing interface ECU of the system Translator Sender BUS outputs Reads information Send orders Translates information from ECU to multiplexing language Emits or receive the frames.

13 The frames are sent one by one on the bus. The space between two frames is called «INTER FRAME SPACE»

14 - THE FRAME STRUCTURE The frame structure is defined by the communication procedure. DATA DATA bits = 5 bytes The frame is composed with several parts called «FIELDS»

15 THE FRAME Station A Station B Station C A1, A2,A3,A4;B1,B2,B3;C1,C2 Example of frame language ( with 7 fields) on the bus sof Ident. Com. data control ack eof SOF : start of frame (envelope) IDENT : identification (12 bits) (address) Com. : command field (4 bits) (recorded delivery DATA : information field (letter) Control : control field (15 bits) (signing) Ack : acknowledgement (recorded delivery response) EOF : end of frame

16 - The Frame. SOF IDENT. COM. DATA CTRL ACK. EOF Permits to inform the stations connected to the bus on the length of the following field ( data). Permits to synchronize The ECU clocks. Permits to fix the priority level and to identify the sender of the frame.

17 -The frame. SOF IDENT. COM. DATA CTRL ACK. EOF Permits the receptor to check if the frame has been received completely. The transmitter waits in this field for the response of the receptor ( to know if the frame has been correctly received). Indicates the end of the frame.

18 - THE PRIORITY LEVEL The bus can accept only one frame at a same time. So each frame is given by a priority level to avoid «bugs» 0 is DOMINANT 1 is RECESSIVE SOF Com. DATA station A CTRL Ack. EOF station A SOF Com. DATA station B CTRL Ack. EOF station B SOF Com. DATA station C CTRL Ack. EOF station C SOF Com. DATA station C CTRL Ack. EOF On the Bus

19 - priority level. Début Com. Informations de A Contrôle Ack. Fin Station A SOF Com. DATA station B CTRL Ack. EOF Station B SOF Com. DATA station C CTRL Ack. EOF Station C SOF Com. DATA station C CTRL Ack. EOF On the Bus

20 - priority level Début Com. Informations de A Contrôle Ack. Fin station A Début Com. Informations de B Contrôle Ack. Fin Station B Début Com. DATA station C CTRL Ack. EOF Station C Début Com. DATA station C CTRL Ack. EOF Station C has the highest priority level on the bus

21 A car is fitted with several different buses. (ECU with the same level of performance are grouped on the same bus). More performant. More reliable.

22 - EXCHANGE OF DATA ON THE SAME BUS Injection ECU Engine speed encoding Engine speed sensor INTERFACE BUS CAN I/S INTERFACE (x tops par tour) ABS wheel sensor 7800 ESP

23 Injection ECU Engine speed encoding Engine speed sensor INTERFACE BUS CAN I/S INTERFACE Codage de la vitesse ABS wheel sensor 7800 ESP

24 injection ECU Engine speed encoding - DATA is shared Engine speed sensor INTERFACE BUS CAN I/S INTERFACE Codage de la vitesse ABS wheel sensor 7800 ESP

25 Injection ECU Engine speed encoding Engine speed sensor INTERFACE BUS CAN I/S INTERFACE INTERFACE Codage de la vitesse ABS wheel sensor ESP 1630 BVA

26 injection ECU Engine speed encoding BSI Engine speed sensor INTERFACE INTERFACE BUS CAN I/S INTERFACE INTERFACE Codage de la vitesse ABS wheel sensor ESP 1630 automatic gear box

27 - EXCHANGE OF DATA ON TWO DIFFERENT BUSES. (BSI is a bridge between the buses) Engine ECU Engine speed encoding BSI Engine speed sensor INTERFACE INTERFACE INTERFACE BUS CAN I/S INTERFACE INTERFACE INTERFACE Codage de la vitesse ABS wheel sensor 7800 ESP 1630 Automatic gear box BUS VAN COMFORT 0004 Instrument panel

28 Injection ECU BSI BUS VAN BODY INTERFACE Engine speed encoding INTERFACE Engine speed sensor INTERFACE INTERFACE INTERFACE BUS CAN I/S INTERFACE INTERFACE INTERFACE Codage de la vitesse ABS wheel sensor 7800 ESP 1630 automatic gear box BUS VAN COMFORT 0004 Instrument panel

29 B.S.I

30 MAIN NETWORKS USED ON CITROËN CARS CODE NAME CAR MODELS VAN Vehicle Area Network Xsara, xsara picasso, C3, C2,C5 CAN HS (I/S) CAN LS (FT) Control Area Network High Speed ( Inter / Systems) Control Area Network Low Speed ( Fault Tolerant) Xsara, xsara picasso, C3, C2,C5 C3 II,C4,C4 picasso,c5 II, C6 LIN Local Interconnect Network C3 II,C4,C4 picasso,c5 II, C6

31 THE VAN NETWORK

32 VAN (Vehicle Area Network). - Historical /86 Born of VAN, Test one model of car (XM), - ( ) Mass production End of production

33 - Example of architecture VAN CAN, (C3) Platines de portes AVG et AVD Calculateur d additivation carburant Boîtier Alarme antieffraction ECM BSM BVA COM 2000 Capteur angle volant Calculateur Airbag ESP ABS Changeur de CD Calculateur de navigation Climatisation Combiné Autoradio Afficheur multifonctions

34 VAN very well adapted to car environment. M E M E M E M E M Maximum 16 ECU on the same bus.

35 Architecture CAN / VAN (C8) 1 + VAN

36 - Synoptic diagram (C8)

37 - Supply of the stations (C8) (+VAN).

38 - Electric signals on the bus VAN 2 wires on the bus called DATA and DATA/. 4.5 V max 5 V DATA 2.8 V Udiff 0.5 V min DATA / t DATA : t Udiff = V DATA V DATA/ if Udiff > 0 the bit is 1 ( recessive) if Udiff < 0 the bit is 0 ( dominant)

39 - Advantages of the differential reading : - The data is not modified by electromagnetic perturbations 4.5 V max 5 V DATA 2.8 V Udiff 0.5 V min DATA / t

40 - FAULT TOLERANCE: Short circuit to earth Short circuit to + supply Wire cut With these faults, the VAN still works ( in downgraded mode).

41 - Characteristics of the VAN NETWORK : Very well adapted for car applications. Transfer speed : 250 KTs (Kilo time slot / second) maximum 125 KTs for VAN Comfort, 62.5 KTs for VAN Body. Length of the data field 28 Bytes maximum. Maximum 16 ECU on the same bus. Downgraded mode possible.

42 THE CAN High Speed ( Inter/Systems) NETWORK

43 CAN (Controller Area Network). - Historical : Born of CAN : First vehicle fitted with CAN network : CAN High-Speed is standardized (transfert speed 1 Mbit/s) : CAN Low-Speed Fault Tolerant is standardized (transfert speed 125 Kbits/s) : CAN Low-Speed Fault Tolerant replace the VAN network on CITROËN cars.

44 - Since 2004 all CITROËN carshave been FULL CAN - CAN became a standard for all car builders. - The transfert speed of the VAN NETWORK was not enough for high performance ECU. - CAN LS (FR) has the same qualities than the VAN.

45 -Electric signals on the bus CAN. 2 wires on the bus called CAN High and CAN Low. 3.5 V max 5 V 1.5 V min 2.5 V CAN H CAN L Udiff t DATA : t Udiff = V CAN H V CAN L if Udiff 2 the bit is 0 ( dominant) if Udiff = 0 the bit is 1 (recessive)

46 - - Advantages of the differential reading : - The data is not affected by electromagnetic perturbations 3.5 V max 5 V 1.5 V min 2.5 V CAN H CAN L Udiff t

47 - FAULT TOLERANCE: Short circuit to earth Short circuit to + supply CAN H CAN L CAN H CAN L Wire cut Short circuit in the bus CAN H CAN L CAN H CAN L With these faults, the CAN cannot work. (no downgraded mode)

48 - Architecture of the bus CAN cm mini 1320 BSI 40 m maxi - Maximum 8 ECU on the same BUS, - 2 resistances at each end of the bus.

49 - Network Architecture. The resistances are located in the BSI and in the injection ECU on CITROËN cars. BSI 1320 T T

50 Two possibilities to connect ECU on the CAN bus parallel Daisy Chain ( serial)

51 - Characteristics of the CAN High Speed (Inter System) NETWORK: 2 resistances at the end of the bus. Transfer speed : 1 MBit/s (Mega Bit / second) maxi 250 Kbits/s for CITROËN cars (Full MUX) Length of the data field 8 Bytes maximum. Maximum 8 ECU on the same bus. The bus can not «wake up» the ECUs with a frame. No downgraded mode.

52 THE «FULL CAN» ARCHITECTURE

53 1 network CAN HS I/S 2 networks CAN LS. -Example C4

54 2 Example new C5

55 THE CAN Low Speed (Fault Tolerant) NETWORK

56 - Electric signals on the bus CAN LS. 4.8 V min 5 V CAN L 3.6 V max 1.4 V max 0.2 V max 2.5 V CAN H t DATA: t

57 - FAULT TOLERANCE: Short circuit to earth Short circuit to + supply CAN H CAN L CAN H CAN L Wire cut Short circuit in the bus CAN H CAN L CAN H CAN L With these faults, the CAN LS still works ( downgraded mode)

58 - Characteristics of the CAN LS NETWORK : No resistance at the end of the bus. Maximum 20 ECU on the same bus. Downgraded mode possible. Transfer speed, 125 Kbits/s. The bus CAN LS can wake up the ECUs with a frame.

59 THE LIN NETWORK

60 Characteristics of the LIN NETWORK: - The bus is made of only 1 wire. - Maximum 17 ECU on the same bus. 1 Master, 16 slaves 1 wire for the bus PSF1 - The response is in the same frame than the question. Question of the master Response of the slave

61 - THE FRAME STRUCTURE. Sent by the master Sent by the slave SOF Synchro Identification Data CTRL 10 bits octets 9 dominant bits(0) 8 bits 8 bits

62 The LIN FRAME

63 Example of LIN network BSI CAN LS/Car LIN BSM + CAN master + LIN wiper (slave 1) wiper (slave 2)

64 Front Windscreen-wipers C4 picasso

65 Example of LIN network C4 HDI FULL CAN UC Brakes Tank tap sensor + fuel gauge CMM CAN I/S BSI (master) LIN Interface MUX Pump (slave) sensor pump Pump additive

66 - Characteristics of the LIN NETWORK : No Downgraded mode possible. Transfert speed, 19,2 Kbits/s. LIN network is used for many functions ( directionnal head lamps, alternator remote control, )

67 LEXICAL

68 Glossary. VAN : Vehicle Area Network. CAN : Controler Area Network. LIN : Local Interconnect Network. MOST : Media Oriented Systems Transport. Bit : elementary Information in the binary language (1 or 0). BYTE : Group of 8 bits. Récessive : Bit = 1. Dominant : Bit = 0 Frame : Information composed with a package of fields. Transfer speed : number of bits transmitted in one second(kb/s or Kts/s).