Automotive electronics - part 3

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Transcript of Automotive electronics - part 3

  • Ideas today forthe cars of tomorrow

    Automotive electronics

    What you need to know! Part 3

    Lighting ElectricsThermalManagement

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  • 2Passive Entry / GoControl unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3ID transmitter (identification transmitter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4ID transmitter design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Doorhandle Electronic modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Aerials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Radio communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Passive Entry / Go system functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Special features /safety circuits of the Passive Entry / Go system . . . . . . . . . . . . . . . . . . . . . . . . . . 9Diagnosis and possible fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

    Airbag System SRS (Supplemental Restraint System)Airbag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11The crash sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12The safing sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Airbag design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13The airbag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14The contact coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15The seat user recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15The belt tensioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16The belt tension limiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Battery cut-off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Airbag cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Airbag system testing and diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

    Battery ManagementAudi A6/A8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Overview of the battery management system . . . . . . . . . . . . . . . . . . . . . . . . . . .20The tasks of the functional modules in detail . . . . . . . . . . . . . . . . . . . . . . . . . . . 21The six switch-off stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Dynamic management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24BMW 5 Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26The function of the IBS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

    Electromechanical Parking Brake (EMP)Electromechanical parking brake (EMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30The parking brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32Dynamic emergency brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Adaptive starting assistant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Brake pad wear control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Emergency release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Changing brake pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Function test on dynamometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

    Contents

  • 3Passive Entry / Go

    In this issue we would like to discuss the Passive Entry/Go system. Thesesystems provide a passive means of both locking/unlocking the vehicleand starting/stopping the engine, that is to say, owners of these latest-generation systems only need to carry the RF key along with them.They no longer need to look for the RF key or have it in their hand toactuate a function by actively pressing the appropriate button on it. Theseaccess and driver authentication systems provide a plus in convenienceand make it much easier to get into the car. Here we would like toexplain the components and what they do. The text is illustrated withPassat B6 components. To obtain more detailed information about avehicle-specific system, please refer to the technical data provided bythe relevant manufacturer.

    The Passive Entry/Go function requires a couple of system componentsto be added on to the conventional central locking system, including:

    In a Passat B6, the Passive Entry/Go functions are controlled by thecentral control unit for convenience systems. This so-called conveniencecontrol unit is located underneath the dashboard towards the right andbehind the glove compartment.Functions controlled by the convenience control unit include:n Central lockingnMotor-driven opening/closing of windows and sun roofn Car alarm systemn Tyre pressure controln Steering column lock

    Another task of the control unit is to check the system for errors and storea log of any errors encountered.The RF key and the control unit communicate at different frequencyranges, i.e. 433 MHz or 315 MHz, depending on the region.

    Control unit

  • 4The ID transmitter is an RF key, the expanded functionality of which(identification transmitter) includes the passive functions. It thereforeclassifies as a combination of a "simple remote control" and an identification transmitter.Active locking or unlocking the vehicle at distances of up to 100mrequires the keys on the ID transmitter to be pressed manually. Passiveunlocking is done by gripping the door handle, whereas passive lockingis done by touching a sensor spot on the door handle. For safety reasons,passive operation is restricted to the immediate vicinity of the ID transmitter(approx. 2m). The ID transmitter uses radio signals to communicate withthe control unit.

    It also contains a mechanical emergency key that the driver can use tomanually unlock the car, e.g. if the battery in the RF key is empty.

    The ID transmitter consists of a splash-proof housing for the electroniccircuitry, the aerials and the key panel.The keys for the manual control of functions (e.g. unlocking, locking,boot lid, panic button) are located on the top of the housing.

    And there is a small LED that will light up when a button is pressed, forexample. A 3D LF aerial in conjunction with a LF pre-stage IC with integral microcontroller allow an accurate measuring of field strengthsreceived from all three directions in space and, thus, to reliably differentiatebetween the inside and outside of the vehicle. The UHF receiver aerial islocated on the circuit board. The ID transmitter also has a batterymonitoring feature.

    ID transmitter(identification trans-mitter)

    ID transmitter design

    Passive Entry / Go

  • 5When the battery is discharged down to a critical level an alert will appearon the dashboard display and the small LED will no longer light up whena button is pressed.To save battery energy, intelligent wake-up algorithms ensure that the IDtransmitter is not "woken up" unnecessarily (e.g. by other radio systems).An integral day counter enables a power-down mode for ID generatorsthat are not used (e.g. a second key). This ensures that the batteryretains a sufficient level of capacity for extended periods of time.

    The receiving aerials and the proximity and locking sensors for recognising,unlocking or locking the vehicle are located in the front door handles. The sensors in the rear door handles are only there to recognise, unlockor lock the vehicle.

    The proximity sensors are capacitive sensors, i.e. when the driver's handenters the capture area of the proximity sensors the capacitive sensorswill detect it and output a signal to notify the convenience control unit.

    Aerials Aerials are not only located in the door handles but also alongthe outer shell and on the interior of the vehicle.An outside aerial is the rear-end aerial which is installed in the rear bumperwhere it is responsible for proper rear-end reception.

    Doorhandle-Electronic modules

    Aerials

    Front door handle

    Rear aerial

    Rear door handle

    Passive Entry / Go

  • 6The interior, boot and rear shelf aerials make up the set of aerials installedinside the vehicle.

    The interior, boot and rear-end aerials consist of a ferrite coil and capacitorand make up a series resonance circuit.The rear shelf aerial is a flexible circuit board with a conductor loop thatgenerates the field.

    Before a vehicle function is performed, the system checks whether thevehicle user is carrying an authorised ID transmitter.When the control unitreceives a signal from the capacitive proximity switch in the door handleit returns a signal to the ID transmitter which responds by sending aresponse telegram via a UHF channel fr