Advance Safety Electronics
Advanced Safety Electronics ASE is the passive safety system on the E85. The system is based on the same technology as the Intelligent Safety and Integration System (ISIS) of the E65/E66.
The ASE system consists of the Safety Information Module SIM and several control units, called satellites, that are linked across the byteflight bus. In the case of the MRS system there was only one central control unit. On the E85, the acceleration sensors are integrated into the satellites.
The actuators are directly connected to the satellites and are activated by the satellites. The satellites are fitted at strategic points in the car. The distributed sensor system in the car enables measurement of the accelerations occurring as close as possible to the outer shell of the body and at the location of the collision.
The direct recording and processing of the information in the control unit mean that significantly shorter reaction times can be achieved. The mechanical time lag within the body to a central control unit is eliminated.
The distributed sensors in the satellites provide redundant information that is interchanged via the byteflight . This leads to even more reliable trigger decisions. In comparison to the MRS systems used to date, the ASE enables, (for example in the event of a side-on collision) earlier triggering.
Advantages Of The ASE System
- Networked airbag control system with optical bus byteflight
- More exact crash detection regarding the direction and strength of the impact
- Battery cable diagnosis with cutoff of the safety battery terminal when required
- Airbag switch for deactivation/activation of the front airbags on passenger side, side airbags and knee airbag on US models
- Deployment of a knee airbag for driver and passenger on US model
The crash situation is detected more precisely than on the multiple restraint system MRS. In the event of a crash, only those actuators are triggered that are necessary for optimum protection of the driver and passenger. This leads to lower repair costs and thus more favorable insurance classifications.
A number of acceleration sensors in the vehicle record the vehicle deceleration. The satellites exchange acceleration data. This provides an exact picture of the crash situation, enabling a timely and selective triggering of the actuators depending on the crash situation.
Scheme 14
System Components
The ASE system consists of the following components
- byteflight bus
- Control Units SIM - With acceleration sensors SBSL - satellite b-pillar on left side of vehicle SBSR - satellite b-pillar on right side of vehicle
- Sensors STVL - pressure sensor left door STVR - pressure sensor right door Seat occupancy sensor B+ Cable Monitoring Seat Belt Switches -Driver and Passenger Airbag Switch
- Actuators Driver's Side Airbag (2 stage) Passenger Side Airbag (2 stage) Side Airbags (2) Knee Airbag Driver's Side Knee Airbag Passenger Side Seat Belt Tensioners (2) BST Airbag Indicator Light
Byteflight
The increasing complexity of in-car electronics and the growing amount of sensors, actuators and electronic control units place higher demands on the high-speed data communication protocols.
None of the communication solutions available until now have been able to fulfill all these demands.
BMW together with several semi-conductor companies have developed byteflight a new protocol for safety-critical applications in automotive vehicles.
The byteflight is the bus system used exclusively for the ASE System (Intelligent Safety Integration System). This ASE Sytem of the E85 contains the Safety and Information Module (SIM) and 4 additional satellite control modules.
The ASE System is a bus composed of Fiber Optic cables and control modules arranged in a STAR pattern with the SIM at the center of the system.
Since the byteflight is a star structure as opposed to the continuous ring structure of the MOST bus, the fiber optic cables carry the data bi-directionally, a single fiber optic cable connects each satellite directly to the SIM.
Each satellite contains a transmitter/receiver module for receiving and sending data to the SIM. The SIM contains 4 transmitter receiver modules for communication with the satellites simultaneously.
All information from each satellite is made available to every other satellite by the SIM.
Note. Repairs to the byteflight fiber-optic cable are not permitted. Damaged cables must be replaced with new fiber optic cables.
Scheme 15
Because of the use of byteflight , the ASE system has the following advantages
- High communication speed
- Highest level of system security
- Faster trigger decisions
- Redundant information provided by the sensor
- Software update via bus
- Self-diagnostic procedure
- Mechanical safety switch is unnecessary
- No electromagnetic disturbances due to fiber-optic communication
- No electrical connection between transmitter and receiver module
- Simple system upgrade
Scheme 16
Located on the transmission tunnel behind the handbrake assembly, the Safety and Information Module (SIM) performs the following functions
- Supplies voltage to the satellites and the pressure sensors (SBSL,SBSR and STVL,STVR) and supplies the voltage reserve for component activation.
- Bus Master functions for the optical bus communication system ( byteflight ).
- Gateway functions between byteflight and K-bus.
- Triggers Emergency Call System (If Phone equipped)
- Signals the DME for deactivation of fuel pump.
- Signals the GM to switch on interior lights, hazard warnings and unlock the doors.
- Monitors the integrated acceleration sensors.
- Allows airbag activation.
- Allows BST activation.
Scheme 17
Power Supply
The SIM is supplied with voltage KL terminals 30 and ground from KL31. If the vehicle voltage is sufficient then a switching controller is supplied first, which supplies voltage to the intelligent Star Coupler and the power supply.
The second switching controller is supplied by KL 30 during operation and is controlled by the microprocessor via the cable SHDN 2. The capacitor is charged as of KL R.
The charging of the capacitor forms the emergency energy reserve. The capacitor voltage is 33V. (Energy Reserve in the E65 is 400v.)
Bus Master Functions
The SIM has two tasks to perform as Bus Master for the byteflight.
- Generation of the synchronization pulses (Sync. Pulse)
- Setting the satellites in alarm mode (Alarm Pulse)
In the ASE, the SIM is configured as byteflight master (bus master). In principle, any satellite can be configured by software as bus master. However, there may only be one bus master in the system.
All other satellites (bus slaves) use the sync pulse for internal synchronization. Each slave can transmit telegrams between the sync. pulses on the byteflight .
The SIM provides the synchronization pulses at intervals of 250 mues. The alarm mode is transmitted across the width of the sync. pulse. The duration of a sync. pulse in alarm status is approx. 2 mues. Normally, the synchronization pulse lasts approx. 3 mues.
The duration of a complete telegram can vary between 4.6 to 16 mues.
On the basis of all the available information provided by the sensors, the bus master (SIM) must decide whether the satellites are to be set in the alarm mode.
When the alarm mode is set by the SIM, all the trigger circuits (B+) of the ASE are placed on trigger standby.
Scheme 18
Gateway
The SIM contains the gateway function between the byteflight and K-bus. This means that telegrams can be sent by the byteflight to the K-bus and vice versa.
The gateway function transfers both the content of functional telegrams as well as the telegrams for diagnosis.
Gateway from K Bus To Byteflight
Information and messages for the ASE system are forwarded by the K-bus as telegrams to the byteflight (gateway function of the SIM). The telegrams are processed in the SIM.
The following telegrams are transmitted
- Terminal status
- Kilometer reading
- Vehicle identification number
Gateway From Byteflight To The K-Bus
The messages and information from the byteflight that are meant for other nodes on the K-bus are converted by the gateway function into a K-bus telegram. The following signals are transmitted in a telegram (crash telegram)
- Switch on airbag warning lamp, AWL
- Switch off electric fuel pump
- Switch off alternator
- Transmit emergency call
- Open central locking system
- Switch on passenger-compartment lighting and hazard warning light
B-Pillar Satellites (SBSL And SBSR)
The left side B-Pillar Satellite (SBSL) controls and monitors the actuators for the left front airbag, the left side airbag (in the drivers door), the left seat belt tensioner and the left knee airbag.
The right side B-Pillar Satellite (SBSR) controls and monitors the actuators for the right front airbag, the right side airbag (in the passenger door), the right seat belt tensioner, the right knee airbag and the BST.
Both B-Pillar Satellites function as monitors for the BST.
Scheme 19
Scheme 20
The B-Pillar satellites are connected to the SIM via the byteflight. The power supply of the satellites is also from the SIM and it is buffered by the memory backup capacitor.
An acceleration sensor for the longitudinal and transversal acceleration is integrated in each B-Pillar satellite. The sensor provides voltage as a measured variable and transfers the value via the byteflight to the SIM and all other satellites.
The voltage signal is a measurement of positive and negative car acceleration and is evaluated in each satellite. The voltage signal is continuously provided to the SIM and other satellites.
Door Satellites (STVL/STVR)
The Door Satellites (STVL/STVR) are located in the left/right passenger doors.
The door satellites are connected to the SIM via the byteflight. Power supply for the door satellites is also provided by the SIM and is buffered by the memory backup capacitor.
A pressure sensor, which constantly monitors the pressure in the door, is integrated into each door satellite. Pressure changes in the door that occur during penetration of the outer door skin are evaluated and passed on through the SIM for airbag deployment activation.
Scheme 21
Scheme 22
Seat Occupancy Sensor
A seat occupancy detection mat is installed in the seat cushion of the passenger seat. The sensor mat is identical to the mats used in previous models for the MRS systems. The sensor system consists of pressure sensors that use an electronic evaluation unit (SBE) to detect whether there is weight on the seat.
When a weight (such as a passenger) is added to the seat, the system recognizes the seat as occupied. The electronic evaluation unit of the seat occupation mat is connected to the SBSR satellite.
The information regarding seat occupation is required for activation of the following functions
- Airbag activation
- Activation of the seatbelt tensioners
B+ Cable Monitoring
The E85 B+ Battery Cable is routed from trunk area along the underside of the car into the engine compartment. If the cable is damaged in an accident or while driving over an obstacle, the BST is activated, protecting the vehicle from further electrical problems.
Scheme 23
The battery cable monitoring occurs via the low impedance shield of the battery cable, the monitoring shield. The monitoring point in the trunk at the BST is connected to the SBSR and the other monitoring connection in the engine compartment is connected to the SBSL.
Seat Belt Switches
The Seat Belt Switches are located in the seatbelt buckles of the driver and passenger seat belt. The switch is a two wire hall switch and is supplied with voltage by the respective left and right B-Pillar satellites (SBSL/SBSR). The voltage is pulsed to the switch to reduce voltage consumption.
The seat belt switches are used to detect whether or not the seat belts have been fastened. The input from the switches is required for the following functions
- Selective triggering of actuators in the event of a crash
- Activation of the Seat Belt Warning Lamp
- Out of the acoustic warning
Scheme 24
The airbag switch is located on the right side of the dashboard at the A-Pillar and the indicator lamp for is located in the center console.
The airbag switch makes its possible for the driver to determine if the passenger front and side bags are active. The front passenger and passenger side airbag are activated or deactivated together only.
To prevent accidental activation or deactivation of the passenger airbags the switch may only be operated by the ignition key while the car is not moving and the passenger door is open.
The airbag indicator lamp consists of a number of LED's controlled by the SIM.
Driver's Airbag
The Driver's Airbag is located in the impact pad of the three spoke steering wheel.
The Bag is equipped with a 2-stage gas generator and has a volume of approximately 60 liters.
Scheme 25
Three colors are available to match the interior colors. (Black, Brown, Grey)
Scheme 26
Scheme 27
Passenger Airbag
The Passenger Airbag is located beneath an invisible flap in the dashboard. The airbag is a 2-stage design with a volume of approximately 125 liters. Depending on the severity of the crash, the two stages are ignited so the bag can unfold in a defined manner.
Scheme 28
Scheme 29
The side airbags in the doors reduce the risk of occupant injury in the torso region of the body in the case of a side-on crash.
The side airbags are located behind the door trim. The side airbags are secured to the inner door panel with 3 screws.
The side airbags are folded up in an aluminum housing with a plastic cover. The plastic cover has defined breaking points.
Scheme 30
Scheme 31
In the event of a crash, the knee airbag supports the knee, especially if the driver or passenger are not wearing seatbelts. This initiates a controlled forward shift of the upper body, which is cushioned by the relevant airbag.
The knee airbag is a one-stage airbag with gas generator. The volume is approx. 13 litres.
Seat Belt Tensioner
The pyrotechnic seatbelt tensioner has the task in the event of a crash to remove or reduce any belt slack in the pelvic and shoulder region.
The seatbelt tensioner is located on the driver's and/or passenger seat. The seat belt tensioners form a unit with the seat belt buckle.
The seatbelt tensioner consists of priming cap, generator, plunger and operating cable. The belt buckle switch is integrated in the seatbelt buckle.
Scheme 32
Scheme 33
Battery Safety Terminal
In the event of a crash of sufficient severity or if the battery cable diagnosis is activated, the starter/alternator line is electrically and mechanically cut from the positive terminal of the battery.
The safety battery terminal is located directly at the positive terminal of the battery.
Scheme 34
The airbag indicator lamp is activated when the airbag switch assigns the state "Passenger Airbag OFF."
The airbag indicator lamp is activated by the SIM.
The airbag indicator lamp is diagnosed and monitored. If a fault is found in the power supply or at the lamp, a fault entry is made in the SIM.
The airbag warning lamp is activated.
Principle of Operation
The SIM now has 4 transmit/receive modules to which the satellites are connected. The energy reserve in the SIM has been reduced to 33 V (ASE 400 V), as now only 4 satellites have to be supplied with voltage in the event of a crash.
New additions are the acceleration sensors for the X/Y direction.
The acceleration sensors for the X/Y direction measure the longitudinal and transversal acceleration of the vehicle and are evaluated in the SIM. The sensors continuously provide the values determined. The values are transferred across the byteflight to all satellites, as are the measured values of the satellites. The algorithms in the satellites work with these measured values. The SIM compares the values and triggers the alarm mode via synchronization pulses if the severity is sufficient.
The alarm mode places the satellites in a triggerable state. Depending on the crash severity and the stored trigger algorithms, the actuators required in each case are activated.
Note. If an airbag switch is fitted and the switch is in the position "deactivated," the front airbag on the passenger side and the side airbag are not placed in the triggerable state. The knee airbag and the seat belt tensioner are also not place in the triggerable state.
The vehicle center satellite has been eliminated, as the SIM is fitted in the middle of car and the acceleration sensors are integrated in the SIM.
Scheme 35
Airbag Triggering
Numerous crash and road tests under extreme conditions have been used to set the BMW triggering thresholds for all possible types of accidents.
The triggering thresholds are primarily divided into 4 groups according to crash severity
- CS 0: no crash (parking damage) CS=Crash Severity
- CS 1: light crash
- CS 2: crash of medium severity
- CS 3: severe crash
The triggering thresholds have been set depending on the crash severity and including other factors such as direction, overlap on collision, and depending on the evaluation as to whether the occupant was wearing a seatbelt or not.
This results in the various trigger thresholds for the activation of the various restraint systems.
Triggering In The Event Of Errors
If a fault is detected in the seatbelt buckle detection system, it is assumed that the seatbelt is not fastened. The triggering threshold is lowered. In spite of the fault recognition, an attempt is made to activate the seatbelt lock tensioner.
If a fault is detected in the seat occupation detection system, it is assumed that the seat is occupied. The restraint systems are activated.
If a fault is detected in the airbag switch, it is assumed that a child's seat is fitted. The front airbag and side airbag on the passenger side are not triggered.
Triggering In The Event Of A Crash
The following examples illustrate the actuators that can be activated
- Front-end crash
- Side-on collision
- Rear crash
Front-End Crash
In the event of a front-end crash, a distinction is made between crash severity "light to medium collision" or "severe collision" (CS 3).
In the case of crash severity from light to medium collision (CS 1/CS 2), the driver's/front passenger's airbag are not triggered if it is detected that the occupants are wearing seatbelts.
If the occupants are not wearing seatbelts, the driver's and front passenger's airbag would be triggered.
The seatbelt tensioners are triggered in all cases.
As of crash severity CS 2, the driver's/front passenger's airbag as well as the seatbelt tensioners are triggered. The safety battery terminal is activated, the electric fuel pump is switched off, and an emergency call is placed if a correspondingly prepared telephone is present in the vehicle.
In the US version, the knee airbags are also triggered.
Side-On Collision
In the event of a side-on collision, a crash severity distinction is made between medium and severe collisions.
As of crash severity of CS 2 (medium collision), the side airbag is triggered on the impact side. In the event of crash severity CS 3 (severe collision), the safety battery terminal is also activated, the electric fuel pump is switched off, and an emergency call is placed if a correspondingly prepared telephone is present in the vehicle.
Rear Crash
As of crash severity CS 2 (medium collision), the seatbelt tensioners are triggered.
In the event of crash severity CS 3 (severe collision), the safety battery terminal is also triggered, the electric fuel pump is switched off, and an emergency call is placed if a correspondingly prepared telephone is present in the vehicle.
Knee Airbag
In the event of a crash of sufficient severity, the gas generator is ignited. The escaping gas fills the airbag, which tears open the cover of the knee airbag so that the airbag can emerge.
The airbag spreads out beneath the steering column and/or in front of the glove compartment and cushions the lower thighs of the occupant.
The support of the lower thighs initiates a controlled forward shift of the upper body, which is cushioned by the driver or passenger airbag.
The knee airbags can only be seen by the lettering "AIRBAG" on the cover of the airbag module as well as on the cable connection for the airbag module.
Scheme 36
Battery Cable Monitoring
The battery cable is diagnosed by a special circuit between the SBSL and SBSR satellites.
The battery cable diagnosis takes place across the low impedance shield of the battery cable (monitoring shield). The monitoring shield monitors the state of the battery cable as follows
There are connections to the left B-pillar satellite and the right B-pillar satellite at both ends of the shield. This means that there is usually the same voltage at the analog/digital converters in the satellites. If the voltages differ, there is a fault.
The monitoring shield consists of a low-impedance metal mesh. A connection cable exits from each end of the monitoring shield (at the safety battery terminal in the luggage compartment and at the battery earth point in the engine compartment).
The connection at the safety battery terminal in the luggage compartment is connected to the right B-pillar satellite. The second connection cable in the engine compartment is connected to the left B-pillar satellite.
The satellites contain analog/digital converters that are connected to the microprocessor of the satellite. The connection cables of the battery cable diagnosis are connected to the A/D converters.
The right B-pillar satellite contains a pull-up resistor.
The left B-pillar satellite contains a pull-down resistor of the same size.
The voltage supply of the satellite (approx. 10 V) is applied at the pull-up resistor. Ground is applied at the pull-down resistor.
The very low-impedance cable and the resistors of the same size mean that around half the voltage (approx. 5 V) is applied at the A/D converters.
In the following cases, the battery cable is cut off by the safety battery terminal from the battery and the alternator is switched off
- Short circuit to ground (body)
- Short to battery positive
If the outer insulation is damaged (e.g. due to friction/scuffing), but the monitoring shield has no connection to ground, the following case could occur
Moisture (rain) would mean that the voltage would gradually fall. A short circuit to ground would be detected, but the safety battery terminal would not be triggered.
The entry "Implausible measured value" is set in the fault code memory. This would be indicated to the driver by the airbag warning lamp.
| State | Measured Value SBSL | Measured Value SBSR |
|---|---|---|
| Battery Cable OK | 5V | 5V |
| Interuption of the diagnostic connection | 0V | 10V |
| Short circuit to ground | 0V | 0V |
| Short to B+ | 12v | 12v |
MEASURED VALUE SBSL
Service Notes
The following must be observed during service
- Battery cable diagnosis
- Safety battery terminal
- Airbag warning lamp
Battery Cable Diagnosis
If the shielding of the battery cable is damaged, the battery cable must be replaced completely. It is not permitted to repair the shielding.
Safety Battery Terminal
If the safety battery terminal is activated, the battery cable must be replaced completely. Repair is not intended.
Airbag Warning Lamp
If there is a fault and the airbag warning lamp is switched on, the mileage is also documented in the fault code memory in the instrument cluster.
A mileage reading that has been entered can not be overwritten. For this reason, in the case of an airbag fault, the fault code memory in the instrument cluster must also be checked and deleted.