184000359 - INTRODUCTION - INSTRUMENT/GAUGE ELECTRICAL CIRCUITS

MINI F.L.Ore.N.C.E. ELECTRICAL AND ELECTRONIC SYSTEM

GENERAL SPECIFICATIONS

In conventional electrical systems, functions are activated with the aid of dedicated point-to-point linesThe increase in the number of electrical/electronic devices on board cars has given rise to heavier and more complex connections. This is partly due to the complexity of the functions implemented in the burgeoning number of electronic units - which also need to exchange data continually: all this makes new electrical systems more difficult to install and increases the complexity of fault diagnosis.Many problems have been overcome and new electrical systems have been optimised compared to conventional systems by using a network form of connection. This provides a more effective means of managing communication on the board the car and of transferring data between the various subsystems. Information is distributed via serial pathways (buses) that may take the form of: individual wires, twisted wire pairs or even optical fibres. Let us now take a look at the move from traditional systems to those known as multiplexing systems.

Conventional solution

The four control units illustrated below require a number (N) of wires for each input/output data item in order to perform their function. This multiplied the amount of cable required to the point that systems are made more complex (design and manufacture) and more voluminous (weight, bulk, cost). Some 40 kg of wiring looms are required that stretch for more than 2 km - and this figure could double every 10 years because even now a car could be equipped wiht 20 to 40 electronic control units (ECUs).1 - Climate control management node2 - Engine management node3 - Engine temperature sensor (for engine management node)4 - Instrument panel node5 - Engine temperature sensor (for instrument panel warning light)6 - Engine cooling fan7 - Engine temperature bulbThe first step towards reducing the volume and complexity of wiring looms was to group several electronic functions in a single unit, therefore: LESS COMPONENTS = LESS WIRES.

Examples of integation

The multifunction control unit manages the: central locking, electric windows, courtesy light timer, heated rear windscreen and heated, external rear view mirrors timer.1 - Multifunction control unit2 - Central locking3 - Electric windows control unit4 - Centre courtesy light5 - Rear courtesy light6 - Heated rear windscreen / Heated door mirrors

The itegration of the electrical/electronic functions in a single unit has made it possible to improve:

  • the management of current consumption
  • the operation of the consumers because they are managed by a single control unit
  • the search for faults by means of autodiagnosis of the control unit
This first stage made it possible to reduce the number of electronic units but not to reduce the volume of the cable looms to a sufficient extent.

Multiplexing solution

This solution makes it possible to reduce the volume of the cable looms and to considerably improve the transmission of information between various electronic units.These transmissions takes place via a BUS channel comprising 2 cables (the main one already used for the telephone, radio, television network, etc.)A - B - C: NODES (CONTROL UNITS)D: MASTER CONTROL UNIT OR BODY COMPUTERA1 - A2, B1 - B2, C1 - C2: COMMUNICATION BUSIn addition to reducing and simplfying the wiring and improving communication between electronic units, the multiplexing solution also makes it possible to reduce the number of sensors (INFORMATION SHARING).A - Conventional solutionB - Multiplexing solution1 - Climate control management node2 - Engine management node3 - Engine temperature sensor (for engine management node)4 - Instrument panel node5 - Engine temperature sensor (for instrument panel warning light)6 - Engine cooling fan7 - Engine temperature bulb8 - Instrument panel node9 - Climate control management node10 - Engine temperature information11 - Body Computer Node12 - Engine management node13 - Engine temperature sensor (for engine management node)

In general terms, in order to transmit data via a multiplexing system we need to define the following:

  • (A) THE TRANSMISSION CHANNEL (electric wires, fibre optics, radio waves, etc.)
  • (B) THE TYPE OF SIGNAL (voltage, current, light, etc.)
  • (B) THE COMMUNICATION PROTOCOL (all the rules that allow management of analogue or digital transmission type, code type, address, transmission order, error detection etc.).
On this model the transmission channel (A) comprises a pair of electrical wires and is known as BUS.The type of signal (B) is VOLTAGE and the communication protocol (C) is the CAN (Controller Area Network) developed by BOSCH.

F.L.Ore.N.C.E. ARCHITECTURE

The "MINI F.L.Ore.N.C.E." system has been designed for the optimum management of the vehicle''s electrical and electronic functions.The system interacts with all electrical system functions to directly control the so-called bodywork functions (visibility, access, on-board information, comfort, communications etc.) and supports information exchange between traction control systems (engine, braking, gearbox etc.).To optimise the system, each control unit (electronic or electromechanical) is located in a central position in relation to the functions it manages. This allows the power and signal distribution system to be minimised. This is also made possible through extensive use of serial communication networks that allow us to overcome problems of space-saving, reliability, weight and cost.Power is distributed via the junction units and/or fuse boxes. These are connected to control elements (relays and static actuators) to ensure maximum electrical protection and minimum complexity.

There are considerable advantages with systems such as the MINI FLORENCE such as, for example:

  • the sensors in the various sub-systems are available to the network so that they can be shared and there is no need for similar sensors
  • new functions may be added simply by changing the software (developments throughout the car''s lifetime),
  • wiring design is simplified and the number of connectors reduced
  • the operational safety of electronic devices is increased to improve the reliability of information transmitted.
  • because a diagnostic function is built-in, service operations on electric/electronic components are easier.

The system structure on this vehicle is composed of:

  • 2 CAN communication NETWORKS which connect NODES belonging to two different areas: one for the dynamic control of the vehicle and one for the so-called "bodywork" functions.
  • a W SERIAL LINE for immobilizer recovery
  • different K SERIAL LINES for the fault diagnosis of several NODES/CONTROL UNITS
  • a serial line known as A - BUS
NODES are all the electrical/electronic devices and control units that contain a specific interface (NETWORK INTERFACE) that allow data, information and signals travelling via the CANs to be transmitted and received.
The table below contains all the elements (nodes/control units/devices) that make up the mini FLORENCE structure in its most complete configuration.

Mini florence structure components

CABAir Bag control unit
CDCCD-Changer
CPAParking Sensor Node
CPLDashboard control unit
CSPRain/dusk sensor control unit
CVMEngine compartment control unit
CVSClock spring
DEVSteering column switch unit
DSPAudio amplifier
NBCBody Computer Node
NCLClimate Control Node
NCMEngine Management Node
NCRRobotized gearbox node
NFRBraking System Node
NGEElectric steering node
NPGDriver''s door node
NPPPassenger Door Node
NQSInstrument Panel Node
NRRRadio Receiver Node
NVBLuggage compartment node
NYLLateral yaw node (slewing sensor)

The two C-CAN and B-CAN networks are physically separate, but both flow into the BODY COMPUTER NODE; the latter, which is considered the MASTER node for the two networks, contains a GATEWAY function which allows the transfer of information/data from one network to another even if the two networks are operating at different speeds:

  • B-CAN transmission speed = 50Kbit/sec.
  • C-CAN transmission speed = 500 Kbit/sec.
The fault diagnosis of the NODESs connected to the B-CAN network is carried out via the CAN network, whilst for those connected to the C-CAN this is carried out by means of the specific K SERIAL LINES. The K lines and the B-CAN flow into the EOBD diagnostic connector located on the BODY COMPUTER.
The "mini F.L.Ore.N.C.E" structure is summarized below.Refer to the previous table for the description of the nodes.

B-can connection

The B-CAN (low speed) network comprises 2 electrical wires, one White/Pink shown in the wiring diagram as the CAN-A cable and one Black/Pink one shown in the wiring diagram as the CAN-B cable.The information is transmitted via this pair of wires on 2 voltage levels (V), one High and one Low associated with the CAN-A and the CAN-B cables, respectively; the mathematical difference between these two levels produces two associated voltage values at two logic levels 0 or 1.The latter constitute the elementay information unit known as a BIT (binary figure) and, suitably combined, make up the information to be transmitted.V Can A - V Can B = 3.6 - 1.4 = + 2.2 V (bit 0)V Can A - V Can B = 0.2 -4.8 = -4.6 V (bit 1)

C-can connection

The C-CAN (high speed) network comprises 2 twisted electrical wires, one Green shown in the wiring diagram as the CAN-H cable and one Brown shown in the wiring diagram as the CAN-L cable.The transmission of information is similar to that of the B-CAN; in this case the High voltage level is associated with the CAN-H cable, whilst the Low voltage level is associated with the CAN-L cable.For the C-CAN too, it is the mathematical difference between these two voltage levels that gives rise to the two logic levels 0 and 1, but with one difference illustrated in the diagram:

The network interface cannot communicate via the C-CAN network if one of the following situations arises:

  • Interruption of one of the two CAN cables (H and L),
  • Short circuit between the two CAN cables (H and L)
  • Short circuit of the CAN-H cable or CAN-L cable to +Vbatt.
  • Short circuit of the CAN-H cable or CAN-L cable to earth.
Priority in case of transmission conflict for several nodesThe system protocol allows the mini F.L.Ore.N.C.E. to handle superimposition problems when several nodes need to emit a frame simultaneously. The node that transmits the lower priority message immediately interrupts its transmission and makes way for the node that is transmitting a higher priority message. In practice, the high priority message is sent to the network without any interruption or delay. _ - The higher priority frame gains the right to be transmitted on the BUS; a dominant level (0) always takes precedence over a recessive level (1).Simultaneous access to the network by several control units can cause a conflict on the C-CAN line (BUS); it can be seen that the engine management control unit (NCM) and the braking system control unit (NFR) send identical frames (data packages) at the same time to point (D); the two fames have a conflicting bit from point (E).From this moment, since in addition to transmitting the frame the NFR also simultaneously checks (reads) it, as soon as it notices that the recessive value bit it wishes to transmit (1) is opposing a dominant value bit (0) in the network, it immeidately interrupts the transmission of its frame in favour of the NCM node which is transmitting a higher priority frame listening until the NCM node has finished transmitting and the line becomes free again. The frame transmitted on the network is the one for the NCM node and at this point the NFR node can try and gain access again to the line for transmitting its frame which was interrupted previously. As long as there is not another collision.

A-bus line connection

The A-BUS serial line is designed to ensure the exchange of information/commands between different electronic control units.

The following control units are present on this vehicle:

  • Steering column switch unit electronic module
  • Dusk/rain sensor
  • Body Computer Node
The A-BUS transmission speed is 4.8 kbit/sec.The communication on the A-BUS takes place via the exchange of data packages between the different control units.Each control unit connected to the A-BUS has its own electronic address; when a control unit has to send a command/information to another control unit it mus always include the address of the destination control unit in the data package.The transmission always takes place from a transmitter control unit to a receiver control unit (one-way).When the reception of data is over, the receiving control unit should send the result to the transmitter control unit thereby ending the exchange of the data package.Unlike CAN NETWORKS, on the A-BUS the t
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